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Nicola Hillgruber - One of the best experts on this subject based on the ideXlab platform.
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temporal and ontogenetic variability in trophic role of four groundfish species walleye pollock pacific cod arrowtooth flounder and pacific halibut around kodiak island in the gulf of alaska
Transactions of The American Fisheries Society, 2012Co-Authors: Jennifer M. Marsh, Nicola HillgruberAbstract:Abstract Changes in trophic position estimates of Commercial Fishery catches are used as an ecosystem-based indicator for sustainability, but often these estimates do not incorporate species-specific seasonal feeding dynamics and ontogenetic diet changes. Using stable isotope analysis, we obtained a fine-scale resolution of ontogenetic and temporal (interannual and seasonal) variations in the trophic roles of four Commercially and ecologically important groundfish species in the Gulf of Alaska: walleye pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, arrowtooth flounder Atheresthes stomias, and Pacific halibut Hippoglossus stenolepis. For each groundfish taxon, the nitrogen stable isotope signature (δ15N) increased with total length. In contrast, the lipid-normalized carbon stable isotope signature (δ13C′) significantly varied with size-class only for walleye pollock. There were species-specific differences in trophic position; adult Pacific cod fed at the highest trophic position, and wall...
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Temporal and Ontogenetic Variability in Trophic Role of Four Groundfish Species—Walleye Pollock, Pacific Cod, Arrowtooth Flounder, and Pacific Halibut—around Kodiak Island in the Gulf of Alaska
Transactions of The American Fisheries Society, 2012Co-Authors: Jennifer M. Marsh, Nicola HillgruberAbstract:Abstract Changes in trophic position estimates of Commercial Fishery catches are used as an ecosystem-based indicator for sustainability, but often these estimates do not incorporate species-specific seasonal feeding dynamics and ontogenetic diet changes. Using stable isotope analysis, we obtained a fine-scale resolution of ontogenetic and temporal (interannual and seasonal) variations in the trophic roles of four Commercially and ecologically important groundfish species in the Gulf of Alaska: walleye pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, arrowtooth flounder Atheresthes stomias, and Pacific halibut Hippoglossus stenolepis. For each groundfish taxon, the nitrogen stable isotope signature (δ15N) increased with total length. In contrast, the lipid-normalized carbon stable isotope signature (δ13C′) significantly varied with size-class only for walleye pollock. There were species-specific differences in trophic position; adult Pacific cod fed at the highest trophic position, and wall...
M Costa - One of the best experts on this subject based on the ideXlab platform.
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environmental influence on Commercial Fishery landings of small pelagic fish in portugal
Regional Environmental Change, 2016Co-Authors: Célia Dos Santos Teixeira, Rita Gamito, Francisco Leitão, Alberto G. Murta, Henrique N. Cabral, Karim Erzini, M CostaAbstract:Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river discharge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mackerel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in landings of these small pelagic fishes and detected the effects of environmental factors in this Fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965–2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North–South and East–West wind components) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in landings associated with changes in sea water temperature and NAO index.
Jennifer M. Marsh - One of the best experts on this subject based on the ideXlab platform.
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temporal and ontogenetic variability in trophic role of four groundfish species walleye pollock pacific cod arrowtooth flounder and pacific halibut around kodiak island in the gulf of alaska
Transactions of The American Fisheries Society, 2012Co-Authors: Jennifer M. Marsh, Nicola HillgruberAbstract:Abstract Changes in trophic position estimates of Commercial Fishery catches are used as an ecosystem-based indicator for sustainability, but often these estimates do not incorporate species-specific seasonal feeding dynamics and ontogenetic diet changes. Using stable isotope analysis, we obtained a fine-scale resolution of ontogenetic and temporal (interannual and seasonal) variations in the trophic roles of four Commercially and ecologically important groundfish species in the Gulf of Alaska: walleye pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, arrowtooth flounder Atheresthes stomias, and Pacific halibut Hippoglossus stenolepis. For each groundfish taxon, the nitrogen stable isotope signature (δ15N) increased with total length. In contrast, the lipid-normalized carbon stable isotope signature (δ13C′) significantly varied with size-class only for walleye pollock. There were species-specific differences in trophic position; adult Pacific cod fed at the highest trophic position, and wall...
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Temporal and Ontogenetic Variability in Trophic Role of Four Groundfish Species—Walleye Pollock, Pacific Cod, Arrowtooth Flounder, and Pacific Halibut—around Kodiak Island in the Gulf of Alaska
Transactions of The American Fisheries Society, 2012Co-Authors: Jennifer M. Marsh, Nicola HillgruberAbstract:Abstract Changes in trophic position estimates of Commercial Fishery catches are used as an ecosystem-based indicator for sustainability, but often these estimates do not incorporate species-specific seasonal feeding dynamics and ontogenetic diet changes. Using stable isotope analysis, we obtained a fine-scale resolution of ontogenetic and temporal (interannual and seasonal) variations in the trophic roles of four Commercially and ecologically important groundfish species in the Gulf of Alaska: walleye pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, arrowtooth flounder Atheresthes stomias, and Pacific halibut Hippoglossus stenolepis. For each groundfish taxon, the nitrogen stable isotope signature (δ15N) increased with total length. In contrast, the lipid-normalized carbon stable isotope signature (δ13C′) significantly varied with size-class only for walleye pollock. There were species-specific differences in trophic position; adult Pacific cod fed at the highest trophic position, and wall...
Célia Dos Santos Teixeira - One of the best experts on this subject based on the ideXlab platform.
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environmental influence on Commercial Fishery landings of small pelagic fish in portugal
Regional Environmental Change, 2016Co-Authors: Célia Dos Santos Teixeira, Rita Gamito, Francisco Leitão, Alberto G. Murta, Henrique N. Cabral, Karim Erzini, M CostaAbstract:Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river discharge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mackerel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in landings of these small pelagic fishes and detected the effects of environmental factors in this Fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965–2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North–South and East–West wind components) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in landings associated with changes in sea water temperature and NAO index.
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Environmental influence on Commercial Fishery landings of small pelagic fish in Portugal
Regional Environmental Change, 2015Co-Authors: Célia Dos Santos Teixeira, Rita Gamito, Francisco Leitão, Alberto G. Murta, Henrique N. Cabral, Karim Erzini, María José CostaAbstract:Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river discharge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mackerel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in landings of these small pelagic fishes and detected the effects of environmental factors in this Fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965–2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North–South and East–West wind components) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in landings associated with changes in sea water temperature and NAO index.
Dereje Tewabe - One of the best experts on this subject based on the ideXlab platform.
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status of lake tana Commercial Fishery ethiopia
International Journal of Aquaculture, 2015Co-Authors: Dereje TewabeAbstract:The status of Lake Tana Fishery was evaluated from analysis of Commercial catch data of number I fishers cooperative. The data collection has been carried out from September 2003 to September 2009. Results indicated that Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus) and species flock of endemic, large Labeobarbus spp. were the three main species groups targeted by Commercial gillnet Fishery of Lake Tana and form 65 %, 20 % and 15 % of the annual catch compositions of fish species during the study period respectively. There was significant variability among sampling years encompassing temporal aspects.
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status of lake tana Commercial Fishery ethiopia
ABC Research Alert, 2013Co-Authors: Dereje TewabeAbstract:The status of Lake Tana Fishery was evaluated from analysis of Commercial catch data of number I fishers cooperative. The data collection has been carried out from September 2003 to September 2009. Results indicated that Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus) and species flock of endemic, large Labeobarbus spp. were the three main species groups targeted by Commercial gillnet Fishery of Lake Tana and form 65 %, 20 % and 15 % of the annual catch compositions of fish species during the study period respectively. There was significant variability among sampling years encompassing temporal aspects. Especially, Commercial catch of O. niloticus were significantly booming up to 2007 and declining after wards. The most likely explanations for the declining catch of O. niloticus and others are the illegal use of undersized monofilament gillnet imported from Sudan town (Gelabat) and the harmful increase of the Commercial gillnet Fishery targeting the spawning aggregations of L. barbus spp. and C. gariepinus in the river mouths and littoral areas. The observed decline in the Commercial catch of O. niloticus and others stress the need for the urgent development of a management plan focusing on controlling import of undersized monofilament gillnet ,fishing effort and gear restrictions in the river mouths and major tributaries during the breeding seasons and implementing the regional Fishery legislation.