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Journal articles on the topic 'Fish populations'
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1
CUSHING, D. H. "Understanding fish populations." Journal of Biogeography 25, no. 3 (May 1998): 610–11. http://dx.doi.org/10.1046/j.1365-2699.1998.25306093.x.
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Simpson, S. D., I. Barber, and I. J. Winfield. "Understanding fish populations." Journal of Fish Biology 92, no. 3 (March 2018): 563–68. http://dx.doi.org/10.1111/jfb.13574.
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Minto, Coilín, Ransom A. Myers, and Wade Blanchard. "Survival variability and population density in fish populations." Nature 452, no. 7185 (March 2008): 344–47. http://dx.doi.org/10.1038/nature06605.
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Chilcote, M. W., K. W. Goodson, and M. R. Falcy. "Reduced recruitment performance in natural populations of anadromous salmonids associated with hatchery-reared fish." Canadian Journal of Fisheries and Aquatic Sciences 68, no. 3 (March 2011): 511–22. http://dx.doi.org/10.1139/f10-168.
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We found a negative relationship between the reproductive performance in natural, anadromous populations of steelhead trout ( Oncorhynchus mykiss ), coho salmon ( O. kisutch ), and Chinook salmon ( O. tshawytscha ), and the proportion of hatchery fish in the spawning population. We used intrinsic productivity as estimated from fitting a variety of recruitment models to abundance data for each population as our indicator of reproductive performance. The magnitude of this negative relationship is such that we predict the recruitment performance for a population composed entirely of hatchery fish would be 0.128 of that for a population composed entirely of wild fish. The effect of hatchery fish on reproductive performance was the same among all three species. Further, the impact of hatchery fish from “wild type” hatchery broodstocks was no less adverse than hatchery fish from traditional, domesticated broodstocks. We also found no support for the hypothesis that a population's reproductive performance was affected by the length of exposure to hatchery fish. In most cases, measures that minimize the interactions between wild and hatchery fish will be the best long-term conservation strategy for wild populations.
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Hindar, Kjetil, Nils Ryman, and Fred Utter. "Genetic Effects of Cultured Fish on Natural Fish Populations." Canadian Journal of Fisheries and Aquatic Sciences 48, no. 5 (May 1, 1991): 945–57. http://dx.doi.org/10.1139/f91-111.
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This paper addresses the genetic consequences of aquaculture on natural fish populations. The study is motivated by rapidly increasing numbers of intentionally and accidentally released fish and is based on empirical observations reported in the literature. A wide variety of outcomes, ranging from no detectable effect to complete introgression or displacement, has been observed following releases of cultured fish into natural settings. Where genetic effects on performance traits have been documented, they always appear to be negative in comparison with the unaffected native populations. These findings are consistent with theoretical considerations of the implications of elevated levels of gene flow between cultured and locally adapted natural populations; they raise concerns over the genetic future of many natural populations in the light of increasing numbers of released fish. Strategies for the genetic protection of native populations from the effects of aquaculture are outlined including more secure containment, the use of sterilized fish, and modifying the points of rearing and release. We recommend strong restrictions on gene flow from cultured to wild populations and effective monitoring of such gene flow.
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Šunderić, Miloš, Dragana Robajac, Nikola Gligorijević, Goran Miljuš, Olgica Nedić, Katarina Smilkov, Darinka Gjorgieva Ackova, Vesna Rudić-Grujić, and Ana Penezić. "Is There Something Fishy About Fish Oil?" Current Pharmaceutical Design 25, no. 15 (August 19, 2019): 1747–59. http://dx.doi.org/10.2174/1381612825666190705185800.
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Background: Fish is consumed as food worldwide and is considered as a rich source of essential nutrients required for a healthy life. Supplementation with fish oil has been adopted as a solution to prevent or cure many pathophysiological states and diseases by both the professionals and the civil population. The beneficial effects are, however, being questioned, as some controversial results were obtained in clinical and population studies. Methods: Critical evaluation of studies regarding known effects of fish oil, both in favour of its consumption and related controversies. Results: From the literature review, contradictory allegations about the positive action of the fish oil on human health emerged, so that a clear line about its beneficial effect cannot be withdrawn. Conclusion: Scientific results on the application of fish oil should be taken with caution as there is still no standardised approach in testing its effects and there are significantly different baselines in respect to nutritional and other lifestyle habits of different populations.
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Le Cam, Sabrina, Charles Perrier, Anne-Laure Besnard, Louis Bernatchez, and Guillaume Evanno. "Genetic and phenotypic changes in an Atlantic salmon population supplemented with non-local individuals: a longitudinal study over 21 years." Proceedings of the Royal Society B: Biological Sciences 282, no. 1802 (March 7, 2015): 20142765. http://dx.doi.org/10.1098/rspb.2014.2765.
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While introductions and supplementations using non-native and potentially domesticated individuals may have dramatic evolutionary effects on wild populations, few studies documented the evolution of genetic diversity and life-history traits in supplemented populations. Here, we investigated year-to-year changes from 1989 to 2009 in genetic admixture at 15 microsatellite loci and in phenotypic traits in an Atlantic salmon ( Salmo salar ) population stocked during the first decade of this period with two genetically and phenotypically distinct source populations. We detected a pattern of temporally increasing introgressive hybridization between the stocked population and both source populations. The proportion of fish returning to the river after a single winter at sea ( versus several ones) was higher in fish assigned to the main source population than in local individuals. Moreover, during the first decade of the study, both single-sea-winter and multi-sea-winter (MSW) fish assigned to the main source population were smaller than local fish. During the second decade of the study, MSW fish defined as hybrids were lighter and smaller than fish from parental populations, suggesting outbreeding depression. Overall, this study suggests that supplementation with non-local individuals may alter not only the genetic diversity of wild populations but also life-history traits of adaptive significance.
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Tyler, A. V. "Dynamics of Marine Fish Populations." Transactions of the American Fisheries Society 117, no. 1 (January 1, 1988): 95–101. http://dx.doi.org/10.1577/1548-8659-117.1.95.
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Crisp, D. T., and W. R. C. Beaumont. "Fish populations in Plynlimon streams." Hydrology and Earth System Sciences 1, no. 3 (September 30, 1997): 541–48. http://dx.doi.org/10.5194/hess-1-541-1997.
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Abstract. In Plynlimon streams, brown trout (Salmo trutta L.) are widespread in the upper Wye at population densities of 0.03 to 0.32 fish m-2 and show evidence of successful recruitment in most years. In the upper Severn, brown trout are found only in an area of c. 1670 -2 downstream of Blaenhafren Falls at densities of 0.03 to 0.24 fish -2 and the evidence suggests very variable year to year success in recruitment (Crisp & Beaumont, 1996). Analyses of the data show that temperature differences between afforested and unafforested streams may affect the rates of trout incubation and growth but are not likely to influence species survival. Simple analyses of stream discharge data suggest, but do not prove, that good years for recruitment in the Hafren population were years of low stream discharge. This may be linked to groundwater inputs detected in other studies in this stream. More research is needed to explain the survival of the apparently isolated trout population in the Hafren.
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González-de-Canales, M. L. "Saprolegniasis In Wild Fish Populations." Ciencias Marinas 27, no. 1 (February 1, 2001): 125–37. http://dx.doi.org/10.7773/cm.v27i1.373.
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MacCall, Alec D., and Brian J. Rothschild. "Dynamics of Marine Fish Populations." Copeia 1987, no. 3 (August 5, 1987): 820. http://dx.doi.org/10.2307/1445688.
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Gulland, J. A. "Fish populations and their management." Journal of Fish Biology 35 (January 24, 2006): 1–9. http://dx.doi.org/10.1111/j.1095-8649.1989.tb03040.x.
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Sugihara, G., J. Beddington, C. h. Hsieh, E. Deyle, M. Fogarty, S. M. Glaser, R. Hewitt, et al. "Are exploited fish populations stable?" Proceedings of the National Academy of Sciences 108, no. 48 (November 16, 2011): E1224—E1225. http://dx.doi.org/10.1073/pnas.1112033108.
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Beverton, R. J. H. "Recruitment in marine fish populations." Trends in Ecology & Evolution 6, no. 2 (February 1991): 64–65. http://dx.doi.org/10.1016/0169-5347(91)90128-k.
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Toline, C. Anna, and Allan J. Baker. "Foraging tactic as a potential selection pressure influencing geographic differences in body shape among populations of dace (Phoxinus eos)." Canadian Journal of Zoology 71, no. 11 (November 1, 1993): 2178–84. http://dx.doi.org/10.1139/z93-306.
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Geographic differences in body shape among 18 populations of northern redbelly dace in three regions of Ontario (Sudbury, Algonquin Provincial Park, and Kingston) were quantified with truss analysis. Principal component analysis of size-adjusted residuals of the trusses revealed that 35.11% of the morphological variation in body shape is explained on principal component I. This axis describes the major trend in body shape variation, ranging from populations in which fish are relatively deep-bodied to those in which fish are more shallow-bodied. Shape variation among populations in Algonquin Park spanned the range observed among all three regions in Ontario. Experiments were thus conducted on two Algonquin populations differing considerably in body shape, and it was found that deeper bodied fish from one population were significantly more adept at capturing evasive prey than were relatively shallow-bodied fish from another population. This finding is not only consistent with functional analysis of fish shape but also fits predictions from foraging theory. Fish catching plentiful but evasive prey should rely on ambush predation, and thus have a large body depth, which increases body area relative to mass, in order to optimize acceleration. Conversely, fish catching less evasive food occurring at low density should use a tactic of wide foraging, for which they need a streamlined anterior body suitable for cruising over extended periods of time. Samples from the natural population revealed that deep-bodied fish had a significantly greater number of evasive prey in their guts, and that the more shallow-bodied fish had relatively few. Furthermore, the pond in which the deeper bodied fish occurred had significantly higher prey density than the pond inhabited by the shallow-bodied fish. Because the Algonquin populations experience sufficient gene flow to prevent differentiation due to drift alone, the most likely explanation for population differentiation resides in selection on body shape for foraging tactic.
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Abdulraheem, I. "Sex distributions and growth response in different populations of catfish (Clarias gariepinus)." Nigerian Journal of Animal Production 47, no. 3 (December 17, 2020): 162–72. http://dx.doi.org/10.51791/njap.v47i3.151.
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This study evaluated the gender ratio in Clarias gariepinus production from five different populations. 300 Juveniles fish each were sourced from five (5) fish farms. The fish were grouped based on the farms into five populations (i.e. treatments) and were replicated thrice with each replicate stocked with 100 fish in a square shaped experimental plastic tanks of 1m x 1m x 1m. Data obtained from the experiment were subjected to one-way analysis of variance. Significant differences (p<0.05) were recorded in the values of final weight, mean weight gain, specific growth rate, percentage survival and daily growth rate. The male-female ratio showed that the females were more in number compared to their male counterpart. There was no significant difference in the number of males, number of females and weight of males across the populations. The female C. gariepinus in population 5 had the highest value (246.41±2.73g) of final weight while those in population 3 had the least value (205.95±13.17g) of weight. The fish in population 2 displayed a better growth curve compared to other populations while fish in population 3 displayed the least curve. The curve revealed that the fish grows at almost the same rate from day 0 to day 42 after which their growth pattern changed. This study showed that the number of female fish in any production outweighs the number of males.
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Niwa, Hiro-Sato. "Random-walk dynamics of exploited fish populations." ICES Journal of Marine Science 64, no. 3 (February 15, 2007): 496–502. http://dx.doi.org/10.1093/icesjms/fsm004.
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Abstract Niwa, H-S. 2007. Random-walk dynamics of exploited fish populations. – ICES Journal of Marine Science, 64: 496–502. Fished populations have been heavily fished over a wide range of stock sizes, and the data for such stocks are potentially of great interest. Population variability in stock histories has focused attention on the predictability of conditions of sustainability when harvesting fish. Here, I examine empirically the time-series data on 27 commercial fish stocks in the North Atlantic. The variability in population growth rate (i.e. the annual changes in the logarithms of population abundance) is described by a Gaussian distribution. The signs (up or down) of successive changes in the population trajectory are independent, as if determined by the toss of a coin. The process of population variability therefore corresponds to a geometric random walk.
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Piorski, NM, A. Sanches, LF Carvalho-Costa, T. Hatanaka, M. Carrillo-Avila, PD Freitas, and PM Galetti Jr. "Contribution of conservation genetics in assessing neotropical freshwater fish biodiversity." Brazilian Journal of Biology 68, no. 4 suppl (November 2008): 1039–50. http://dx.doi.org/10.1590/s1519-69842008000500011.
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Human activities have a considerable impact on hydrographic systems and fish fauna. The present review on conservation genetics of neotropical freshwater fish reveals that DNA analyses have been promoting increased knowledge on the genetic structure of fish species and their response to environmental changes. This knowledge is fundamental to the management of wild fish populations and the establishment of Evolutionary Significant Units capable of conserving genetic integrity. While population structuring can occur even in long-distance migratory fish, isolated populations can show reduced genetic variation and be at greater risk of extinction. Phylogeography and phylogeny have been powerful tools in understanding the evolution of fish populations, species and communities in distinct neotropic environments. Captive fish can be used to introduce new individuals and genes into the wild and their benefits and disadvantages can be monitored through genetic analysis. Understanding how fish biodiversity in neotropical freshwaters is generated and maintained is highly important, as these habitats are transformed by human development and fish communities are increasingly exploited as food sources to sustain a growing human population.
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Pratama, Eka Kusuma, Musriatun Napiah, Sujiliani Heristian, and Arina Selawati. "Pengembangan Sistem Kontrol Populasi Ikan Berbasis Arduino Uno dengan Sensor Ultrasonik." Jurnal Teknik Komputer 10, no. 1 (January 3, 2024): 42–47. http://dx.doi.org/10.31294/jtk.v10i1.20151.
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Fish populations are one of the important assets in maintaining the balance of aquatic ecosystems. To manage fish populations effectively, an innovative and automated approach is needed. This research aims to develop an Arduino Uno-based fish population control system with ultrasonic sensors as an environmentally friendly and efficient solution. The developed system uses ultrasonic sensors to detect the presence of fish in a pond or water container. The detection data from the ultrasonic sensor is then processed by the Arduino Uno microcontroller. The system can identify the number of fish in aquatic containers and take appropriate action to control fish populations. This research integrates ultrasonic sensor technology with Arduino Uno control capabilities to provide an accurate and automated solution in controlling fish populations. In trials, this system succeeded in identifying and controlling fish populations well, maintaining the balance of aquatic ecosystems without the need for direct human intervention The results of this research have great potential in fish farming applications, environmental research, and natural resource conservation. With the proposed automated approach, it is expected to make a positive contribution in maintaining the balance of aquatic ecosystems and supporting environmental sustainability
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Hickman, Gary D., and Mary L. Brown. "Proposed Methods and Endpoints for Defining and Assessing Adverse Environmental Impact (AEI) on Fish Communities/Populations in Tennessee River Reservoirs." Scientific World JOURNAL 2 (2002): 204–18. http://dx.doi.org/10.1100/tsw.2002.216.
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Two multimetric indices have been developed to help address fish community (reservoir fish assemblage index [RFAI]) and individual population quality (sport fishing index [SFI]) in Tennessee River reservoirs. The RFAI, with characteristics similar to the index of biotic integrity (IBI) used in stream fish community determinations, was developed to monitor the existing condition of resident fish communities[1,2,3]. The index, which incorporates standardized electrofishing of littoral areas and experimental gill netting for limnetic bottom-dwelling species, has been used to determine residential fish community response to various anthropogenic impacts in southeastern reservoirs.The SFI is a multimetric index designed to address the quality of the fishery for individual resident sport fish species in a particular lake or reservoir[4]. The SFI incorporates measures of fish population aspects and angler catch and pressure estimates. This paper proposes 70% of the maximum RFAI score and 10% above the average SFI score for individual species as “screening” endpoints for balanced indigenous populations (BIP) or adverse environmental impact (AEI). Endpoints for these indices indicate: (1) communities/populations are obviously balanced indigenous populations (BIP) indicating no adverse environmental impact (AEI), or are “screened out”; (2) communities/populations are considered to be potentially impacted; and (3) where the resident fish community/population should be considered adversely impacted. Suggestions are also made concerning how examination of individual metric scores can help determine the source or cause of the impact.
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Guti, G. "Significance of side-tributaries and floodplains for Danubian fish populations." River Systems 13, no. 1-2 (January 1, 2002): 151–63. http://dx.doi.org/10.1127/lr/13/2002/151.
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Hadie, L. E., E. K. M. Kontara, Kusdiarti, and A. W. M. Putri. "The effectiveness of brood stock management in captive breeding of marine ornamental Fish." IOP Conference Series: Earth and Environmental Science 1137, no. 1 (January 1, 2023): 012028. http://dx.doi.org/10.1088/1755-1315/1137/1/012028.
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Abstract Nowadays, the trade in marine ornamental fish is growing to be a multimillion-dollar industry. Because marine ornamental fish are successfully being bred in captivity, the industry can flourish. The breeding process is progressively applied through collecting fish from their natural habitat, inventory and domestication. An important stage in the breeding process of marine ornamental fish is the efficient management of brood stocks. A considerable number of initial populations become one of the keys to success in breeding marine ornamental fish. The principle of high genetic diversity in populations at the beginning of the collection is also an important indicator of the sustainability of the breeding process. The study aims to evaluate the management of brood stocks for marine ornamental fish in captive breeding. The observed parameters are the number of brood stocks populations, effective population size, and the utility of inbreeding in a population. The success of its cultivation is determined by the genetic diversity in the basic population which needs to be monitored from the start of the captive program.
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Shields, Barbara A., Kevin S. Guise, and James C. Underhill. "Chromosomal and Mitochondrial DNA Characterization of a Population of Dwarf Cisco (Coregonus artedii) in Minnesota." Canadian Journal of Fisheries and Aquatic Sciences 47, no. 8 (August 1, 1990): 1562–69. http://dx.doi.org/10.1139/f90-177.
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This study compared the chromosome complement and mitochondrial DNA profile of a population of dwarf cisco in Ten Mile Lake, Cass County, Minnesota, to two populations of normal-sized Coregonus artedii in order to determine if the dwarf fish were conspecific with C. artedii. Chromosomal analysis revealed a diploid chromosome number (2n = 80) the same as reported for C. artedii. Mitochondrial DNA (mtDNA) analysis revealed unexpected levels of intrapopulational diversity in each study population, with the dwarf fish displaying the highest level of mtDNA diversity. Heteroplasmy, restriction site polymorphisms, and three size variants were documented. Each population was characterized by a unique profile of mtDNA clonal types, yet interpopulational comparisons revealed more similarities between the dwarf fish in Ten Mile Lake and the two normal populations than between the populations of normal-sized fish. Based on these data, the dwarf fish of Ten Mile Lake should be considered conspecific with Coregonus artedii.
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Perry, Elgin, Greg Seegert, Joe Vondruska, Timothy Lohner, and Randy Lewis. "Modeling Possible Cooling-Water Intake System Impacts on Ohio River Fish Populations." Scientific World JOURNAL 2 (2002): 58–80. http://dx.doi.org/10.1100/tsw.2002.167.
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To assess the possible impacts caused by cooling-water intake system entrainment and impingement losses, populations of six target fish species near power plants on the Ohio River were modeled. A Leslie matrix model was constructed to allow an evaluation of bluegill, freshwater drum, emerald shiner, gizzard shad, sauger, and white bass populations within five river pools. Site-specific information on fish abundance and length-frequency distribution was obtained from long-term Ohio River Ecological Research Program and Ohio River Sanitation Commission (ORSANCO) electrofishing monitoring programs. Entrainment and impingement data were obtained from 316(b) demonstrations previously completed at eight Ohio River power plants. The model was first run under a scenario representative of current conditions, which included fish losses due to entrainment and impingement. The model was then rerun with these losses added back into the populations, representative of what would happen if all entrainment and impingement losses were eliminated. The model was run to represent a 50-year time period, which is a typical life span for an Ohio River coal-fired power plant. Percent changes between populations modeled with and without entrainment and impingement losses in each pool were compared to the mean interannual coefficient of variation (CV), a measure of normal fish population variability. In 6 of the 22 scenarios of fish species and river pools that were evaluated (6 species × 5 river pools, minus 8 species/river pool combinations that could not be evaluated due to insufficient fish data), the projected fish population change was greater than the expected variability of the existing fish population, indicating a possible adverse environmental impact. Given the number of other variables affecting fish populations and the conservative modeling approach, which assumed 100% mortality for all entrained fish and eggs, it was concluded that the likelihood of impact was by no means assured, even in these six cases. It was concluded that in most cases, current entrainment and impingement losses at six Ohio River power plants have little or no effect at the population level.
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Абакумов, А. И., and A. I. Abakumov. "The Harvesting Effect on a Fish Population." Mathematical Biology and Bioinformatics 11, no. 2 (September 27, 2016): 191–204. http://dx.doi.org/10.17537/2016.11.191.
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Fishery is one of the main environmental factors affecting fish population. In this paper we study the dynamics of population’s dimensional distribution under the influence of environmental variations with and without a fishery impact. The characteristics of population under consideration correspond to pelagic or semi-pelagic population, such as the populations of pollack (Theragra chalcogramma) inhabiting the northern seas of Pacific Ocean. To study the effect of fishery upon a population the problem of harvesting optimization with the amount of profit for a given time period as a criterion function is solved. The impact of population replenishment on the population and catch dynamics was studied and the smoothing influence of dimensional structure on the changes of environment and fishery was revealed. The seasonal changes of environment only increase the population stability.
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Segura, AM, R. Wiff, AJ Jaureguizar, AC Milessi, and G. Perera. "A macroecological perspective on the fluctuations of exploited fish populations." Marine Ecology Progress Series 665 (April 29, 2021): 177–83. http://dx.doi.org/10.3354/meps13662.
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The natural variability of fish populations is increased by exploitation, but the specific mechanisms driving this variability are still debated. We propose a macroscopic approach combining the size-density relationship and Taylor’s law to predict the temporal variance of exploited and unexploited fish populations. Using information from 11 years of fishery-independent abundance surveys, we showed that the body-size dependence of the variance of exploited (targeted) and unexploited (non-targeted or bycatch) fish populations can be accurately predicted. Targeted fish populations showed a variability that was 2 orders of magnitude greater than that of non-targeted fish populations. Such variability was explained solely by the higher relative abundance of the former, regardless of their specific trophic position, while aggregated community fluctuation was lower in a high trophic position group. This study showed the usefulness of the macroscopic approach to predict fish variability and fishing effect in the whole community. This approach is complementary to other modeling strategies and seems to be useful in tackling the problem of variability in population fluctuations of exploited fish, particularly in cases where specific details of the interacting species are lacking.
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Lammens, Eddy H. R. R., Henrik W. de Nie, Jacobus Vijverberg, and Wim L. T. van Densen. "Resource Partitioning and Niche Shifts of Bream (Abramis brama) and Eel (Anguilla anguilla) Mediated by Predation of Smelt (Osmerus eperlanus) on Daphnia hyalina." Canadian Journal of Fisheries and Aquatic Sciences 42, no. 8 (August 1, 1985): 1342–51. http://dx.doi.org/10.1139/f85-169.
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The resource partitioning of the bream (Abramis brama) and eel (Anguilla anguilla) populations in Lake Tjeukemeer, The Netherlands, was related to the variation in abundance of their most important food organisms, Daphnia hyalina and larval chironomids. Niche shifts of both bream and eel populations were related to the abundance of young planktivorous fish, particularly smelt (Osmerus eperlanus). When these fish were abundant the D. hyalina population was dominated by small individuals and bream switched from a planktivorous to a benthivorous diet, the condition of mature bream deteriorated, and its gonads developed poorly. Under these circumstances the eel population switched from a diet of chironomid pupae and molluscs to one of predominantly fish. The condition of eels smaller than 35 cm decreased and the chironomid population decreased in numbers and biomass. Conversely, when the recruitment of planktivorous fish was poor, the size of D. hyalina was large and diets and conditions of bream and eel populations changed again. Because of the hydrological regime the stock of the young planktivorous fish is determined to a great extent by the immigration of allochthonous larval smelt and varies markedly, but the biomass of the bream and eel populations is comparatively stable.
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Kendall, Neala W., and Thomas P. Quinn. "Effects of population-specific variation in age and length on fishery selection and exploitation rates of sockeye salmon (Oncorhynchus nerka)." Canadian Journal of Fisheries and Aquatic Sciences 66, no. 6 (June 2009): 896–908. http://dx.doi.org/10.1139/f09-047.
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Conspecific salmonid populations often differ in age and body size at maturity, and these differences can cause fishery exploitation rates and patterns of directional selection on size to vary among populations. Based on age and length data on five representative spawning populations of sockeye salmon ( Oncorhynchus nerka ) in the Wood River system, Bristol Bay, Alaska, USA, we estimated exploitation rates and population-specific patterns of selection from a gillnet fishery between 1963 and 2007. Exploitation rates have differed among age groups and have varied greatly over time, likely due to changes in fishery selectivity. Populations with older, larger fish were more heavily exploited than populations with small, young fish. Differential fishery selection was detected among the populations, linked to persistent differences in size and age of fish among the populations. Specifically, we found evidence of stronger size selectivity on populations with smaller-bodied fish and less directional selection on populations dominated by larger-bodied fish. These results reveal the complex variation in the intensity and selectivity of fishing that can result from exploitation of populations that differ in age and size at maturity and shape. Evolutionary responses to this selection may be taking place, but natural processes provide countervailing selection.
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Ward, Ashley J. W., Michael M. Webster, and Paul J. B. Hart. "Social recognition in wild fish populations." Proceedings of the Royal Society B: Biological Sciences 274, no. 1613 (February 6, 2007): 1071–77. http://dx.doi.org/10.1098/rspb.2006.0231.
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The ability of animals to gather information about their social and physical environment is essential for their ecological function. Odour cues are an important component of this information gathering across taxa. Recent laboratory studies have revealed the importance of flexible chemical cues in facilitating social recognition of fishes. These cues are known to be mediated by recent habitat experience and fishes are attracted to individuals that smell like themselves. However, to be relevant to wild populations, where animals may move and forage freely, these cues would have to be temporally flexible and allow spatial resolution. Here, we present data from a study of social recognition in wild populations of three-spined sticklebacks ( Gasterosteus aculeatus ). Focal fish preferentially associated with conspecifics from the same habitat as themselves. These preferences were changed and updated following translocation of the focal fish to a different site. Further investigation revealed that association preferences changed after 3 h of exposure to different habitat cues. In addition to temporal flexibility, the cues also allowed a high degree of spatial resolution: fish taken from sites 200 m apart produced cues that were sufficiently different to enable the focal fish to discriminate and associate with fish captured near their own home site. The adaptive benefits of this social recognition mechanism remain unclear, though they may allow fish to orient within their social environment and gain current local information.
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Feyrer, Frederick, James Hobbs, Shawn Acuna, Brian Mahardja, Lenny Grimaldo, Melinda Baerwald, Rachel C. Johnson, and Swee Teh. "Metapopulation structure of a semi-anadromous fish in a dynamic environment." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 5 (May 2015): 709–21. http://dx.doi.org/10.1139/cjfas-2014-0433.
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The Sacramento splittail (Pogonichthys macrolepidotus) is a relatively large (400 mm), long-lived (8 years) demersal cyprinid of conservation importance endemic to the San Francisco Estuary (SFE), California, USA. It exhibits a semi-anadromous life cycle spending adult life in low to moderate salinity (0–12) habitat with migrations into upstream freshwater rivers and floodplains for spawning during winter–spring. The species persists as two genetically distinguishable populations — one dominant and one subordinate — separated by discrete spawning habitats that we suggest resemble an island–mainland metapopulation structure. The populations overlap in distribution in the SFE, yet segregation is maintained with individuals tending to aggregate or school with others of similar population heritage and natal origin. The populations are spatially connected via dispersal of the dominant population into the subordinate population’s spawning habitat when climate patterns produce freshwater outflow sufficient to form a bridge of suitable low salinity habitat across the upper SFE. Habitat affinities of the two populations, hydrodynamic modeling studies, and historical outflow records together suggest such conditions occur in approximately 1/3 of years overall with an irregular frequency. This dynamic pattern of spatial connectivity controlled by climate variability may be an important driver of gene flow between the two populations.
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Oleksiak, M. F. "Genomic approaches with natural fish populations." Journal of Fish Biology 76, no. 5 (April 2010): 1067–93. http://dx.doi.org/10.1111/j.1095-8649.2010.02563.x.
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Quinn, Terrance J., and Alec D. McCall. "Dynamic Geography of Marine Fish Populations." Copeia 1991, no. 3 (August 1, 1991): 861. http://dx.doi.org/10.2307/1446418.
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Putland, R. L., and A. F. Mensinger. "Acoustic deterrents to manage fish populations." Reviews in Fish Biology and Fisheries 29, no. 4 (October 28, 2019): 789–807. http://dx.doi.org/10.1007/s11160-019-09583-x.
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Downing, John A., and Céline Plante. "Production of Fish Populations in Lakes." Canadian Journal of Fisheries and Aquatic Sciences 50, no. 1 (January 1, 1993): 110–20. http://dx.doi.org/10.1139/f93-013.
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Biological production estimates of 100 fish populations from 38 lakes worldwide were gathered from the literature. The relationship between the annual production of fish populations (P, kilograms per hectare per year), annual mean standing biomass (B, kilograms per hectare), and maximum individual body mass (W, grams) was approximately log10P = 0.32 + 0.94 log10B − 0.17 log10W (R2 = 0.84). This relationship is similar to one observed for lotic invertebrate populations and shows that P declines with W. Major axis regression indicated that the P/B:W relationship had an exponent similar to that predicted by allometric theory. The residuals from this multivariate equation suggest that fish production is positively correlated with temperature, lake phosphorus concentration, chlorophyll a concentration, primary production, and with pH. The results suggest a general bottom-up control of lake ecosystem components. The morphoedaphic index is not a good predictor of the production of fish populations. Assuming that sustainable yield is about 10% of production, sustainable yield would be less than 15% of the standing biomass for the majority of fish populations analyzed. Exploited populations were found to be about 70% more productive, on average, than unexploited populations of the same standing biomass and body-mass.
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Cortés, Enric, Elizabeth N. Brooks, and Kyle W. Shertzer. "Risk assessment of cartilaginous fish populations." ICES Journal of Marine Science 72, no. 3 (September 8, 2014): 1057–68. http://dx.doi.org/10.1093/icesjms/fsu157.
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Abstract We review three broad categories of risk assessment methodology used for cartilaginous fish: productivity-susceptibility analysis (PSA), demographic methods, and quantitative stock assessments. PSA is generally a semi-quantitative approach useful as an exploratory or triage tool that can be used to prioritize research, group species with similar vulnerability or risk, and provide qualitative management advice. Demographic methods are typically used in the conservation arena and provide quantitative population metrics that are used to quantify extinction risk and identify vulnerable life stages. Stock assessments provide quantitative estimates of population status and the associated risk of exceeding biological reference points, such as maximum sustainable yield. We then describe six types of uncertainty (process, observation, model, estimation, implementation, and institutional) that affect the risk assessment process, identify which of the three risk assessment methods can accommodate each type of uncertainty, and provide examples mostly for sharks drawn from our experience in the United States. We also review the spectrum of stock assessment methods used mainly for sharks in the United States, and present a case study where multiple methods were applied to the same species (dusky shark, Carcharinus obscurus) to illustrate differing degrees of model complexity and type of uncertainty considered. Finally, we address the common and problematic case of data-poor bycatch species. Our main recommendation for future work is to use Management Strategy Evaluation or similar simulation approaches to explore the effect of different sources of uncertainty, identify the most critical data to satisfy predetermined management objectives, and develop harvest control rules for cartilaginous fish. We also propose to assess the performance of data-poor and -rich methods through stepwise model construction.
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Holmlund, Cecilia M., and Monica Hammer. "Ecosystem services generated by fish populations." Ecological Economics 29, no. 2 (May 1999): 253–68. http://dx.doi.org/10.1016/s0921-8009(99)00015-4.
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BAGGE, A. M., R. POULIN, and E. T. VALTONEN. "Fish population size, and not density, as the determining factor of parasite infection: a case study." Parasitology 128, no. 3 (March 2004): 305–13. http://dx.doi.org/10.1017/s0031182003004566.
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The diversity and abundance of parasites vary widely among populations of the same host species. These infection parameters are, to some extent, determined by characteristics of the host population or of its habitat. Recent studies have supported predictions derived from epidemiological models regarding the influence of host population density: parasite abundance and parasite species richness are expected to increase with increasing host population density, at least for directly transmitted parasites. Here, we test this prediction using a natural system in which populations of the crucian carp, Carassius carassius (L.), occur alone, with no other fish species, in a series of 9 isolated ponds in Finland. The ectoparasite communities in these fish populations consist of only 4 species of monogeneans (Dactylogyrus formosus, D. wegeneri, D. intermedius and Gyrodactylus carassii); the total and relative abundance of these 4 species varies among ponds, with one or two of the species missing from certain ponds. Across ponds, only one factor, total fish population size, explained a significant portion of the variance in both the mean number of monogenean species per fish and the mean total abundance of monogenean individual per fish. In contrast, fish population density did not influence either monogenean abundance or species richness, and neither did any of the other variables investigated (mean fish length per pond, number of fish examined per pond, distance to the nearest lake, and several water quality measures). In our system, proximity among fish individuals (i.e. host population density) may not be relevant to the proliferation of monogeneans; instead, the overall availability of host individuals in the host population appeared to be the main constraint limiting parasite population growth.
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Radulescu, Victorita. "Environmental Conditions and the Fish Stocks Situation in the Black Sea, between Climate Change, War, and Pollution." Water 15, no. 6 (March 7, 2023): 1012. http://dx.doi.org/10.3390/w15061012.
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Climate change, pollution, capture, invasive species, and the war from Ukraine have a significant impact on the environment and fish populations in the Black Sea. In June last year, on the Romanian and Bulgarian seashore, large amounts of algae, dead fish, and jellyfish were discovered. The ongoing depletion of fish stocks necessitates extensive research, concerning their living conditions, reproduction, population, and migration. This paper starts by presenting the environmental conditions for air, sediment, and water up to 60 m, based on direct monitoring and measurements realized between 2014 and 2020. The recent war has affected the environmental conditions of the sea, especially near Snake Island and Crimea Peninsula, well known for fish reproduction. A dedicated paragraph presents the sources of water pollution, with direct effects on eutrophication, fish reproduction, and their populations. The appearance and development of some invasive species, which influence the local fish populations, are also illustrated. All these new factors associated with the capture quotas are responsible for decreasing the number of fish species and their populations in the Black Sea. Finally, some discussions are mentioned, which are necessary to be followed in order to restore the fish stocks.
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Gro Vea Salvanes, Anne, and Victoria Braithwaite. "The need to understand the behaviour of fish reared for mariculture or restocking." ICES Journal of Marine Science 63, no. 2 (January 1, 2006): 345–54. http://dx.doi.org/10.1016/j.icesjms.2005.11.010.
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AbstractFollowing severe stock collapses in many natural populations, efforts are now being invested in farming marine species, and in rehabilitating populations through controlled releases. While the development of cod farming is still relatively new, it may be wise to consider some of the problems other fish farming industries have encountered. For example, farmed fish generally have a different genotype from that of local wild populations, and these artificially selected fish are typically bigger and more aggressive than wild fish. These differences can be problematic if farmed fish escape and begin breeding with local wild populations. An alternative approach to farming is to rehabilitate local wild populations through restocking. To date, however, this approach has had mixed success. Fish behaviour develops during early life stages through a combination of innate characteristics and experience. Apparently, the capacity for behavioural flexibility later in life is affected by the early experiences of juvenile fish. Here, we review the literature concerning the role of population origin and juvenile experience on fish behaviour. We highlight our recent studies on Atlantic cod, which demonstrate that variability in the nursery habitat generates behaviourally flexible fish. We discuss these issues in the context of gadoid mariculture and restocking. We conclude that behavioural studies are an important part of applied research for developing an industry of fish farming in gadoids, as well as for research concerning restocking and conservation of marine resources.
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BABCOCK, RUSSELL C., DANIEL P. EGLI, and COLIN G. ATTWOOD. "Incorporating behavioural variation in individual-based simulation models of marine reserve effectiveness." Environmental Conservation 39, no. 3 (June 1, 2012): 282–94. http://dx.doi.org/10.1017/s0376892912000148.
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SUMMARYEffective spatial management of marine species requires informed planning, as well as ongoing assessment. For mobile species such as fish, knowledge of the scale and variation in movement is central to key planning decisions, such as the size and shape of marine reserves and the interpretation of the response of protected populations. For example, populations of species that require large areas of habitat may not show increases in abundance inside small reserves, but calculating optimal reserve size is complicated by individual variations in behaviour. Fish movements can be used to quantitatively inform marine reserve planning and assessment. An individual based numerical simulation model including acoustic telemetry and census data was used to simulate changes in populations of snapper Pagrus auratus in north-eastern New Zealand. Four behavioural categories and offshore migration were used to represent the observed variability in movement. Age-structures of modelled fish populations in fully exploited areas, marine reserves and virgin populations differed substantially. However, the population structure within reserves resembled a fully fished population more closely than an unfished population. Due to the range of movement types shown by snapper, fish were not ‘locked up’ by reserves, and fish with centres of activity based in reserves were predicted to have a relatively high chance of being caught outside these reserves. Furthermore, the model showed that the response of fish populations within marine reserves was dependent on levels of exploitation in fished areas. For snapper in coastal reef areas, reserves c. 40 km2 or more may be required to achieve abundances > 50% of the unfished stock. On balance, while marine reserves with sizes similar to Leigh and Tawharanui (c. 5 km2) can achieve significant levels of protection for snapper, they are too small to fully protect resident reserve snapper populations.
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Luo, Yang, Yufeng Zhang, Ruli Cheng, Qinghua Li, Yu Zhang, Yingwen Li, and Yanjun Shen. "Genetic Diversity of Jinshaia sinensis (Cypriniformes, Balitoridae) Distributed Upstream of the Yangtze River." Fishes 8, no. 2 (January 28, 2023): 75. http://dx.doi.org/10.3390/fishes8020075.
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The upper reaches of the Yangtze River (upper YR) are a biological zone with extremely rich fish diversity, especially endemic fish. However, long-term human interference, such as environmental pollution and cascade hydropower construction, has significantly changed the habitat of many fish and is threatening the number and genetic diversity of fish populations. Jinshaia sinensis is a typical small and endemic but rare fish that is found in the upper YR, and its genetic diversity and structure still need further study. To understand the current levels of genetic diversity in J. sinensis, we analyzed the genetic diversity, population history, genetic structure, etc., of three J. sinensis populations based on two mitochondrial genes (the cytochrome-c oxidase subunit I, COI, and cytochrome-b gene, Cytb) and two nuclear genes (recombination-activating protein 1, RAG1, and rhodopsin, RH). The genetic diversity analysis indicated that J. sinensis had high genetic diversity, with high haplotype diversity (h) and nucleotide diversity (Pi). Population pairwise FST analysis revealed a significant genetic divergence between the Lijiang and Luzhou populations for all genes and between the Panzhihua and Luzhou populations, except for the COI gene; however, analyses of molecular variance (AMOVA) showed no significant geographic genetic structure among populations, and gene flow analysis also indicated a certain degree of gene exchange among populations. Haplotype network structure analyses revealed low levels of shared haplotypes among populations. Neutrality test and mismatch distribution results indicated that only the Lijiang population had experienced obvious population expansion. Overall, these results indicate that J. sinensis is still a single evolutionarily significant unit, but when considering the threat of habitat disturbance to the population, it is still necessary to carry out long-term genetic monitoring on J. sinensis and on other endemic fishes with similar ecological habits in order to maintain the genetic diversity of fishes in the upper YR.
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Chen, Huijuan, Dengqiang Wang, Xinbin Duan, Shaoping Liu, Daqing Chen, and Yun Li. "Hatchery-reared enhancement program for silver carp (Hypophthalmichthys molitrix) in the middle Yangtze River: monitoring the effectiveness based on parentage analysis." PeerJ 7 (May 6, 2019): e6836. http://dx.doi.org/10.7717/peerj.6836.
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Introduction A hatchery-reared silver carp (Hypophthalmichthys molitrix) program has been intensively carried out since 2010 to enhance the rapidly declining fisheries production in the middle Yangtze River. However, only a little information regarding the effectiveness of the enhancement program has been reported. In this context, this study investigates on an enhancement program through monitoring the efficacy based on parentage analysis. Methods A total of 1,529 hatchery-reared fish and 869 larvae were sampled from the middle Yangtze River in 2016 and 2017 and were genotyped by thirteen microsatellite loci. Based on the results of parentage analysis the larvae were divided into three populations: (1) larvae population with both parents being hatchery-reared fish (=R), (2) larvae population with only a male or a female parent being hatchery-reared fish (=H), and (3) larvae population with no hatchery-reared fish parent (=W). The following analyses were also carried out: (1) assessing the contribution of hatchery-reared offspring to larval resources, and (2) evaluating the genetic effect of stock enhancement on the wild population. Results In total, 10.37% and 11.56% of larvae were identified as the offspring produced by hatchery-reared fish released in 2016 and 2017, respectively. In 2017, some of the larvae were assigned unambiguously to hatchery-reared fish released in 2016. In terms of the number of offspring produced, the hatchery-reared fish have shown significant variations. No significant differences were found among all the larvae populations concerning genetic parameters for diversity. High levels of genetic diversity of all larvae populations were obtained. Low FSTvalues obtained from pairwise FST analysis, as well as the analysis of molecular variance (AMOVA), revealed high genetic structural similarity among all the larvae populations. The genetic composition of the W larvae population in 2017 was different from that of all other larvae populations (all larvae populations in 2016, and R and H larvae populations in 2017), as demonstrated from the results of STRUCTURE and PCA analyses. Conclusion It was demonstrated that hatchery-reared fish are successful in producing the offspring in the natural environment during multiple years, which might assist in increasing the abundance of larvae. The hatchery-reared fish had variations in terms of the success rates on reproduction. Also, the hatchery-reared enhancement program had no significant effect on the genetic diversity or the genetic structure of wild populations. However, the genetic component of the W larvae population in 2017 was changed as compared to 2016, which was not due to the hatchery-reared enhancement program for silver carp. This could be due to flooding, but the specific causes need further studies. Our results clearly show the necessity to continuously inspect the genetic impact of the enhancement program so that historical information can be utilized for further research.
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Sergaliev, Nurlan Habibullovich, Murat Galikhanovich Kakishev, Yerzhan Sakhypzhanovich Sultanov, Aibek Ertleuovich Sarmanov, and Serik Samigullovich Bakiyev. "Monitoring of natural reproduction of fish populations of Edilsor Lake." Bulletin of the Karaganda University. “Biology, medicine, geography Series” 108, no. 4 (December 30, 2022): 126–31. http://dx.doi.org/10.31489/2022bmg4/126-131.
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The article presents the results of monitoring the commercial fish populations of Edilsor Lake. Edilsor is one of the large lakes of the West Kazakhstan region of fishery importance, in connection with which the monitoring of the natural numbers of populations of aboriginal commercial fish species of the studied reservoir is relevant. Control catches were used to analyze the state of natural fish populations. As tools for catching biological objects, commercial fish, lake plug-in nets with mesh sizes of 30–70 mm were used. Control catches of aboriginal commercial fish were carried out during the period of field studies. The captured biological objects were subjected to the analysis of such biological indicators as species, age composition, ratio of females and males in the catch, weight, length of the whole body of fish, according to the results obtained, the average values were determined. As a result of control catches, the species composition of the ichthyofauna of Lake Edilsor included the following species of aboriginal commercial fish: carp — 7.1 %, bream — 16.7 %, blue bream — 7.1 %, crucian carp — 4.8 %, perch — 64.3 %. The largest population was characterized by the perch population, which amounted to 27 individuals, the bream was less common — 7 individuals, the carp and blue bream — 3 individuals, the smallest number was observed in the population of crucian carp, which amounted to 2 individuals. According to the weight ratio, fish species are located as follows: perch — 40 %, carp — 32.5 %, bream — 15.8 %, crucian carp — 8.5 %, blue bream — 3.2 %. The largest mass falls on representatives of perch — 6.94 kg, followed by carp — 5.63 kg, bream — 2.73 kg, crucian carp — 1.47 kg, blue bream — 0.56 kg.
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Sánchez-Hernández, Javier, and Fernando Cobo. "Foraging behaviour of brown trout in wild populations: can population density cause behaviourally-mediated foraging specializations?" Animal Biology 63, no. 4 (2013): 425–50. http://dx.doi.org/10.1163/15707563-00002423.
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Brown trout is considered as a territorial fish, in which negative density effects on growth and survival rates can be mediated through competition mechanisms. Here, in order to examine whether competition mechanisms can affect the foraging behaviour of wildSalmo truttawith respect to active-bottom, benthic-drift or surface-drift foraging, three neighbouring populations under different levels of fish density (high, intermediate and low) were studied. We analysed the foraging behaviour of each population according to niche breadth, prey preferences, the modified Costello graphical method and prey trait analysis. The results revealed a remarkable similarity in the feeding behaviour among these feral fish populations, suggesting a foraging behaviour convergence in response to site-specific prey accessibility. A generalist foraging behaviour was the prevailing feeding strategy, independent of fish density. Hence, this study offered evidence for the occurrence of density-independent individual foraging behaviour when food is abundant and available; however, density-dependent foraging behaviour might occur when resource limitation exists. Studies under natural conditions like the present study are needed to increase ecological realism, and indeed this study opens promising research directions for future feeding studies in territorial fish species.
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Schultz, Eric T., David O. Conover, and Amir Ehtisham. "The dead of winter: size-dependent variation and genetic differences in seasonal mortality among Atlantic silverside (Atherinidae: Menidia menidia) from different latitudes." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 5 (May 1, 1998): 1149–57. http://dx.doi.org/10.1139/f97-320.
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Genetic differences among populations of Atlantic silverside (Menidia menidia) are hypothesized to be evolutionary responses to intense, size-selective winter mortality at high latitudes. Three experiments were conducted to test features of winter mortality. In the first experiment, we varied size and whether food was provided or withheld; temperatures were permitted to follow ambient (New York) wintertime fluctuations. Mortality and depletion of energy reserves were more rapid in the units receiving no food. Small fish died before larger fish in these units, but not in the units receiving food. Energy depletion of fish in the no-food treatment resembled that of fish in the wild. In the second experiment, we varied size and population of origin, representing high-latitude (Nova Scotia), midlatitude (New York), and low-latitude (South Carolina) populations. These fish were provided food and showed minimal depletion of energy reserves, but mortality rates were high when water temperatures were low. Mortality did not vary with size in New York and South Carolina fish, but was highest in intermediate-size fish from Nova Scotia. There was a pronounced population difference in survival rate (Nova Scotia > New York > South Carolina). In the third experiment, food was withheld and extreme low temperatures were moderated. Energy depletion was rapid and small fish died before large fish. We conclude that populations in seasonal environments are likely to be subject to size-selective winter mortality when energy reserves are depleted and that juvenile growth rates have evolved in response to this selection pressure. In addition, high-latitude populations have evolved greater tolerance to other winter stresses associated with low temperatures.
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Sanz, Núria, José-Luis García-Marín, and Carles Pla. "Divergence of brown trout (Salmo trutta) within glacial refugia." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 11 (November 1, 2000): 2201–10. http://dx.doi.org/10.1139/f00-199.
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The Pleistocene glaciations produced a range of changes that affected the genetic population structure of fish species. Usually, studies focused on the population structure of species in postglacial recolonized areas and less attention was devoted to species differentiation within refuge areas. Allelic frequencies for 21 polymorphic protein-coding loci were compared among 25 collections within a northwestern Iberian glacial refuge of brown trout (Salmo trutta) using adjusted frequencies for nine populations to account for introgressions with exogenous hatchery fish. The high divergence observed (FST = 0.645) and geographical patterns of allelic variation are interpreted to reflect the existence of strong population structuring among native populations of this refuge. Four major geographic groups were defined within the region: (i) in the Tajo River, (ii) in the Duero River, (iii) in the Sil River, and (iv) among Cantabrian Sea flowing rivers including present anadromous populations. These gene pools have diverged genetically and ecologically in response to climatic oscillations. Anthropogenic effects on habitat and fish populations seriously compromise their future.
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Rennie, Michael D., Nicholas C. Collins, Brian J. Shuter, James W. Rajotte, and Patrice Couture. "A comparison of methods for estimating activity costs of wild fish populations: more active fish observed to grow slower." Canadian Journal of Fisheries and Aquatic Sciences 62, no. 4 (April 1, 2005): 767–80. http://dx.doi.org/10.1139/f05-052.
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Activity costs can account for a major proportion of fish energy budgets and may trade off against observed growth rates in wild fish populations. Recent approaches to estimating activity costs in situ have used a contaminantbioenergetic mass balance modelling approach, allowing for a broader examination of activity costs among populations compared with time-consuming alternative approaches. We report the results of this contaminantbioenergetic modelling approach to estimating in situ activity costs compared with two alternative independent methods of assessing in situ activity costs. Comparisons were made between a fast- and slow-growing yellow perch (Perca flavescens) population. Contaminantbioenergetic estimates of activity costs in the fast-growing population were 39% lower than those in the slow-growing population. Activity estimated from recorded swimming behaviours was 37% lower in the fast-growing population and 22%29% lower in the fast-growing population based on published relationships between activity costs and axial white muscle glycolytic enzyme capacities. Consumption rates were actually 32% lower in the fast-growing population, implying that lower activity costs more than compensated for lower food intake. The agreement among the three independent measures of activity costs strongly support the idea that activity costs, rather than food intake, are a major determinant of growth differences in these two wild fish populations.
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Carim, Kellie J., Scott Relyea, Craig Barfoot, Lisa A. Eby, John A. Kronenberger, Andrew R. Whiteley, and Beau Larkin. "Ultrasound imaging identifies life history variation in resident Cutthroat Trout." PLOS ONE 16, no. 2 (February 3, 2021): e0246365. http://dx.doi.org/10.1371/journal.pone.0246365.
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Human activities that fragment fish habitat have isolated inland salmonid populations. This isolation is associated with loss of migratory life histories and declines in population density and abundance. Isolated populations exhibiting only resident life histories may be more likely to persist if individuals can increase lifetime reproductive success by maturing at smaller sizes or earlier ages. Therefore, accurate estimates of age and size at maturity across resident salmonid populations would improve estimates of population viability. Commonly used methods for assessing maturity such as dissection, endoscopy and hormone analysis are invasive and may disturb vulnerable populations. Ultrasound imaging is a non-invasive method that has been used to measure reproductive status across fish taxa. However, little research has assessed the accuracy of ultrasound for determining maturation status of small-bodied fish, or reproductive potential early in a species’ reproductive cycle. To address these knowledge gaps, we tested whether ultrasound imaging could be used to identify maturing female Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). Our methods were accurate at identifying maturing females reared in a hatchery setting up to eight months prior to spawning, with error rates ≤ 4.0%; accuracy was greater for larger fish. We also imaged fish in a field setting to examine variation in the size of maturing females among six wild, resident populations of Westslope Cutthroat Trout in western Montana. The median size of maturing females varied significantly across populations. We observed oocyte development in females as small as 109 mm, which is smaller than previously documented for this species. Methods tested in this study will allow researchers and managers to collect information on reproductive status of small-bodied salmonids without disrupting fish during the breeding season. This information can help elucidate life history traits that promote persistence of isolated salmonid populations.
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Staurnes, Magne, Trygve Sigholt, Grete Lysfjord, and Odd A. Gulseth. "Difference in the Seawater Tolerance of Anadromous and Landlocked Populations of Arctic Char (Salvelinus alpinus)." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 3 (March 1, 1992): 443–47. http://dx.doi.org/10.1139/f92-051.
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The seawater tolerance of juvenile fish from an anadromous and a landlocked population of Arctic char (Salvelinus alpinus), reared in freshwater under a constant light regime, was compared by making repeated seawater challenge tests from one summer to the next. Fish from the landlocked population had higher mortality rates and higher blood plasma Na+ concentrations after transfer to seawater than those from the anadromous population. The gill Na-K-ATPase activity of the landlocked fish was lower than that of the anadromous fish. For both populations, the smallest fish showed the lowest seawater tolerance, but hypoosmoregulatory ability was independent of fish size for fish larger than about 60 g. By June of the second summer, fish from the anadromous, but not those from the landlocked population, developed seawater tolerance 10 d after transfer to seawater. This increase in hypoosmoregulatory ability was accompanied by a doubling of the gill Na-K-ATPase activity.
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Borgstrøm, Reidar. "Effect of Population Density on Gillnet Catchability in Four Allopatric Populations of Brown Trout (Salmo trutta)." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 8 (August 1, 1992): 1539–45. http://dx.doi.org/10.1139/f92-170.
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The gillnet catchability of allopatric brown trout (Salmo trutta) populations was studied in four Norwegian high-mountain lakes, with large differences in population densities. The number of fish and the length composition of the populations were estimated by mark–recapture. The catchability coefficient and the catch per unit effort were described by power functions, and the catchability was inversely related to number of fish present. An important fisheries management implication is that brown trout populations with low densities are more vulnerable to gillnets than populations with high densities. Furthermore, the use of gillnet catches as an estimator of brown trout population density will be biased.