Accurately delineating the spatial extent of fish stocks and the degree to which stocks mix is important for understanding the effects of fisheries management and environmental change. This paper describes migratory behaviors of Atlantic halibut (Hippoglossus hippoglossus L.) tagged with conventional wire tags in the U.S. portion of the Gulf of Maine between 2000 and 2017. There were 412 recaptures reported out of 2 573 releases, a return rate of 16.0%. These returns illustrate that although most fish are recaptured close to the release point with a median distance at recapture of 38 km, Gulf of Maine Atlantic halibut also engage in dispersive behavior with some fish travelling at least 1 564 km. Returns from Canadian waters accounted for 43.2% of total recaptures. A generalized linear model found greater distances at recapture related to greater days at liberty and during winter. Fish size explained a negligible proportion (<1%) of the variability in recapture distance. Most (76%) recaptures were from waters of the Gulf of Maine and the Western Scotian Shelf off Canada, suggesting a higher level of mixing within this transnational boundary area than to elsewhere. This contrasts common assumptions about stock structure made for assessment and management purposes.
{"title":"Diverse migratory behaviors of Atlantic halibut (Hippoglossus hippoglossus, L.) based on the 2000–2017 Maine halibut tagging program","authors":"M. Kersula, A. Seitz","doi":"10.2960/J.V50.M719","DOIUrl":"https://doi.org/10.2960/J.V50.M719","url":null,"abstract":"Accurately delineating the spatial extent of fish stocks and the degree to which stocks mix is important for understanding the effects of fisheries management and environmental change. This paper describes migratory behaviors of Atlantic halibut (Hippoglossus hippoglossus L.) tagged with conventional wire tags in the U.S. portion of the Gulf of Maine between 2000 and 2017. There were 412 recaptures reported out of 2 573 releases, a return rate of 16.0%. These returns illustrate that although most fish are recaptured close to the release point with a median distance at recapture of 38 km, Gulf of Maine Atlantic halibut also engage in dispersive behavior with some fish travelling at least 1 564 km. Returns from Canadian waters accounted for 43.2% of total recaptures. A generalized linear model found greater distances at recapture related to greater days at liberty and during winter. Fish size explained a negligible proportion (<1%) of the variability in recapture distance. Most (76%) recaptures were from waters of the Gulf of Maine and the Western Scotian Shelf off Canada, suggesting a higher level of mixing within this transnational boundary area than to elsewhere. This contrasts common assumptions about stock structure made for assessment and management purposes.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47313007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Atlantic chub mackerel (Scomber colias) stock is commercially exploited throughout the Atlantic and Mediterranean and has been recently targeted by a small, but emerging, fishery off the Northeast coast of the United States. Recent efforts by the Mid-Atlantic Fishery Management Council to manage the Northwest Atlantic stock have necessitated the description of its life-history characteristics. The objectives of this study were to evaluate the utility of ageing methods, describe the length-at-age and weight-at-length relationships, and compare estimated growth parameter values to those reported from other regions. We found that whole otoliths provided the most precise method for age determination of Atlantic chub mackerel. Age estimates were derived for adult (n = 422) and larval fish (n = 60). Parameter estimates of individual growth models were determined using a Bayesian framework. The length-at-age relationship was described using four non-linear candidate growth models, which were fit to total length (TL, cm) and age estimates (y). We found that the three-parameter VBGF (L∞ = 33.56 cm TL, k = 1.75 y-1, t0 = 0.07 y) was the best candidate model to describe the length-atage relationship. A power function was used to describe the weight-at-length relationship from 1 136 individuals (a = 0.0258, b = 2.72). We found that individuals exhibit a greater rate of growth and reach smaller average maximum length when compared to published estimates in other regions. The rate of increase of weight relative to length was found to be significantly lower than that reported in other regions. These results can be used to inform assessment of the Atlantic chub mackerel stock in the Northwest Atlantic.
{"title":"Age and growth of Atlantic chub mackerel (Scomber colias) in the Northwest Atlantic.","authors":"T. Daley, R. Leaf","doi":"10.2960/j.v50.m717","DOIUrl":"https://doi.org/10.2960/j.v50.m717","url":null,"abstract":"The Atlantic chub mackerel (Scomber colias) stock is commercially exploited throughout the Atlantic and Mediterranean and has been recently targeted by a small, but emerging, fishery off the Northeast coast of the United States. Recent efforts by the Mid-Atlantic Fishery Management Council to manage the Northwest Atlantic stock have necessitated the description of its life-history characteristics. The objectives of this study were to evaluate the utility of ageing methods, describe the length-at-age and weight-at-length relationships, and compare estimated growth parameter values to those reported from other regions. We found that whole otoliths provided the most precise method for age determination of Atlantic chub mackerel. Age estimates were derived for adult (n = 422) and larval fish (n = 60). Parameter estimates of individual growth models were determined using a Bayesian framework. The length-at-age relationship was described using four non-linear candidate growth models, which were fit to total length (TL, cm) and age estimates (y). We found that the three-parameter VBGF (L∞ = 33.56 cm TL, k = 1.75 y-1, t0 = 0.07 y) was the best candidate model to describe the length-atage relationship. A power function was used to describe the weight-at-length relationship from 1 136 individuals (a = 0.0258, b = 2.72). We found that individuals exhibit a greater rate of growth and reach smaller average maximum length when compared to published estimates in other regions. The rate of increase of weight relative to length was found to be significantly lower than that reported in other regions. These results can be used to inform assessment of the Atlantic chub mackerel stock in the Northwest Atlantic.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45550406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Larsen, B. Herrmann, M. Sistiaga, E. Grimaldo, Jesse Brinkhof, Ivan Tatone
Greenland halibut (Reinhardtius hippoglossoides) is a commercially important species in the northeast Atlantic trawl fishery. However, direct fishing for it is not allowed and it can only be harvested as bycatch. We investigated for the first time the size selection of Greenland halibut in a newly developed double steel grid system designed for the cod and haddock bottom trawl fishery. In this sorting system the first grid (lower grid) replaced the lifting panel present in the traditional Sort-V single grid system often applied in the fishery. Thus, it contributed to the fish sorting process and simultaneously guided fish to the second grid (upper grid). However, the results showed that nearly all Greenland halibut escapees left through the second grid. The release efficiency of the first grid was estimated to be low, and only 11% of the Greenland halibut entering the grid zone made contact with this grid in a way that provided a size-dependent release probability. In contrast, the estimations showed that all Greenland halibut, still in the gear after the first grid, made contact with the second grid. However, this contact was suboptimal for size selection of most individuals, as the estimated 50% retention length (based on the morphology of Greenland halibut) was below the expected value. Comparison of the release efficiency of the new double grid system relative to that of the grid systems used in the fishery today revealed that the new system did not improve the release of undersized Greenland halibut. Moreover, we found that the existing Sort-V single grid system released significantly more Greenland halibut than the new double grid system.
{"title":"Size selection of Greenland halibut (Reinhardtius hippoglossoides) in the Norwegian bottom trawl fishery with a newly developed double grid system","authors":"R. Larsen, B. Herrmann, M. Sistiaga, E. Grimaldo, Jesse Brinkhof, Ivan Tatone","doi":"10.2960/J.v49.m715","DOIUrl":"https://doi.org/10.2960/J.v49.m715","url":null,"abstract":"Greenland halibut (Reinhardtius hippoglossoides) is a commercially important species in the northeast Atlantic trawl fishery. However, direct fishing for it is not allowed and it can only be harvested as bycatch. We investigated for the first time the size selection of Greenland halibut in a newly developed double steel grid system designed for the cod and haddock bottom trawl fishery. In this sorting system the first grid (lower grid) replaced the lifting panel present in the traditional Sort-V single grid system often applied in the fishery. Thus, it contributed to the fish sorting process and simultaneously guided fish to the second grid (upper grid). However, the results showed that nearly all Greenland halibut escapees left through the second grid. The release efficiency of the first grid was estimated to be low, and only 11% of the Greenland halibut entering the grid zone made contact with this grid in a way that provided a size-dependent release probability. In contrast, the estimations showed that all Greenland halibut, still in the gear after the first grid, made contact with the second grid. However, this contact was suboptimal for size selection of most individuals, as the estimated 50% retention length (based on the morphology of Greenland halibut) was below the expected value. Comparison of the release efficiency of the new double grid system relative to that of the grid systems used in the fishery today revealed that the new system did not improve the release of undersized Greenland halibut. Moreover, we found that the existing Sort-V single grid system released significantly more Greenland halibut than the new double grid system.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49303634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Winton, C. Huntsberger, D. Rudders, G. DeCelles, K. Thompson, K. Goetting, R. Smolowitz
Bycatch is a constraint to the Atlantic sea scallop fishery, the most valuable single-species fishery along the eastern coast of the United States. To characterize trends in the bycatch of three flatfish species, a fishery-independent scallop dredge survey was conducted in two sea scallop access areas (Closed Areas I and II) on Georges Bank from 2011 to 2014. Generalized additive mixed models were used to identify seasonal bycatch hotspots of yellowtail, winter, and windowpane flounder. In all cases, spatially explicit models best fit the data (deviance explained: 47–73%) and provided insight into the spatial distribution underlying the seasonal trends in each area. Modeled catch rates for the three flatfish species suggested localized catches at discrete times of the year. Catches of yellowtail and windowpane flounder were highest in Closed Area II in the fall and winter, respectively. Winter flounder were caught in the highest numbers in Closed Area I during the summer and fall, and were largely absent from catches in Closed Area II. Our results suggest consistent seasonal trends that may help managers identify the optimal times to open the access areas to the scallop fleet in order to reduce flatfish bycatch.
{"title":"Spatiotemporal patterns of flatfish bycatch in two scallop access areas on Georges Bank","authors":"M. Winton, C. Huntsberger, D. Rudders, G. DeCelles, K. Thompson, K. Goetting, R. Smolowitz","doi":"10.2960/J.V49.M710","DOIUrl":"https://doi.org/10.2960/J.V49.M710","url":null,"abstract":"Bycatch is a constraint to the Atlantic sea scallop fishery, the most valuable single-species fishery along the eastern coast of the United States. To characterize trends in the bycatch of three flatfish species, a fishery-independent scallop dredge survey was conducted in two sea scallop access areas (Closed Areas I and II) on Georges Bank from 2011 to 2014. Generalized additive mixed models were used to identify seasonal bycatch hotspots of yellowtail, winter, and windowpane flounder. In all cases, spatially explicit models best fit the data (deviance explained: 47–73%) and provided insight into the spatial distribution underlying the seasonal trends in each area. Modeled catch rates for the three flatfish species suggested localized catches at discrete times of the year. Catches of yellowtail and windowpane flounder were highest in Closed Area II in the fall and winter, respectively. Winter flounder were caught in the highest numbers in Closed Area I during the summer and fall, and were largely absent from catches in Closed Area II. Our results suggest consistent seasonal trends that may help managers identify the optimal times to open the access areas to the scallop fleet in order to reduce flatfish bycatch.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45123257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Canada’s Department of Fisheries and Oceans (DFO) Sustainable Fisheries Framework and the associated Decision Making Framework Incorporating the Precautionary Approach policies (DMF), implemented in 2009, provide a context with potential to improve fisheries management. A Provisional Harvest Control Rule (PHCR) is proposed in the DMF to allow adjustments of the annual total allowable catch based on a scientific assessment of the state of the stock. The DMF defines three spawning stock biomass Zones (Critical, Cautious and Healthy). The PHCR adjusts fishing mortality dependent on the Zone within which the spawning stock biomass is estimated to fall. Elements of the PHCR have been incorporated in the scientific advice and management approaches for a number of Canadian fish stocks. In this study, initial evaluation of the PHCR was carried out on three simulated depleted fish populations with different life histories under a variety of combinations of process error on recruitment and measurement error on spawning stock biomass. The simulations represent “bestcase” scenarios because reference points were assumed to be known exactly and the magnitude of the errors was moderate. The simulation results suggested that fish stocks in the Critical Zone should rebuild to the Healthy Zone under the PHCR with high probability (>0.78) irrespective of life history differences and the combinations of process and observations errors. However, the time to rebuild was up to twice as long as it took in the absence of fishing and the PHCR was not effective in ensuring the DMF requirement of a low probability (<0.1) of the population returning to the Cautious Zone. The PHCR was also not effective in keeping fishing mortality below the level that generates maximum sustainable yield when the stock was in the Cautious Zone and subject to measurement error. Variation in the annual catch generated by the PHCR in the simulations increased with increasing process and observation errors to a maximum CV of 0.6, which may be inconsistent with the fishing industry’s desire for low variation in annual catch.
{"title":"Initial tests of the robustness of the provisional harvest control rule in Canada’s Sustainable Fisheries Policy to process and measurement errors using simulated depleted fish populations","authors":"P. Shelton","doi":"10.2960/j.v49.m707","DOIUrl":"https://doi.org/10.2960/j.v49.m707","url":null,"abstract":"Canada’s Department of Fisheries and Oceans (DFO) Sustainable Fisheries Framework and the associated Decision Making Framework Incorporating the Precautionary Approach policies (DMF), implemented in 2009, provide a context with potential to improve fisheries management. A Provisional Harvest Control Rule (PHCR) is proposed in the DMF to allow adjustments of the annual total allowable catch based on a scientific assessment of the state of the stock. The DMF defines three spawning stock biomass Zones (Critical, Cautious and Healthy). The PHCR adjusts fishing mortality dependent on the Zone within which the spawning stock biomass is estimated to fall. Elements of the PHCR have been incorporated in the scientific advice and management approaches for a number of Canadian fish stocks. In this study, initial evaluation of the PHCR was carried out on three simulated depleted fish populations with different life histories under a variety of combinations of process error on recruitment and measurement error on spawning stock biomass. The simulations represent “bestcase” scenarios because reference points were assumed to be known exactly and the magnitude of the errors was moderate. The simulation results suggested that fish stocks in the Critical Zone should rebuild to the Healthy Zone under the PHCR with high probability (>0.78) irrespective of life history differences and the combinations of process and observations errors. However, the time to rebuild was up to twice as long as it took in the absence of fishing and the PHCR was not effective in ensuring the DMF requirement of a low probability (<0.1) of the population returning to the Cautious Zone. The PHCR was also not effective in keeping fishing mortality below the level that generates maximum sustainable yield when the stock was in the Cautious Zone and subject to measurement error. Variation in the annual catch generated by the PHCR in the simulations increased with increasing process and observation errors to a maximum CV of 0.6, which may be inconsistent with the fishing industry’s desire for low variation in annual catch.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43988857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Biomass estimates for Atlantic cod, haddock, American plaice and yellowtail flounder in NAFO divisions 3NO and Subdivision 3Ps were calculated from research vessel bottom trawl (RV) surveys conducted in the 1950s and 1960s using a transect survey design. Although these data are not currently included in resource assessment, they represent some of the earliest available data for these stocks and provide a means to examine population dynamics prior to the start of the stratified random surveys. Analyses of the survey data demonstrates that there was a deepening in the distribution of cod, haddock and American plaice, in 3Ps in response to changes in water temperatures during the late 1980s and early 1990s, and that this accounted for much of the reduction in biomass in shallow waters. Comparisons of RV estimates of population parameters with those from Sequential Population Analyses for cod in 3NO and 3Ps concluded that the latter provided valid measures of changes in population during the 1960s and 1970s.
{"title":"Perspectives provided by bottom trawl transect surveys conducted in the 1950s and 1960s on the dynamics of commercially exploited groundfish species on southern Grand Bank and St. Pierre Bank","authors":"A. Pinhorn, R. G. Halliday","doi":"10.2960/J.v48.m712","DOIUrl":"https://doi.org/10.2960/J.v48.m712","url":null,"abstract":"Biomass estimates for Atlantic cod, haddock, American plaice and yellowtail flounder in NAFO divisions 3NO and Subdivision 3Ps were calculated from research vessel bottom trawl (RV) surveys conducted in the 1950s and 1960s using a transect survey design. Although these data are not currently included in resource assessment, they represent some of the earliest available data for these stocks and provide a means to examine population dynamics prior to the start of the stratified random surveys. Analyses of the survey data demonstrates that there was a deepening in the distribution of cod, haddock and American plaice, in 3Ps in response to changes in water temperatures during the late 1980s and early 1990s, and that this accounted for much of the reduction in biomass in shallow waters. Comparisons of RV estimates of population parameters with those from Sequential Population Analyses for cod in 3NO and 3Ps concluded that the latter provided valid measures of changes in population during the 1960s and 1970s.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Seitz, Mark D. Evans, Michael B. Courtney, J. Kanwit
In the Northwest Atlantic, emerging evidence suggests that different stocks of Atlantic halibut (Hippoglossus hippoglossus) exist in Canadian and U.S. waters. To examine the movement of Atlantic halibut that occupy the Gulf of Maine in U.S. waters during the summer, two types of electronic tags were attached to large adult fish (n = 70) in 2007–2009. None of the recovered tags (n = 12) provided evidence that the fish occupied the relatively deep waters of the continental slope during the winter, where Canadian Atlantic halibut have been shown to spawn. This observation provides additional evidence for the hypothesis that different stocks of Atlantic halibut exist in Canadian and U.S. waters. Furthermore, this observation requires reexamination of the long-standing assumptions made by fisheries scientists that all Atlantic halibut spawn in deep water on the continental slope and that the majority of mature Atlantic halibut spawn annually. This information may be important for understanding the population dynamics of Atlantic halibut in U.S. waters.
{"title":"Continental shelf residency by adult Atlantic halibut electronic tagged in the Gulf of Maine","authors":"A. Seitz, Mark D. Evans, Michael B. Courtney, J. Kanwit","doi":"10.2960/J.V48.M713","DOIUrl":"https://doi.org/10.2960/J.V48.M713","url":null,"abstract":"In the Northwest Atlantic, emerging evidence suggests that different stocks of Atlantic halibut (Hippoglossus hippoglossus) exist in Canadian and U.S. waters. To examine the movement of Atlantic halibut that occupy the Gulf of Maine in U.S. waters during the summer, two types of electronic tags were attached to large adult fish (n = 70) in 2007–2009. None of the recovered tags (n = 12) provided evidence that the fish occupied the relatively deep waters of the continental slope during the winter, where Canadian Atlantic halibut have been shown to spawn. This observation provides additional evidence for the hypothesis that different stocks of Atlantic halibut exist in Canadian and U.S. waters. Furthermore, this observation requires reexamination of the long-standing assumptions made by fisheries scientists that all Atlantic halibut spawn in deep water on the continental slope and that the majority of mature Atlantic halibut spawn annually. This information may be important for understanding the population dynamics of Atlantic halibut in U.S. waters.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The majority of cetacean research pertaining to the western North Atlantic Ocean has focused on the waters between North Carolina in the United States and the Scotian Shelf in Canada; little is known about cetacean occurrence and distribution in the waters off southeast Florida (FL) where the subject study was conducted. Our study describes opportunistic, ship-based sightings of cetaceans during 1989-2006 in nearshore and offshore waters located in the Gulf Stream between the Bahamas and Palm Beach, FL. Nine species were observed during 60 sightings. For two of the documented species (false killer whale, Pseudorca crassidens, and Fraser’s dolphins, Lagenodelphis hosei), very little existing information was available with respect to sightings and distribution in the study area. The other seven species were observed in waters south of their documented distributions, based on sightings data from dedicated surveys conducted along the US East Coast, but which only extended to central FL. We documented distinctive physical attributes of offshore ecotype bottlenose dolphins (Tursiops truncatus) and described foraging behavior of false killer whales. Our opportunistic observations highlight the importance of conducting regular surveys in this little-researched region. Data gathered during our study may have important implications for cetacean stock assessments and conservation strategies.
{"title":"Opportunistic Sightings of Cetaceans in Nearshore and Offshore Waters of Southeast Florida","authors":"D. Herzing, C. Elliser","doi":"10.2960/J.V48.M709","DOIUrl":"https://doi.org/10.2960/J.V48.M709","url":null,"abstract":"The majority of cetacean research pertaining to the western North Atlantic Ocean has focused on the waters between North Carolina in the United States and the Scotian Shelf in Canada; little is known about cetacean occurrence and distribution in the waters off southeast Florida (FL) where the subject study was conducted. Our study describes opportunistic, ship-based sightings of cetaceans during 1989-2006 in nearshore and offshore waters located in the Gulf Stream between the Bahamas and Palm Beach, FL. Nine species were observed during 60 sightings. For two of the documented species (false killer whale, Pseudorca crassidens, and Fraser’s dolphins, Lagenodelphis hosei), very little existing information was available with respect to sightings and distribution in the study area. The other seven species were observed in waters south of their documented distributions, based on sightings data from dedicated surveys conducted along the US East Coast, but which only extended to central FL. We documented distinctive physical attributes of offshore ecotype bottlenose dolphins (Tursiops truncatus) and described foraging behavior of false killer whales. Our opportunistic observations highlight the importance of conducting regular surveys in this little-researched region. Data gathered during our study may have important implications for cetacean stock assessments and conservation strategies.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. González-Costas, D. González-Troncoso, M. Morgan, H. Murua, D. Garcia
We tested whether our perception of the performance of the adopted Harvest Control Rule (HCR) for Greenland halibut was robust to using different measures of Reproductive Potential (RP) combined with different assumptions about the stock recruit relationship to drive the stock dynamics in simulations. We tested the HCR using alternative stock recruitment functions (segmented regression, Ricker and modified Ricker) with different RP indices which vary in the level of biological complexity. The RP indices used in increasing order of biological information were: Biomass 10+, SSB with varying maturity at age (SSB), female SSB (FSB), and Total Egg Production (TEP). All Operating Models (OM) were based on the current accepted XSA assessment. Understanding the basis of uncertainty in the S/R relationships is generally the most difficult outstanding problem in fisheries assessment and management and it is a key problem in Management Strategy Evaluation (MSE). A Ricker stock recruitment function fits the Greenland halibut stock recruitment data better than the segmented regression for all the RP indices, except TEP. The results show that the inclusion of more biological information when estimating Reproductive Potential does not improve the stock recruitment fit for either (segmented regression or Ricker). The best fits in both cases were obtained in descending order with: 10+Biomass, SSB, FSB, and TEP. All the OMs based on the segmented regression have very similar results and seem to be robust to assumptions about RP. However, there was variability in the results of the different indices of RP in the Ricker and modified Ricker OMs and some impact on whether performance targets were met. The choice of stock recruit function had a greater impact than the inclusion of more biological information in the index of RP. The inclusion of alternative indices of RP is likely to have more of an impact for stocks with depleted reproductive capacity and/or where alternative indices have a greater effect on the S/R relationships.
{"title":"The impact of different assumptions about reproductive potential and recruitment on a Management Strategy Evaluation for the Greenland halibut stock in NAFO Subarea 2 and Division 3KLMNO","authors":"F. González-Costas, D. González-Troncoso, M. Morgan, H. Murua, D. Garcia","doi":"10.2960/J.V48.M705","DOIUrl":"https://doi.org/10.2960/J.V48.M705","url":null,"abstract":"We tested whether our perception of the performance of the adopted Harvest Control Rule (HCR) for Greenland halibut was robust to using different measures of Reproductive Potential (RP) combined with different assumptions about the stock recruit relationship to drive the stock dynamics in simulations. We tested the HCR using alternative stock recruitment functions (segmented regression, Ricker and modified Ricker) with different RP indices which vary in the level of biological complexity. The RP indices used in increasing order of biological information were: Biomass 10+, SSB with varying maturity at age (SSB), female SSB (FSB), and Total Egg Production (TEP). All Operating Models (OM) were based on the current accepted XSA assessment. Understanding the basis of uncertainty in the S/R relationships is generally the most difficult outstanding problem in fisheries assessment and management and it is a key problem in Management Strategy Evaluation (MSE). A Ricker stock recruitment function fits the Greenland halibut stock recruitment data better than the segmented regression for all the RP indices, except TEP. The results show that the inclusion of more biological information when estimating Reproductive Potential does not improve the stock recruitment fit for either (segmented regression or Ricker). The best fits in both cases were obtained in descending order with: 10+Biomass, SSB, FSB, and TEP. All the OMs based on the segmented regression have very similar results and seem to be robust to assumptions about RP. However, there was variability in the results of the different indices of RP in the Ricker and modified Ricker OMs and some impact on whether performance targets were met. The choice of stock recruit function had a greater impact than the inclusion of more biological information in the index of RP. The inclusion of alternative indices of RP is likely to have more of an impact for stocks with depleted reproductive capacity and/or where alternative indices have a greater effect on the S/R relationships.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fish Assemblages at the Abstract During 2006 and 2008 two bottom trawl surveys were conducted at East Greenland to 72°N covering depths down to 1500 m. In the 149 trawl hauls in total 113 fish species were recorded of which 37 were considered pelagic and excluded from the analyses. As a first step the abundance data for the 76 benthic species were used for analyses of the fish fauna diversity and fish assemblages. Nine assemblages were found by a standard type of cluster analysis. A Bayesian multinomial logit model was then applied to calculate vectors of probabilities defining the likelihood of each haul belonging to each of the nine clusters. By means of a geostatistical tool the spatial distribution of the conditional probabilities for each cluster (assemblage) was mapped. Each of the nine assemblages was further defined by indicator species, depth and temperature. The assemblages were well defined regarding geographical distribution, species composition, temperature and depth. Three of the assemblages were located in the cold Iceland Sea while six were found in the somewhat warmer Irminger Sea.
{"title":"Bottom fish assemblages at the shelf and continental slope off East Greenland","authors":"O. Jørgensen, C. Hvingel, P. Møller","doi":"10.2960/J.V47.M706","DOIUrl":"https://doi.org/10.2960/J.V47.M706","url":null,"abstract":"Fish Assemblages at the Abstract During 2006 and 2008 two bottom trawl surveys were conducted at East Greenland to 72°N covering depths down to 1500 m. In the 149 trawl hauls in total 113 fish species were recorded of which 37 were considered pelagic and excluded from the analyses. As a first step the abundance data for the 76 benthic species were used for analyses of the fish fauna diversity and fish assemblages. Nine assemblages were found by a standard type of cluster analysis. A Bayesian multinomial logit model was then applied to calculate vectors of probabilities defining the likelihood of each haul belonging to each of the nine clusters. By means of a geostatistical tool the spatial distribution of the conditional probabilities for each cluster (assemblage) was mapped. Each of the nine assemblages was further defined by indicator species, depth and temperature. The assemblages were well defined regarding geographical distribution, species composition, temperature and depth. Three of the assemblages were located in the cold Iceland Sea while six were found in the somewhat warmer Irminger Sea.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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