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Thomas P Hurst - One of the best experts on this subject based on the ideXlab platform.

  • elevated co2 alters behavior growth and lipid composition of Pacific Cod larvae
    Marine Environmental Research, 2019
    Co-Authors: Thomas P Hurst, Louise A Copeman, Scott A Haines, Summer D Meredith, Kamilya Daniels, Kalyn M Hubbard
    Abstract:

    Abstract High-latitude seas, which support a number of commercially important fisheries, are predicted to be most immediately impacted by ongoing ocean acidification (OA). Elevated CO2 levels have been shown to induce a range of impacts on the physiology and behavior of marine fish larvae. However, these responses have yet to be characterized for most fishery species, including Pacific Cod (Gadus macrocephalus). Based on laboratory experiments, we present a multi-faceted analysis of the sensitivity of Pacific Cod larvae to elevated CO2. Fish behavior in a horizontal light gradient was used to evaluate the sensitivity of behavioral phototaxis in 4–5 week old Cod larvae. Fish at elevated CO2 levels (∼1500 and 2250 μatm) exhibited a stronger phototaxis (moved more quickly to regions of higher light levels) than fish at ambient CO2 levels (∼600 μatm). In an independent experiment, we examined the effects of elevated CO2 levels on growth of larval Pacific Cod over the first 5 weeks of life under two different feeding treatments. Fish exposed to elevated CO2 levels (∼1700 μatm) were smaller and had lower lipid levels at 2 weeks of age than fish at low (ambient) CO2 levels (∼500 μatm). However, by 5 weeks of age, this effect had reversed: fish reared at elevated CO2 levels were slightly (but not significantly) larger and had higher total lipid levels and storage lipids than fish reared at low CO2. Fatty acid composition differed significantly between fish reared at high and low CO2 levels (p

  • connectivity between spawning and nursery areas for Pacific Cod gadus macrocephalus in the gulf of alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2018
    Co-Authors: Sarah Hinckley, Benjamin J Laurel, William T Stockhausen, Kenneth O Coyle, Georgina A Gibson, Carolina Parada, Albert J Hermann, Miriam J Doyle, Thomas P Hurst
    Abstract:

    Abstract We present the results of a study of the connectivity between Pacific Cod spawning and nursery areas, and settlement of Pacific Cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this hypothesis, we developed a Lagrangian, biophysical, individual-based model of Pacific Cod early life history and dispersal using the Dispersal Model for Early Life Stages (DisMELS) framework. This model is driven by currents and scalars such as temperature from a version of the Regional Oceanographic Model System (ROMS) developed for the Gulf of Alaska. Results of our study show connectivity patterns predicted by the model that agree with our understanding (based on genetic analyses) that there is a high degree of localized retention in Pacific Cod. The results indicate that the Shumagin Islands and Prince William Sound regions may serve as important collectors of Pacific Cod recruits from upstream spawning areas. We also find correlations between individual-based model outputs and several large-scale climate indicators that appear to show settlement in several important nursery areas, and recruitment overall, are positively affected by slower gyre circulation in the Gulf of Alaska. We hypothesize that this is due to enhancement of retention, settlement in the Shumagin Island region, and reduction of transport of young Cod out of the Gulf of Alaska to the southwest.

  • WITHDRAWN: Connectivity between spawning and nursery areas for Pacific Cod (Gadus macrocephalus) in the Gulf of Alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2018
    Co-Authors: Sarah Hinckley, Benjamin J Laurel, Thomas P Hurst, William T Stockhausen, Kenneth O Coyle, Georgina A Gibson, Carolina Parada, Albert J Hermann, Miriam J Doyle, André E. Punt
    Abstract:

    Abstract We present the results of a study of the connectivity between Pacific Cod spawning and nursery areas, and settlement of Pacific Cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this hypothesis, we developed a Lagrangian, biophysical, individual-based model of Pacific Cod early life history and dispersal using the Dispersal Model for Early Life Stages (DisMELS) framework. This model is driven by currents and scalars such as temperature from a version of the Regional Oceanographic Model System (ROMS) developed for the Gulf of Alaska. Results of our study show connectivity patterns predicted by the model that agree with our understanding (based on genetic analyses) that there is a high degree of localized retention in Pacific Cod. The results indicate that the Shumagin Islands and Prince William Sound regions may serve as important collectors of Pacific Cod recruits from upstream spawning areas. We also find correlations between individual-based model outputs and several large-scale climate indicators that appear to show settlement in several important nursery areas, and recruitment overall, are positively affected by slower gyre circulation in the Gulf of Alaska. We hypothesize that this is due to enhancement of retention, settlement in the Shumagin Island region, and reduction of transport of young Cod out of the Gulf of Alaska to the southwest.

  • spatial and temporal variation in otolith elemental signatures of age 0 Pacific Cod gadus macrocephalus in the gulf of alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2017
    Co-Authors: Mary Elizabeth Matta, Kimberly M Rand, Thomas P Hurst, Thomas E. Helser, Jessica A Miller, Jonathan A Short, Olav Aleksander Ormseth
    Abstract:

    Abstract Shallow coastal waters of the Gulf of Alaska (GOA) serve as nursery habitats for young-of-year Pacific Cod ( Gadus macrocephalus ). However, little is known regarding the relative contribution of these areas to the adult offshore stock. Trace elements incorporated into the otolith matrix can reflect the environmental conditions to which a fish has been exposed during its lifetime. When analyzed together, a suite of elements can serve as a natural marker, characteristic of a particular environment. We evaluated the potential of otolith elemental signatures to identify nursery habitats of age-0 Pacific Cod, focusing on spatial patterns within and across the eastern and western GOA. Fish were collected from shallow nearshore areas within five large embayments in summer and fall, and element:calcium ratios were measured from two different time stanzas within the otolith. Elemental ratios were found to change over short (2 month) time periods and were related to seasonal changes in temperature and salinity. Fish were classified to nursery habitats using quadratic discriminant analysis based on their otolith elemental signatures; classification accuracy to individual bays ranged from 30% to 95%, with an overall success rate of 59%. Classification accuracy improved to 78% at greater spatial scales (eastern versus western GOA). Our results point out the limitations of this application to Gulf of Alaska Pacific Cod and other widely distributed species residing in coastal embayments. While some nursery habitats impart unique chemical signatures to otoliths, it may not be possible to distinguish among specific areas without considering additional factors. However, our work demonstrates that otolith microchemistry may be a useful tool for understanding source contributions to the Pacific Cod population at larger regional scales within the GOA.

  • spawning phenology and geography of aleutian islands and eastern bering sea Pacific Cod gadus macrocephalus
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2014
    Co-Authors: Sandra K Neidetcher, Thomas P Hurst, Lorenzo Ciannelli, Elizabeth A Logerwell
    Abstract:

    Pacific Cod (Gadus macrocephalus) is an economically and ecologically important species in the south- eastern Bering Sea and Aleutian Islands, yet little is known about the spawning dynamics of Pacific Cod in these regions. To address this knowledge gap, we applied a gross anatomical maturity key for Pacific Cod to describe temporal and spatial patterns of reproductive status over three winter spawning seasons: 2005, 2006, and 2007. Maturity status of female Pacific Cod was assessed by fishery observers during sampling of commercial catches and used to construct maps showing spawning activity in the Bering Sea and Aleutian Islands. Most spawning activity was observed on the Bering Sea shelf and Aleutian Island plateaus between 100 and 200 m depth. Data for those days when a high percentage of spawning stage fish were observed were used to identify areas with concentrations of spawning fish. Spawning concentrations were identified north of Unimak Island, in the vicinity of the Pribilof Islands, at the shelf break near Zhemchug Canyon, and adjacent to islands in the central and western Aleutian Islands along the continental shelf. The spawning season was found to begin in the last days of February or early March and extend through early to mid-April. Variation in spawning time (averaging � 10 days between years) may have been associated with a change from warm (2005) to cold (2007) climate conditions during the study period. Our information on Pacific Cod spawning patterns will help inform fishery management decisions, models of spawning and larval dispersal and the spatial structure of the stock. Published by Elsevier Ltd.

Benjamin J Laurel - One of the best experts on this subject based on the ideXlab platform.

  • Loss of spawning habitat and prerecruits of Pacific Cod during a Gulf of Alaska heatwave
    Canadian Journal of Fisheries and Aquatic Sciences, 2020
    Co-Authors: Benjamin J Laurel, Lauren A. Rogers
    Abstract:

    Pacific Cod (Gadus macrocephalus) stocks in the Gulf of Alaska experienced steep, unexpected declines following an unprecedented 3-year marine heatwave (i.e., “warm blob”) from 2014 to 2016. We con...

  • connectivity between spawning and nursery areas for Pacific Cod gadus macrocephalus in the gulf of alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2018
    Co-Authors: Sarah Hinckley, Benjamin J Laurel, William T Stockhausen, Kenneth O Coyle, Georgina A Gibson, Carolina Parada, Albert J Hermann, Miriam J Doyle, Thomas P Hurst
    Abstract:

    Abstract We present the results of a study of the connectivity between Pacific Cod spawning and nursery areas, and settlement of Pacific Cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this hypothesis, we developed a Lagrangian, biophysical, individual-based model of Pacific Cod early life history and dispersal using the Dispersal Model for Early Life Stages (DisMELS) framework. This model is driven by currents and scalars such as temperature from a version of the Regional Oceanographic Model System (ROMS) developed for the Gulf of Alaska. Results of our study show connectivity patterns predicted by the model that agree with our understanding (based on genetic analyses) that there is a high degree of localized retention in Pacific Cod. The results indicate that the Shumagin Islands and Prince William Sound regions may serve as important collectors of Pacific Cod recruits from upstream spawning areas. We also find correlations between individual-based model outputs and several large-scale climate indicators that appear to show settlement in several important nursery areas, and recruitment overall, are positively affected by slower gyre circulation in the Gulf of Alaska. We hypothesize that this is due to enhancement of retention, settlement in the Shumagin Island region, and reduction of transport of young Cod out of the Gulf of Alaska to the southwest.

  • WITHDRAWN: Connectivity between spawning and nursery areas for Pacific Cod (Gadus macrocephalus) in the Gulf of Alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2018
    Co-Authors: Sarah Hinckley, Benjamin J Laurel, Thomas P Hurst, William T Stockhausen, Kenneth O Coyle, Georgina A Gibson, Carolina Parada, Albert J Hermann, Miriam J Doyle, André E. Punt
    Abstract:

    Abstract We present the results of a study of the connectivity between Pacific Cod spawning and nursery areas, and settlement of Pacific Cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this hypothesis, we developed a Lagrangian, biophysical, individual-based model of Pacific Cod early life history and dispersal using the Dispersal Model for Early Life Stages (DisMELS) framework. This model is driven by currents and scalars such as temperature from a version of the Regional Oceanographic Model System (ROMS) developed for the Gulf of Alaska. Results of our study show connectivity patterns predicted by the model that agree with our understanding (based on genetic analyses) that there is a high degree of localized retention in Pacific Cod. The results indicate that the Shumagin Islands and Prince William Sound regions may serve as important collectors of Pacific Cod recruits from upstream spawning areas. We also find correlations between individual-based model outputs and several large-scale climate indicators that appear to show settlement in several important nursery areas, and recruitment overall, are positively affected by slower gyre circulation in the Gulf of Alaska. We hypothesize that this is due to enhancement of retention, settlement in the Shumagin Island region, and reduction of transport of young Cod out of the Gulf of Alaska to the southwest.

  • role of temperature on lipid fatty acid composition in Pacific Cod gadus macrocephalus eggs and unfed larvae
    Marine Biology, 2012
    Co-Authors: Benjamin J Laurel, Louise A Copeman, Christopher C Parrish
    Abstract:

    During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific Cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific Cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures <8 °C was consistent with homeoviscous adaptation theory. However, with the possible exception of embryos at 0 °C, the relative amounts of essential fatty acids (e.g., EPA, DHA, AA) were conserved in a similar manner across incubation temperatures. Collectively, these data suggest Pacific Cod are capable of homeoviscous adaptation but cannot tolerate temperatures approaching 0 °C despite their possible ability to biosynthesize PUFAs from other energetic sources.

  • Role of temperature on lipid/fatty acid composition in Pacific Cod (Gadus macrocephalus) eggs and unfed larvae
    Marine Biology, 2012
    Co-Authors: Benjamin J Laurel, Louise A Copeman, Christopher C Parrish
    Abstract:

    During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific Cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific Cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures

Daniel G Nichol - One of the best experts on this subject based on the ideXlab platform.

  • age validation of Pacific Cod gadus macrocephalus using high resolution stable oxygen isotope δ 18o chronologies in otoliths
    Fisheries Research, 2017
    Co-Authors: Craig R. Kastelle, Thomas E. Helser, Jennifer L. Mckay, Chris G. Johnston, Delsa M. Anderl, Mary Elizabeth Matta, Daniel G Nichol
    Abstract:

    The Pacific Cod (Gadus macrocephalus) fishery in Alaska is large and economically important; in 2014 its ex-vessel value was $203.8 million. Management relies on integrated assessments that employ survey abundance trends and fishery catches as well as age compositions from assessment surveys. However, Pacific Cod age determination based on otolith growth zone counts has historically been difficult, adding to the uncertainty in biological reference points. Further, a mismatch exists where modes in fish length frequencies are larger than mean lengths at otolith-based age. To address ageing inaccuracy, we conducted an age validation study using stable oxygen isotopes (δ18O). This approach is based upon the principle that variability in marine carbonate δ18O is inversely related to water temperature, which we independently verified in Pacific Cod otoliths (r2 = 0.74). We sequentially microsampled 40 Pacific Cod otoliths from the core to the margin and measured the aragonite δ18O by isotope ratio mass spectrometry. This provided a detailed δ18O life history chronology for each specimen. First, we identified seasonal variation (the cyclical pattern of otolith δ18O values) and determined whether the number of δ18O maxima, considered to represent “true fish age,” was consistent with the age estimated from growth zone counts. Second, we estimated the probability of bias in the ages determined from growth zone counts. Overall, the probability of assigning an age (based on the number of counted growth zones) equal to the true age (number of δ18O maxima) was approximately 61%. However, the probabilities of over- or underestimating the age by 1 year were 25% and 13%, respectively. The probability of over- or underestimating true age by 2 or more years was very low (<2%). The probability of age misclassification was used to correct bias in mean length at age.

  • Age validation of Pacific Cod (Gadus macrocephalus) using high-resolution stable oxygen isotope (δ 18O) chronologies in otoliths
    Fisheries Research, 2016
    Co-Authors: Craig R. Kastelle, Thomas E. Helser, Jennifer L. Mckay, Chris G. Johnston, Delsa M. Anderl, Mary Elizabeth Matta, Daniel G Nichol
    Abstract:

    The Pacific Cod (Gadus macrocephalus) fishery in Alaska is large and economically important; in 2014 its ex-vessel value was $203.8 million. Management relies on integrated assessments that employ survey abundance trends and fishery catches as well as age compositions from assessment surveys. However, Pacific Cod age determination based on otolith growth zone counts has historically been difficult, adding to the uncertainty in biological reference points. Further, a mismatch exists where modes in fish length frequencies are larger than mean lengths at otolith-based age. To address ageing inaccuracy, we conducted an age validation study using stable oxygen isotopes (δ18O). This approach is based upon the principle that variability in marine carbonate δ18O is inversely related to water temperature, which we independently verified in Pacific Cod otoliths (r2 = 0.74). We sequentially microsampled 40 Pacific Cod otoliths from the core to the margin and measured the aragonite δ18O by isotope ratio mass spectrometry. This provided a detailed δ18O life history chronology for each specimen. First, we identified seasonal variation (the cyclical pattern of otolith δ18O values) and determined whether the number of δ18O maxima, considered to represent “true fish age,” was consistent with the age estimated from growth zone counts. Second, we estimated the probability of bias in the ages determined from growth zone counts. Overall, the probability of assigning an age (based on the number of counted growth zones) equal to the true age (number of δ18O maxima) was approximately 61%. However, the probabilities of over- or underestimating the age by 1 year were 25% and 13%, respectively. The probability of over- or underestimating true age by 2 or more years was very low (

  • observations of seasonal movement from a single tag release group of Pacific Cod in the eastern bering sea
    Marine and Coastal Fisheries: Dynamics Management and Ecosystem Science, 2014
    Co-Authors: Kimberly M Rand, Peter Munro, Sandra K Neidetcher, Daniel G Nichol
    Abstract:

    AbstractThe Pacific Cod Gadus macrocephalus in the eastern Bering Sea is the target of one of the most lucrative fisheries in Alaska; however, relatively little is known about the movement of Pacific Cod and how this interacts with intense fishing on local spawning aggregations of Cod every spring (January–April). This study aimed to draw inferences on Pacific Cod movement using a single tag release group of fish and the fishery as a representative for movement by qualitatively examining both temporal and spatial patterns of tag recoveries. Based on the tag recoveries in this study and past genetic studies, there is evidence that Pacific Cod show both homing tendencies and site fidelity during the spring when large aggregations of Cod form to spawn. This study also supports results from an earlier study on Pacific Cod movement in this region and presents new insights into Cod movement patterns. The Cod in this tag release group were widely distributed across the Bering Sea during the summer and fall month...

  • proximity of Pacific Cod to the sea floor using archival tags to estimate fish availability to research bottom trawls
    Fisheries Research, 2007
    Co-Authors: Daniel G Nichol, Taina Honkalehto, Grant G. Thompson
    Abstract:

    Abstract The percentage of Pacific Cod available to Alaskan bottom trawl surveys was estimated from the proximity of tagged Cod to the seafloor. Archival tags recorded time and depth data at 15- or 30-min intervals. The distance of a Cod above the bottom was computed by subtracting tag depth from bottom depth, estimated as the maximum depth recorded during each 24-h day. These estimates of bottom depth are based on the assumption that Cod approach the seafloor at least once a day, and do not undergo migrations up or down bottom gradients. To ensure that migrations over variable bottom gradients did not confound our estimates of bottom depth, we narrowed our analysis to 11 tagged Cod that were recaptured in areas of flat bathymetry, and only analyzed data recorded within one month prior to recapture (N = 29,462 depth recordings). Pacific Cod maintained short distances above the seafloor that often differed between day and night. Over 95% of the daytime tag recordings occurred within 10 m of the seafloor. Average effective headrope heights for survey bottom trawls currently used in the eastern Bering Sea and Alaska Gulf/Aleutian Islands groundfish surveys are approximately 2.5 and 7 m, respectively. In the absence of any behavior responses to an approaching trawl, we would expect 47.3% of the Cod within the water column are available to the trawl used on the eastern Bering Sea survey and 91.6% are available to the trawl used on the Gulf/Aleutian Islands surveys. This study demonstrated that Pacific Cod are highly demersal, and current values of trawl survey catchability (Q) used in current stock assessments are consistent with estimates of Cod availability to the trawl gear.

Thomas E. Helser - One of the best experts on this subject based on the ideXlab platform.

  • spatial and temporal variation in otolith elemental signatures of age 0 Pacific Cod gadus macrocephalus in the gulf of alaska
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2017
    Co-Authors: Mary Elizabeth Matta, Kimberly M Rand, Thomas P Hurst, Thomas E. Helser, Jessica A Miller, Jonathan A Short, Olav Aleksander Ormseth
    Abstract:

    Abstract Shallow coastal waters of the Gulf of Alaska (GOA) serve as nursery habitats for young-of-year Pacific Cod ( Gadus macrocephalus ). However, little is known regarding the relative contribution of these areas to the adult offshore stock. Trace elements incorporated into the otolith matrix can reflect the environmental conditions to which a fish has been exposed during its lifetime. When analyzed together, a suite of elements can serve as a natural marker, characteristic of a particular environment. We evaluated the potential of otolith elemental signatures to identify nursery habitats of age-0 Pacific Cod, focusing on spatial patterns within and across the eastern and western GOA. Fish were collected from shallow nearshore areas within five large embayments in summer and fall, and element:calcium ratios were measured from two different time stanzas within the otolith. Elemental ratios were found to change over short (2 month) time periods and were related to seasonal changes in temperature and salinity. Fish were classified to nursery habitats using quadratic discriminant analysis based on their otolith elemental signatures; classification accuracy to individual bays ranged from 30% to 95%, with an overall success rate of 59%. Classification accuracy improved to 78% at greater spatial scales (eastern versus western GOA). Our results point out the limitations of this application to Gulf of Alaska Pacific Cod and other widely distributed species residing in coastal embayments. While some nursery habitats impart unique chemical signatures to otoliths, it may not be possible to distinguish among specific areas without considering additional factors. However, our work demonstrates that otolith microchemistry may be a useful tool for understanding source contributions to the Pacific Cod population at larger regional scales within the GOA.

  • a 200 year archaeozoological record of Pacific Cod gadus macrocephalus life history as revealed through ion microprobe oxygen isotope ratios in otoliths
    Journal of Archaeological Science: Reports, 2017
    Co-Authors: Thomas E. Helser, Craig R. Kastelle, Aron L Crowell, Takayuki Ushikubo, Ian J Orland, Reinhard Kozdon, John W Valley
    Abstract:

    Abstract We measured δ18O values in modern and archaeological Pacific Cod (Gadus macrocephalus) otoliths recovered from Aialik Bay on the Pacific coast of the Kenai Peninsula, Alaska, using a high precision ion microprobe. Values of δ18O were measured in as many as sixty 10-μm spots along 2–3 mm transects from the otolith core to its margin with high spot-to-spot analytical precision (δ18O ± 0.3‰). We obtained sample densities along a linear transect that were at least 2 to 3 times greater than micromilling/conventional mass spectrometry techniques. From modern Pacific Cod otoliths (using in situ temperatures from electronic archive tags) we calibrated an empirical fractionation equation of aragonite δ18O to sea water temperature (r2 = 0.75, p

  • age validation of Pacific Cod gadus macrocephalus using high resolution stable oxygen isotope δ 18o chronologies in otoliths
    Fisheries Research, 2017
    Co-Authors: Craig R. Kastelle, Thomas E. Helser, Jennifer L. Mckay, Chris G. Johnston, Delsa M. Anderl, Mary Elizabeth Matta, Daniel G Nichol
    Abstract:

    The Pacific Cod (Gadus macrocephalus) fishery in Alaska is large and economically important; in 2014 its ex-vessel value was $203.8 million. Management relies on integrated assessments that employ survey abundance trends and fishery catches as well as age compositions from assessment surveys. However, Pacific Cod age determination based on otolith growth zone counts has historically been difficult, adding to the uncertainty in biological reference points. Further, a mismatch exists where modes in fish length frequencies are larger than mean lengths at otolith-based age. To address ageing inaccuracy, we conducted an age validation study using stable oxygen isotopes (δ18O). This approach is based upon the principle that variability in marine carbonate δ18O is inversely related to water temperature, which we independently verified in Pacific Cod otoliths (r2 = 0.74). We sequentially microsampled 40 Pacific Cod otoliths from the core to the margin and measured the aragonite δ18O by isotope ratio mass spectrometry. This provided a detailed δ18O life history chronology for each specimen. First, we identified seasonal variation (the cyclical pattern of otolith δ18O values) and determined whether the number of δ18O maxima, considered to represent “true fish age,” was consistent with the age estimated from growth zone counts. Second, we estimated the probability of bias in the ages determined from growth zone counts. Overall, the probability of assigning an age (based on the number of counted growth zones) equal to the true age (number of δ18O maxima) was approximately 61%. However, the probabilities of over- or underestimating the age by 1 year were 25% and 13%, respectively. The probability of over- or underestimating true age by 2 or more years was very low (<2%). The probability of age misclassification was used to correct bias in mean length at age.

  • Age validation of Pacific Cod (Gadus macrocephalus) using high-resolution stable oxygen isotope (δ 18O) chronologies in otoliths
    Fisheries Research, 2016
    Co-Authors: Craig R. Kastelle, Thomas E. Helser, Jennifer L. Mckay, Chris G. Johnston, Delsa M. Anderl, Mary Elizabeth Matta, Daniel G Nichol
    Abstract:

    The Pacific Cod (Gadus macrocephalus) fishery in Alaska is large and economically important; in 2014 its ex-vessel value was $203.8 million. Management relies on integrated assessments that employ survey abundance trends and fishery catches as well as age compositions from assessment surveys. However, Pacific Cod age determination based on otolith growth zone counts has historically been difficult, adding to the uncertainty in biological reference points. Further, a mismatch exists where modes in fish length frequencies are larger than mean lengths at otolith-based age. To address ageing inaccuracy, we conducted an age validation study using stable oxygen isotopes (δ18O). This approach is based upon the principle that variability in marine carbonate δ18O is inversely related to water temperature, which we independently verified in Pacific Cod otoliths (r2 = 0.74). We sequentially microsampled 40 Pacific Cod otoliths from the core to the margin and measured the aragonite δ18O by isotope ratio mass spectrometry. This provided a detailed δ18O life history chronology for each specimen. First, we identified seasonal variation (the cyclical pattern of otolith δ18O values) and determined whether the number of δ18O maxima, considered to represent “true fish age,” was consistent with the age estimated from growth zone counts. Second, we estimated the probability of bias in the ages determined from growth zone counts. Overall, the probability of assigning an age (based on the number of counted growth zones) equal to the true age (number of δ18O maxima) was approximately 61%. However, the probabilities of over- or underestimating the age by 1 year were 25% and 13%, respectively. The probability of over- or underestimating true age by 2 or more years was very low (

Louise A Copeman - One of the best experts on this subject based on the ideXlab platform.

  • elevated co2 alters behavior growth and lipid composition of Pacific Cod larvae
    Marine Environmental Research, 2019
    Co-Authors: Thomas P Hurst, Louise A Copeman, Scott A Haines, Summer D Meredith, Kamilya Daniels, Kalyn M Hubbard
    Abstract:

    Abstract High-latitude seas, which support a number of commercially important fisheries, are predicted to be most immediately impacted by ongoing ocean acidification (OA). Elevated CO2 levels have been shown to induce a range of impacts on the physiology and behavior of marine fish larvae. However, these responses have yet to be characterized for most fishery species, including Pacific Cod (Gadus macrocephalus). Based on laboratory experiments, we present a multi-faceted analysis of the sensitivity of Pacific Cod larvae to elevated CO2. Fish behavior in a horizontal light gradient was used to evaluate the sensitivity of behavioral phototaxis in 4–5 week old Cod larvae. Fish at elevated CO2 levels (∼1500 and 2250 μatm) exhibited a stronger phototaxis (moved more quickly to regions of higher light levels) than fish at ambient CO2 levels (∼600 μatm). In an independent experiment, we examined the effects of elevated CO2 levels on growth of larval Pacific Cod over the first 5 weeks of life under two different feeding treatments. Fish exposed to elevated CO2 levels (∼1700 μatm) were smaller and had lower lipid levels at 2 weeks of age than fish at low (ambient) CO2 levels (∼500 μatm). However, by 5 weeks of age, this effect had reversed: fish reared at elevated CO2 levels were slightly (but not significantly) larger and had higher total lipid levels and storage lipids than fish reared at low CO2. Fatty acid composition differed significantly between fish reared at high and low CO2 levels (p

  • role of temperature on lipid fatty acid composition in Pacific Cod gadus macrocephalus eggs and unfed larvae
    Marine Biology, 2012
    Co-Authors: Benjamin J Laurel, Louise A Copeman, Christopher C Parrish
    Abstract:

    During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific Cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific Cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures <8 °C was consistent with homeoviscous adaptation theory. However, with the possible exception of embryos at 0 °C, the relative amounts of essential fatty acids (e.g., EPA, DHA, AA) were conserved in a similar manner across incubation temperatures. Collectively, these data suggest Pacific Cod are capable of homeoviscous adaptation but cannot tolerate temperatures approaching 0 °C despite their possible ability to biosynthesize PUFAs from other energetic sources.

  • Role of temperature on lipid/fatty acid composition in Pacific Cod (Gadus macrocephalus) eggs and unfed larvae
    Marine Biology, 2012
    Co-Authors: Benjamin J Laurel, Louise A Copeman, Christopher C Parrish
    Abstract:

    During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific Cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific Cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures

  • experimental evidence of fatty acid limited growth and survival in Pacific Cod larvae
    Marine Ecology Progress Series, 2010
    Co-Authors: Louise A Copeman, Benjamin J Laurel
    Abstract:

    Changing environmental conditions in the North Pacific are altering the lipid/fatty acid (FA) composition of zooplankton assemblages, but the consequences to resident fish larvae are unknown. In the laboratory, we reared Pacific Cod Gadus macrocephalus larvae over 4 wk on prey enriched with varying levels of 2 essential FAs (docosahexaenoic acid, DHA, 22:6ω-3, and eicosapen- tanoic acid, EPA, 20:5ω-3) to determine how this species responded to such changes in prey quality. Ratios of DHA:EPA were chosen to represent the natural variation observed in zooplankton of the North Pacific. We tested the hypotheses whether (1) energetically similar diets comprised of varying levels of DHA and EPA affect growth and survival in Pacific Cod larvae, and (2) the highest levels of DHA:EPA (2:1) are optimal for Pacific Cod larvae, as it has been shown for Atlantic species. Pacific Cod larvae grew fastest with diets containing high levels of ω-3 polyunsaturated fatty acids (PUFA > 22%). Diets with the same total lipid content but different DHA:EPA ratios (<0.1:1 to 2:1) also medi- ated growth and lipid composition of the larvae. Unlike Atlantic Cod, Pacific Cod larvae did not show as high a requirement for DHA relative to EPA but rather achieved largest size-at-age with interme- diate DHA:EPA ratios (0.8:1 to 1.1:1). This range most closely resembled DHA:EPA ratios reported from North Pacific copepods, suggesting anomalous years with an over- or under-abundance of DHA-rich dinoflagellates or EPA-rich diatoms may be detrimental to survival and growth of Pacific Cod larvae in the field.

  • Experimental evidence of fatty acid limited growth and survival in Pacific Cod larvae
    Marine Ecology Progress Series, 2010
    Co-Authors: Louise A Copeman, Benjamin J Laurel
    Abstract:

    Changing environmental conditions in the North Pacific are altering the lipid/fatty acid (FA) composition of zooplankton assemblages, but the consequences to resident fish larvae are unknown. In the laboratory, we reared Pacific Cod Gadus macrocephalus larvae over 4 wk on prey enriched with varying levels of 2 essential FAs (docosahexaenoic acid, DHA, 22:6ω-3, and eicosapen- tanoic acid, EPA, 20:5ω-3) to determine how this species responded to such changes in prey quality. Ratios of DHA:EPA were chosen to represent the natural variation observed in zooplankton of the North Pacific. We tested the hypotheses whether (1) energetically similar diets comprised of varying levels of DHA and EPA affect growth and survival in Pacific Cod larvae, and (2) the highest levels of DHA:EPA (2:1) are optimal for Pacific Cod larvae, as it has been shown for Atlantic species. Pacific Cod larvae grew fastest with diets containing high levels of ω-3 polyunsaturated fatty acids (PUFA > 22%). Diets with the same total lipid content but different DHA:EPA ratios (