P. Pomeroy, S. Smout, S. Moss, S. Twiss, Ruth King
This study is concerned with changes in the recruitment of UK grey seal pups into the adult breeding population. Pups were marked over two decades at North Rona and the Isle of May. The proportion of these animals observed to recruit as adults was at best 0.10 on North Rona and 0.31 on the Isle of May. Double-tagged cohorts were re-sighted at the highest rates, compared with cohorts that were marked with single tags or with brands. There was also evidence of substantial interannual variation, and no individuals were ever re-sighted for certain cohorts. Estimates of absolute tag loss were higher at North Rona than at the Isle of May, but not sufficient to explain the low re-sight rates there. Recruitment at the Isle of May appears to be occurring later in recent years and this is consistent with the effects of density dependence. There are too few tag returns from North Rona to allow the investigation of any time-dependence in recruitment, but this lack and the continued decline of pup production on North Rona suggests that recruitment there may be low. These findings have direct implications for models of UK grey seal population dynamics.
{"title":"Low and Delayed Recruitment at Two Grey Seal Breeding Colonies in the UK","authors":"P. Pomeroy, S. Smout, S. Moss, S. Twiss, Ruth King","doi":"10.2960/J.42.M651","DOIUrl":"https://doi.org/10.2960/J.42.M651","url":null,"abstract":"This study is concerned with changes in the recruitment of UK grey seal pups into the adult breeding population. Pups were marked over two decades at North Rona and the Isle of May. The proportion of these animals observed to recruit as adults was at best 0.10 on North Rona and 0.31 on the Isle of May. Double-tagged cohorts were re-sighted at the highest rates, compared with cohorts that were marked with single tags or with brands. There was also evidence of substantial interannual variation, and no individuals were ever re-sighted for certain cohorts. Estimates of absolute tag loss were higher at North Rona than at the Isle of May, but not sufficient to explain the low re-sight rates there. Recruitment at the Isle of May appears to be occurring later in recent years and this is consistent with the effects of density dependence. There are too few tag returns from North Rona to allow the investigation of any time-dependence in recruitment, but this lack and the continued decline of pup production on North Rona suggests that recruitment there may be low. These findings have direct implications for models of UK grey seal population dynamics.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"42 1","pages":"125-133"},"PeriodicalIF":0.0,"publicationDate":"2010-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69247394","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 examines the variability in the hydrographic conditions in the waters off West Greenland with a focus on the influence of the Polar Water off East Greenland and its associated sea ice or “Storis”. During the mid-1970s, mid-1980s and early-1990s, maxima of Polar Water were observed in the upper water layers off Fyllas Bank, West Greenland. At a station located on the offshore bank slope in about 900 m of water, the upper 75 m of the water column are primarily influenced by the Polar Water and the “Storis”. There, monthly mean temperatures are maximum and salinities a minimum during August–September. In years of larger than usual amounts of “Storis”, cold diluted surface waters appear along the west coast of Greenland. Observations of sea surface temperature anomalies off Fyllas Bank during July indicate strong warming from 1989 to 2008, going from what appears to be the coldest year to close to the warmest. Warm anomalies were actually re-established in 1996. Warmer-than-normal sub-surface conditions peaked in 2003, a year with no “Storis”. From 2002 onwards, a phenomenon is observed which seems to indicate a new structure in the distribution of SST anomalies: a band of colder-than-normal waters on the shelves off East and West Greenland. It is assumed that the continuous warming has led to massive sea ice melt off East Greenland, and the ice drifts with the East Greenland Current along the shelves off East and West Greenland, strongly influencing the temperature and salinity characteristics of the surface waters.
{"title":"Impacts of \"Storis\" on the Thermohaline Stratification off West Greenland","authors":"M. Stein","doi":"10.2960/J.V43.M655","DOIUrl":"https://doi.org/10.2960/J.V43.M655","url":null,"abstract":"This paper examines the variability in the hydrographic conditions in the waters off West Greenland with a focus on the influence of the Polar Water off East Greenland and its associated sea ice or “Storis”. During the mid-1970s, mid-1980s and early-1990s, maxima of Polar Water were observed in the upper water layers off Fyllas Bank, West Greenland. At a station located on the offshore bank slope in about 900 m of water, the upper 75 m of the water column are primarily influenced by the Polar Water and the “Storis”. There, monthly mean temperatures are maximum and salinities a minimum during August–September. In years of larger than usual amounts of “Storis”, cold diluted surface waters appear along the west coast of Greenland. Observations of sea surface temperature anomalies off Fyllas Bank during July indicate strong warming from 1989 to 2008, going from what appears to be the coldest year to close to the warmest. Warm anomalies were actually re-established in 1996. Warmer-than-normal sub-surface conditions peaked in 2003, a year with no “Storis”. From 2002 onwards, a phenomenon is observed which seems to indicate a new structure in the distribution of SST anomalies: a band of colder-than-normal waters on the shelves off East and West Greenland. It is assumed that the continuous warming has led to massive sea ice melt off East Greenland, and the ice drifts with the East Greenland Current along the shelves off East and West Greenland, strongly influencing the temperature and salinity characteristics of the surface waters.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"43 1","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2010-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256660","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 pup production of the Greenland Sea populations of hooded and harp seals were assessed in aerial surveys using two aircrafts for reconnaissance flights and photographic surveys along transects over the whelping areas from 14 March to 3 April 2007. One helicopter, operated from the applied expedition vessel, flew reconnaissance flights, monitored the distribution of seal patches and performed age-staging of the pups. The total estimate of hooded seal pup production was 16 140 (SE = 2 140, CV = 13.3%), which is similar to an estimate obtained for comparable surveys in 2005. The total pup production estimate obtained for harp seals was 110 530 (SE = 27 680, CV = 25.0%), which is slightly higher than an estimate obtained for a similar survey in 2002. The pup production and the uncertainty of the pup production estimate were estimated using a standard method for analyzing this type of survey data and a recently developed method that utilized Generalized Additive Models (GAMs). Using the two estimation methods on data from all three surveys (2002, 2005, 2007), comparable estimates of pup production were obtained. In scenarios where pups were clustered, the estimated uncertainty of the pup production estimate was much lower for the GAM method than for the conventional method. This resulted in a considerable reduction of the estimated coefficient of variation. In scenarios where pups were uniformly distributed, both methods performed the same.
{"title":"Estimation of Pup Production of Hooded and Harp Seals in the Greenland Sea in 2007: Reducing Uncertainty Using Generalized Additive Models","authors":"Tor Arne Øigård, T. Haug, K. Nilssen, A. Salberg","doi":"10.2960/J.V42.M642","DOIUrl":"https://doi.org/10.2960/J.V42.M642","url":null,"abstract":"The pup production of the Greenland Sea populations of hooded and harp seals were assessed in aerial surveys using two aircrafts for reconnaissance flights and photographic surveys along transects over the whelping areas from 14 March to 3 April 2007. One helicopter, operated from the applied expedition vessel, flew reconnaissance flights, monitored the distribution of seal patches and performed age-staging of the pups. The total estimate of hooded seal pup production was 16 140 (SE = 2 140, CV = 13.3%), which is similar to an estimate obtained for comparable surveys in 2005. The total pup production estimate obtained for harp seals was 110 530 (SE = 27 680, CV = 25.0%), which is slightly higher than an estimate obtained for a similar survey in 2002. The pup production and the uncertainty of the pup production estimate were estimated using a standard method for analyzing this type of survey data and a recently developed method that utilized Generalized Additive Models (GAMs). Using the two estimation methods on data from all three surveys (2002, 2005, 2007), comparable estimates of pup production were obtained. In scenarios where pups were clustered, the estimated uncertainty of the pup production estimate was much lower for the GAM method than for the conventional method. This resulted in a considerable reduction of the estimated coefficient of variation. In scenarios where pups were uniformly distributed, both methods performed the same.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"42 1","pages":"103-123"},"PeriodicalIF":0.0,"publicationDate":"2010-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256350","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 U.S. Marine Mammal Protection Act mandates monitoring of incidental marine mammal mortality and serious injury attributable to commercial fishing operations. Generalized linear models (GLM) applied to data collected on a sample of the fisheries were utilized to estimate incidental bycatch rates of pilot whales (Globicephela macrorhynchus and G. melas), white-sided dolphin (Lagenorhynchus acutus), and common dolphin (Delphinus delphis) in U.S. bottom trawl fisheries operating off the Northeast coast of the U.S. during 2000–2005. Spatial, habitat, environmental and fishing practice covariates were significant in the best fitting GLM models. Highest bycatch rates (observed bycatch per observed days fished) occurred in deeper waters with low sea surface temperature (whitesided dolphin), on vessels in the Mid-Atlantic region fishing in deeper waters (pilot whales), and in offshore waters (common dolphin). Estimated bycatch rates were expanded by total bottom trawl effort (days fished) to derive the mean annual bycatch mortality for each of the three species. The estimated mean annual bycatch during 2000–2005 for pilot whales, white-sided dolphin, and common dolphin in U.S. Atlantic bottom trawl fisheries is 72, 212 and 142 animals, respectively. These estimates are 29%, 42%, and 14%, respectively, of their current potential biological removal (PBR) levels for these three species. The importance of animal behavior in conjunction with vessel and gear characteristics associated with bycatch should be investigated further to learn more about potential mechanisms entrapping cetaceans in bottom trawl nets.
{"title":"Estimated Bycatch of Small Cetaceans in Northeast US Bottom Trawl Fishing Gear during 2000-2005","authors":"M. C. Rossman","doi":"10.2960/J.V42.M650","DOIUrl":"https://doi.org/10.2960/J.V42.M650","url":null,"abstract":"The U.S. Marine Mammal Protection Act mandates monitoring of incidental marine mammal mortality and serious injury attributable to commercial fishing operations. Generalized linear models (GLM) applied to data collected on a sample of the fisheries were utilized to estimate incidental bycatch rates of pilot whales (Globicephela macrorhynchus and G. melas), white-sided dolphin (Lagenorhynchus acutus), and common dolphin (Delphinus delphis) in U.S. bottom trawl fisheries operating off the Northeast coast of the U.S. during 2000–2005. Spatial, habitat, environmental and fishing practice covariates were significant in the best fitting GLM models. Highest bycatch rates (observed bycatch per observed days fished) occurred in deeper waters with low sea surface temperature (whitesided dolphin), on vessels in the Mid-Atlantic region fishing in deeper waters (pilot whales), and in offshore waters (common dolphin). Estimated bycatch rates were expanded by total bottom trawl effort (days fished) to derive the mean annual bycatch mortality for each of the three species. The estimated mean annual bycatch during 2000–2005 for pilot whales, white-sided dolphin, and common dolphin in U.S. Atlantic bottom trawl fisheries is 72, 212 and 142 animals, respectively. These estimates are 29%, 42%, and 14%, respectively, of their current potential biological removal (PBR) levels for these three species. The importance of animal behavior in conjunction with vessel and gear characteristics associated with bycatch should be investigated further to learn more about potential mechanisms entrapping cetaceans in bottom trawl nets.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"42 1","pages":"77-101"},"PeriodicalIF":0.0,"publicationDate":"2010-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256195","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}
Based on tag-recapture experiments, this paper shows that previous age determinations of Northeast Atlantic Greenland halibut from whole otolith surfaces greatly underestimates the age of older individuals. It also shows that the mean individual annual growth of adults is slightly below one cm per year. Surface methods are much more effective than other more time-intensive methods, which is an important consideration for use in stock assessment. The paper describes a new surface method that is in accordance with growth increments from tag-recaptures. The method relies on improved protocols relating to storing, imaging, choice of reading axis, and definition of annuli. The definitions of the first two annuli were validated by length frequencies of juveniles. The new reading axis and annuli of older otoliths were validated by tagging experiments involving injection of OTC, a chemical tag that incorporates into the otolith as a visual band marking the otolith size at time of release. With the new method, several measures of otolith size were correlated with age after correcting for fish length. This is expected for an accurate age determination method and was not apparent with the traditional method.
{"title":"Towards Accurate Age Determination of Greenland Halibut","authors":"O. T. Albert, M. Kvalsund, T. Vollen, A. Salberg","doi":"10.2960/J.V.40.M659","DOIUrl":"https://doi.org/10.2960/J.V.40.M659","url":null,"abstract":"Based on tag-recapture experiments, this paper shows that previous age determinations of Northeast Atlantic Greenland halibut from whole otolith surfaces greatly underestimates the age of older individuals. It also shows that the mean individual annual growth of adults is slightly below one cm per year. Surface methods are much more effective than other more time-intensive methods, which is an important consideration for use in stock assessment. The paper describes a new surface method that is in accordance with growth increments from tag-recaptures. The method relies on improved protocols relating to storing, imaging, choice of reading axis, and definition of annuli. The definitions of the first two annuli were validated by length frequencies of juveniles. The new reading axis and annuli of older otoliths were validated by tagging experiments involving injection of OTC, a chemical tag that incorporates into the otolith as a visual band marking the otolith size at time of release. With the new method, several measures of otolith size were correlated with age after correcting for fish length. This is expected for an accurate age determination method and was not apparent with the traditional method.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"355 1","pages":"81-95"},"PeriodicalIF":0.0,"publicationDate":"2009-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69247414","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}
It is now considered important to monitor the fecundity of fish stocks as this provides an indication of the Stock Reproductive Potential (SRP). There is currently very little data on the fecundity of the West-Nordic stock of Greenland halibut (Reinhardtius hippoglossoides), which includes Greenland halibut in Icelandic waters. In order to achieve a reference point of fecundity for fish in Icelandic waters, the fecundity was estimated for 48 fish caught in October 1998. Potential fecundity showed a high variation between individuals and was in the range of 8–152 thousand oocytes for fish of 57–99 cm total length. The fecundity – length relationship was Fecundity = 1.942×10-3 Length3.93. The fecundity was compared to previous fecundity estimations for Greenland halibut in other areas. There were significant differences between the estimates for the different areas, however, due to the fecundity being from only a single year, no conclusions on long term differences in fecundity could be drawn.
{"title":"Fecundity of Greenland Halibut (Reinhardtius hippoglossoidesW.) in the Waters of Iceland","authors":"A. C. Gundersen, E. Hjorleifsson, J. Kennedy","doi":"10.2960/J.V40.M656","DOIUrl":"https://doi.org/10.2960/J.V40.M656","url":null,"abstract":"It is now considered important to monitor the fecundity of fish stocks as this provides an indication of the Stock Reproductive Potential (SRP). There is currently very little data on the fecundity of the West-Nordic stock of Greenland halibut (Reinhardtius hippoglossoides), which includes Greenland halibut in Icelandic waters. In order to achieve a reference point of fecundity for fish in Icelandic waters, the fecundity was estimated for 48 fish caught in October 1998. Potential fecundity showed a high variation between individuals and was in the range of 8–152 thousand oocytes for fish of 57–99 cm total length. The fecundity – length relationship was Fecundity = 1.942×10-3 Length3.93. The fecundity was compared to previous fecundity estimations for Greenland halibut in other areas. There were significant differences between the estimates for the different areas, however, due to the fecundity being from only a single year, no conclusions on long term differences in fecundity could be drawn.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"40 1","pages":"75-80"},"PeriodicalIF":0.0,"publicationDate":"2009-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69255794","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}
Discard reduction of juvenile fish and other unwanted bycatch species has been identified as a primary tool in achieving rebuilding and mortality objectives of current fishery management plans. Management of the offshore Loligo pealei squid fishery is particularly challenging because the legal codend mesh size is smaller than other regulated commercial fisheries. Co-occurrence of adult Loligo with juveniles and other Mid-Atlantic species of concern, coupled with the high volume of landings may lead to high discarding of non-target species. Accordingly, an increase in codend mesh size from the 2005 legal size of 1.875" was evaluated as a means to reduce the capture of submarket-size squid, butterfish, and other species of concern, without materially impacting the catch of market-size squid. To evaluate the influence of fishing practice, a commercial-scale test was undertaken. A 2.5" mesh codend, in addition to the desired reduction of small Loligo, resulted in a substantial decrease in the catch of intermediate-size, but marketable (10–13 cm), squid without significant reduction in the bycatch of butterfish, silver hake or spiny dogfish. To recover total catch of market-size squid with the 2.5" mesh codend would require an increase in fishing effort of 73.9%. Even with that increase, total discards of small squid would be reduced by 52.7%. However, total discards of bycatch species would be substantially increased. Codend mesh size is an effective option only if discarding of bycatch species is inconsequential or if avoidance of unwanted catch can be achieved through area management.
{"title":"Effect of an Increase in Codend Mesh Size on Discarding in theLoligoSquid-Directed Fishery: A Commercial-Scale Test","authors":"Sarah E. King, E. Powell, E. Bochenek","doi":"10.2960/J.V40.M631","DOIUrl":"https://doi.org/10.2960/J.V40.M631","url":null,"abstract":"Discard reduction of juvenile fish and other unwanted bycatch species has been identified as a primary tool in achieving rebuilding and mortality objectives of current fishery management plans. Management of the offshore Loligo pealei squid fishery is particularly challenging because the legal codend mesh size is smaller than other regulated commercial fisheries. Co-occurrence of adult Loligo with juveniles and other Mid-Atlantic species of concern, coupled with the high volume of landings may lead to high discarding of non-target species. Accordingly, an increase in codend mesh size from the 2005 legal size of 1.875\" was evaluated as a means to reduce the capture of submarket-size squid, butterfish, and other species of concern, without materially impacting the catch of market-size squid. To evaluate the influence of fishing practice, a commercial-scale test was undertaken. A 2.5\" mesh codend, in addition to the desired reduction of small Loligo, resulted in a substantial decrease in the catch of intermediate-size, but marketable (10–13 cm), squid without significant reduction in the bycatch of butterfish, silver hake or spiny dogfish. To recover total catch of market-size squid with the 2.5\" mesh codend would require an increase in fishing effort of 73.9%. Even with that increase, total discards of small squid would be reduced by 52.7%. However, total discards of bycatch species would be substantially increased. Codend mesh size is an effective option only if discarding of bycatch species is inconsequential or if avoidance of unwanted catch can be achieved through area management.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"40 1","pages":"41-58"},"PeriodicalIF":0.0,"publicationDate":"2009-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256157","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}
Histological examination conducted on gonads of Rockall haddock showed that asynchronous vitellogenesis of oocytes and batch spawning are typical of this stock. The post-spawning features could be observed in ovaries and testes until September. The maximum values of the gonadosomatic index (GSI) (12.0–19.6%) were found in pre-spawning females (stage IVa) in March–April. In the process of spawning, GSI of females gradually decreased to 0.9–2.4% in May when the last batch of eggs were spawned (stage VI). The minimum values of GSI (0.4–0.8%) were observed during the post-spawning recovery from the end of August to the end of September. The bulk of spawning took place in March–April when 11–19 batches of eggs were spawned. The percent size of an egg batch did not change greatly with age and varied from 5.3 to 9.5% of the total number of eggs found per female. The majority of individuals, at a length of 25 cm at the age of 2 years, become mature. The minimum length of a mature female was 22 cm, and that of a mature male, 18 cm. Absolute potential fecundity (the mean value of individual potential fecundities per age) was 78 thousand eggs in first spawning fish at the age of two years, 340 thousand eggs in four-year-olds, 947 thousand eggs in eight-year-olds.
{"title":"The Reproductive Biology of Haddock (Mellanogrammus aeglefinus) at the Rockall Bank","authors":"E. A. Filina, V. Khlivnoy, V. Vinnichenko","doi":"10.2960/J.V40.M639","DOIUrl":"https://doi.org/10.2960/J.V40.M639","url":null,"abstract":"Histological examination conducted on gonads of Rockall haddock showed that asynchronous vitellogenesis of oocytes and batch spawning are typical of this stock. The post-spawning features could be observed in ovaries and testes until September. The maximum values of the gonadosomatic index (GSI) (12.0–19.6%) were found in pre-spawning females (stage IVa) in March–April. In the process of spawning, GSI of females gradually decreased to 0.9–2.4% in May when the last batch of eggs were spawned (stage VI). The minimum values of GSI (0.4–0.8%) were observed during the post-spawning recovery from the end of August to the end of September. The bulk of spawning took place in March–April when 11–19 batches of eggs were spawned. The percent size of an egg batch did not change greatly with age and varied from 5.3 to 9.5% of the total number of eggs found per female. The majority of individuals, at a length of 25 cm at the age of 2 years, become mature. The minimum length of a mature female was 22 cm, and that of a mature male, 18 cm. Absolute potential fecundity (the mean value of individual potential fecundities per age) was 78 thousand eggs in first spawning fish at the age of two years, 340 thousand eggs in four-year-olds, 947 thousand eggs in eight-year-olds.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"40 1","pages":"59-73"},"PeriodicalIF":0.0,"publicationDate":"2009-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69255738","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 Antarctic minke whale (Balaenoptera bonaerensis) is the most abundant baleen whale species in the Southern Ocean. Quantitative information on prey consumption of whales is useful to understand their feeding ecology and role in the ecosystem. The purposes of this study are 1) to investigate the feeding habit of Antarctic minke whales based on information on prey species, freshness and diurnal change in stomach contents, and 2) to estimate the amount of prey consumed by whales. Estimates are made for whales of different sexual maturity classes as it is expected that the energy requirements vary among them. The analysis is based on the data from whales taken by JARPA (Japanese Whale Research Program under Special Permit in the Antarctic) in a longitudinal sector between 35o E and 145o W, and south of 60o S. Sampling was conducted in the austral summer seasons from 1987/1988 to 2004/2005, mainly in the months from December to March. Daily prey consumption by the whales in each sexual maturity class was estimated using energy-requirement and energy deposition. The whales feed mainly before 05:00 h, which suggest that they cease to feed early in the day. Daily prey consumptions were estimated to be 83.7–325.5 kg, equivalent to 2.7–4.0% of body weight. The mean prey consumptions per capita during feeding season were 7.5 and 16.4 t for immature and mature male, 12.5 and 39.1 t for immature and mature female, respectively. In Area IV (70°–130°E), total prey consumptions of krill by Antarctic minke whales in 1999/2000 and 2001/2002 seasons were estimated to be 0.9 and 1.1 million t, respectively. In Area V (130° E–170° W including the Ross Sea), these estimates in 2000/2001 and 2002/2003 seasons were 3.9 and 4.1 million t, respectively. The estimations of feeding impact on krill resources by Antarctic minke whales in Areas IV and V were from 2.7 to 3.2%, and from 18.2 to 18.9% of krill biomasses, respectively. These results on prey consumption are important input data for the development of ecosystem modeling in the Southern Ocean.
{"title":"Feeding Habits and Prey Consumption of Antarctic Minke Whale (Balaenoptera bonaerensis) in the Southern Ocean","authors":"T. Tamura, K. Konishi","doi":"10.2960/J.V42.M652","DOIUrl":"https://doi.org/10.2960/J.V42.M652","url":null,"abstract":"The Antarctic minke whale (Balaenoptera bonaerensis) is the most abundant baleen whale species in the Southern Ocean. Quantitative information on prey consumption of whales is useful to understand their feeding ecology and role in the ecosystem. The purposes of this study are 1) to investigate the feeding habit of Antarctic minke whales based on information on prey species, freshness and diurnal change in stomach contents, and 2) to estimate the amount of prey consumed by whales. Estimates are made for whales of different sexual maturity classes as it is expected that the energy requirements vary among them. The analysis is based on the data from whales taken by JARPA (Japanese Whale Research Program under Special Permit in the Antarctic) in a longitudinal sector between 35o E and 145o W, and south of 60o S. Sampling was conducted in the austral summer seasons from 1987/1988 to 2004/2005, mainly in the months from December to March. Daily prey consumption by the whales in each sexual maturity class was estimated using energy-requirement and energy deposition. The whales feed mainly before 05:00 h, which suggest that they cease to feed early in the day. Daily prey consumptions were estimated to be 83.7–325.5 kg, equivalent to 2.7–4.0% of body weight. The mean prey consumptions per capita during feeding season were 7.5 and 16.4 t for immature and mature male, 12.5 and 39.1 t for immature and mature female, respectively. In Area IV (70°–130°E), total prey consumptions of krill by Antarctic minke whales in 1999/2000 and 2001/2002 seasons were estimated to be 0.9 and 1.1 million t, respectively. In Area V (130° E–170° W including the Ross Sea), these estimates in 2000/2001 and 2002/2003 seasons were 3.9 and 4.1 million t, respectively. The estimations of feeding impact on krill resources by Antarctic minke whales in Areas IV and V were from 2.7 to 3.2%, and from 18.2 to 18.9% of krill biomasses, respectively. These results on prey consumption are important input data for the development of ecosystem modeling in the Southern Ocean.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"42 1","pages":"13-25"},"PeriodicalIF":0.0,"publicationDate":"2009-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257006","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}
Julie M. Andersen, Y. F. Wierma, G. Stenson, M. Hammill, A. Rosing-Asvid
Movement patterns of hooded seals (Cystophora cristata) in the Northwest Atlantic in the period following moulting and prior to breeding are not well known. Here, we describe in detail the movement patterns of 21 seals for this period based on information gathered from satellite linked time depth recorders (SLTDRs). This study provides important baseline information necessary to understand the ecological requirements and patterns in habitat selection for the species. Adult and sub-adult hooded seals were tagged with SLTDRs directly after moulting in SE Greenland during July 2004, 2005 and 2007. Due to variation in tag date and arrival date to the breeding grounds, data between 1 Aug–28 Feb were used which gave all seals a track duration of 211 days (212 in 2005) except for one juvenile where the tag lasted for only 154 days. The tags yielded 36 107 location fixes (SD = 410.64, mean = 1 719.38). Although there was individual variation between seal trajectories during migration, the population shared a similar overall pattern. After moulting in July individuals travelled along the continental shelf area up to Davis Strait and Baffin Bay, thereafter moving southwards along the Labrador shelf until they arrived at the breeding grounds by March. Females tended to cut across the Labrador Sea and arrived at the Labrador shelf before heading up to the Baffin Bay area, while males tended to move straight there. The majority of the seals ended up at the Front (off Newfoundland and Southern Labrador) by March although a few of the tagged seals may have belonged to the Davis Strait breeding population and one male belonged to the Gulf of St. Lawrence breeding population. Seven seals displayed an eastward migratory pull and might have overlapped with the Northeast Atlantic population. This would support the theory of a panmitic population structure.
西北大西洋斑海豹(Cystophora cristata)在蜕皮后和繁殖前的运动模式尚不为人所知。在此，我们根据卫星链接时间深度记录仪(SLTDRs)收集的信息，详细描述了这一时期21只海豹的运动模式。本研究为了解该物种的生态需求和生境选择模式提供了重要的基线信息。2004年7月和2007年7月，在格陵兰岛东南部，用sltdr直接标记成年和亚成年斑海豹。由于标签日期和到达繁殖地的日期不同，使用的数据为8月1日至2月28日，所有海豹的追踪时间为211天(2005年为212天)，除了一只幼海豹的标签持续时间仅为154天。标签共产生36107个位置固定(SD = 410.64, mean = 1 719.38)。尽管在迁徙过程中海豹的迁徙轨迹存在个体差异，但总体上海豹的迁徙轨迹是相似的。在7月换羽后，个体沿着大陆架区域前往戴维斯海峡和巴芬湾，然后沿着拉布拉多大陆架向南移动，直到3月到达繁殖地。雌性倾向于穿过拉布拉多海，到达拉布拉多大陆架，然后前往巴芬湾地区，而雄性则倾向于直接前往那里。大多数海豹在3月份结束在前线(纽芬兰和拉布拉多南部)，尽管一些被标记的海豹可能属于戴维斯海峡的繁殖种群，一只雄性海豹属于圣劳伦斯湾的繁殖种群。七只海豹表现出向东迁徙的吸引力，可能与东北大西洋的种群重叠。这将支持大流行人口结构理论。
{"title":"Movement Patterns of Hooded Seals (Cystophora cristata) in the Northwest Atlantic Ocean during the Post-Moult and Pre-Breed Seasons","authors":"Julie M. Andersen, Y. F. Wierma, G. Stenson, M. Hammill, A. Rosing-Asvid","doi":"10.2960/J.V42.M649","DOIUrl":"https://doi.org/10.2960/J.V42.M649","url":null,"abstract":"Movement patterns of hooded seals (Cystophora cristata) in the Northwest Atlantic in the period following moulting and prior to breeding are not well known. Here, we describe in detail the movement patterns of 21 seals for this period based on information gathered from satellite linked time depth recorders (SLTDRs). This study provides important baseline information necessary to understand the ecological requirements and patterns in habitat selection for the species. Adult and sub-adult hooded seals were tagged with SLTDRs directly after moulting in SE Greenland during July 2004, 2005 and 2007. Due to variation in tag date and arrival date to the breeding grounds, data between 1 Aug–28 Feb were used which gave all seals a track duration of 211 days (212 in 2005) except for one juvenile where the tag lasted for only 154 days. The tags yielded 36 107 location fixes (SD = 410.64, mean = 1 719.38). Although there was individual variation between seal trajectories during migration, the population shared a similar overall pattern. After moulting in July individuals travelled along the continental shelf area up to Davis Strait and Baffin Bay, thereafter moving southwards along the Labrador shelf until they arrived at the breeding grounds by March. Females tended to cut across the Labrador Sea and arrived at the Labrador shelf before heading up to the Baffin Bay area, while males tended to move straight there. The majority of the seals ended up at the Front (off Newfoundland and Southern Labrador) by March although a few of the tagged seals may have belonged to the Davis Strait breeding population and one male belonged to the Gulf of St. Lawrence breeding population. Seven seals displayed an eastward migratory pull and might have overlapped with the Northeast Atlantic population. This would support the theory of a panmitic population structure.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":"42 1","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"2009-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256539","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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