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1
Zhang, Yafei. "Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis)." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78094.
Full textAbstract:
Quantitative population dynamics modeling is needed to evaluate the stock status and fisheries management plans to provide robust model and management strategies. Atlantic Weakfish (Cynoscion regalis), one important commercial and recreational fish species along the west coast of Atlantic Ocean that was found to be declining in recent years, was selected as an example species. My study aimed to explore the possible spatial heterogeneity of CPUE (catch per unit effort) year trend based on three fishery independent surveys and explore the influence of nonstationary natural mortality on the fisheries management through a MSE (Management Strategy Evaluation) algorithm based on the Weakfish stock assessment results. Five models for catch rate standardization were constructed based on the NEAMAP (NorthEast Area Monitoring and Assessment Program) survey data and the ‘best' two models were selected based on the ability to capture nonlinearity and spatial autocorrelation. The selected models were then used to fit the other two survey data to compare the CPUE year trend of Weakfish. Obvious differences in distribution pattern of Weakfish along latitude and longitude were detected from these three surveys as well as the CPUE year trend. To test the influence of the model selection on the MSE, five stock-recruitment models and two forms of statistical catch-at-age models were used to evaluate the fishery management strategies. The current biomass-based reference point tends to be high if the true population dynamics have nonstationary natural mortality. A flexible biomass based reference point to match the nonstationary process is recommended for future fisheries management.Master of Science
2
Srisurichan, Sukanlaya. "Time series modelling of the environmental factors affecting the daily catch rate of western rock lobster." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2001. https://ro.ecu.edu.au/theses/1511.
Full textAbstract:
The western rock lobster fishery is one of the most significant and valuable single species fisheries in Australia and in the world. It generates a gross commercial value of $200-300 million dollars per year for the economy of Western Australia. The impact of environmental factors on the daily catch rate of the western rock lobster is of particular interest to the W.A. Marine Research Laboratories, at the Ministry of Fisheries, Western Australia. Considerable time and effort has been invested into building and developing suitable models to measure such impact on this fishery. While past research has focussed on monthly or seasonal data, this study investigated appropriate time series analyses to model the effect of major environmental factors such as lunar cycle, swell, and sea water temperature on the daily catch rate data of the western rock lobster at different depths. The variation in western rock lobster daily catch rate data for two periods ("whites" and "reds") and four categories (undersize, legal size, spawner, and setose ), was examined for three management zones, A, B, and C. Regression and transfer function models for relationships between catch rates and environmental data were considered and compared. Results show that the lunar cycle especially the presence of the full moon and the swell has a significant impact on the daily catch rates of the Western rock lobster. The results of this research assist in the development of improved models to support the management of this very valuable resource.
3
Haag, Lucas A. "Effects of spatially variable plant available water on optimal corn seeding rate -- field scale and site-specific approaches." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/818.
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Murray, David Vernon. "The effect of maximal isometric training on doublet-induced force enhancement and its relationship with changes in voluntary rate of force development." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2074.
Full textAbstract:
Motor unit double discharges (i.e. doublets), which are excitatory potentials that occur at shorter-than-normal intervals (e.g. 5-10 ms) during normal muscle activation, are known to cause muscle force to exceed that predicted from a standard, linear summation of twitch forces. However, although a marked increase in the occurrence of motor unit doublets at the onset of a contraction has been observed after explosive-type exercise training, and has been correlated with changes in RFD (Van Cutsem et al., 1998), little is known about the influence of strength training on the physiological and biomechanical benefits derived from the phenomenon. The present research examined the effects of 4 weeks of ‘explosive’ isometric knee extensor strength training on voluntary and electrically-evoked contractile RFD (calculated as the time derivative of the moment-time curve) in 8 untrained male participants. Electrical stimulation (NMES) trains were delivered to the muscle at 20 Hz and 40 Hz and incorporated short (5 and 10 ms) inter-pulse intervals (IPIs) at the onset of stimulation (i.e. variable-frequency trains; VFT). The influence of the short inter-pulse interval was assessed by comparison to a constant frequency train (i.e. the VFT:CFT ratio). Following the training, substantial improvements in maximum isometric knee extensor strength (MVC) (24.3 ± 13.3%, p = 0.002) and RFD measured to time intervals of 50 (55.5 ± 50.3%, p = 0.011), 100 (34.0 ± 47.2%, p = 0.01) and 150 ms (31.9 ± 38.2%, p = 0.02) were observed. RFD normalised to MVC (RFDnorm), measured to time intervals of 50 and 100 ms from the onset of contraction, improved by 44.9 ± 38.8% (p = 0.04) and 13.8 ± 12.2% (p = 0.01), respectively. There was a significant reduction in the VFT:CFT ratio after training when a 10-ms IPI preceded a 20-Hz train when measured to 30 (-13.7 ± 11.3%, p = 0.03), 50 (-13.9 ± 8.4%, p = 0.007), 100 (-8.6 ± 10.2%, p = 0.04), and 200 ms (-8.1 ± 5.3%, p = 0.009) as well as in the interval 100-200 ms (-7.4 ± 6.6%, p = 0.02). However, no significant changes were observed for other stimulation frequency-IPI combinations. Moderate-to-very strong positive correlations were observed between changes in RFDnorm and changes in VFT:CFT when measured within some time periods, particularly in the early phase of the contraction (r = 0.02 – 0.91). In conclusion, the effect of a high-frequency double discharge at stimulation onset remained unchanged or, under some conditions, was reduced after 4 weeks of explosive-type knee extensor training. Additionally, training-dependent improvements in the ability to rapidly reach a specified torque level relative to peak MVC torque (i.e. RFDnorm) were greater for those participants whose VFT:CFT ratio either did not decline or declined the least. These data provide evidence that explosive training may reduce the effect of a high frequency discharge at the onset of a contraction, and that greater increases in RFD may occur in those who most retain this ability.
5
Ungewiß, Judith [Verfasser]. "Assessment of vigilance and response quality during static automated perimetry. A study using the method of constant stimuli (MoCS) and an enhanced presentation rate of catch trials / Judith Ungewiß." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1214639836/34.
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6
Aidoo, Eric. "Geostatistical modelling of recreational fishing data: A fine-scale spatial analysis." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1813.
Full textAbstract:
The sustainability of recreational fisheries resources rely on effective management of the fishery which includes monitoring of any changes in the fishery. In order to facilitate the ongoing management of the recreational fishery, an understanding of the spatial dynamics of catch per unit effort (catch rate), fishing effort and species diversity is important for fishery managers to make area-specific decisions and to develop strategies for ecosystem based fisheries management. These indices are critical components of information used to inform on recreational fishing activities and evaluate the changes in the fishery resources.
Geostatistical techniques such as kriging can provide useful tools for characterising the spatial distributions of these indices. However, most recreational fishing data are highly skewed, zero-inflated and when expressed as ratios are impacted by the small number problem, which can influence estimates obtained from the traditional kriging. In addition, the use of recreational fishing data obtained through surveys may influence mapping and area-specific decisions as such data are associated with uncertainty.
In Western Australia, recreational fishing has a participation rate of approximately 30%. Data for this thesis were collected from boat-based recreational fishers through phone-diary surveys at spatial resolution that supports spatial analysis and mapping through geostatistical techniques. In this thesis, geostatistical modelling techniques were used to analyse those recreational fishing data in the West Coast Bioregion of Australia, with the development and evaluation of a data transformation approach that takes into account data characteristics and uncertainty. As a first step in the analysis, a suitable kriging estimator for recreational fishing data was determined. This was based on the application of ordinary, ordinary indicator and Poisson kriging estimators for seven aquatic species with different behaviours and distribution patterns. Some of these estimators can handle different distribution properties including high skewness, zero-inflation and small number problems. In general, the indicator kriging performed similarly across species with different life history characteristics and distribution patterns and provided accurate estimates of catch rates for most of those species. To evaluate the incorporation of measurement uncertainty, the study presents a soft indicator kriging approach that uses a logistic function transformation, which is combined with probability field simulation to determine the effect of measurement uncertainty on mapping and fishing area delineation. The results suggest that the incorporation of the measurement uncertainty improves the ability to draw valid conclusions about the estimation results, which may influence any decision regarding the delineation of areas with high catch rates for spatial management. The recreational fishing data used also provided the basis for studying the spatial patterns in species diversity in the entire fishery. The analysis revealed that species diversity, dominance and evenness display similar spatial patterns on a global scale.
The study highlighted the inherent spatial variability in catch rate, fishing effort and species diversity, illustrating areas with high values, or hotspots of these indices. This statistical-based modelling approach is important as it allows prediction of these indices in specific locations taking into account data characteristics and uncertainty. The estimated maps are important for supporting fishery resources management.
7
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.
8
Klaer, Neil L., and n/a. "Changes in the structure of demersal fish communities of the South Eastern Australian Ccontinental Shelf from 1915 to 1961." University of Canberra. Resource, Environmental & Heritage Sciences, 2006. http://erl.canberra.edu.au./public/adt-AUC20060804.154133.
Full textAbstract:
Haul-by-haul steam trawler catch and effort data for 1918�23, 1937�43 and 1952�57,
which covers a large portion of the history of steam trawling in the Australian South
East Fishery, were examined in detail for the first time. There were 64,371 haul records
in total. The catch-rate for all retained catch combined shows a strong decline overall,
with a brief recovery during World War II, probably due to increased retention of
previously discarded species. The fishing fleet moved to more distant fishing grounds
and deeper waters as the catch-rate declined. The catch-rates of the main commercial
species followed a similar pattern in a number of regions within the fishery. The catchrate
of the primary target species � tiger flathead (Neoplatycephalus richardsoni) �
dropped considerably from the early, very high, catch-rates. Chinaman leatherjacket
(Nelusetta ayraudi) and latchet (Pterygotrigla polyommata) � species that were
apparently abundant in the early years of the fishery � virtually disappeared from
catches in later years. The appearance of greater catches of jackass morwong
(Nemadactylus macropterus), redfish (Centroberyx affinis), and shark/skate during the
war and afterwards was probably due to increased retention of catches of these species.
The disappearance of certain species from the catch may be due to high fishing pressure
alone, or to a combination of fishing pressure, changes in the shelf habitat possibly
caused by the trawl gear, and environmental fluctuations.
Catch-rates in weight per haul per species were standardised to annual indices of
abundance using a log-linear model. Standardised annual index trends for flathead,
latchet and leatherjacket indicate a strong to severe decline over the period covered by
the data. All species showed seasonal patterns, but the peak season varied depending on
the species. The distribution of standardised catch-rate by area also differed greatly by
species, and no single area showed consistent differences across all species. Day trawls
caught more flathead, redfish and latchet, while night trawls caught more morwong and
leatherjacket. Moon phase had less influence on catch-rates than the other factors
examined. Correlation of annual index trends with a number of annual mean
environmental factors was examined and no strong correlations were found.
Annual catches of the major commercial trawl species on the SE Australian shelf were
estimated from recorded total trawl catches, catch species composition from subsamples
and estimates of the rate of discarding. These annual catches, standardised
indices of abundance and biological population parameters were used in single-species
stock reduction models to estimate absolute biomass trends. Biological population
parameters and the biomass estimates were used to calculate management reference
point fishing mortality rates F0.1, Fspr30 and Fmsy. Results showed that simple plausible
population models can be constructed that account for catches over the long period of
time from 1915 to 1961.
Simple mass-balance ecosystem models were built for the demersal community of the
SE Australian shelf for 1915 and 1961 using the Ecopath software. Model inputs were
consistent with a more comprehensive SE marine ecosystem model in development by
CSIRO. The models demonstrate that biomass estimates produced by the single species
stock reduction models can be consistently integrated into simple plausible massbalance
ecosystem models.
Modern stock assessments for the main commercial species in this fishery today mostly
used data collected since about 1985. Abundance indices and total catch estimates from
this study have been used in the most recent assessments for tiger flathead and
morwong, allowing construction of the exploitation history for these species spanning
almost 100 years. Use of the historical information has increased confidence in the
estimates of the modern stock assessments � particularly management reference points,
and has allowed us to quantify changes in fish abundance that have simply been
documented anecdotally in the past.
9
Lewis, S. J. "Studies in catch-up growth in the rat skeleton." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382473.
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10
Vallaud, Thierry. "La rentabilité de la fidélisation du consommateur : 3 essais complémentaires." Thesis, Paris, CNAM, 2013. http://www.theses.fr/2013CNAM0873/document.
Full textAbstract:
Dans cette thèse sur travaux, l’auteur part de deux travaux précédents sur la rentabilité de la fidélisation et la détermination du potentiel client pour faire un constat : une partie de la rentabilité de la fidélisation et du potentiel pour une marque est basée sur la part captable du chiffre d’affaire fait à la concurrence ; le taux de captation.Dans ce nouveau travail il s’agit de montrer que le taux de captation est basé sur l’élasticité du taux de nourriture. A partir d’une analyse de la littérature et de plusieurs modélisations sur des données de panel scannérisées, l’auteur démontre, sur plusieurs marchés, que l’élasticité du taux de nourriture est contrainte et prévisible.C’est donc en tenant compte de cet écart limité qu’une marque peut estimer le taux de captation et donc la rentabilité de la fidélisation ainsi que le potentiel clientIn this thesis based on works the author goes from two previous studies on the profitability of loyalty and customer potential determination to make a statement : part of the profitability of loyalty and of the potential for a brand is based on the reachable share of turnover done by the competition ; the catch rate.In this new work it is shown that the catch rate is based on the elasticity of the share of category requirement. From a review of the literature and several modeling on scanning panel data the author demonstrates on several markets that elasticity of the share of category requirement is limited and predictable.Then it’s in taking into account this small difference that a brand can estimate the “catchable” rate and therefore the profitability of loyalty and potential of a customer
11
Yang, Zun-Yu, and 楊尊宇. "Common Shock, Catch-up Index and Malnutrition Rate." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/63742502400965395076.
Full textAbstract:
碩士淡江大學
產業經濟學系碩士班
104
This study investigates the relation between the catch-up index and malnutrition rates under the common shocks. The data are mainly drawn from WDI data collected by the World Bank. The data cover 81 countries from 1995 to 2014. We refer Woo, (2012) of the United States per capita GDP in terms of purchasing power parity index as Catch-Up Index concept is put forward. In this way, we compare the change in different national income levels relative to prevalence of malnutrition across countries. In accordance with the World Bank WDI data classification, countries are divided into low and high income countries. It mainly use the common correlated effects mean group estimation method, -fixed effects model, random effects model and GMM model. Our results show that malnutrition rates mostly accept the existence of cross-sectional dependence hypothesis. Most countries'' catch-up index increased year by year in the 2002-2014 period, implying that those countries are more like the U.S. in terms of income level. In high income countries, malnutrition rates are significantly below the world average, between 2002 to 2004. It has not changed much, close to flat, until 2005. However, in low-income countries have the same trend, and for low income countries, malnutrition rate is still higher than average of the world. To improve the malnutrition rate around the world, catch-up index can be a goal to discuss. The paper also consider the roles of government efficiency and female labor force participation rate, which allow us to find out whether the government subsidies and administrative efficiency can be improved malnutrition rate or not. The results are shown to improve the income level does effectively reduce the incidence of malnutrition, and government efficiency in high-income countries also have the effect of reducing the rate of malnutrition.
12
Bodine, Kristopher A. "Temperature- and habitat- specific length bias and catch rate of electrofishing for blue catfish (Ictalusrus Furcatus)." 2009. http://digital.library.okstate.edu/etd/Bodine_okstate_0664M_10243.pdf.
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13
Chen, Yu-Hong, and 陳昱宏. "Effect of climate variability on the catch rate and spatial distribution of bigeye tuna in Indian Ocean." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/29558171650680243512.
Full textAbstract:
碩士國立臺灣海洋大學
環境生物與漁業科學學系
103
Bigeye tuna (Thunnus obesus) is one of the important commercial species of the Taiwanese longline fishery in the Indian Ocean. In this study, we collected the Taiwanese LL data, environment variables and climate index during the period of 1998-2011. The Generalized Additive Models (GAM) was used to explore the correlation between deep longline (DLL) catch rate of bigeye tuna (CPUE), oceanic environmental factors and climate index to evaluate the impacts of climate variability on the spatial distribution of bigeye tunas. The model selection processes of GAMs showed the cumulative deviances explained were 46.9%. The results showed the catch rates were significantly correlated with the temporal (year and month), spatial (longitude and latitude), environmental variables of sea surface temperature (SST), net primary production (NPP) and mixed layer depth (MLD) and climate index (dipole mode index (DMI) and Nino3.4 index). We observed a positive association between catch rates and SST between 27-29°C, around 250-400 mgC/m^2 d^1 of NPP and MLD within 40-60 m. The result also shows the positive correlation with climatic indices (DMI and Nino3.4) and standardized CPUE. The higher predict CPUE co-occur with higher SST, lower NPP and shallower MLD. The analysis of fishing catch gravity illustrated the seasonal movement of potential fishing ground. Whem the DMI is positive value, the fishing catch gravity would shift westward and shift to eastward in the negative value. In the El Niño years, the fishing catch gravity would shift westward and shift to eastward in the La Niña years. These findings from satellite remote sensing provide preliminary insights into some of the climate variability driving the environmental changes on the catch rate and spatial distribution of bigeye tuna in Indian Ocean.
14
Chen, Ming-Wen, and 陳明雯. "Effects of climate variability on catch rate of yellowfin tuna (Thunnus albacares) cohort in the Indian Ocean." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/a37xjh.
Full textAbstract:
碩士國立臺灣海洋大學
環境生物與漁業科學學系
105
The yellowfin tuna (Thunnus albacares; YFT) is one of the important commercial species for longline fisheries in the Indian Ocean. In this study, we collected the long-term (2003-2012) records of yellowfin tuna catch rates, length data of longline fisheries with the marine environmental data, including sea surface temperature (SST), chlorophyll-a concentration (CHL), mixed layer depth (MLD), sea surface height (SSH). Empirical orthogonal function (EOF) analysis were used to investigate the relationship between the environment variables and the catch rates for speculating the distribution of the feeding grounds and spawning grounds on each cohort of YFT. The relationships between each cohort and the environmental data with climatic indices showed that the distributions of larvae were affected by the MLD and the CHL, concentrated in the northwest Indian Ocean in the first and second season, and in southwest Indian Ocean in third and fourth season. The juvenile in the first and fourth season were affected by the DMI event, the variation of MLD would affected the distribution of Arabian sea and western and central Indian ocean. In the second season, SST and SSH would affect the distribution in Gulf of Oman and the mid-western Indian Ocean. The SST in Somalia decreased and the CHL increased, the juvenile would move to the east Indian Ocean in the third season. The distribution of spawning group in Madagascar and western and central Indian ocean would affected by CHL in the first and fourth season. The variation of SST would affect the spawning group, their distribution in mid-Western showed horizontal variability in the second season. In the third season, the SSH affected the distribution in Gulf of Oman, and the distribution in Madagascar would be affected by the MLD. The MLD and CHL influenced the distribution in Gulf of Oman, the waters off Madagascar and the Bay of Bengal. As a result, we speculating that migrations takes place between the spawning ground and feeding ground.
15
Lee, Yu-Lin, and 李育林. "The impact of climate variability on threadfin catch rate and distribution during the winter of Taiwan Strait." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/muszh4.
Full textAbstract:
碩士國立臺灣海洋大學
環境生物與漁業科學學系
104
Threadfin is one of the most important commercial species of fish in the coastal fisheries of Taiwan. The catch of threadfin exhibiting a peak in 1988 and its population has rapidly declined. However, direct studies related to fishery oceanography of threadfin in Taiwan Strait are scarce. In this study, we collected the annual landing data of threadfin in the Taiwan Strait from 1958~2013 and the total tonnages of trawl vessel from fisheries yearbook and daily logbook data from coastal gillnet fisheries to construct different temporal and spatial fishery data. Furthermore, we also collected climate indices and sea surface temperature data to investigate the influences of marine variations on catch rate by using time series wavelet analysis and suitability index at different multiple time scales. The result showed the major fishing season is in the winter and also showed the seasonal variations in the latitudinal catch percentage of threadfin in the Taiwan Strait. In addition, the landing data of threadfin distribution revealed the northward migrated trend. The time series analysis displayed the significant correlation among the catch rate and autumn PDO, autumn SST, winter Nino3.4, winter SOI, winter WP, which PDO, SST, Nino3.4, SOI have 4 to 6-year periodicity in 1975~1995. PDO and Nino3.4 were positively correlated to the catch rate, while the SOI and SST were negative correlated. Additionally, the catch rate and WP showed fairly good positive correspondence and have 4 to 8-year periodicity during the study period. Furthermore, the high suitability range (SI>0.8) of SST were in the range between 21.42~22.18℃. When El Nino or WP positive phase occurred which led to the winter SST rises in Taiwan Strait, thus expanding the high suitability habitat of threadfin increased and the annual catch rate approximately 17.63% and 19.21% respectively than in the nominal events. In contrast, La Niña or WP negative phase resulting the winter SST decrease in Taiwan Strait, thus the high suitability habitat of threadfin shrinking, however, its impact on the catch rate is not obvious.
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Huang, Min-Chien, and 黃敏茜. "Albacore (Thunnus alalunga) catch rate in relation to oceanographic conditions in the South Pacific Ocean using GAM-based empirical model." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/53072342896551626276.
Full textAbstract:
碩士國立臺灣海洋大學
環境生物與漁業科學學系
100
Albacore (Thunnus alalunga) catch rate for Taiwan distant-water longline fishery in the South Pacific in relation to different oceanographic conditions was studied using generalized additive model (GAM). Satellite remote sensed sea surface temperature (SST), chlorophyll-a (SSC), sea surface height (SSH) and mixed layer depth (MLD), subsurface ocean temperature at certain depths (T105M, T205M and T303M) from 1998 to 2007 were utilized as covariates for assessing regular longline (RLL) and Deep longline (DLL) catch rate in the South Pacific. GAM results indicated that water temperature changes were the most important factors for albacore catch rate, in which subsurface ocean temperature was better compared to SST. T205M and T303M warming had positive effect on RLL and DLL catch rate, respectively. However, SST has the advantages of accurate and rapid observation, yet still plays an important role in fisheries researches. Other parameters such as SSH and SSC, their influences on tuna catch rate were still uncertain. Catch rates forecast for RLL and DLL by using the established GAM models was identical to observed value. In addition, predicted and observed values were significant for the three areas (0~10°S；10~30°S；30~50°S).
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Liu, Te-Cheng, and 劉德晟. "The relationship between Albacore (Thunnus alalunga) catch rate and marine environmental variance in the Indian Ocean using GAM and HSI model." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/32608899054208166101.
Full textAbstract:
碩士國立臺灣海洋大學
環境生物與漁業科學學系
104
Albacore tuna (Thunnus alalunga) is one of the important commercial species of the Taiwanese longline fishery in the Indian Ocean. The purpose of this study was to investigate the relationship between environmental variations and catch rates to explore the underlying processes influencing albacore distributions and habitat in the Indian Ocean. Using the Generalized Additive Model (GAM) and Habitat Suitability Index(HSI) model, and its impacts of fishing condition possibly influencing by the climate scenarios. The results of the cumulative deviances by the selected GAM were 69.6% , positive association between catch per unit effort (CPUE) and sea surface temperature between 17-21 °C, sea surface high of 0.4–0.6 m, net primary production around 250-450 mg C/m2d1 and mixed layer depth within 60-120 m in the Indian Ocean. HSI model also underpinned that albacore have high sensitivity to the habitat changes in its ocean environments. Based on four climate scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) from the low to high future carbon emissions in the period of 2015 to 2045, the CPUE was increased from 2.2 N/1000 hooks in years of 2015-2020 to about 4 N/1000 hooks in years of 2040-2045. In addition, the change of possible habit was also estimated.
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SHAO, WAN-CHIEH, and 邵琬絜. "Analysis of observer’s data and standardized catch rate of blue shark caught by the Taiwanese large-scale longline fishery in the Indian Ocean." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/99340996659268295818.
Full textAbstract:
碩士國立高雄海洋科技大學
漁業生產與管理研究所
104
The blue shark catch and effort data from observers’ records of the Taiwanese large longline fishing vessels operating in the Indian Ocean from 2004-2013 were analyzed. Based on the effort distribution and fishing grounds of the target species, four areas, namely, A (north of 10°S, east to 70°E), B (north of 10°S, 70°E-120°E), C (south of 10°S, 20°E-60°), D (south of 10°S, 60°E-120°E) were categorized. To cope with the large percentage of zero shark catch, the catch per unit effort (CPUE) of blue shark, as the number of fish caught per 1,000 hooks, was standardized using a two-step delta-lognormal model that treats the proportion of positive sets and the CPUE of positive catches separately. Each model includes the main variables year, quarter, longitude, latitude,area, hooks per basket (HPB), and all two-way interactions between quarter, area and HPB. Standardized indices with 95% bootstrapping confidence intervals were reported. In India Ocean, the high shark bycatch number was found in major fishing ground for the bigeye tuna fleet, the highest proportion was blue shark. The standardized CPUE showed a stable trend for blue sharks from 2004 to 2008 and increased steadily thereafter with peaks in 2013. The results obtained in this study can be improved if longer time series observers' data are available.
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CHEN, PO-WEN, and 陳柏妏. "Analysis of observer data and standardized catch rate of blue shark caught by the Taiwanese large scale longline fishery in the Atlantic Ocean." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/sn295u.
Full textAbstract:
碩士國立高雄海洋科技大學
漁業生產與管理研究所
106
This study was based on observers’ records of the Taiwanese tuna longline fishing fleets operating in the Atlantic Ocean in the period 2004-2015. Observers’ data analysis included those of operation area, fishing effort, species composition, shark by-catch species composition, shark discard/release rates, and catch per unit effort (CPUE) of blue shark from Atlantic Ocean. Five areas: A (north of 20°N), B (5°N-20°N), C (5°N-15°S), D (15°S-50°S, west to 20°W) and E (15°S-50°S, 20°W-20°E) were categorized based on the blue shark nominal CPUE distribution. To cope with the high zero shark catch percentage, the CPUE of blue shark, calculated as the number of fish caught per 1,000 hooks, was standardized using a two-step delta-lognormal approach that treats the proportion of positive sets and the CPUE of positive catches separately. Standardized indices with 95% bootstrapping confidence intervals were reported. Major shark by-catch species were blue shark (Prionace glauca) (75.74%), bigeye thresher shark (Alopias superciliosus) (8.91%), shortfin mako (Isurus oxyrinchus) (4.53%) in the North Atlantic Ocean and blue shark (67.70%), crocodile shark (Pseudocarcharias kamoharai) (14.38%), cookiecutter shark (Isistius brasiliensis) (5.68%) in the South Atlantic Ocean. The standardized CPUE showed a stable trend for blue sharks from 2007 to 2014. The results obtained in this study can be improved if longer time series observers' data are available.
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Yin, Yih-Huei, and 殷毅輝. "The Influence of Environment Changes on Catch Rate of Yellowfin Tuna(Thunnus albacarest ) and Bigeye Tuna (Thunnus obesus) of Longline Fishery in South China Sea." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/60273474774508767878.
Full textAbstract:
碩士國立高雄海洋科技大學
漁業生產與管理研究所
95
In order to understand how the marine environment changes in South China Sea affects the catch rate of yellowfin tuna and bigeye tuna for longline fishery, the data of SST (Sea Surface Temperature) and Chlorophyll a between 1990 and 2004 were collected in this study as the index of marine environment changes, along with the catch data of 5 degree square space provided by SPC (Secretariat of the Pacific Community) and carried out the correlation coefficient test. The results suggest that the CPUE of yellowfin tuna decreases with increasing of SST between 1990 and 2004, which shows significant negative correlation (r=-0.53, p<0.05). Meanwhile, the increasing CPUE of bigeye tuna increases with increasing of SST, which shows obviously positive relation (r=0.76, p<0.05). The Chlorophyll a and SST in South China Sea between 1990 and 2004 show an significant negative correlation (r=-0.53, p<0.01), in other words, the higher sea surface temperature involving with the lower Chlorophyll a. There was an significant positive correlation（r=0.52, p<0.05）between the changes of Chlorophyll a and CPUE of yellowfin tuna during the period of abnormal high temperature in South China Sea (1997.09-1999.04, 2000.12-2001.06, 2002.11-2003.04). But Anomalies of Chlorophyll a and CPUE of yellowfin tuna during the whole period (1997.09-2004.12) did not present an significant positive correlation (r=0.18, p＞0.05), according to correlation coefficient test. Therefore the results indicate that the increase of SST would cause the reduction of Chlorophyll a and indirectly conduct the decrease of CPUE of yellowfin tuna. However no matter what period is, the whole period or abnormal higher temperature period, the bigeye tuna seemed to be not affected by the change of Chlorophyll a.
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Alves, Rita Barreiros. "Efeito do tipo de anzol nas capturas acessórias de tartaruga comum, Caretta caretta (Linnaeus, 1758) nas pescas de palangre de superfície dos Açores." Master's thesis, 2018. http://hdl.handle.net/10400.12/6896.
Full textAbstract:
Dissertação de mestrado apresentada no ISPA – Instituto Universitário para obtenção de grau de Mestre na especialidade de Biologia Marinha e Conservação.Atualmente, as capturas acessórias são uma das principais ameaças antropogénicas nos sistemas marinhos e afetam muitas populações de animais, como por exemplo as tartarugas comuns. Nas águas dos Açores, maioritariamente utilizadas pelos juvenis de tartaruga comum, este tipo de pesca é dirigido ao espadarte e tintureira. Os dados deste estudo foram recolhidos durante uma experiência de modificação de parâmetros na pesca de palangre, entre 2000 e 2004 (entre os meses julho e dezembro). Foram capturadas 491 tartarugas comuns em 335 lances de pesca. Os resultados mostraram que um maior número de capturas ocorre nos meses de agosto e setembro, sugerindo um padrão de sazonalidade na distribuição das tartarugas. Foi ainda possível concluir que o tipo de anzol tem uma influência significativa na captura de tartarugas, sendo o anzol RT o que obteve uma maior taxa de captura e os anzóis CLP18O, CLP18 e JM9O os que estiveram associados a menores taxas de captura. Os resultados mostraram um efeito significativo do tipo de anzol relativamente ao local do corpo onde ficou ferrado e os anzóis circulares tiveram uma maior tendência para ficar ferrados na boca ou externamente do que na garganta, comparativamente aos anzóis “J”. Em relação ao tamanho das tartarugas capturadas, verificou-se que a arte de pesca é seletiva, com preferência por indivíduos de maiores dimensões (média> 50 cm CCL para todos os anzóis). Assim, modificações na arte de pesca parecem ter potencial para reduzir a captura acidental de tartarugas, mas a implementação de alterações no aparelho devem ser efetuadas com precaução
Currently, bycatch is one of the main anthropogenic threats on marine systems worldwide and affect many animal populations, such as loggerhead turtles. In Azorean waters, mainly used by loggerhead juveniles, this type of fishing targets swordfish and dyer. The data of this study were collected during a longline gear modification experiment, between 2000 and 2004 (from July to December). 491 common turtles were caught in 335 fishing sets. The results showed that the great majority of catches occur in August and September, suggesting a seasonal pattern in the distribution of turtles. It was also possible to conclude that the type of hook has a significant influence on the catch rate of turtles, with the RT hook associated with a higher catch rate and CLP18O, CLP18 and JM9O hooks associated with lower ones. A significant effect of the hook type regarding the body location was also found, with circular hooks having a greater tendency to be hooked in the mouth or externally rather than in the throat, compared to “J" hooks. Regarding the size of the turtles captured, the fishing gear is selective, with preference for larger individuals (mean> 50 cm CCL for all hooks). Thus, modifications in the fishing gear seem to have potential to reduce turtles’ bycatch. Nevertheless, the implementation of changes should be carried out with caution. Keywords: loggerhead turtle,