Dissertations / Theses on the topic 'Perch fishes'
To see the other types of publications on this topic, follow the link: Perch fishes.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Perch fishes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Miller, Peggy E. "Diagnosis, prevalence, and prevention of the spread of the parasite Heterosporis sp. (Microsporida: Pleistophoridae) in yellow perch (Perca flavescens) and other freshwater fish in northern Minnesota, Wisconsin, and in Lake Ontario /." Connect to online version, 2009. http://minds.wisconsin.edu/handle/1793/37972.
Full text
2
Gallinat, Michael P. "Population analysis and food habits of the yellow perch, Perca flavescenes (Mitchill), in Indiana waters of Lake Michigan, 1984-86." Virtual Press, 1987. http://liblink.bsu.edu/uhtbin/catkey/483967.
Full textAbstract:
Yellow perch, Perca flavescens (Mitchill), were collected by trawling and gillnetting in Indiana waters of Lake Michigan near Michigan City, Indiana. Sampling was conducted during the months of June, July and August from 1984 through 1986.Growth rates and length-weight relationships were found to be considerably lower than those reported previously. Males declined 38 mm at age I, 55 mm at age II, 56 mm at age III and 35 mm at age IV comparing 1986 to 1976. Females showed similar declines for the same period at 40 mm for age I, 58 mm at age II, 66 mm at age III and 53 mm at age IV. The primary reason for the decrease in growth appears to be due to the current high population density of yellow perch in Indiana waters of Lake Michigan.Maturation of males for 1986 appears to be slower than that of 1984. All male perch were mature by age III in 1984. However, only 68x of the males were mature at the same age in 1986. In 1984, 94% of the females were mature by age IV while 86% were mature at the same age in 1986.Differences in maturation rate may be a reflection of the reduced growth rates. Size at maturity was found to be similar for both sexes in 1984 and 1986. All females were mature by 230-239 mm in 1984 and 220-229 mm in 1986. All male perch were mature at 180-189 mm in 1984 and 220-229 mm in 1986.Total estimated average annual percent mortalities of 79, 58, 66 and 55 were calculated for combined sexes from age composition analyses end trawl catch data for 1976 and 1984-86. Yellow perch production for 100 fish was estimated for June through August using the Allen curve method. Biomass of substock ( <130 mm), stock ( >129 mm) and quality fish (200 mm or larger) were estimated using Proportional Stock Density to investigate population structure. The Allen curve biomass models were modified to more accurately reflect the trawl catch density data as an index of population changes in 1976 compared to 1984-86. Theoretical biomass for the substock component increased 23 fold from 1976 to 1986. Biomass of the stock sized fish was estimated as 15 times greater in 1986 compared to 1976. Quality fish biomass varied from year to year with the average for 1984-86 estimated as 14 times greater than 1976. The most apparent factor now influencing deterioration of growth and resultant quality of the population is decreased mortality/increased survival with increase in biomass. If the low mortality rates observed for 1984-86 remain unchanged, the data indicate continued population density increases will result in even lower growth rates, and a population dominated by a higher percentage of small, non-quality fish.Food habit analyses for 1984 were compared to a diet study of yellow perch in 1972 for the study area. Zooplankton increased from 0.4x in 1972 to 9% of the volume in 1984 for 100-175 mm perch. This trend may reflect an increase in zooplankton populations in response to the population decline of the planktivorous alewife. Young-of-the-year yellow perch made up 85% of the stomach volume for 176-225 mm perch in 1984 while none were found in samples for 1972. This clearly shows yellow perch are resorting to cannibalism resulting from excessive intraspecific competition.Diet analyses by month revealed alewife eggs were moat important during peak abundance in June and July. Yellow perch (YOY) and Pontocoreia affinis became important during August. Analysis by size interval showed zooplankton and insects (primarily Chironomidae) were important to the diet of perch in the 30-59 mm (YOY) size interval. Copepoda were important by percent volume until approximately 60 mm when the zooplankton component switched to Cladocera. Data for 60-119 mm (age I+) fish indicates alewife eggs were important during June but insects became increasingly more important during July and August. Diversity in food items consumed diminished with increase in size as diet of 120-159 mm (age II+) yellow perch consisted largely of fish. Increases in percent volume of rainbow smelt in June and July, and Y0Y perch in August for age II+ and older perch compared to younger/smaller fish may be related to increased capture success. Diet of fish larger than 160 mm (age III+ and older) consisted almost entirely of rainbow smelt and Y0Y yellow perch.Ball State UniversityMuncie, IN 47306
3
Tolentino, Scott A. "An analysis of the relative weight (Wr) of yellow perch from Indiana waters of Lake Michigan, 1984-91." Virtual Press, 1992. http://liblink.bsu.edu/uhtbin/catkey/834610.
Full textAbstract:
Relative weight (Wr) of yellow perch (Perca flavescens) was evaluated for fish collected from the Indiana waters of Lake Michigan in June, July and August of 1976 and 1984-1991. Computation of Wr was completed for individual fish in 20 mm intervals over the size range from 100-219 mm using Wr = (W/Ws) 100 where W=weight of a fish in grams and Ws=standard weight for a fish of the same length. Length was highly correlated with weight in all years for males, females and sexes combined (r=0.97-0.99). Distributions of predicted weights for fish at 130 mm and 250 mm were at or near modes of the populations used to construct the Ws equation for yellow perch. Relative weights consistently decreased with increasing size in all years for males, females and sexes combined. Using 1976 length-weight data when the yellow perch population was sparse and fast growing as a standard (100%) for comparison, relative condition factors (Q) increased with increasing size in some years and decreased with increasing size in others for males females and sexes combined and it did not appear to be length dependent. When comparing Wr at 100 mm and 200 mm by sex and month, f hales had higher Wr than males at 100 mm in seven of nine years in June, six of nine years in July and only four of nine years in August. Female fish also had higher Wr than males at 200 mm in eight of nine years in June and July and six of nine years in August. There appeared to be no consistent pattern or trend of Wr increasing or decreasing by month for males, females or sexes combined. When Kn was evaluated for 100 mm and 200 mm fish by sex and year, male fish had higher Kn than females at 100 mm in all eight years. Male and female fish at 200 mm were more similar; male fish had higher Kn in three years, lower Kn in three years and equal Kn in two years. No relationships were found at 200 mm comparing Wr or Kn and CPE (quality/ h) for males (r=0.43; r=0.42), females (r=0.12; r=0.13) or sexes combined (r=0.28; r=0.22). Simple linear correlations of proportional stock density (PSD) with Wr and Kn revealed relative weights increased with PSD for 100 mm (r=0.51) and 200 mm (r=0.72) fish. Relative condition factors also increased with PSD for 100 mm fish, however the relationship was weak (r=0.30) but a strong correlation was found between Kn and PSD (r=0.81) for 200 mm fish. Based on these results, it appears that either Kn or Wr may be used inassessing the condition of yellow perch from the Indiana waters of Lake Michigan.Department of Biology
4
Stettner, Craig R. "An analysis of the population dynamics of the yellow perch in Indiana waters of Lake Michigan." Virtual Press, 1989. http://liblink.bsu.edu/uhtbin/catkey/560277.
Full textAbstract:
Age, growth, and abundance data were collected on yellow perch, Perca fla vescen, in Indiana waters of Lake Michigan in 1987 and 1988. The data collected were compared to data on yellow perch in Indiana waters of Lake Michigan dating back to 1975.Changes in growth, mortality, and abundance between 1975 and 1988 were clearly illustrated by the data. Growth has decreased; back-calculation indicates that "quality" (> 200 mm) perch in 1975 were about age II, however, "quality" perch in 1988 were over age V. Annual mortality values produced from following a cohort or comparing age classes indicate that mortality has decreased since 1981, most sharply in 1987 and 1988. Changes in growth and mortality are likely resultant of large changes in abundance. Indices of abundance (biomass and catch-per-uniteffort) reveal that the yellow perch population has become much more dense in the late 1980's than the 1970's and early 1980's. The percentage of quality perch has decreased, however, the abundance of quality perch has increased and peaked in 1988.Department of Biology
5
Danley, Melody L. M. "Effects of AQUI-S® exposure in 3 species of fish from the Sacramento-San Joaquin Delta, California." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5762.
Full textAbstract:
Thesis (Ph. D.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains iii, 33 p. : ill. Includes abstract. Includes bibliographical references (p. 17-21).
6
Wellington, Colleen G. "Effects of turbidity and prey density on the foraging success of age-0 yellow perch (Perca flavescens)." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1216751590.
Full textAbstract:
Thesis (M.S.)--University of Toledo, 2008.Typescript. "Submitted as partial fulfillments of the requirements for The Master of Science Degree in Biology (Ecology-track)." "A thesis entitled"--at head of title. Bibliography: leaves 19-23.
7
Russell, David John. "Some aspects of the biology of the Barramundi, Lates calcarifer (Bloch) in Eastern Queensland." Thesis, Queensland University of Technology, 1990. https://eprints.qut.edu.au/35966/1/35966_Russell_1990.pdf.
Full textAbstract:
The Barramundi (Lates calcarifer Bloch) is a large, percoid fish, highly valued as a commercial and recreational species. In Queensland, it is distributed in estuaries, coastal habitats and freshwater areas accessible to the sea north from about the Noosa River. This study reports on a three year investigation of the
movements, reproduction and growth of barramundi at 15 sites along the east Queensland coast. Of the 524 adult and sub-adult barramundi tagged in coastal areas and estuaries of eastern Queensland between 1981 and 1984, 136 (26%) were recaptured. Most
recaptures (75%) occurred within a year of the fish being tagged
and 32% were recaptured within three months of release. Movements of tagged fish were usually less than five kilometres, with 25 km regarded as rare. While most fish were recaptured at or near the location where they were released (usually an estuary), in the Burdekin delta area there were movements along coastal foreshores and into adjacent streams. Unlike other parts of Australia and Papua New Guinea, barramundi in eastern Queensland
are generally not catadromous. The large proportion of short and ephemeral rivers and an increasing number of barriers across the larger river systems have restricted the freshwater habitat available for barramundi.
In eastern Queensland, peak spawning occurs from November to February although some spawnings do occur as early as September and as late as April. Gametogenesis commences in August/September and is apparently initiated by a seasonal increase in water temperature and photoperiod. Only weak evidence was found
supporting multiple spawning and only one modal size class of
developing eggs was generally present in ovaries. Fecundity was high and was found to be exponentially related to length. Barramundi mature as males and later, between about 900 and 1000 mm total length, change sex to females. Length-weight relationships, for both sexes, in all areas were strongly linear. In most areas there were significant differences between male and female length-weight regressions. For each area, estimates of the von Bertalanffy growth parameters K, L00 and t 0 ranged from 0.23 to 0.25, 1189 mm to 1274 mm and -0.44 to -0.49 years respectively. Growth rates were initially faster than those established for barramundi in the Northern Territory, Gulf of Carpentaria and Papua New Guinea, and this as considered to be a possible response to heavy exploitation or environmental conditions.
8
Arumugam, Phillip T. "An experimental approach to golden perch (Macquaria ambigua) fry-zooplankton interactions in fry rearing ponds, south-eastern Australia /." Title page, contents and introduction only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09pha793.pdf.
Full text
9
Nagel, Cody J. "Effects of spatial and temporal variation on sampling strategies targeting a community of fishes." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1391678.
Full textAbstract:
Yellow perch, alewife, spottail shiner and round goby trawl catch per unit effort (CPUE) was evaluated in the Indiana waters of Lake Michigan from 1984-2006 to determine whether spatial or temporal variation in CPUE for these species occurred. Differences in CPUE among sites or periods were not clearly distinguished within a single sampling year. However, when compared over a 23 year time frame, spatial and temporal differences became evident. To determine the minimum number of samples needed to detect differences among sites and periods, we ran a Monte Carlo simulation using 23 years of empirical data. This compared favorably to results obtained from a power analysis that identified the minimum number of samples required to identify statistical differences. Sampling effort needed to distinguish differences in CPUE varied both spatially and temporally among the four species. Differences in sampling only became evident when multi-year efforts were employed. In addition, spatial and temporal differences in male and female (mature and immature) yellow perch proportions was also evaluated among our sample sites and periods from 1993-2006.Department of Biology
10
Tremblay, Harold. "Effets des variations du niveau d'eau du Lac Saint-Jean (P.Q.) sur la migration saisonnière de quelques espèces de poissons, en particulier de la perchaude (Perca flavescens) dans le petit marais de Saint-Gédéon /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.
Full text
11
Ng, Rebecca Yuen Wah 1977. "Life history responses of yellow perch (Perca flavescens) to mass removal." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82300.
Full textAbstract:
This study evaluates the life history responses of yellow perch to mass removal and the potential for population recovery. We removed approximately 94% of a perch population from Nepawin Lake, a 35 hectare oligotrophic lake in Algonquin Provincial Park, Ontario, as part of a study designed to enhance the recruitment success of brook trout. Several response variables were examined both before and after mass removal: (1) condition, which includes growth, diet and overall condition responses, and (2) reproduction, which includes size at maturity and fecundity. We examine the question of whether compensatory life history responses in the yellow perch will overcome brook trout predation leading to a reestablishment of a high density perch population. Results showed that prior to the manipulation, perch exhibited a narrow size distribution, high dietary overlap, and low condition, typifying a stunted population. After mass removal, the perch population remained in a narrow size distribution, exhibited decreased growth rates for older age classes, showed increased mean condition and increased consumption of zooplankton in all size classes. Perch also exhibited increased size at maturity and decreased fecundity immediately following the mass removal. A time lag is expected before compensatory recruitment is possible in the population, but it is likely that the perch will recover from the mass removal because of strong age 0+ and 1+ cohorts. However, stunting and bottlenecking may still occur in the population. Continued monitoring and management is necessary to observe further changes to the perch population dynamics in Nepawin Lake.
12
Shortridge, Megan G. Shortridge. "Diet Analysis of Maumee River Fishes using Cytochrome C Oxidase (COI) DNA Metabarcoding ― Insights into a Critical Time of Year." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1471540717.
Full text
13
Schmitz, Mark Harvey. "Comparative Growth of All-Female Versus Mixed Sex Yellow Perch (Perca flavescens) in Recirculating Aquaculture Systems." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/42798.
Full textAbstract:
Nine, production-scale, recirculating aquaculture systems were utilized to
compare the growth parameters between all-female and mixed sex yellow perch stocks.
Each system was stocked with 455 fish m-3 and contained one of three different biofilter
types: a rotating biological contactor, a trickling filter or a bead filter. The all-female
fingerlings (S1) used were originally derived from Lake Mendota, Wisconsin. The
mixed-sex fingerlings (S2) used were originally derived from Lake Erie. Temperature
and photoperiod (23oC, 16H-L) were maintained at levels for optimal growth.
Absolute growth rates ranged from 0.27-0.48 g/day. Mean final density within
treatments was 42.8 kg/m3 and ranged from 37.2-50.2 kg/m3. The main effect of stock
did not have a significant effect on growth (p > .1). All-female treatments exhibited more
uniform growth. The main effect of filter type did have a significant effect on fish
growth (p < .01), with fish in tanks containing trickling filters exhibiting significantly
higher growth. Total feed conversion averaged 1.61 across all treatments and ranged
from 1.38-1.78. S1 treatments consumed a significantly higher percent body weight per
day than S2 treatments (p < .05).
Analysis of PIT tagged individuals revealed that the mean relative growth rate
was significantly higher in S2 individuals (513.9%) compared to S1 individuals (315.3%:
p < .01). S2 females (597.8%) grew 1.9 times faster than S1 females (315.3%: p < .01).
Within S2 individuals, females (597.8%) grew 1.5 times faster than males (395.2%: p <
.05). For all individuals, 33.6% of the variation in final weight was explained by the
variation in initial weight. Differences in the geographic strain or culture history of these
stocks may have had a larger overall effect on growth than sexual classification (all-
female or mixed sex).
Dress percentage of skin-on butterfly fillets was examined in 20 individuals per
stock and in six groups of 20 individuals per stock. Within S2 individuals, 73.7% were
female. Mean fillet yield was significantly greater in S1 individuals (47.6%) compared to
S2 individuals (43.0%: p < .01). Mean GSI in S1 individuals (1.01%) was significantly
higher than S2 individuals (0.54%: p < .05). Within S2 individuals, mean GSI was
significantly higher in females (0.70%) when compared to males (0.08%: p < .05). Fillet
yield was significantly greater in S1 groups (47.2%) compared to S2 groups (44.9%: p <
.01). Within each stock fillet yield increased with size.
The difference in fillet yield demonstrated between these stocks may be a result of
differences in strain of origin. The identification of superior yellow perch strains or
strain crosses with regard to growth rate and fillet percentage is of considerable
importance to the industry.Master of Science
14
Strand, Åsa. "The growth and energetics of perch (Perca fluviatilis L.) in intensive culture." Umeå : Dept. of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200971.pdf.
Full text
15
Crouch, Ryan T. "Adding value to upground drinking water reservoirs: what makes a good yellow perch (Perca flavescens) fishery?" Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1291841439.
Full text
16
Robak, Enbratt Emelie. "Eurasian perch (Perca fluviatilis) is negatively affected by lake browning in southern Sweden." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-42381.
Full textAbstract:
Climate change and human land use leads to browning of waters with decreased visual conditions. This impacts the fish community via changes in foraging ability and food chain efficiency. There are indications that brownification leads to decreased body size of the Eurasian perch (Perca fluviatilis) and that roach (Rutilus rutilus) are favoured over perch in brown lakes since roach is less dependent on its eyesight when foraging. The aim with this project is to examine how browning impacts the fish community in lakes in the south of Sweden and if browning reduces the size of perch in relation to their age. Data on water colour and length-at-age for 1+ and 5+ perch as well as the number of perch and roach captured was collected from 20 lakes. The data was examined using linear regression and paired samples T-test in SPSS. The results show that browning does reduce the body size of perch. Perch is smaller in relation to their age in brown lakes. There was however no evidence indicating that roach is favoured over perch in brown lakes, but there was a difference between the number of 1+ and 5+ perch caught in relation to roach. The perch: roach ration decreased for older fish (from 1+ to 5+) indicating that there is a difference in survival rate. Survival rate of perch was however not dependent on water colour or TOC. This shows that climate change and increased browning could result in changes of the fish community and size structure of fish.
17
Yu, Hao. "Spatial and temporal population dynamics of yellow perch (Perca flavescens) in Lake Erie." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28586.
Full textAbstract:
Yellow perch (Perca flavescens) in Lake Erie support valuable commercial and recreational fisheries critical to the local economy and society. The study of yellow perch's temporal and spatial population dynamics is important for both stock assessment and fisheries management. I explore the spatial and temporal variation of the yellow perch population by analyzing the fishery-independent surveys in Lake Erie. Model-based approaches were developed to estimate the relative abundance index, which reflected the temporal variation of the population. I also used design-based approaches to deal with the situation in which population density varied both spatially and temporally.
I first used model-based approaches to explore the spatial and temporal variation of the yellow perch population and to develop the relative abundance index needed. Generalized linear models (GLM), spatial generalized linear models (s-GLM), and generalized additive models (GAM) were compared by examining the goodness-of-fit, reduction of spatial autocorrelation, and prediction errors from cross-validation. The relationship between yellow perch density distribution and spatial and environmental factors was also studied. I found that GAM showed the best goodness-of-fit shown as AIC and lowest prediction errors but s-GLM resulted in the best reduction of spatial autocorrelation. Both performed better than GLM for yellow perch relative abundance index estimation. I then applied design-based approaches to study the spatial and temporal population dynamics of yellow perch through both practical data analysis and simulation. The currently used approach in Lake Erie is stratified random sampling (StRS). Traditional sampling designs (simple random sampling (SRS) and StRS) and adaptive sampling designs (adaptive two-phase sampling (ATS), adaptive cluster sampling (ACS), and adaptive two-stage sequential sampling (ATSS)) for fishery-independent surveys were compared. From accuracy and precision aspect, ATS performed better than the SRS, StRS, ACS and ATSS for yellow perch fishery-independent survey data in Lake Erie. Model-based approaches were further studied by including geostatistical models. The performance of the GLM and GAM models and geostatistical models (spatial interpolation) were compared when they are used to analyze the temporal and spatial variation of the yellow perch population through a simulation study. This is the first time that these two types of model- based approaches have been compared in fisheries. I found that arithmetic mean (AM) method was only preferred when neither environment factors nor spatial information of sampling locations were available. If the survey can not cover the distribution area of the population due to biased design or lack of sampling locations, GLMs and GAMs are preferable to spatial interpolation (SI). Otherwise, SI is a good alternative model to estimate relative abundance index. SI has rarely been realized in fisheries.
Different models may be recommended for different species/fisheries when we estimate their spatial-temporal dynamics, and also the most appropriate survey designs may be different for different species. However, the criteria and approaches for the comparison of both model-based and design-based approaches will be applied for different species or fisheries.Ph. D.
18
Towne, Kristen Marie. "Sex Reversal in Yellow Perch (Perca flavescens) to Produce Functional Neomale Sperm Donors." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu148063934730826.
Full text
19
Degger, Brian. "Fish insulin-like growth factors : their role in growth from a functional perspective." Thesis, Queensland University of Technology, 2001.
Find full text
20
Andersson, Magnus. "Selective predation by perch (Perca fluviatilis) on a freshwater isopod, in two macrophyte substrates." Thesis, Linköpings universitet, Ekologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-58018.
Full textAbstract:
Recent studies show that populations of the freshwater isopod Asellus aquaticus L. can rapidly become locally differentiated when submerged stonewort (Chara spp.) vegetation expands in lakes. In the novel Chara habitat, isopods become lighter pigmented and smaller than in the ancestral reed stands. In this study, I used laboratory experiments to investigate if selective predation by fish could be a possible explanation for these phenotypic changes. Predation from fish is generally considered to be a strong selective force on macroinvertebrate traits. In the first experiment I measured perch (Perca fluviatilis L.) handling time for three size classes of Asellus to see which size of those that would be the most profitable to feed upon. No difference in handling time was detected between prey sizes, hence the largest size would be the most beneficial to feed upon. In a second experiment I let perch feed on a mixture of Asellus phenotypes in aquaria manipulated to mimic the substrates in either the Chara or the reed habitats. Remaining isopods were significantly smaller and lighter pigmented in the fish aquaria than in the controls, showing that the perch preferred to feed on large and dark individuals. In the Chara habitat, selection on isopod pigmentation was according to what could be expected from background matching, but in the reed habitat selection was quite the opposite. These results support the hypothesis that predation from fish is a strong selective force behind the rapid local adaptation seen in Asellus populations in the novel Chara habitat.
21
Bowden, Brent. "Pharmacokinetic Profiles of Oxytetracycline in Yellow Perch (Perca flavescens) as Determined by Plasma Concentration Following Different Routes of Administration." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31752.
Full textAbstract:
Oxytetracycline (OTC) is one of two antibiotics currently available and approved by the U.S. Food and Drug Administration for use as a chemotherapeutic agent in food fish and is widely used in the aquaculture industry. Previous pharmacokinetic studies of OTC have been conducted in cold water and warm water species of fish. However, no pharmacokinetic studies have been conducted on a cool water species such as yellow perch (Perca flavescens). The yellow perch is a cool water game and commercial species with high aquaculture potential. The pharmacokinetic profiles of oxytetracycline (OTC) was determined by measuring plasma concentrations in yellow perch following intraperitoneal (i.p.), intramuscular (i.m.), per os (p.o.), and intracardiac (i.c.) administration at a single dose of 50 mg/kg body weight. Using a modification of a high-performance-liquid-chromatographic (HPLC) technique, the plasma OTC concentrations were determined for each of the four routes of administration. Plasma concentrations were also evaluated in yellow perch exposed to a static 48-hour OTC water bath (100 mg/l). The terminal half-lives (t1/2) of OTC in yellow perch for i.p., i.m., p.o., and i.c. administrations were 112, 124, 50, and 28 h, respectively. The t1/2 for the i.m. route of administration was significantly longer than in any of the published i.m. OTC fish studies to date. However, the times of maximum OTC concentration (tmax) for the i.p., i.m. and p.o. administrations (2, 4, and 15 h, respectively) occurred relatively early in the plasma concentration-time curves. This suggests, that in yellow perch, OTC is initially absorbed very rapidly. The area under the plasma concentration-time curves (AUC) for the i.p., i.m., p.o., and i.c. routes of administration were 1718, 2659, 383, and 134 mcg·h/ml, respectively. No OTC was detected in the plasma of yellow perch following the water bath route of exposure. Finally, in yellow perch, effective therapy (plasma OTC concentrations above MIC values for most bacteria pathogenic to fish â 4 mcg/ml) would be achieved for up to 168 hours following a single i.p. or i.m. injection of 50 mg/kg and for up to 15 hours following a single p.o dose of 50 mg/kg.Master of Science
22
Kwasek, Karolina Anna. "The nutritional and genetic effects on body growth, reproduction and molecular mechanisms responsible for muscle growth in yellow perch Perca flavescens." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331052970.
Full text
23
Cwalinski, Tim A. "Simulated forecasting of yellow perch (Perca flavescens) relative population density for Indiana waters of Lake Michigan : responses to varying harvest and alewife density." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1036196.
Full textAbstract:
The yellow perch, (Perca flavescens), is an important commercial and sport fish in Indiana waters of Lake Michigan. The population is currently managed by temporary restrictions of commercial harvest. A computer simulation model was developed to examine the effects of various constant harvest quotas and alewife densities on yellow perch relative numbers.Model design is based on the SLAM II simulation language incorporating a FORTRAN biological subroutine. The age-structured population model includes measured or predicted biological characteristics of the dynamic pool model. Recruitment is based on a preestablished three-dimensional Ricker stock-recruitment function including alewife (Alosa pseudoharengus) species interaction as a constant or stochastic factor. Sex-specific natural mortality rates were established through life history parameter analysis and the von Bertalanffy growth factors. Density-dependent growth is incorporated into each year of a model run and fluctuates with the simultaneous density of fish. Constant levels of commercial harvest ranging from 0 to 700,000 kg were used in 20-year forecasts. Initial conditions for model runs were 1984 and 1994 trawl CPUE levels when yellow perch were at high and low levels, respectively according to standardized sampling. Response variables were examined as mean catches over each forecast length and included: age 2 fish, spawning stock (z 190 mm), and total catch > age 1.Alewife densities had a tremendous impact on mean catches of the response variables. Highest catches under any forecast period occurred when alewife was considered absent from the system. Catches declined as alewife density was increased as a 20-year constant under each harvest regimen.Catches of spawning size fish were maintained at highest levels for all forecast periods when harvest was set to zero. Catches of young fish were moderate with this harvest regimen if initial catch conditions were high such as in 1984. Catches of young fish were always higher in the absence of a commercial fishery if initial catch conditions were low such as in 1994. Low to moderate harvest quotas could maintain moderate levels of young fish for the forecast length if initial model conditions were high. However, these quota levels for the 1984-2004 forecast length resulted in lower mean catches of spawning size fish as compared to the no commercial fishery regimen. The best case scenario for all response variables when initial catch conditions were low was under a no commercial harvest regimen.Department of Biology
24
Gonzalez, Artola Sonia. "Chemical, Physical and Sensorial Compositions of Farmed and Wild Yellow Perch (Perca flavescens), Southern Flounder (Paralichthys lethostigma) and Coho Salmon (Oncorhynchus kisutch)." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29854.
Full textAbstract:
This study compared chemical, physical and sensorial properties of wild and farmed fish.
Farmed yellow perch fillets showed higher lipid contents (2.78% vs. 1.39%); softer texture (0.41 J/g vs. 0.53 J/g); whiter color (higher L* and lower b*values); different fatty acid profile (higher n-3/n-6 ratio), and mineral composition, when compared to their wild counterparts. Similar amino acid profiles and flavor were found between treatments.
Dietary protein by itself influenced color and flavor of yellow perch fillets. Yellow perch fed the highest protein concentrations exhibited higher b* (yellow) values and overall flavor was significantly different (p â ¤ 0.05) between fish fed a 45% and 55% crude protein (CP) diet.
A 12-week feeding trial determined that southern flounder protein requirement to achieve maximum weight was around 50% CP.
Farmed southern flounder were found to be higher in lipid content (3.04 % vs. 1.61%), softer (0.24 J/g vs. 0/33 J/g), different in color (lower a* [green to red]), mineral, fatty acid composition (higher n-3/n-6 ratio) and flavor, than wild.
The effect of a crab meal-supplemented diet, on flavor and body composition of flounder was analyzed. The inclusion of crab meal as a flavor enhancer affected the flavor and also influenced color of the fillets (lower L* [lightness] and higher b* values).
Wild, farmed and growth-enhanced transgenic coho salmon (market-size) were compared, regarding their body composition and nutritional value. All treatments showed highest lipid levels in the ventral frontal sections and lowest in the tail (p â ¤ 0.05). Overall wild fish showed lower lipid levels and firmer values in the tail sections (p â ¤ 0.05). The insertion of the growth hormone gene affected lipid deposition, texture and color, since transgenic fish showed firmer texture than farmed and similar lipid contents even when fed a high-energy diet. L*, a* and b* values were similar for wild and transgenic coho in most of the body zones. Fillet mineral and amino acid profiles were similar across all groups. No differences were observed in flavor between farmed and wild coho, while panelists preferred the appearance of farmed, when compared to transgenic coho.Ph. D.
25
Hansson, Tomas. "Biomarkers in perch (Perca fluviatilis) used in environmental monitoring of the Stockholm recipient and background areas in the Baltic Sea." Doctoral thesis, Stockholms universitet, Institutionen för tillämpad miljövetenskap (ITM), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8143.
Full textAbstract:
This thesis reports the results of biomarker measurements in three environmental monitoring projects. In the first project, which was part of the Swedish national environmental monitoring, biomarkers were measured annually in female perch (Perca fluviatilis) in two background areas in the Baltic Sea during 1988–2000, resulting in a unique 13-year series of measurements. The most important results were a strong decreasing temporal trend in the gonadosomatic index (GSI) and a strong increasing temporal trend in the hepatic ethoxyresorufin O-deethylase (EROD) activity in the Baltic Proper. In the second project, biomarkers and concentrations of classic pollutants were measured in female perch in the Stockholm recipient 1999–2001. This was the first time a large city was investigated as a point source of pollution, and the gradient was longer and included more stations than customary. Severe pollution conditions in central Stockholm were indicated by the poor health status of the perch: retarded growth, decreased frequency of sexually mature females, low GSI, disturbed visceral fat metabolism, increased hepatic EROD activity, decreased muscle acetylcholinesterase activity, increased frequency of hepatic DNA adducts, and a high concentration of biliary 1-pyrenol. Muscle ΣDDT and ΣPCB were measured as pollution indicators and were 10–28 respectively 12–35 times higher than the background levels in perch from the Baltic Proper. In the Stockholm archipelago two superimposed gradients were found. Whereas the response of several biomarkers consistently decreased with increasing distance from central Stockholm, the response of others first decreased from Stockholm to the middle archipelago and then increased to the open Baltic Sea. The latter biomarkers included the frequency of sexually mature females, GSI, hepatic EROD activity, and hepatic DNA adducts. In the third project, potential toxicity from munitions on the seafloor, at a dumpsite in the Stockholm archipelago, was analysed by the nanoinjection of sediment extracts into newly fertilised rainbow trout (Oncorhynchus mykiss) eggs, followed by the measurement of biomarkers in the developing larvae. No biological effects of the dumped munitions were found. The same stations in the Stockholm archipelago as in the second project were investigated as a positive control. The results of the three projects agreed well, which demonstrated the continuous pollution of the Baltic Sea and the severe pollution conditions and adverse biological effects in central Stockholm. Further investigations are urgently needed to identify which pollutants or other factors are causing the observed biological effects, both in the background areas in the Baltic Sea and in the Stockholm recipient.
26
Kemski, Megan Marie. "Fish meal replacement with soybean meal in yellow perch (Perca flavescens) diets: responses of nutritional programming on growth, transcriptome and isoflavone accumulation." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534465279444556.
Full text
27
Almeida, Tainá Rocha de. "Study of gene expression patterns in Eurasian perch (Perca fluviatilis Linnaeus, 1758) eggs related to their quality and to the domestication process." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0288.
Full textAbstract:
Avec le déclin grandissant des prises de pêches, une augmentation de la production piscicole est attendue pour les prochaines années. Cependant, de nombreux problèmes de reproduction sont observés dans les élevages, principalement une mortalité élevée au début de la vie. Cela concerne principalement des espèces piscicoles pour lesquelles le processus de domestication commence. Mon travail de thèse a visé à mieux comprendre et potentiellement aider à améliorer les performances de reproduction en étudiant le contenu transcriptomique des œufs de perche commune (Perca fluviatilis) en lien avec leur qualité. Ces résultats participent à la compréhension des mécanismes moléculaires impliqués dans la mortalité embryonnaire précoce. Cette espèce, en cours de domestication, revêt une grande importance dans le contexte de la diversification des espèces d’intérêt aquacole en Europe continentale. J’ai utilisé des analyses par puce à ADN et RT-qPCR pour caractériser les profils d'expression génique dans les œufs de perche de qualité variables. Les expériences ont été menées dans deux contextes scientifiques. Dans un premier temps, j’ai comparé l’effet des méthodes d’évaluation de la qualité des œufs sur les résultats transcriptomiques obtenus. Ainsi, les œufs ont été classés dans des groupes de qualité (bonne ou mauvaise) en utilisant divers critères liés au développement embryonnaire (taux de survie, taux de malformation) et divers seuils limites pour borner ces groupes. L’utilisation de critères de survie embryonnaire précoces a permis d'identifier des profils d'expression génique distincts entre les groupes de qualité. Cependant, le nombre et la nature des gènes exprimés de manière différentielle (DEG) étaient variables. Un seul gène était exprimé de manière différentielle dans toutes les analyses, quelles que soient les conditions. Cela montre à quel point les résultats transcriptomiques sont sensibles aux méthodes d’évaluation qui doivent être sérieusement pris en compte en amont de comparaisons intra et inter-espèces. Dans un deuxième temps, j’ai comparé le contenu transcriptomique d’œufs de femelles avec des histoires de domestication différentes. Dans cette étude, les femelles les plus proches des populations sauvages présentaient une meilleure qualité d'œufs. En outre, deux modèles distincts d'expression génique ont été observés et plus de 300 DEG ont été identifiés entre les populations. Étant donné que les causes de la variabilité élevée des performances de reproduction des espèces en cours de domestication sont mal connues, cette découverte pourrait ouvrir de nouvelles hypothèses d’investigation. Enfin, il devenait important de déterminer le moment où le gène identifié dans les approches précédentes soutiendrait exclusivement le développement embryonnaire précoce. Dans ce but, une étude préliminaire a permis de faire une première évaluation de l’activation du génome zygotique (ZGA) chez cette espèce. L’ensemble de ces résultats ouvre la voie vers l’établissement de nouvelles méthodes d’investigation de la qualité des gamètes chez la perche commune. Ces méthodes permettront de faire des études précises de l’évolution du succès de développement à chaque génération au cours d’un processus de domestication. Des méthodes similaires pourraient être établies chez d’autres espèces en prenant en compte leurs particularités. Il serait alors intéressant de tenter d’étudier des espèces présentant des caractères communs ou divergents. Nous pourrons alors tenter de comprendre les régulations propres à chaque espèce ou au contraire largement retrouvés chez plusieurs espèces de poissonIn the aquaculture context, increase on production are expected for the next years and yet, many reproductive issues are reported, including high mortality during early life stages. It concerns mostly species for which the domestication process is at the very beginning. My PhD work aimed at better understanding and potentially helping improving reproductive performance by investigating eggs the transcriptomic content of the Eurasian perch (Perca fluviatilis) eggs in association with their quality which may constitute one of the sources for embryonic mortality. Eurasian perch is a species, in process of domestication, with strong importance for aquaculture diversification in inland Europe. We employed microarray and RT-qPCR analyses to characterize gene expression patterns of Eurasian perch eggs presenting different potential to develop properly after fertilization. The experiments were conducted in two scientific contexts. In the first one, different methods to access egg quality were employed and their potential impacts on the transcriptomic results were evaluated. Therefore, when eggs were classified into the respective quality groups (high or low) using early embryonic survival as criteria, we were always able to identify distinct patterns of gene expression between quality groups. However, the number and nature of the differentially expressed genes (DEG) were variable and only one gene was commonly differentially expressed no matter the methods employed. This shows how transcriptomic results are sensitive to methods and should be deeply considered for intra- and inter-species comparisons. The second context consisted of investigating whether females presenting different histories of domestication would differ in their eggs mRNA content, and how it affects egg quality. In this study, females closest to wild populations presented better egg quality. In addition, two distinct patterns of gene expression were observed and more than 300 DEG were identified between populations. Because not much is known about the causes of high variability in reproductive performance in species in process of domestication, this finds could open new hypothesis of investigation. Finally, it became important to determine the moment until which the gene identified in the previous approaches were exclusively supporting embryonic early development. With this purpose, a preliminary study allowed making a first evaluation of the zygotic genome activation (ZGA) in this species. As a whole, this study identified numerous maternal-effect genes which implication in embryos early development should be further investigated. In addition, these results suggest that more comparable methods to investigate egg quality in Eurasian perch could be established. These methods will make possible more precise studies in the variation of the development success under the influence of distinc factors, such the domestication process. Similar methods could also be established in other species considering their own common or divergent characters. It would help understanding molecular mechanisms species specific or widely found in finfish species
28
Marshall, Carina Rynn Ecremen. "Evolutionary genetics of barramundi (Lates calcarifer) in the Australian region." Thesis, Marshall, Carina Rynn Ecremen (2005) Evolutionary genetics of barramundi (Lates calcarifer) in the Australian region. PhD thesis, Murdoch University, 2005. https://researchrepository.murdoch.edu.au/id/eprint/181/.
Full textAbstract:
Barramundi (Lates calcarifer) is a centropomid teleost with a wide distribution across the Indo Pacific. In Australia, barramundi are native to the tropical zone from Exmouth Gulf in Western Australia, across the northern part of the continent, to the Mary River in Queensland. Barramundi are protandrous hermaphrodites, and are euryhaline, with a catadromous life history. Barramundi are a valuable Australian resource, with important commercial and recreational fisheries and aquaculture production to the value of $11 million dollars per year. Recent declines in the availability of the fish in some rivers has led to an interest in the possibility of restocking rivers with barramundi from other areas.
Determining the genetic structure of barramundi populations in Australia is important for understanding biogeographic history, and appropriate management practices for both aquaculture and recreational and commercial fishing. Previous studies have concentrated on the east coast of Australia, and have largely ignored the western populations. In this study, I obtained DNA data from barramundi populations across the Australian range of the species, as well as populations from Papua New Guinea and Indonesia. The aims of this study were to use the genetic data to determine: 1. if populations in Western Australia show genetic differences between geographic regions 2. if these populations show an ancestral split from populations in the east of Australia and 3. the ancestral origins of Australian barramundi.
Previous studies of DNA data from barramundi have discovered an east/west split occurring at the Torres Strait that was assumed to be caused by the closing of the strait during lowered sea levels. However, these studies suffered from a bias in sampling area, concentrating either on the eastern half of the range of barramundi, or on the western tip of the range. Data from these studies were combined and reanalyzed. Two major clades were discovered, with considerable biogeographic structuring, but their geographic locations did not coincide with the reported vicariance event at the Torres Strait. Instead,historical divisions among freshwater drainage systems appeared to have driven the evolutionary history of barramundi in Australia.
In order to investigate these historical divisions further, a 290 bp section of the mitochondrial DNA control region was sequenced in 284 barramundi from seven populations across the Australian geographic range of the species and from one population in Papua New Guinea and one population in Indonesia. Analyses of molecular variance within and among populations showed significant geographic structuring, based on biogeographical provinces and drainage divisions. Nested clade analyses indicated that these geographical associations were the result of restricted gene flow, range expansion, and past fragmentation events. I hypothesise that the Ord River area in the west of the continent was the ancestral source population for the rest of the species' range across Australia, with Indonesia being the most likely origin of this source. Populations of barramundi from the Pilbara region are genetically distinct and geographically isolated, with strong evidence of an ancestral divide along geographical barriers to dispersal. There is a strong association between Papua New Guinea and Australia, although further investigations using the cytochrome b region of mitochondrial DNA indicated a more ancestral divide between the two than is currently evident, which could reflect an ancient geographical divide between the two, or could be evidence of a secondary migration route to Australia.
For a more detailed study of evolutionary processes acting on populations of barramundi in Western Australia, allelic diversity was examined at five microsatellite loci. All loci were polymorphic and genotypic frequencies conformed to Hardy-Weinberg expectations, with no significant linkage between loci evident in any population. Measures of within population diversity were significantly related to latitude, suggesting southerly migration from a northern source population. The Ord River was the most genetically diverse population, and the most likely ancestral migration source to the area, with diversity decreasing down the west coast. Although there were significant differences among populations, the nuclear microsatellite data do not indicate the same degree of genetic structuring as is evident in the mitochondrial data. This may be a consequence of rapid evolutionary change at microsatellite loci, with past separations or population differences masked by recombination and back mutation of the microsatellite alleles. However, the nature of nuclear and mitochondrial inheritance may also indicate life history differences between the sexes, where significant genetic contribution to gene flow by males and limited female gene flow may lead to preservation of maternally inherited population substructure.
The principal findings from this study are:
* There is no genetic evidence for an east/west division of barramundi populations in Australia, as suggested by previous research.
* Despite barramundi's catadromous life history, and ability to disperse through marine waters, the present genetic structure indicates a division principally among river drainages. From a population genetic viewpoint, the species can be regarded as freshwater, rather than marine.
* The most likely origin of barramundi in Australia is the Ord River region, with Indonesia as the route of migration.
* Differences in the population structure demonstrated by nuclear and mitochondrial data indicate possible life history differences between the sexes.
* Barramundi populations in different biogeographical provinces may have been substantially isolated over a long period of time, and may therefore represent independently evolving populations. This has important implications for fishery management and translocation issues for restocking rivers.
29
Marshall, Carina Rynn Ecremen. "Evolutionary genetics of barramundi (Lates calcarifer) in the Australian region." Marshall, Carina Rynn Ecremen (2005) Evolutionary genetics of barramundi (Lates calcarifer) in the Australian region. PhD thesis, Murdoch University, 2005. http://researchrepository.murdoch.edu.au/181/.
Full textAbstract:
Barramundi (Lates calcarifer) is a centropomid teleost with a wide distribution across the Indo Pacific. In Australia, barramundi are native to the tropical zone from Exmouth Gulf in Western Australia, across the northern part of the continent, to the Mary River in Queensland. Barramundi are protandrous hermaphrodites, and are euryhaline, with a catadromous life history. Barramundi are a valuable Australian resource, with important commercial and recreational fisheries and aquaculture production to the value of $11 million dollars per year. Recent declines in the availability of the fish in some rivers has led to an interest in the possibility of restocking rivers with barramundi from other areas.
Determining the genetic structure of barramundi populations in Australia is important for understanding biogeographic history, and appropriate management practices for both aquaculture and recreational and commercial fishing. Previous studies have concentrated on the east coast of Australia, and have largely ignored the western populations. In this study, I obtained DNA data from barramundi populations across the Australian range of the species, as well as populations from Papua New Guinea and Indonesia. The aims of this study were to use the genetic data to determine: 1. if populations in Western Australia show genetic differences between geographic regions 2. if these populations show an ancestral split from populations in the east of Australia and 3. the ancestral origins of Australian barramundi.
Previous studies of DNA data from barramundi have discovered an east/west split occurring at the Torres Strait that was assumed to be caused by the closing of the strait during lowered sea levels. However, these studies suffered from a bias in sampling area, concentrating either on the eastern half of the range of barramundi, or on the western tip of the range. Data from these studies were combined and reanalyzed. Two major clades were discovered, with considerable biogeographic structuring, but their geographic locations did not coincide with the reported vicariance event at the Torres Strait. Instead,historical divisions among freshwater drainage systems appeared to have driven the evolutionary history of barramundi in Australia.
In order to investigate these historical divisions further, a 290 bp section of the mitochondrial DNA control region was sequenced in 284 barramundi from seven populations across the Australian geographic range of the species and from one population in Papua New Guinea and one population in Indonesia. Analyses of molecular variance within and among populations showed significant geographic structuring, based on biogeographical provinces and drainage divisions. Nested clade analyses indicated that these geographical associations were the result of restricted gene flow, range expansion, and past fragmentation events. I hypothesise that the Ord River area in the west of the continent was the ancestral source population for the rest of the species' range across Australia, with Indonesia being the most likely origin of this source. Populations of barramundi from the Pilbara region are genetically distinct and geographically isolated, with strong evidence of an ancestral divide along geographical barriers to dispersal. There is a strong association between Papua New Guinea and Australia, although further investigations using the cytochrome b region of mitochondrial DNA indicated a more ancestral divide between the two than is currently evident, which could reflect an ancient geographical divide between the two, or could be evidence of a secondary migration route to Australia.
For a more detailed study of evolutionary processes acting on populations of barramundi in Western Australia, allelic diversity was examined at five microsatellite loci. All loci were polymorphic and genotypic frequencies conformed to Hardy-Weinberg expectations, with no significant linkage between loci evident in any population. Measures of within population diversity were significantly related to latitude, suggesting southerly migration from a northern source population. The Ord River was the most genetically diverse population, and the most likely ancestral migration source to the area, with diversity decreasing down the west coast. Although there were significant differences among populations, the nuclear microsatellite data do not indicate the same degree of genetic structuring as is evident in the mitochondrial data. This may be a consequence of rapid evolutionary change at microsatellite loci, with past separations or population differences masked by recombination and back mutation of the microsatellite alleles. However, the nature of nuclear and mitochondrial inheritance may also indicate life history differences between the sexes, where significant genetic contribution to gene flow by males and limited female gene flow may lead to preservation of maternally inherited population substructure.
The principal findings from this study are:
* There is no genetic evidence for an east/west division of barramundi populations in Australia, as suggested by previous research.
* Despite barramundi's catadromous life history, and ability to disperse through marine waters, the present genetic structure indicates a division principally among river drainages. From a population genetic viewpoint, the species can be regarded as freshwater, rather than marine.
* The most likely origin of barramundi in Australia is the Ord River region, with Indonesia as the route of migration.
* Differences in the population structure demonstrated by nuclear and mitochondrial data indicate possible life history differences between the sexes.
* Barramundi populations in different biogeographical provinces may have been substantially isolated over a long period of time, and may therefore represent independently evolving populations. This has important implications for fishery management and translocation issues for restocking rivers.
30
Nyboer, Elizabeth. "Movement, home range, and ecological divergence in the commercially fished Nile perch in Lake Nabugabo, Uganda." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114515.
Full textAbstract:
The large piscivorous Nile perch (Lates niloticus) was introduced to the Lake Victoria basin in the 1950s and 1960s and eventually became one of the most valuable commercial species of East Africa's inland fisheries. Intense fishing-induced mortality may be contributing to dramatic ecological change in this species (reductions in body size and biomass; shifts in distribution and diet), and reinforcing patterns of ecological divergence in some lakes in the region. In this thesis I use an evolutionary ecology approach to explore habitat associated ecological divergence in the Nile perch in Lake Nabugabo, Uganda. I describe home range, movement, and habitat selection of Nile perch, and quantify divergence in phenotypic traits between major habitat types and across Nile perch ontogeny. Using radio telemetry I tracked 14 Nile perch for 5 months and used ArcGIS 9.3 to quantify movement patterns throughout Lake Nabugabo. I used movement data in combination with detailed ecological information to quantify habitat selection in the heavily fished inshore zones of the lake. Geometric morphometric and colour analyses were used to quantify divergence in body shape and skin colour across different size classes of Nile perch from ecologically distinct wetland and forest edge habitats. Nile perch exhibited low levels of daily movement and relatively small home ranges; and they preferred regions of the lake characterized by low temperature and high dissolved oxygen. Geometric morphometric and colour analyses revealed habitat-associated phenotypic divergence in both skin colour and body shape, although not all trends were consistent across size classes. The source of phenotypic divergence (genetic vs. plastic) remains unknown; however the level of site tenacity exhibited by Nile perch suggests that ecological isolation between forest edge and wetland fish may be higher than expected. These results have important implications for development of territorial jurisdiction by Beach Management Units, the decentralized structure of fisheries management in the region. Knowing that Nile perch, one of the most important commercial catches in the Lake Victoria basin, have definable home ranges provides a biologically relevant rationale for the insertion of territorial boundaries for BMUs. Clearly defined resource-use boundaries may provide additional incentives for members to follow fishery rules and may prove to be instrumental in improving BMU efficacy.La grande perche du Nile piscivore (Lates Niloticus) a été introduite dans le bassin du lac Victoria dans les années cinquantes et soixantes pour devenir une des espèces les plus précieuses pour l'économie de la pêche en intérieure de l'Afrique de l'est. Un taux de mortalité très élevé relié à la pêche contribuerait à des changements écologiques dramatiques pour l'espèce (réduction de la taille du corps et de la biomasse; changements dans la distribution et le régime alimentaire), et renforcerait les conventions de divergence écologique dans certains lacs de la région. Dans cette thèse, j'utilise une approche écologique évolutive pour explorer l'écosystème associé à la divergence écologique de la perche du Nile dans le lac Nabugabo en Uganda. J'identifie le domaine vital, les schémas de mouvement et l'utilisation de l'habitat de la perche du Nile, et quantifie ainsi la divergence des phénotypes dans les différents habitats et toute l'ontogenèse de la perche du Nile. En utilisant la technique de la radiotélémesure, j'ai traqué 14 perches du Nile pendant 5 mois et avec l'ArcGIS 9.3, j'ai quantifié les schémas de mouvements dans le lac Nabugabo. J'ai associé les données des schémas de mouvement avec des données écologiques détaillées pour quantifier l'utilisation de l'habitat dans les zones de pêche intense du lac. La géométrie morphométrique et les analyses de couleur ont été utilisées pour quantifier les divergences dans la taille, forme et couleur des différentes classes de perche du Nile dans les habitats distincts de bord de forêts et de marécages. La perche du Nile a démontré des niveaux de mouvements journaliers peu élevés pour un domaine vital plutôt restreint; Elle préférait les régions du lac de basse température à oxygène hautement dissous. La géométrie morphométrique et les analyses de couleur ont révélé des divergences phénotypiques associées à l'écosystème dans la forme et la couleur de la perche, bien que ces tendances n'aient pas été constantes à travers toutes les classes de tailles. La source de la divergence phénotypique (génétique contre plastique) demeure inconnue; par contre, le niveau de ténacité au choix du site manifesté par la perche du Nile suggère que l'isolation écologique entre le bord de forêt et les marécages serait plus élevé que prévu. Ces résultats ont des implications importantes pour le développement d'une juridiction territoriale dans les Unités de Gestion des Plages (UPG), la structure décentralisée qui gère la pêche dans la région. Sachant que la perche du Nile, une des plus espèces les plus importantes pour la pêche commerciale dans le bassin du lac Victoria, démontre des domaines vitaux définissables fournit une raison biologique pour favoriser des délimitations territoriales de pêche par les UGP. Ces délimitations de ressources clairement définies pourraient motiver les membres des UPG à suivre le règlement des consignes de pêche et devenir essentiel pour améliorer l'efficacité des UGP.
31
Hancock, Andrew (Boze) T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." University of Western Australia. School of Animal Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.
Full textAbstract:
The Roe’s abalone (Haliotis roei) fishery near Perth, Western Australia, is uniquely accessible, and highly vulnerable to overexploitation. The sustainability of this intensively utilized fishery requires robust assessment. To facilitate an assessment, this research aimed to provide rigorous and detailed biological information with appropriate interpretation. Four critical aspects of the species’ biology and population dynamics were investigated: (1) the stock structure; (2) the recreational catch; (3) an appropriate growth curve and description of size at age; and (4) abundance measures against which to assess the impact of fishing mortality. Allozyme electrophoresis was used to investigate stock structure across the species’ distribution. Standardized variance in allelic frequencies between 10 sites in south-western Australia indicated high levels of gene flow across the 3000 km sampled (mean FST = 0.009). An isolation-by-distance was evident when pairwise measures of GST were related to geographic distance (r=0.45, P<0.001). The area of complete genetic mixing was estimated from samples within the Perth fishery to be less than the distance between the two nearest sites, or 13 km. Consequently, the Perth fishery comprises numerous discrete stocks, each requiring independent assessment. A possible mechanism for this population structure is the retention of larvae in the wind driven currents oscillating in the near-shore lagoons, with rare pulses of long distance dispersal via the southerly Leeuwin current, running further offshore. The presumed impact of intensive recreational fishing, combined with substantial commercial quotas for the Perth fishery, had led to tight restrictions on fishing effort, without any quantitative measure of the recreational catch. A stratified creel survey was adapted to estimate the effort, catch rate and mean weight of abalone harvested by the recreational sector. Catches were estimated for reef complexes, or stocks, of less than 10 nautical miles (18.5 km) of coast. Between 1997 and 2000 the recreational catch varied from 30 to 45 tonnes whole weight, approximately equivalent to the commercial quota of 36 tonnes. On average 88% of the recreational catch came from two stocks, while 98% of the commercial catch came from these two, and one additional, stocks. The incidental mortality from recreational fishing, measured as the number of abalone left dead on the reef as a proportion of the estimated catch, was approximately 7% and 20% at two sites surveyed. Spatial and temporal patterns of growth were examined on the west coast of Western Australia. Growth increments were measured for abalone larger than about 30 mm from tagging studies at five sites in the Perth fishery, a site at the northern extent of the species’ distribution and a site in the southwest. Mean annual growth increments of the 0+ year class were obtained by fitting components to length frequencies from five sites in the Perth fishery, and combined with growth increments from each Perth tag site for model fitting. A von Bertalanffy growth curve provided a slightly better fit to the tag data, but a Gompertz growth curve was a much better fit when the mean increment from the 0+ to 1+ cohort was included, with the inflection occurring at about 40 mm, the size at sexual maturity. There was no difference in annual growth between the two years studied. There was significant variation in growth between the reef platform and adjacent sub-tidal reef, but this variation was site specific and faster growth rates were not consistently associated with either habitat. There was no latitudinal trend in growth rate. Growth at the Perth sites was the fastest and similar at all five sites with growth increments greater in summer than in winter. Size and abundance of abalone were measured using fixed transects and quadrats. Abalone densities were highest on the outer edge of the platform, intermediate in the middle of the reef platform, and lowest on both the inner platform and the sub-tidal reef. The pattern of mean lengths of abalone was the inverse of the density. Mean length and abundance were driven by the presence of post-settlement juveniles on the outer and middle reef habitats. There was a high spatial variation in abundance, with densities varying between transects at the same site, but the trend between years for each transect at a site was not significantly different. Abalone abundances, by size class, were examined from sites sampled between 1996 and 2002. A low density of post-settlement juveniles at all sites in 1997 was reflected in low densities of the 1+ and 2+ year classes in subsequent years. Abalone abundances at an unfished site were steady over the seven years. Two sites were located within each of the main stocks utilised by the recreational fishery. Abundance was stable or increasing in one stock, corresponding to a stable total catch. In the second stock the total catch increased over time and abundances declined. Perth is the focus of the Roe’s abalone fishery, with recreational and commercial fishers take about equal shares of the annual catch. Stocks are highly subdivided, with most of this catch coming from only 3 stocks occupying about 20 nautical miles of coast. Growth rates were found to be lower than previous estimates, and more similar to other commercial species of abalone. All life history stages are highly habitat specific, particularly the recruits, and the distribution and abundance through time indicate that the main stocks are near, or slightly over, the limit of sustainable fishing.
32
Kiggundu, Rose. "Innovation systems and development the journey of a Beleaguered Nile Perch Fishery in Uganda /." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Universiteit Maastricht [host], 2006. http://arno.unimaas.nl/show.cgi?fid=5736.
Full text
33
DeKluyver, Tertius Vitus. "Development of larval barramundi under conditions of intense culture." Thesis, Queensland University of Technology, 1998.
Find full text
34
Farmer, Troy M. "Climate Change Effects on Lake Erie Yellow Perch Reproduction and Recruitment." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386038579.
Full text
35
Bodamer, Scarbro Betsy L. "The Physiological and Behavioral Responses of Yellow Perch to Hypoxia." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396521163.
Full text
36
Harris, Johnathan. "Impacts of the Invasive White Perch on the Fish Assemblage of Kerr Reservoir, Virginia." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32914.
Full textAbstract:
The white perch (Morone americana) is a highly successful invader of freshwater systems, with negative consequences to some resident fishes. White perch are ovivores and may prey upon as well as compete with juvenile sportfishes. Since 1988, an introduced population of white perch has proliferated in the 19,790-ha Kerr Reservoir, NC-VA, potentially threatening popular sport fisheries for largemouth bass (Micropterus salmoides), crappie (Pomoxis spp.), and self-sustaining striped bass (Morone saxatilis). Trophic relationships between white perch and resident sportfish were examined in the Kerr Reservoir system to determine the white perchâ s impact on them.
Striped bass eggs were found in the stomach contents of white perch collected from the Roanoke River during their concurrent spawning runs in May, and at times egg predation was intense (frequency of egg occurrence in white perch individuals up to 100 %). However, modeling simulations indicated that observed densities of white perch in the Roanoke River during the peak spawning period of striped bass (May) were too low to have a substantial effect on striped bass recruitment. Crappie eggs were found in the diets of white perch collected from Kerr Reservoir during April, but the significance of this predation was not determined.
Trophic overlap (Schoenerâ s Index) was high (> 0.5) between age-0 white perch and age-0 crappie, largemouth bass, and striped bass in June, but only remained high between white perch and crappie in the remainder of the growing season (July â September). After June, largemouth and striped bass were primarily piscivorous, whereas white perch and crappie remained primarily invertivorous. Trophic overlap was high between adult white perch and adult crappie (> 0.6), but not between white perch and any other species of adult sportfish.
The utilization of white perch by adult piscivores (Ictalurids, Pomoxis spp., Moronids, and Percids) as a food source was low (< 2% of diets by weight). Piscivorous sportfish primarily ate clupeids, which are highly abundant in Kerr Reservoir.
Analysis of sportfish performance before (1974 â 1987) versus after (1996 â 2005) white perch establishment indicated no change in abundance and growth of striped bass and largemouth bass. Performance data for crappie prior to white perch introductions were unavailable, but observed egg predation by and trophic overlap with white perch suggests that crappie have the highest potential to suffer deleterious interactions with the white perch. Abundance of white bass has significantly declined in years since white perch introductions. Future research in Kerr Reservoir should concentrate on interactions between white perch and these two species.Master of Science
37
Hancock, Andrew. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery /." Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.
Full text
38
Hancock, Andrew T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." Connect to this title online, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068/.
Full text
39
Kahwa, David. "Gametogenesis, gonadal recrudescence, restraint and spawning patterns in Nile perch, Lates niloticus (Linnaeus, 1758)." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001834.
Full textAbstract:
The Nile perch, Lates niloticus (Linnaeus, 1758), is a predacious freshwater fish widely distributed throughout the Afro-tropic eco-zone. The species was introduced to Lake Victoria in the early 1950s and by 1980 it had dominated the fisheries of Lake Victoria. This was followed by a dramatic decrease in the Nile perch fisheries production due to uncontrolled exploitation. The purpose of this thesis is to provide fundamental knowledge that can be applied in aquaculture and fisheries management through the study of the reproductive biology of L. niloticus. The research was aimed at the studying of the diverse aspects of the reproductive biology of L. niloticus in the Lake Victoria, Ugandan populations. This included reproductive patterns in relation to proximate environmental conditions, size at sexual maturity, gonad and gamete structure, gametogenesis and induced ovulation. The size at 50% sexual maturity for female Nile perch was 59.4 cm, which is lower than the earlier reported size of greater than 90 cm total length. Male L. niloticus matured at 57.8 cm total length in Lake Victoria. Microscopy revealed that L. niloticus from Lake Victoria had one spawning period that started in November and ended in March. Type I atresia occurred at high frequency from March to June, and type III atresia was present from July to September and between November and December. Spermatogenesis in L. niloticus is cystic and sperm development is the result of asynchronous activation of the germ cells. Type II spermatozoa are simple, uni-flagellate aquasperm with no acrosome. Oogenesis in L. niloticus differed from that of other fishes in that no cortical alveoli were present in any stage of oogenesis. Numerous oil globules were present in the primary yolk vesicle stage. This formed one centrally positioned, large oil globule in the tertiary yolk vesicle oocytes during final oocyte maturation. Clove oil was an effective sedative and an anaesthetic for the handling of L. niloticus. Induction time was more rapid at clove oil concentrations of 50 - 100 μl L⁻¹ than in fish exposed to clove oil concentrations less than 50 μl L⁻¹. Fish exposed to high concentrations exhibited significantly short induction times of less than 240 seconds. On average, fish recovered within 673 ± 58 seconds for all the concentrations used. Prolonged exposure of L. niloticus to low clove oil concentrations of 2.5 - 10 μl L⁻¹ did not change the blood plasma cortisol, glucose, and the lactate and chloride ion concentration, relative to the control treatment. Captive breeding was attempted by conducting induced spawning experiments. Only final oocyte maturation was achieved using a decapeptide Gonadotropin Releasing Hormone (Dargin, sGnRH-MET), combined with a water-soluble dopamine receptor antagonist metoclopramide. This thesis suggests a research approach that provides a basis for aquaculture of the new species by first studying reproductive biology patterns and then linking the information to gonad and gamete structure so that spawning times can be estimated. It further provides insights into aspects of the reproductive biology of the species and the effects of hormonal intervention on oocytes by showing at which stage of oocyte development hormones should be applied in L. niloticus. Clove oil can be used to sedate and anaesthetise L. niloticus broodfish to reduce the stress related to the handling of large specimens.
40
Headley, Heath C. "Fluctuating abundance of yellow perch and their relationship to growth in southern Lake Michigan, 1984-2004." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1339149.
Full textAbstract:
The relationship between yellow perch Perca flavescens abundance and growth rates were evaluated in the Indiana waters of Lake Michigan from 1984 to 2004. Relative abundance values were taken from trawl catch per unit effort (CPUE), while growth rates were determined by back-calculation. Abundance CPUE during the mid 1980's, was approximately one order of magnitude higher when compared to the 1990 to 2004 period. Growth rates were inversely related to relative abundance and were sexually dimorphic, with females growing faster than males. Regression analysis indicated approximately half of this observed variation in growth was due to abundance, and was most apparent with the smaller and younger fish. Both intraspecific competition and physiological changes associated with maturity are plausible explanations for the relationship.Department of Biology
41
Allen, Paul J. "A computer simulation model for the yellow perch population in the Indiana waters of Lake Michigan." Virtual Press, 2000. http://liblink.bsu.edu/uhtbin/catkey/1177967.
Full textAbstract:
A computer simulation model was developed to examine the effects of various levels of alewife densities, harvest, and bycatch rates on yellow perch Perca flavescens relative densities in Indiana waters of Lake Michigan. The model utilized STELLA® Research software to develop the age-structured population model to include measured or predicted biological characteristics of density-dependent growth, recruitment, and mortality.The model was validated by simulating historically documented yellow perch catch per unit effort (CPUE) from 1984 - 1998. A strong linear relationship (R2= 0.70) between the model predicted CPUE values and the actual CPUE values was found. Twenty year model projections were performed using 1998 yellow perch trawl CPUE as starting values. Alewife abundance was established as either constantly high, constantly low, or allowed to fluctuate randomly and forecasts made used the average of 100 runs. Harvest was imposed on the yellow perch population at 20, 40, and 60% rate levels for fish >_ 200 mm coupled with bycatch at20, 40 and 60% rate levels for fish ranging from 165 - 200 mm.Alewife abundance was the major factor determining the relative abundance of the yellow perch population. On average, constantly high alewife abundance with no harvest or bycatch resulted in projected continuing suppression of yellow perch abundance from 1998 levels. The model predicted the population to rebound using constant low and random alewife abundance with no harvest or bycatch to approximately 1,100 fish/h and 700 fish/h, respectively.The model revealed harvest to have a generally negative impact on the yellow perch population. Increasing harvest and bycatch rate levels resulted in the suppression of projected increases in yellow perch relative abundance. Additionally, increasing harvest and bycatch rates resulted in greater predicted declines in yellow perch abundance.Department of Biology
42
Tonkin, Zeb D. "From processes to populations: understanding the drivers and dynamics of Macquarie perch Macquaria australasica populations." Thesis, Griffith University, 2019. http://hdl.handle.net/10072/388980.
Full textAbstract:
This thesis is presented as a series of journal publications that have been published or are in review. The overall structure of the thesis includes; a brief introduction on the processes and dynamics of fish populations; an introduction to the study species, Macquarie perch (Macquaria australasica); five data chapters as publications which relate to specific population processes and population dynamics, and finally, a synthesis of these chapters and concluding remarks. The publication status of each chapter is provided at the beginning of the chapter together with detailed information on authorship and contributions.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text
43
Thomas, Nathan D. "Trawl and gill net selectivity of yellow perch in southern Lake Michigan, 1993-2006." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1366503.
Full textAbstract:
Selectivity of trawl and experimental gill nets was determined for yellow perch taken from southern Lake Michigan in 1993 to 2006. Gill nets were comprised of 51-, 64-and 76-mm size mesh and showed female modal lengths of 205-, 245-, and 295-mm, respectively, while values for males were 200-, 230-, and 267-mm. Differences between females and males increased with mesh size and was significant. Comparison of nine anterior morphometric features of female and male fish indicated no differences in shape were identified that would cause the disparity in selectivity. Rather, differences in male and female selectivity were more likely due the variant population size structure of the local population sampled, with females the larger sex. A new method to estimate trawl selectivity was developed using a modified catch-curve analysis, which showed a maximum selectivity length value (1.0) of 190-mm for females and 170-mm for males. However, trawls fail to capture larger yellow perch when compared to gill nets using based on length-frequency distributions. Revealing such gear biases may lead to more efficient capture methods, resulting in improved sampling and quantitative assessment of fish populations.Department of Biology
44
Rydell, Joseph J. "The influence of abiotic factors on gill-net catch rates and the evaluation of mortality rates for yellow perch in southern Lake Michigan." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1391675.
Full textAbstract:
I determined differences in yellow perch gill-net catch-per-unit-effort (CPUE) at two depths (10 and 15 m) in the Indiana waters of Lake Michigan during June, July, and August from 1989 to 2006. I evaluated the abiotic factors of water temperature, water clarity, wave height, and wind direction to determine whether they influence the differences in yellow perch CPUE. This study suggests that yellow perch in southern Lake Michigan may select habitat based on water temperature during the summer, moving in response to thermocline changes. We also evaluated mortality rates for two distinct periods (1984-1994 and 2000-2007) in order to identify the response of the population to changes in exploitation. Yellow perch during 1984-1994 (high exploitation) and 2000-2007 (low exploitation) displayed an increase in mortality for fish of harvestable size. In addition, during 2000-2007 (low exploitation) we identified that female yellow perch reached exploitable size earlier in life than males.Department of Biology
45
Ingram, Brett A. "Rearing juvenile Australian native percichthyid fish in fertilised earthen ponds." Connect to this title online, 2001. http://tux.lib.deakin.edu.au/adt-VDU/public/adt-VDU20050418.172221/.
Full text
46
Mlolwa, Mwanaidi Ramadhani. "Application of Hazard Analysis Critical Control Points (HACCP) in improving the global competitiveness of the fish industry with special reference to the Nile Perch (Tanzania)." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51618.
Full textAbstract:
Thesis (MPhilAgric)--Stellenbosch University, 2000.ENGLISH ABSTRACT: Not only have non-trade barriers been applied in Europe and the US to agricultural products from developing countries, but protective policy is also likely to continue. Owing to the omission of fish from the discussions in the final round of agreement at Uruguay, where tariffs were significantly reduced for other agricultural products, the fish industry has not had any non tarriff barier relief in recent years. The failure of the November 1999 World Trade Organisation Meeting at Seattle to reach any agreement, has again shattered hopes of international relief for fishery products. The main assumption underlying the study was that the production of fish in Tanzania could improve significantly if the HACCP (Hazard Analysis Critical Control Points) principles were applied rigorously. It was believed that neither the prerequisite programmes, nor HACCP principles were probably applied as stringently as international standards require. The aim of the study was to review the literature on HACCP, programmes that are prerequisite for HACCP and factors that_ determine competitiveness in business and to examine the Tanzanian Nile perch industry against this background. The overall goal was to determine how the industry could become more internationally competitive. This was achieved by comparing the socio-economic reality of Tanzania with factors that are considered in the literature to affect competitiveness in general and in the fish industry specifically. To achieve the first of these aims, Tanzania's socioeconomic position as a developing country was examined. To achieve the latter, the commitment of fish processing factories to the application of HACCP principles and their compliance with prerequisite programmes were evaluated in a field study. The literature study confirms that HACCP has received international recognition in the fish industry as a factor to prevent hazards and gain competitiveness in the global fish market. However, conditions in Tanzania were shown to be insufficient to support the fisheries sector in attempting to gain such a competitive advantage. Although, Tanzania has the comparative advantage of a fishery resource base, a favourable trade policy and foreign technology and management, the macro-factors that include the infrastructure, human resource capital, foreign policy environment and the supporting industries are not supportive. For the time being, therefore, improvement can only come from the government and from the industry itself. There are several factors to which the government needs to pay attention in order to support this industry - and others - in achieving international success. These include the provision of infrastructure and facilities, the improvement of the transportation network, technological capabilities, human resource capital and the provision of safe water and electric power. However, the fish industry cannot rely on the government alone. The improvement of their product is also dependent on their own efforts. According to the findings of this study, the industry needs to comply with the basic sanitation factors and provide the necessary training to the employees and fish suppliers. Having examined the situation more closely, the assumption is proved to be correct. The fish industry in Tanzania does indeed appear to have the potential to become internationally competitive. Such success, however, will be heavily dependent on cooperation between the government and the industry
AFRIKAANSE OPSOMMING: Handelsbeperkinge op landbouproduckte vanaf ontwinkkelende in Europa en die Verenigde State toegepas. Daarbenewens sal beskermende beleidsriglyne waarskynlik in stand gehou word. Bespreking van sake met betrekking to vissery is nie by die finale rondte van ooreenstemming te Uruquay, waar tariewe vir ander landbouproduckte betekenisvol verlaag is, ingesluit nie, en daardeur is daar gedurende die laaste aantal jare geen belastingverligting vir die visindustrie gebied nie. By die World Trase Organisation se vergadering om internasionale verligting vir visproducte te verkry, weereens beskaam. Die hoofveronderstelling wat hierdie studie ondersteun, is dat visproduksie III Tanzanie betekenisvol verbeter kan word indien die can HACCP (Hazard Analysis Critical Control Points) streng toegepas word. Dit is veronderstel dat nóg die voorvereiste programme, nóg die HACCP-beginsels wat ten opsigte van internasionale standaarde vereis word, streng volgens voorskriftoegepas word. Die doel van die studie was om 'n oorsig van die literatuur oor HACCP, programme wat as HACCP-voorvereistes geld en faktore wat mededingendheid in die besigheidswereld bepaal, te verkry en om die Tanzaniese Nyl-baarsbedryf teen hierdie agterground te ondersoek. Die oorkoepelende doel was om vas te stel hoe die bedryf internasionaal meer mededingend kan word. Dit is gedoen deur middel van vergelyking tussen die sosio-ekonomiese werklikheid van Tanzanië en die faktore wat mededingendheid in die algemeen, volgens die literatuur, en die visbedryf in besonder, affekteer. Om die eeste van hiedie doelstellings te bereik, is die sosio-ekonomies posisie van Tanzanie as 'n ontwikkelende land ondersoek Om die tweede te bereik, is 'n veldstudie uitgevoer om die mate waartoe fabrieke wat vis verwerk daarop ingestel is om HACCP-beginsels toe te pas en hul gewilligheid om die programme wat as voorvereistes dien, na te kom, te evalueer. Die literatuurstudie het bevestig dat HACCP internasionale erkenning geniet as 'n faktor om risikO in de visbedryf uit te skakel en mededingendheid op die wereldmark vir vis te verwerf. Daar is egter bewys dat toetstande in Tanzanie ontoereikend is om die visserysektor in die verwewing van'n mededingende voorsprong te ondersteun. Alhoewel Tanzanië oor die relatiewe voordele van vissery as 'n hulpbron, gunstige handelsbeleid en buitelandse tegnologie en bestuur bestik, bied die makrofaktore soos infrastruktuur, kapitaal III die vorm van menslike hulpbronne, die buitelandse beleidsomgewing en die ondersteunende bedrywe nie genoeg ondersteuning nie. Vir die hede, kan ontwikkeling dus slegs deur die regering en die bedryf self bewekstelling word. Daar is verskeie faktore waaraan die regering aandag moet skenk om hierdie bedryf-en ander bedrywe-in die verkryging van internasionale sukses te ondersteun. Sulke faktore omvat die daarstelling van infrastruktuur en fasiliteite, die verbetering van die vervoernetwerk, tegnologiese vermoens en menslike hulpbronkapitaal, en voorsiening van onbesmette water en elektriese krag. Die visbedryf kan egter nie net op die regering steun nie. Die verbetering van die product is van die bedryf self afhanklik. Die bevindings van hierdie studie dui daarop dat die bedryf die basiese faktore betreffende sanitêre beginsels moet onderhoue en die vereiste opleiding aan diensnemers moet verskaf. By die nadere ondersoek van die situasie is die oorspronklike veronderstelling korrek bewys. Die visbedryf in Tanzanië beskik oor die potensiaal om internasionaal medengend te word. Sodanige sukses sal egter uiters afhanklik wees van samewerking tussen die regering en die bedryf.
47
Berkelman, James. "Habitat Requirements and Foraging Ecology of the Madagascar Fish-Eagle." Diss., Connect to this title online, 1997. http://scholar.lib.vt.edu/theses/available/etd-5852152749721461/.
Full text
48
Ragnarsson, Henrik. "Biological Diversity of Fish and Bacteria in Space and Time." Doctoral thesis, Uppsala University, Department of Ecology and Evolution, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8494.
Full textAbstract:
Biological diversity is controlled by an array of factors and processes all active at different spatial and temporal scales. Regional factors control what species are available to occur locally, whereas the local factors determine what species are actually capable of colonizing the locality.
I have investigated how these local and regional factors affect species richness and diversity, mainly of fish in Swedish lakes and in order to assess the impact of dispersal mode one study on bacteria was also performed. In addition, potential first steps towards speciation were investigated in perch (Perca fluviatilis) from two different habitats.
Fish species richness and diversity were found to be regulated by history, dispersal limitation and the local environment. In addition, striking similarities were found in the control of community composition for fish and bacteria. Both were regulated by nearly equal parts regional and local factors. The study of morphological and genetical variation in perch (Perca fluviatilis) revealed genetic differentiation at small spatial scales, suggesting that genetic differences can evolve between groups at strikingly small spatial scales, which might have implications for speciation in a long time perspective.
Based on these findings I conclude that space and time matter. Space has the potential to isolate sites. And both dispersal and local extinctions, it seems, might take a long time, as effects of the last ice-age can still be seen on the contemporary fish community richness and composition.
49
Peich, Marco Polo [Verfasser], J. [Akademischer Betreuer] Buchmann, I. [Akademischer Betreuer] Classen-Linke, and B. [Akademischer Betreuer] Fischer. "Einflüsse ubiquitär vorkommender Xenobiotika auf humane immortalisierte endometriale Epithelzellen (hTERT-EEC B37) / Marco Polo Peich. Betreuer: J. Buchmann ; I. Classen-Linke ; B. Fischer." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/102520302X/34.
Full text
50
Kahl, Uwe. "Dominanzverhältnisse, Interaktionen und räumliche Verteilung von Barsch, Plötze und Seeforelle in der mesotrophen Talsperre Saidenbach." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2003. http://nbn-resolving.de/urn:nbn:de:swb:14-1071662087625-16496.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit wurden die in der mesotrophen Talsperre Saidenbach bedeutendsten Fischarten (Plötze, Barsch, Seeforelle) bezüglich ihrer Populationsstruktur, der Nahrung und der Habitatnutzung untersucht. Ziel war einerseits, die Analyse der Ausgangssituation und der Umsteuerungsphase bezüglich biomanipulationsbedingter Effekte, um einen späteren Vorher-Nachher-Vergleich innerhalb des Ganzseenexperimentes zu ermöglichen. Andererseits sollte untersucht werden, ob die Hypothese des konkurrenzbedingten juvenilen Flaschenhalses der Barsche auch auf große und tiefe Gewässer übertragbar ist und welche Faktoren die Zusammensetzung der Fischartengemeinschaft steuern. Es konnte gezeigt werden, dass der trophische Status eines Gewässers nicht die alleinige Steuergröße für die Dominanzverhältnisse in Fischartengemeinschaften ist. Entgegen den Erwartungen dominierten in der Talsperre Saidenbach trotz mesotropher Verhältnisse Plötzen. Eine bedeutende Einflussgröße auf die Dominanzverhältnisse ist die Habitatvariabilität, die auch durch die Morphometrie des Gewässers bestimmt wird. In großen und tiefen Gewässern besteht im Gegensatz zu kleinen und flachen Gewässern die Möglichkeit der Ausbildung zusätzlicher Umweltgradienten (z. B. vertikaler Temperaturgradient). Diese Gradienten erhöhen die Habitatdiversität innerhalb des Gewässers und bilden damit weitere Nischen aus, welche wiederum eine zusätzliche Nischentrennung zwischen konkurrierenden Gruppen ermöglichen. Die höhere Effizienz der Plötzen gegenüber Barschen bei der Nutzung von Zooplankton im Freiwasser scheint eine weitere Ursache für die Dominanz der Plötzen in dem stark pelagisch geprägten Nahrungsnetz der Talsperre Saidenbach zu sein. Darüber hinaus war die Barschpopulation durch die Prädation von piscivoren Barschen in der Talsperre Saidenbach wesentlich stärker beeinflusst als die Plötzenpopulation, was generell ein ausschlaggebender Faktor für die Plötzendominanz in mesotrophen Gewässern sein kann. Barsch, Plötze und Seeforelle wiesen vor allem während der Schichtungsperiode eine räumliche Trennung sowohl in horizontaler als auch in vertikaler Richtung innerhalb des Gewässers auf. Der Grad der Piscivorie der bisher besetzten Seeforellen war noch zu gering, um einen wirksamen fraßbedingten Einfluss auf die Plötzenpopulation ausüben zu können. Für Seeforellen konnte gezeigt werden, dass der Grad der Piscivorie mit zunehmender Länge steigt. Überwiegend piscivor ernährten sich die Seeforellen in der Talsperre Saidenbach ab einer Länge von 50 cm. Sowohl Barsch als auch Plötze zeigten in der Talsperre Saidenbach ein gutes Wachstum. Nach etwa vier Jahren erreichten beide Arten ein Größenrefugium vor Prädation durch andere Raubfische. Plötzen erreichten ein höheres Alter als Barsche und verblieben damit länger in diesem Größenrefugium. Das führte zu einer Akkumulation großer Plötzen im Gewässer. Plötzen aller Größen waren ausgeprägt zooplanktivor. Im Zooplanktonanteil der Nahrung traten fast ausschließlich Daphnien auf. Mit dieser Ernährungsweise übten Plötzen einen hohen Fraßdruck auf das große filtrierende Zooplankton aus. Sowohl 0+ Barsche als auch ältere Barsche nutzten zu einem hohen Anteil Zooplankton als Nahrungsressource. Somit waren die juvenilen Barsche nicht zu einem frühzeitigen Nahrungswechsel zu benthischen Makroinvertebraten gezwungen. Zwischen juvenilen Barschen und Plötzen bestand nur eine geringe Überlappung der Nahrungsnischen. Die erweiterte Nischentrennung von Barsch und Plötze in großen und tiefen Gewässern reduziert sowohl die interspezifische als auch die intraspezifische Konkurrenz. Unter diesen Bedingungen sind Barsch und Plötze fähig, in großen Mengen zu koexistieren ohne dabei Kümmerwachstum zu zeigen. Ein juveniler Flaschenhals existiert trotz der Plötzendominanz offenbar in großen und tiefen Gewässern nicht, so dass die Flaschenhalshypothese auf kleine und flache Gewässer mit geringer Habitatdiversität beschränkt werden muss.