Evacuation rates were determined for Clearnose Skate (Leucoraja eglanteria), an important predator in the mid-Atlantic United States shelf ecosystem. Male Skates (570–730 mm total length) were fed Sand Lance Ammodytes sp. and allowed to digest from 2–48 hr at two different temperatures. At selected times, fish were removed from tanks, sedated with tricaine methanesulfonate, and subjected to gastric lavage. This procedure was successful at removing the food from the stomachs without injury to the fish. Evacuation rates for the two temperature treatments were fit best by exponential models. The evacuation rates, per hour, were faster at 20°C than at 15°C, resulting in empty stomachs by 24 hr at 20°C, and 48 hr at 15°C. Evacuation rates at these temperatures were estimated as 0.102 and 0.059 proportion stomach contents per hour at 20 o C and 15°C. These evacuation rates and their temperature dependence are similar to that of other species of elasmobranchs and some teleosts. Evacuation rates are often combined with stomach content data to estimate consumption. The results of this study indicate that evacuation rates by some skates may be up to five times higher than currently used in multi-species and ecosystem models of the Northeast U.S. Shelf. The implication is that consumption may also be higher, highlighting the need for more research to increase the accuracy in evacuation rates estimates.
{"title":"Gastric evacuation rates in male Clearnose Skate( Leucoraja eglanteria ) in the laboratory","authors":"J. Jech, V. Price, S. Chávez-Rosales, W. Michaels","doi":"10.2960/J.V47.M700","DOIUrl":"https://doi.org/10.2960/J.V47.M700","url":null,"abstract":"Evacuation rates were determined for Clearnose Skate (Leucoraja eglanteria), an important predator in the mid-Atlantic United States shelf ecosystem. Male Skates (570–730 mm total length) were fed Sand Lance Ammodytes sp. and allowed to digest from 2–48 hr at two different temperatures. At selected times, fish were removed from tanks, sedated with tricaine methanesulfonate, and subjected to gastric lavage. This procedure was successful at removing the food from the stomachs without injury to the fish. Evacuation rates for the two temperature treatments were fit best by exponential models. The evacuation rates, per hour, were faster at 20°C than at 15°C, resulting in empty stomachs by 24 hr at 20°C, and 48 hr at 15°C. Evacuation rates at these temperatures were estimated as 0.102 and 0.059 proportion stomach contents per hour at 20 o C and 15°C. These evacuation rates and their temperature dependence are similar to that of other species of elasmobranchs and some teleosts. Evacuation rates are often combined with stomach content data to estimate consumption. The results of this study indicate that evacuation rates by some skates may be up to five times higher than currently used in multi-species and ecosystem models of the Northeast U.S. Shelf. The implication is that consumption may also be higher, highlighting the need for more research to increase the accuracy in evacuation rates estimates.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257293","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}
E. Powell, J. Klinck, D. Munroe, E. Hofmann, Paula Moreno, R. Mann
The response of the surfclam Spisula solidissima to warming of the Mid-Atlantic Bight is manifested by recession of the southern and inshore boundary of the clam's range. This phenomenon has impacted the fishery through the closure of southern ports and the movement of processing capacity north, impacts that may require responsive actions on the part of fishery captains to mitigate a decline in fishery performance otherwise ineluctably accompanying this shift in range. The purpose of this study was to evaluate options in the behavioral repertoire of captains that might provide mitigation. A model capable of simulating a spatially and temporally variable resource harvested by fleets of boats landing in a number of homeports was created. The model includes characterization of each vessel in terms of economics and vessel performance. The model assigns to each vessel a captain with defined behavioral proclivities including the tendency to search, to communicate with other captains, to take advantage of survey data, and to integrate variable lengths of past history performance into the determination of the location of fishing trips. Each captain and vessel operate independently in the simulation providing a spatially and temporally dynamic variability in fishery performance. Simulations showed that a number of behaviors modestly varied performance. Use of survey data and occasional searching tended to increase performance. Reliance on an older catch history tended to reduce performance as did frequent searching. However, in no simulation was this differential large and the differential was little modified by the contraction in the surfclam's range. Simulations showed that the population dynamics of the clam and the low fishing mortality rate imposed by the Fishery Management Plan permit near optimal fishing performance based on a few simple rules: choose locations to fish that minimize time at sea while permitting the landing of a full vessel load; base this choice on the most recent catch history for the vessel. Simulations suggest that the performance of the fishery is primarily determined by surfclam abundance and the location of patches that control LPUE at small geographic scales. Constraints imposed on fishery performance by port location and vessel size far exceed limitations or ameliorations afforded by modifications in the behavior of captains.
{"title":"The Value of Captains' Behavioral Choices in the Success of the Surfclam (Spisula solidissima) Fishery on the U.S. Mid-Atlantic Coast: a Model Evaluation","authors":"E. Powell, J. Klinck, D. Munroe, E. Hofmann, Paula Moreno, R. Mann","doi":"10.2960/J.V47.M701","DOIUrl":"https://doi.org/10.2960/J.V47.M701","url":null,"abstract":"The response of the surfclam Spisula solidissima to warming of the Mid-Atlantic Bight is manifested by recession of the southern and inshore boundary of the clam's range. This phenomenon has impacted the fishery through the closure of southern ports and the movement of processing capacity north, impacts that may require responsive actions on the part of fishery captains to mitigate a decline in fishery performance otherwise ineluctably accompanying this shift in range. The purpose of this study was to evaluate options in the behavioral repertoire of captains that might provide mitigation. A model capable of simulating a spatially and temporally variable resource harvested by fleets of boats landing in a number of homeports was created. The model includes characterization of each vessel in terms of economics and vessel performance. The model assigns to each vessel a captain with defined behavioral proclivities including the tendency to search, to communicate with other captains, to take advantage of survey data, and to integrate variable lengths of past history performance into the determination of the location of fishing trips. Each captain and vessel operate independently in the simulation providing a spatially and temporally dynamic variability in fishery performance. Simulations showed that a number of behaviors modestly varied performance. Use of survey data and occasional searching tended to increase performance. Reliance on an older catch history tended to reduce performance as did frequent searching. However, in no simulation was this differential large and the differential was little modified by the contraction in the surfclam's range. Simulations showed that the population dynamics of the clam and the low fishing mortality rate imposed by the Fishery Management Plan permit near optimal fishing performance based on a few simple rules: choose locations to fish that minimize time at sea while permitting the landing of a full vessel load; base this choice on the most recent catch history for the vessel. Simulations suggest that the performance of the fishery is primarily determined by surfclam abundance and the location of patches that control LPUE at small geographic scales. Constraints imposed on fishery performance by port location and vessel size far exceed limitations or ameliorations afforded by modifications in the behavior of captains.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257349","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}
This paper evaluates the performance of six possible sampling designs to estimate the population abundance index for American lobster using computer simulations. These designs include simple random sampling (SRS), systematic sampling (SYS) and stratified random sampling with four stratification schemes (i.e., based on region, depth, sediment and region × depth). For the stratified random design with region and depth being used for stratification, we evaluated the performances of different strategies for allocating sampling efforts. Simulations were implemented on the “true” populations which were estimated annually from 2002 to 2008 for both spring and fall based on a general additive model model developed in a separate study. Relative Estimation Error (REE), Relative Bias (RB) and design effect were used to measure the precision, accuracy and efficiency of mean estimation for different designs. On average, SYS tended to yield the most precise and efficient estimate of mean with specified sample size. However, its estimates tended to be biased and its performance varied with sample sizes and realizations of “true” population, thus changed with lobster distribution. Appropriate stratification, such as using depth to determine strata, significantly improved the precision and efficiency over SRS. Sediment, which is related to lobster distribution, was found to have little contribution to the improvement of the performance over SRS when it is used to determine strata. Also, allocating samples to each stratum based on variance or mean of previous year improved precision and efficiency. This study suggests that current design ( i.e., region-depth stratified design) used in the survey had stable performance across years and seasons.
{"title":"IAn evaluation of an inshore bottom trawl survey design for American lobster (Homarus americanus) using computer simulations","authors":"Jie Cao, Yong Chen, Jui‐Han Chang, Xinjun Chen","doi":"10.2960/J.V46.M696","DOIUrl":"https://doi.org/10.2960/J.V46.M696","url":null,"abstract":"This paper evaluates the performance of six possible sampling designs to estimate the population abundance index for American lobster using computer simulations. These designs include simple random sampling (SRS), systematic sampling (SYS) and stratified random sampling with four stratification schemes (i.e., based on region, depth, sediment and region × depth). For the stratified random design with region and depth being used for stratification, we evaluated the performances of different strategies for allocating sampling efforts. Simulations were implemented on the “true” populations which were estimated annually from 2002 to 2008 for both spring and fall based on a general additive model model developed in a separate study. Relative Estimation Error (REE), Relative Bias (RB) and design effect were used to measure the precision, accuracy and efficiency of mean estimation for different designs. On average, SYS tended to yield the most precise and efficient estimate of mean with specified sample size. However, its estimates tended to be biased and its performance varied with sample sizes and realizations of “true” population, thus changed with lobster distribution. Appropriate stratification, such as using depth to determine strata, significantly improved the precision and efficiency over SRS. Sediment, which is related to lobster distribution, was found to have little contribution to the improvement of the performance over SRS when it is used to determine strata. Also, allocating samples to each stratum based on variance or mean of previous year improved precision and efficiency. This study suggests that current design ( i.e., region-depth stratified design) used in the survey had stable performance across years and seasons.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257225","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}
Fisheries management frameworks based on maximum sustainable yield reference points have been put forward by all agencies and organizations responsible for providing scientific advice for the management of 22 major North Atlantic cod stocks. These frameworks provide a structure for rebuilding depleted cod stocks and for future sustainable fishing. Unfortunately, in most cases these frameworks have not been fully implemented. Although information is lacking for some stocks, it would appear that a large proportion of North Atlantic cod stocks are either experiencing a fishing mortality rate that exceeds that required to achieve maximum sustainable yield, are at a biomass level far below that which provides maximum sustainable yield, or have both occurring. Despite this general failure, there are some notable successes, which have led to stock rebuilding and substantial fisheries, providing an incentive for striving to achieve rebuilding and sustainable management objectives for other Atlantic cod stocks. Management frameworks based on harvest control rules that result in fishing mortality rates below those associated with maximum sustainable yield are essential when stock size is low in order to rebuild to levels capable of producing maximum sustainable yield.
{"title":"Impact of maximum sustainable yield-based fisheries management frameworks on rebuilding North Atlantic cod stocks","authors":"P. Shelton, M. Morgan, M. Morgan","doi":"10.2960/J.V46.M697","DOIUrl":"https://doi.org/10.2960/J.V46.M697","url":null,"abstract":"Fisheries management frameworks based on maximum sustainable yield reference points have been put forward by all agencies and organizations responsible for providing scientific advice for the management of 22 major North Atlantic cod stocks. These frameworks provide a structure for rebuilding depleted cod stocks and for future sustainable fishing. Unfortunately, in most cases these frameworks have not been fully implemented. Although information is lacking for some stocks, it would appear that a large proportion of North Atlantic cod stocks are either experiencing a fishing mortality rate that exceeds that required to achieve maximum sustainable yield, are at a biomass level far below that which provides maximum sustainable yield, or have both occurring. Despite this general failure, there are some notable successes, which have led to stock rebuilding and substantial fisheries, providing an incentive for striving to achieve rebuilding and sustainable management objectives for other Atlantic cod stocks. Management frameworks based on harvest control rules that result in fishing mortality rates below those associated with maximum sustainable yield are essential when stock size is low in order to rebuild to levels capable of producing maximum sustainable yield.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257243","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 average annual cycle of abundance and the bimonthly distributions of the copepod Pseudocalanus spp. are described for U.S. Northeast continental shelf waters from samples collected on broad-scale plankton surveys 1977–2012. Population levels begin to increase during January–February, surge in March–April, and peak throughout the region during May–June. The copepod’s population density declines sharply after June and becomes minimal from September–December. Spatially, seasonal high levels persist throughout the year in coastal waters surrounding and adjacent to the Cape Cod peninsula. During late spring, dense concentrations are found in Gulf of Maine coastal waters and in a high abundance band that extends southwestward from Georges Bank into the northern half of Middle Atlantic Bight waters. Pseudocalanus spp. interannual abundance variability was substantial; displaying several extended low and high periods through the time series. In general, numbers were high from the late 1970s through the early 1980s, low in the mid-1980s, elevated in the 1990s, and low again in the 2000s. This pattern was correlated negatively with temperature and positively with phytoplankton abundance trends. It is proposed that the copepods low abundance in the 2000s may have been caused by warmer temperatures that indirectly depressed the abundance of phytoplankton that this copepod uses for food. Survey data also indicate that predation pressure from salps and perhaps some additional species may contribute to the precipitous summer decline of Pseudocalanus spp. The copepod’s abundance was found to be independent from the climatic variation associated with either the North Atlantic or Arctic Oscillation.
{"title":"Decadal Distribution and Abundance Trends for the Late Stage Copepodites of Pseudocalanus spp. (Copepoda: Calanoida) in the US Northeast Continental Shelf Ecosystem.","authors":"J. Kane","doi":"10.2960/J.V46.M695","DOIUrl":"https://doi.org/10.2960/J.V46.M695","url":null,"abstract":"The average annual cycle of abundance and the bimonthly distributions of the copepod Pseudocalanus spp. are described for U.S. Northeast continental shelf waters from samples collected on broad-scale plankton surveys 1977–2012. Population levels begin to increase during January–February, surge in March–April, and peak throughout the region during May–June. The copepod’s population density declines sharply after June and becomes minimal from September–December. Spatially, seasonal high levels persist throughout the year in coastal waters surrounding and adjacent to the Cape Cod peninsula. During late spring, dense concentrations are found in Gulf of Maine coastal waters and in a high abundance band that extends southwestward from Georges Bank into the northern half of Middle Atlantic Bight waters. Pseudocalanus spp. interannual abundance variability was substantial; displaying several extended low and high periods through the time series. In general, numbers were high from the late 1970s through the early 1980s, low in the mid-1980s, elevated in the 1990s, and low again in the 2000s. This pattern was correlated negatively with temperature and positively with phytoplankton abundance trends. It is proposed that the copepods low abundance in the 2000s may have been caused by warmer temperatures that indirectly depressed the abundance of phytoplankton that this copepod uses for food. Survey data also indicate that predation pressure from salps and perhaps some additional species may contribute to the precipitous summer decline of Pseudocalanus spp. The copepod’s abundance was found to be independent from the climatic variation associated with either the North Atlantic or Arctic Oscillation.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257170","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}
Approximately 17 tagging studies were conducted on American plaice between 1958 and 1997 throughout the Southern Gulf of St. Lawrence, Scotian Shelf and Bay of Fundy. Only about half these studies were formally analysed and discussed in the literature, and many of those represented in the literature were characterised by appreciable recoveries made subsequent to publication. Analyses of previously untreated data and re-analysis of older studies with updated recoveries was conducted to create a synopsis of likely population identities and movements. These tagging studies demonstrate that American plaice in the Gulf of St. Lawrence are distinct from Scotian Shelf plaice, and support the hypothesis of discrete southern and northern sub-populations of American plaice within the southern Gulf of St. Lawrence. American plaice in Sydney Bight are also distinct from plaice in the Gulf of St. Lawrence, but it remains unknown if they are a discrete spawning group or derive from plaice spawning on Banquereau. Movements of plaice tagged in the vicinity of Passamaquoddy Bay provide some evidence that plaice in the Bay of Fundy might be associated with the Scotian Shelf, possibly by a spawning group on Browns Bank. All the groups of plaice addressed in this study were combined as a single “Designatable Unit”, and assessed as “Threatened in a Species at Risk” context, by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), due to excessive declines in abundance of mature individuals over 2–3 generations (~86% decline in the Gulf, ~67% decline on the Scotian Shelf). Observed long-term dispersion indicates that plaice has some potential to recolonize depleted areas, but such movements are displayed by fish older than are commonly found in the population in recent decades. Seasonal protection of spawning grounds might safeguard components of the population in the short-term until numbers of these older fish can be rebuilt.
{"title":"Dispersion and seasonal movements of American plaice (Hippoglossoides platessoides) tagged in waters of the Gulf of St. Lawrence, Scotian Shelf and Bay of Fundy","authors":"G. M. Fowler","doi":"10.2960/J.V45.M690","DOIUrl":"https://doi.org/10.2960/J.V45.M690","url":null,"abstract":"Approximately 17 tagging studies were conducted on American plaice between 1958 and 1997 throughout the Southern Gulf of St. Lawrence, Scotian Shelf and Bay of Fundy. Only about half these studies were formally analysed and discussed in the literature, and many of those represented in the literature were characterised by appreciable recoveries made subsequent to publication. Analyses of previously untreated data and re-analysis of older studies with updated recoveries was conducted to create a synopsis of likely population identities and movements. These tagging studies demonstrate that American plaice in the Gulf of St. Lawrence are distinct from Scotian Shelf plaice, and support the hypothesis of discrete southern and northern sub-populations of American plaice within the southern Gulf of St. Lawrence. American plaice in Sydney Bight are also distinct from plaice in the Gulf of St. Lawrence, but it remains unknown if they are a discrete spawning group or derive from plaice spawning on Banquereau. Movements of plaice tagged in the vicinity of Passamaquoddy Bay provide some evidence that plaice in the Bay of Fundy might be associated with the Scotian Shelf, possibly by a spawning group on Browns Bank. All the groups of plaice addressed in this study were combined as a single “Designatable Unit”, and assessed as “Threatened in a Species at Risk” context, by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), due to excessive declines in abundance of mature individuals over 2–3 generations (~86% decline in the Gulf, ~67% decline on the Scotian Shelf). Observed long-term dispersion indicates that plaice has some potential to recolonize depleted areas, but such movements are displayed by fish older than are commonly found in the population in recent decades. Seasonal protection of spawning grounds might safeguard components of the population in the short-term until numbers of these older fish can be rebuilt.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257605","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}
Adriana Nogueira, Xabier Paz, Diana González, Troncoso
Data from EU-Spain (Instituto Espanol de Oceanografia) bottom trawl surveys in the NAFO Regulatory Area (2002–2011) were analyzed to examine patterns on the South of Grand Banks (NAFO Div. 3NO) of groundfish assemblage structure and diversity in relation to depth. The 1160 hauls from the slope surveys spanned between 38 and 1460 m in depth. We focused on the 28 most abundant species, which made up 92.6% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth. For the most part, changes in assemblages seem to be fairly continuous, although there were more abrupt changes at 300 m. Five assemblages were identified. Two shallow assemblages were found in the shelf. Assemblage I (Shallow) comprises the strata with depths lesser than 150 and include yellowtail flounder (Limanda ferruginea), American plaice (Hippoglossoides platessoides), Northern sand lance (Ammodytes dubius), moustache sculpin (Triglops murrayi), capelin (Mallotus villosus) and web sculpin (Hemitripterus americanus). Assemblage II (Shallow) includes the strata with depths between 151 and 300 m and comprises Atlantic cod (Gadus morhua), American angler (Lophius americanus), wolfish (Anarichas lupus) and thorny skate (Amblyraja radiata). Assemblage III (Intermediate) contains the depth strata between 301 and 600 m. Redfish (Sebastes spp.), spotted wolfish (Anarichas minor), Arctic eelpout (Lycodes reticulatus), Northern wolfish (Anarichas denticulatus), white hake (Urophycis tenuis), witch flounder (Glyptocephalus cynoglossus) and longfin hake (Phycis chesteri) were included in the intermediate assemblage. Finally, we found two deep clusters: Assemblage IV (Deep) contains the depths between 601 and 1000 m, and Assemblage V (Deep) the depth strata greater than 1001 m. Greenland halibut (Reinhardtius hippoglossoides), marlin-spike (Nezumia bairdii), roughhead grenadier (Macrourus berglax) and spinytail skate (Bathyraja spinicauda) formed Assemblage IV. Snubnosed spiny eel (Notacanthus chemnitzii), blue antimora (Antimora rostrata), Northern cutthroat eel (Syphanobranchus kaupii), roundnose grenadier (Coryphaenoides rupestris), black dogfish (Centroscyllium fabricii), Arctic skate (Amblyraja hyperborea) and longnose chimera (Harriotta raleighana) made up the deepest assemblage. Despite dramatic changes in biomass and abundance of the species in the area, the boundaries and composition of the assemblages seem to be similar to the period before the collapse. Although some changes were evident, the main ones were replacements of the dominant species in several assemblages and bathymetric range extension of distribution of some species. Yellowtail flounder appears to be the dominant species in the shallowest assemblage instead of Atlantic cod and American plaice that were dominant in the period before the collapse in the area; redfish is the dominant species in the second shallow and intermediate assemblages. Diversity appears inversely related to biomass in th
{"title":"Persistence and Variation on the Groundfish Assemblages on the Southern Grand Banks (NAFO Divisions 3NO): 2002-2011","authors":"Adriana Nogueira, Xabier Paz, Diana González, Troncoso","doi":"10.2960/J.V45.M686","DOIUrl":"https://doi.org/10.2960/J.V45.M686","url":null,"abstract":"Data from EU-Spain (Instituto Espanol de Oceanografia) bottom trawl surveys in the NAFO Regulatory Area (2002–2011) were analyzed to examine patterns on the South of Grand Banks (NAFO Div. 3NO) of groundfish assemblage structure and diversity in relation to depth. The 1160 hauls from the slope surveys spanned between 38 and 1460 m in depth. We focused on the 28 most abundant species, which made up 92.6% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth. For the most part, changes in assemblages seem to be fairly continuous, although there were more abrupt changes at 300 m. Five assemblages were identified. Two shallow assemblages were found in the shelf. Assemblage I (Shallow) comprises the strata with depths lesser than 150 and include yellowtail flounder (Limanda ferruginea), American plaice (Hippoglossoides platessoides), Northern sand lance (Ammodytes dubius), moustache sculpin (Triglops murrayi), capelin (Mallotus villosus) and web sculpin (Hemitripterus americanus). Assemblage II (Shallow) includes the strata with depths between 151 and 300 m and comprises Atlantic cod (Gadus morhua), American angler (Lophius americanus), wolfish (Anarichas lupus) and thorny skate (Amblyraja radiata). Assemblage III (Intermediate) contains the depth strata between 301 and 600 m. Redfish (Sebastes spp.), spotted wolfish (Anarichas minor), Arctic eelpout (Lycodes reticulatus), Northern wolfish (Anarichas denticulatus), white hake (Urophycis tenuis), witch flounder (Glyptocephalus cynoglossus) and longfin hake (Phycis chesteri) were included in the intermediate assemblage. Finally, we found two deep clusters: Assemblage IV (Deep) contains the depths between 601 and 1000 m, and Assemblage V (Deep) the depth strata greater than 1001 m. Greenland halibut (Reinhardtius hippoglossoides), marlin-spike (Nezumia bairdii), roughhead grenadier (Macrourus berglax) and spinytail skate (Bathyraja spinicauda) formed Assemblage IV. Snubnosed spiny eel (Notacanthus chemnitzii), blue antimora (Antimora rostrata), Northern cutthroat eel (Syphanobranchus kaupii), roundnose grenadier (Coryphaenoides rupestris), black dogfish (Centroscyllium fabricii), Arctic skate (Amblyraja hyperborea) and longnose chimera (Harriotta raleighana) made up the deepest assemblage. Despite dramatic changes in biomass and abundance of the species in the area, the boundaries and composition of the assemblages seem to be similar to the period before the collapse. Although some changes were evident, the main ones were replacements of the dominant species in several assemblages and bathymetric range extension of distribution of some species. Yellowtail flounder appears to be the dominant species in the shallowest assemblage instead of Atlantic cod and American plaice that were dominant in the period before the collapse in the area; redfish is the dominant species in the second shallow and intermediate assemblages. Diversity appears inversely related to biomass in th","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257591","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 objective of this study was to develop a means to reduce the capture of undersize waved whelk (Buccinum undatum) in small mesh (51–64 mm) conical traps. To achieve this, egress windows were incorporated above the bottom ring of a trap to produce openings of sufficient width to allow undersize whelk to be released as a string of traps is being hauled to the surface. Analysis of the passage of undersize whelk through three egress window sizes revealed that a 30 mm wide window was most suitable. Simulations of two vertical surge distances and two trap angles were carried out in a controlled environment to provide a better understanding of trap performance. Experiments revealed that when a trap is oriented at an angle of 40–45o a substantial percentage (29–36%) of undersize whelk can be removed at vertical surge distances of 0.3–1 m. Few (3–4%) legal size whelk were emitted at a trap angle of 40–45o and all whelk emitted from a trap were observed to pass through an egress window. Increasing the angle of the trap to 70–75o resulted in loss of legal size whelk through the entrance located on top of the trap. The results of these simple experiments are promising but require verification through fishery trials before they can serve management decisions. Trap modifications and a trap line configuration that will maximize the egress of undersize whelk during fishing trials are discussed.
{"title":"Efficacy of an egress window to reduce the capture of undersize waved whelk (Buccinum undatum) in conical traps: laboratory experiments on the effect of vertical surge and trap angle during haul back.","authors":"S. M. Grant","doi":"10.2960/J.V45.M687","DOIUrl":"https://doi.org/10.2960/J.V45.M687","url":null,"abstract":"The objective of this study was to develop a means to reduce the capture of undersize waved whelk (Buccinum undatum) in small mesh (51–64 mm) conical traps. To achieve this, egress windows were incorporated above the bottom ring of a trap to produce openings of sufficient width to allow undersize whelk to be released as a string of traps is being hauled to the surface. Analysis of the passage of undersize whelk through three egress window sizes revealed that a 30 mm wide window was most suitable. Simulations of two vertical surge distances and two trap angles were carried out in a controlled environment to provide a better understanding of trap performance. Experiments revealed that when a trap is oriented at an angle of 40–45o a substantial percentage (29–36%) of undersize whelk can be removed at vertical surge distances of 0.3–1 m. Few (3–4%) legal size whelk were emitted at a trap angle of 40–45o and all whelk emitted from a trap were observed to pass through an egress window. Increasing the angle of the trap to 70–75o resulted in loss of legal size whelk through the entrance located on top of the trap. The results of these simple experiments are promising but require verification through fishery trials before they can serve management decisions. Trap modifications and a trap line configuration that will maximize the egress of undersize whelk during fishing trials are discussed.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257600","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 average spatial distribution and interannual abundance patterns of the cladoceran Penilia avirostris are described from samples collected in the waters of the US Northeast continental shelf ecosystem. Integrated water column samples were collected with a bongo net from 1977–2009 on broad scale surveys of the shelf conducted approximately every two months. Collections were also made with a Continuous Plankton Recorder towed at 10 m depth along two routes; one that crossed the Gulf of Maine (1961–2009), and the other from New York City south-eastward toward Bermuda (1976–2009). P. avirostris was found to have a strong seasonal cycle in the southern half of the ecosystem. High coastal concentrations suddenly appear there in July–August, forming distinct onshore-offshore abundance gradients. The population slowly declines in the autumn months, essentially disappears from the zooplankton community during winter, and does not return again until its abrupt appearance in summer. Only low abundances in isolated patches were found in the northern half of the ecosystem and in the slope waters sampled by the CPR. Both samplers showed that annual abundance levels were variable with no long-term trend evident, nor were environmental measures or broad scale climate indices correlated to these variations. The cladoceransʼ summer population surge was significantly correlated with surface temperature and water column stratification indices. This is the first study to record the presence of P. avirostris in the Gulf of Maine region.
{"title":"Long-Term Abundance and Distribution Trends of the CladoceranPenilia avirostrisin the US Northeast Shelf Ecosystem","authors":"J. Kane","doi":"10.2960/J.V45.M682","DOIUrl":"https://doi.org/10.2960/J.V45.M682","url":null,"abstract":"The average spatial distribution and interannual abundance patterns of the cladoceran Penilia avirostris are described from samples collected in the waters of the US Northeast continental shelf ecosystem. Integrated water column samples were collected with a bongo net from 1977–2009 on broad scale surveys of the shelf conducted approximately every two months. Collections were also made with a Continuous Plankton Recorder towed at 10 m depth along two routes; one that crossed the Gulf of Maine (1961–2009), and the other from New York City south-eastward toward Bermuda (1976–2009). P. avirostris was found to have a strong seasonal cycle in the southern half of the ecosystem. High coastal concentrations suddenly appear there in July–August, forming distinct onshore-offshore abundance gradients. The population slowly declines in the autumn months, essentially disappears from the zooplankton community during winter, and does not return again until its abrupt appearance in summer. Only low abundances in isolated patches were found in the northern half of the ecosystem and in the slope waters sampled by the CPR. Both samplers showed that annual abundance levels were variable with no long-term trend evident, nor were environmental measures or broad scale climate indices correlated to these variations. The cladoceransʼ summer population surge was significantly correlated with surface temperature and water column stratification indices. This is the first study to record the presence of P. avirostris in the Gulf of Maine region.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257581","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}
N. Pleizier, S. Campana, R. Schallert, S. Wilson, B. Block
The stomach contents of 68 Atlantic bluefin tuna (Thunnus thynnus) landed in Port Hood and Canso, Nova Scotia, in 2010, were analyzed to characterize the diet of bluefin tuna at the two locations. Of the sampled fish, 54 stomachs had contents. Pelagic schooling fish such as herring (Clupea harengus) and mackerel (Scomber scombrus) dominated the diets in both regions. However, a number of rare species, including demersal species, were also observed. Despite the difference in location and the significantly larger size of the Atlantic bluefin tuna landed in Port Hood, the diets of the Atlantic bluefin tuna landed at both sites were similar.
{"title":"Atlantic Bluefin Tuna (Thunnus thynnus) Diet in the Gulf of St. Lawrence and on the Eastern Scotian Shelf","authors":"N. Pleizier, S. Campana, R. Schallert, S. Wilson, B. Block","doi":"10.2960/J.V44.M685","DOIUrl":"https://doi.org/10.2960/J.V44.M685","url":null,"abstract":"The stomach contents of 68 Atlantic bluefin tuna (Thunnus thynnus) landed in Port Hood and Canso, Nova Scotia, in 2010, were analyzed to characterize the diet of bluefin tuna at the two locations. Of the sampled fish, 54 stomachs had contents. Pelagic schooling fish such as herring (Clupea harengus) and mackerel (Scomber scombrus) dominated the diets in both regions. However, a number of rare species, including demersal species, were also observed. Despite the difference in location and the significantly larger size of the Atlantic bluefin tuna landed in Port Hood, the diets of the Atlantic bluefin tuna landed at both sites were similar.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256712","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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