Sea surface temperature (SST) records have been collected at Boothbay Harbor, Maine, since 1905. A dramatic change in the structure of the monthly mean SST anomalies occurred around 1950. Prior to 1950, when observations were made with a bucket thermometer, there was a large range in the monthly mean temperature anomalies with warmer summers and cooler winters. After 1950, when a fixed thermistor was used, the difference between winter and summer anomalies were much reduced. We show that the primary cause of the change in the monthly anomaly patterns is related to the difference in the depth of the measurements from near surface (pre-1950) to 1.7 m below mean low water (post-1950) combined with the thermal stratification of Boothbay Harbor waters. The non-homogeneous nature of the surface temperature time series at Boothbay Harbor means that they should not be used for retrospective analyses that cover the entire period. Since 2000, the annual mean Boothbay Harbor temperatures have been much warmer than nearby sites, however the cause of this phenomenon is as yet unclear.
{"title":"A Note on the Long-Term Sea Surface Temperature Records at Boothbay Harbor, Maine","authors":"K. Drinkwater, B. Petrie","doi":"10.2960/J.V43.M663","DOIUrl":"https://doi.org/10.2960/J.V43.M663","url":null,"abstract":"Sea surface temperature (SST) records have been collected at Boothbay Harbor, Maine, since 1905. A dramatic change in the structure of the monthly mean SST anomalies occurred around 1950. Prior to 1950, when observations were made with a bucket thermometer, there was a large range in the monthly mean temperature anomalies with warmer summers and cooler winters. After 1950, when a fixed thermistor was used, the difference between winter and summer anomalies were much reduced. We show that the primary cause of the change in the monthly anomaly patterns is related to the difference in the depth of the measurements from near surface (pre-1950) to 1.7 m below mean low water (post-1950) combined with the thermal stratification of Boothbay Harbor waters. The non-homogeneous nature of the surface temperature time series at Boothbay Harbor means that they should not be used for retrospective analyses that cover the entire period. Since 2000, the annual mean Boothbay Harbor temperatures have been much warmer than nearby sites, however the cause of this phenomenon is as yet unclear.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2011-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256674","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 bathymetry of Baffin Bay with shallow sills both to the north and south creates a relatively isolated body of deep polar water, unique among the Arctic Seas. During 105 trawl hauls completed during autumn 2004, 45 fish species were collected in the northern Baffin Bay between 72o 02' N – 76o 55' N, depth 150–1 418 m. As a first step the abundance data for the 40 benthic species were used for analyses of the fish fauna diversity and fish assemblages. Two species, Greenland halibut (Reinhardtius hippoglossoides) and the sea snail Liparis fabricii were very common and represented in large numbers in almost all trawl hauls. The two species dominated the outcome of the first run of the analysis and were removed from the analysis to allow an analysis of the remaining species. For those remaining 38 species, five 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 five clusters. By means of a geostatistical tool the spatial distribution of the conditional probabilities for each cluster (assemblage) was mapped. Each of the five assemblages was further defined by indicator species, depth and temperature. The study is a continuation of a similar study using the same vessel, sampling scheme and analytical methods previously conducted in the southern part of Baffin Bay and Davis Strait.
{"title":"Identification and Mapping of Bottom Fish Assemblages in Northern Baffin Bay","authors":"O. Jørgensen, C. Hvingel, M. Treble","doi":"10.2960/J.V43.M666","DOIUrl":"https://doi.org/10.2960/J.V43.M666","url":null,"abstract":"The bathymetry of Baffin Bay with shallow sills both to the north and south creates a relatively isolated body of deep polar water, unique among the Arctic Seas. During 105 trawl hauls completed during autumn 2004, 45 fish species were collected in the northern Baffin Bay between 72o 02' N – 76o 55' N, depth 150–1 418 m. As a first step the abundance data for the 40 benthic species were used for analyses of the fish fauna diversity and fish assemblages. Two species, Greenland halibut (Reinhardtius hippoglossoides) and the sea snail Liparis fabricii were very common and represented in large numbers in almost all trawl hauls. The two species dominated the outcome of the first run of the analysis and were removed from the analysis to allow an analysis of the remaining species. For those remaining 38 species, five 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 five clusters. By means of a geostatistical tool the spatial distribution of the conditional probabilities for each cluster (assemblage) was mapped. Each of the five assemblages was further defined by indicator species, depth and temperature. The study is a continuation of a similar study using the same vessel, sampling scheme and analytical methods previously conducted in the southern part of Baffin Bay and Davis Strait.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2011-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256687","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}
Yuying Zhang, D. Brzezinski, J. Chang, K. Stepanek, Yong Chen
The coastal Gulf of Maine provides critical habitats for many commercially important fish species. In this study, using data collected from an inshore bottom trawl survey, we evaluated seasonal and annual variations in the spatial distribution of the fish community in the coastal Gulf of Maine. We identified key environmental drivers important in structuring the fish community, including longitudinal strata, distance offshore, depth, bottom temperature, bottom salinity and substrate type. This study suggests linear relationships between the fish abundances and the environmental variables. This linear relationship is more obvious if integrating fish species as a whole group than clustering them into subgroups. However, as large temporal variability exists for some species subgroups in their spatial structure, environmental variables can still be difficult to predict the spatial distributions of species groups. Despite these current limitations, the information derived in this study contributes to critical information for developing spatially-explicit fisheries management strategies such as area closure in the coastal Gulf of Maine.
{"title":"Spatial structuring of fish community in association with environmental variables in the coastal Gulf of Maine","authors":"Yuying Zhang, D. Brzezinski, J. Chang, K. Stepanek, Yong Chen","doi":"10.2960/J.V43.M669","DOIUrl":"https://doi.org/10.2960/J.V43.M669","url":null,"abstract":"The coastal Gulf of Maine provides critical habitats for many commercially important fish species. In this study, using data collected from an inshore bottom trawl survey, we evaluated seasonal and annual variations in the spatial distribution of the fish community in the coastal Gulf of Maine. We identified key environmental drivers important in structuring the fish community, including longitudinal strata, distance offshore, depth, bottom temperature, bottom salinity and substrate type. This study suggests linear relationships between the fish abundances and the environmental variables. This linear relationship is more obvious if integrating fish species as a whole group than clustering them into subgroups. However, as large temporal variability exists for some species subgroups in their spatial structure, environmental variables can still be difficult to predict the spatial distributions of species groups. Despite these current limitations, the information derived in this study contributes to critical information for developing spatially-explicit fisheries management strategies such as area closure in the coastal Gulf of Maine.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2011-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256753","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}
Harbor porpoise bycatch estimates for federally managed gillnet fisheries in northwestern Atlantic US waters were calculated for a nine-year period (1999–2007) using two new methods, and the results were compared to the traditionally used stratified ratio estimation method. The aims of this research were to improve on the existing methods for estimating harbor porpoise bycatch for the Northeast and Mid-Atlantic US gillnet fisheries, to provide insight into the causes of harbor porpoise bycatch, and to compare bycatch estimation techniques that could be applied to other fisheries and species. The new methods included a model approach, and a ratio estimation approach that incorporated variables from both the regression model and the existing ratio estimation method. Initially, bycatch was modeled using a GAM forward stepwise process and included testing numerous variables describing the time, duration, and location of the fishing gear, the fishing gear configuration, and the environmental characteristics of the fished waters. The final model was simplified to a GLM and included variables describing port groupings, seasons, bottom depth, stretched mesh size, and year categories. The new mixed variable ratio estimation approach calculated both the Northeast and Mid-Atlantic bycatch estimates within the same framework by using the port groupings and mesh size variables from the model, and the season variable from the traditional ratio estimating approach. Bycatch estimates for the entire study area were similar between modeling and ratio estimator approaches, though estimates for the two new techniques were more stable from year to year in areas with less observed bycatch. The CVs for the model based estimates were much lower than ratio based estimates, and CVs for the two ratio estimation approaches were similar to each other. However, the model CVs may have been artificially low, as the model may have been over-parameterized in an attempt to accurately calculate annual estimates. Despite some differences, the estimates were not significantly different between approaches for the majority of comparisons.
{"title":"Protected Species Bycatch Estimating Approaches: Estimating Harbor Porpoise Bycatch in U.S. Northwestern Atlantic Gillnet Fisheries","authors":"C. Orphanides","doi":"10.2960/J.V42.M647","DOIUrl":"https://doi.org/10.2960/J.V42.M647","url":null,"abstract":"Harbor porpoise bycatch estimates for federally managed gillnet fisheries in northwestern Atlantic US waters were calculated for a nine-year period (1999–2007) using two new methods, and the results were compared to the traditionally used stratified ratio estimation method. The aims of this research were to improve on the existing methods for estimating harbor porpoise bycatch for the Northeast and Mid-Atlantic US gillnet fisheries, to provide insight into the causes of harbor porpoise bycatch, and to compare bycatch estimation techniques that could be applied to other fisheries and species. The new methods included a model approach, and a ratio estimation approach that incorporated variables from both the regression model and the existing ratio estimation method. Initially, bycatch was modeled using a GAM forward stepwise process and included testing numerous variables describing the time, duration, and location of the fishing gear, the fishing gear configuration, and the environmental characteristics of the fished waters. The final model was simplified to a GLM and included variables describing port groupings, seasons, bottom depth, stretched mesh size, and year categories. The new mixed variable ratio estimation approach calculated both the Northeast and Mid-Atlantic bycatch estimates within the same framework by using the port groupings and mesh size variables from the model, and the season variable from the traditional ratio estimating approach. Bycatch estimates for the entire study area were similar between modeling and ratio estimator approaches, though estimates for the two new techniques were more stable from year to year in areas with less observed bycatch. The CVs for the model based estimates were much lower than ratio based estimates, and CVs for the two ratio estimation approaches were similar to each other. However, the model CVs may have been artificially low, as the model may have been over-parameterized in an attempt to accurately calculate annual estimates. Despite some differences, the estimates were not significantly different between approaches for the majority of comparisons.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256485","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 sei whale (Balaenoptera borealis) is a medium sized rorqual with basic features similar to the larger fin and blue (Balaenoptera sp.). While the sei whale has an expandable buccal pouch, it’s capacity is substantially reduced by the length of the ventral grooves relative to fin and blue whales. The finer filtration capacity of the baleen allows predation on smaller prey spectra as a skim-feeder, with the option to engulf where prey are larger, or in greater densities. The sei whale exhibits some features of the mouth cross-section which are reminiscent of right whales (Eubalaena sp.) and there appears to be a difference in the degree of arch of the rostrum when comparing the sexes. The dynamics of skim-feeding and prey reaction are discussed.
{"title":"On the Feeding Mechanisms of the Sei Whale (Balaenoptera borealis)","authors":"P. Brodie, G. Víkingsson","doi":"10.2960/J.V42.M646","DOIUrl":"https://doi.org/10.2960/J.V42.M646","url":null,"abstract":"The sei whale (Balaenoptera borealis) is a medium sized rorqual with basic features similar to the larger fin and blue (Balaenoptera sp.). While the sei whale has an expandable buccal pouch, it’s capacity is substantially reduced by the length of the ventral grooves relative to fin and blue whales. The finer filtration capacity of the baleen allows predation on smaller prey spectra as a skim-feeder, with the option to engulf where prey are larger, or in greater densities. The sei whale exhibits some features of the mouth cross-section which are reminiscent of right whales (Eubalaena sp.) and there appears to be a difference in the degree of arch of the rostrum when comparing the sexes. The dynamics of skim-feeding and prey reaction are discussed.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256372","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}
S. Koningson, S. Lunneryd, H. Stridh, F. Sundqvist
The conflicts between grey seals and the cod fisheries in the Swedish Baltic Sea have increased steadily during the past 10 years. In this study we investigated damage to catches caused by seals in the inshore gillnet fishery for cod in the central Baltic Sea. Damage by seals includes both visible catch losses such as fish remains found and hidden losses where fish are removed entirely without leaving any visible fish remains in the net. An observer joined two professional fishermen in two locations, recording the fishing effort and catches on their daily fishing trips for a period of three months each year in 2005 and 2006. To estimate the hidden losses, marked fish were manually entangled in the nets before resetting. When hauling the nets, the number of marked fish either damaged or lost was used to calculate the “hidden” losses. A total of 324 fleets of nets were set and on 169 of these settings, damaged fish were found in the nets when hauled. 59 previously set fleets were selected for experimental trials in which fish were marked and replaced in the nets in order to estimate the extent of the hidden losses, and 39 of these set fleets were found to have been visited by seals. The mean hidden losses were calculated to be 44.2% of the marked fish (95% C.I 33.9–54.5) after allowing for fish lost due to handling of the nets. On average 4.1 fish were lost for each fish found damaged (max. 25.6 and min. 1.6) in 2005 and in 2006 the ratio was 2.7 (max. 11.3 and min. 1.4). Extrapolating these numbers to the actual catches landed in the fishery observed, the hidden losses would correspond to 36% of the total potential catches or 67% of the landed catches in 2005, and to 15% of the total potential catches or 19% of the landed catches in 2006. The results from the present study show that the damage caused by grey seals such as in hidden as well as visible catch losses are significant and that this needs to be taken into account when estimating the total impact of seal predation on fisheries.
在过去的10年里，瑞典波罗的海的灰海豹和鳕鱼渔业之间的冲突不断增加。在这项研究中，我们调查了海豹对波罗的海中部近海刺网捕捞鳕鱼造成的渔获损害。海豹造成的损失既包括看得见的渔获量损失，如仍能找到的鱼，也包括隐藏的损失，即鱼被完全移走，而网中没有留下任何可见的鱼。在2005年和2006年，一名观察员与两名专业渔民在两个地点进行了为期三个月的观察，记录了两名专业渔民每天捕鱼时的渔获量和渔获量。为了估计隐藏的损失，在重新设置渔网之前，人工将标记的鱼缠在渔网中。在拖网时，被标记的受损或丢失的鱼的数量被用来计算“隐藏”损失。共布设了324个渔网船队，其中169个渔网在拖网时发现了受损的鱼。选择了59个先前设定的船队进行试验，在试验中对渔网中的鱼进行标记和更换，以估计隐藏损失的程度，发现其中39个设定的船队曾被海豹拜访过。考虑到因处理渔网而损失的鱼，计算出的平均隐藏损失为标记鱼的44.2% (95% ci . 33.9-54.5)。每发现一条受损鱼，平均损失4.1条鱼。2005年为25.6，最低为1.6)，2006年为2.7(最高为1.6)。11.3和1.4)。将这些数字外推到所观察到的渔业的实际渔获量，隐性损失相当于2005年潜在渔获总量的36%或渔获量的67%，2006年潜在渔获总量的15%或渔获量的19%。本研究的结果表明，灰海豹造成的损害，如隐藏的和可见的渔获量损失是巨大的，在估计海豹捕食对渔业的总体影响时，需要考虑到这一点。
{"title":"Grey Seal Predation in Cod Gillnet Fisheries in the Central Baltic Sea","authors":"S. Koningson, S. Lunneryd, H. Stridh, F. Sundqvist","doi":"10.2960/J.V42.M654","DOIUrl":"https://doi.org/10.2960/J.V42.M654","url":null,"abstract":"The conflicts between grey seals and the cod fisheries in the Swedish Baltic Sea have increased steadily during the past 10 years. In this study we investigated damage to catches caused by seals in the inshore gillnet fishery for cod in the central Baltic Sea. Damage by seals includes both visible catch losses such as fish remains found and hidden losses where fish are removed entirely without leaving any visible fish remains in the net. An observer joined two professional fishermen in two locations, recording the fishing effort and catches on their daily fishing trips for a period of three months each year in 2005 and 2006. To estimate the hidden losses, marked fish were manually entangled in the nets before resetting. When hauling the nets, the number of marked fish either damaged or lost was used to calculate the “hidden” losses. A total of 324 fleets of nets were set and on 169 of these settings, damaged fish were found in the nets when hauled. 59 previously set fleets were selected for experimental trials in which fish were marked and replaced in the nets in order to estimate the extent of the hidden losses, and 39 of these set fleets were found to have been visited by seals. The mean hidden losses were calculated to be 44.2% of the marked fish (95% C.I 33.9–54.5) after allowing for fish lost due to handling of the nets. On average 4.1 fish were lost for each fish found damaged (max. 25.6 and min. 1.6) in 2005 and in 2006 the ratio was 2.7 (max. 11.3 and min. 1.4). Extrapolating these numbers to the actual catches landed in the fishery observed, the hidden losses would correspond to 36% of the total potential catches or 67% of the landed catches in 2005, and to 15% of the total potential catches or 19% of the landed catches in 2006. The results from the present study show that the damage caused by grey seals such as in hidden as well as visible catch losses are significant and that this needs to be taken into account when estimating the total impact of seal predation on fisheries.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257028","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}
Greenland cod (Gadus ogac) and Atlantic cod (Gadus morhua) co-exist and are caught in the same fisheries in coastal waters off western Greenland and eastern Canada. Juveniles (<15–20 cm total length, TL) are similar in morphology and are not easily distinguished in fisheries research surveys or when examining stomach contents of common predators such as seals, small toothed whales, seabirds and gadoid fish. Often only the skeleton and otoliths remain in predator stomachs. Examination of variation in otolith length, width, height and weight in relation to body size and zoogeographic differences indicated otoliths of G. ogac are consistently larger and heavier than otoliths of G. morhua from Greenland and Canadian fish of both sexes and all sizes examined. Discriminant function analyses (DFA) was used to determine if otoliths removed from fish with known identity, can be individually discriminated based on otolith dimensions. Otoliths from the two species can be statistically discriminated based on otolith dimensions alone, primarily otolith length and height with relatively high certainty (71–80%). Discrimination certainty approaches 100% if body size is included. Simple additive statistical models with only a few descriptors and their discriminant functions with linear decision surfaces are provided and should simplify the identification of intact otoliths.
{"title":"A statistical discrimination method using sagittal otolith dimensions between sibling species of juvenile codGadus morhuaandGadus ogacfrom the northwest Atlantic","authors":"J. Nielsen, D. Methven, K. Kristensen","doi":"10.2960/J.V43.M667","DOIUrl":"https://doi.org/10.2960/J.V43.M667","url":null,"abstract":"Greenland cod (Gadus ogac) and Atlantic cod (Gadus morhua) co-exist and are caught in the same fisheries in coastal waters off western Greenland and eastern Canada. Juveniles (<15–20 cm total length, TL) are similar in morphology and are not easily distinguished in fisheries research surveys or when examining stomach contents of common predators such as seals, small toothed whales, seabirds and gadoid fish. Often only the skeleton and otoliths remain in predator stomachs. Examination of variation in otolith length, width, height and weight in relation to body size and zoogeographic differences indicated otoliths of G. ogac are consistently larger and heavier than otoliths of G. morhua from Greenland and Canadian fish of both sexes and all sizes examined. Discriminant function analyses (DFA) was used to determine if otoliths removed from fish with known identity, can be individually discriminated based on otolith dimensions. Otoliths from the two species can be statistically discriminated based on otolith dimensions alone, primarily otolith length and height with relatively high certainty (71–80%). Discrimination certainty approaches 100% if body size is included. Simple additive statistical models with only a few descriptors and their discriminant functions with linear decision surfaces are provided and should simplify the identification of intact otoliths.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256735","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}
S. Murphy, G. Pierce, R. Law, P. Bersuder, P. Jepson, J. Learmonth, M. Addink, W. Dabin, M. Santos, R. Deaville, B. Zegers, A. Mets, E. Rogan, V. Ridoux, R. Reid, C. Smeenk, T. Jauniaux, A. López, J. Farré, C. Lockyer, J. Boon, E. Cabello
As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 μg g -1 total PCBs lipid) were resting mature females, with
{"title":"Assessing the Effect of Persistent Organic Pollutants on Reproductive Activity in Common Dolphins and Harbour Porpoises","authors":"S. Murphy, G. Pierce, R. Law, P. Bersuder, P. Jepson, J. Learmonth, M. Addink, W. Dabin, M. Santos, R. Deaville, B. Zegers, A. Mets, E. Rogan, V. Ridoux, R. Reid, C. Smeenk, T. Jauniaux, A. López, J. Farré, C. Lockyer, J. Boon, E. Cabello","doi":"10.2960/J.V42.M658","DOIUrl":"https://doi.org/10.2960/J.V42.M658","url":null,"abstract":"As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 μg g -1 total PCBs lipid) were resting mature females, with","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69257091","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 total of 1 893 males and 1 124 females of Squalus mitsukurii were collected from latitudes 34o 30' S and 37o 00' S, in the south-western Atlantic Ocean, during early autumn, late autumn and spring 1995, early autumn 1996 and early autumn 1998. Length-frequency distributions significantly varied between sexes for all seasons (P<0.05). Mature males predominated in all seasons throughout the analyzed area, according to their presence in the catches. In all periods sampled, immature females predominated except for late autumn 1995 where mature females were dominant. Significant differences in density among seasons were recorded for immature and mature females and mature males (P<0.05). Density of immature females and mature males were significantly different (P<0.05) for late autumn 1995 and early autumn 1996. Size-at-maturity was 43.1 cm and 55.9 cm total length for males (n = 1 181) and females (n = 862) receptively. The percentage of pregnant females ranged from 21.4% in spring 1995 to 49.8% in late autumn 1995. Ovarian fecundity varied significantly between early autumn 1995 and late autumn 1995 from 1–15 and uterine fecundity from 1–10, respectively. Embryo total length varied from 0.5–22.0 cm, attaining the highest values in autumn months. Sizeat-birth was estimated to be 22–24 cm total length.
{"title":"Size Structure, Abundance and Preliminary Information on the Reproductive Parameters of the Shortspine Spurdog (Squalus mitsukurii) in the Argentinean-Uruguayan Common Fishing Zone from the mid-1990s","authors":"M. Oddone, L. Paesch, W. Norbis","doi":"10.2960/J.V.43.M662","DOIUrl":"https://doi.org/10.2960/J.V.43.M662","url":null,"abstract":"A total of 1 893 males and 1 124 females of Squalus mitsukurii were collected from latitudes 34o 30' S and 37o 00' S, in the south-western Atlantic Ocean, during early autumn, late autumn and spring 1995, early autumn 1996 and early autumn 1998. Length-frequency distributions significantly varied between sexes for all seasons (P<0.05). Mature males predominated in all seasons throughout the analyzed area, according to their presence in the catches. In all periods sampled, immature females predominated except for late autumn 1995 where mature females were dominant. Significant differences in density among seasons were recorded for immature and mature females and mature males (P<0.05). Density of immature females and mature males were significantly different (P<0.05) for late autumn 1995 and early autumn 1996. Size-at-maturity was 43.1 cm and 55.9 cm total length for males (n = 1 181) and females (n = 862) receptively. The percentage of pregnant females ranged from 21.4% in spring 1995 to 49.8% in late autumn 1995. Ovarian fecundity varied significantly between early autumn 1995 and late autumn 1995 from 1–15 and uterine fecundity from 1–10, respectively. Embryo total length varied from 0.5–22.0 cm, attaining the highest values in autumn months. Sizeat-birth was estimated to be 22–24 cm total length.","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69247788","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}
Seasonal changes in energy intake of northwest Atlantic harp seals were modelled and implemented as a Microsoft Excel ™ spreadsheet. Energy intake of adults during the fourth quarter is almost double estimated intake during the second quarter, with intermediate values during the fi rst and third quarters. Reproduction increases female annual energy requirements by 18%, and adds 4% to the estimated population energy intake. The model was sensitive to changes in metabolizable energy, body mass, and the activity factors selected to estimate cost of activity. Changes in blubber conductivity and body composition had intermediate effects, while changes in water and air temperature and activity had little effect on model output. Comparing annual energy intake between a seasonally varying model
{"title":"Seasonal Changes in Energy Requirements of Harp Seals","authors":"M. Hammill, M. Ryg, D. Chabot","doi":"10.2960/J.V42.M660","DOIUrl":"https://doi.org/10.2960/J.V42.M660","url":null,"abstract":"Seasonal changes in energy intake of northwest Atlantic harp seals were modelled and implemented as a Microsoft Excel ™ spreadsheet. Energy intake of adults during the fourth quarter is almost double estimated intake during the second quarter, with intermediate values during the fi rst and third quarters. Reproduction increases female annual energy requirements by 18%, and adds 4% to the estimated population energy intake. The model was sensitive to changes in metabolizable energy, body mass, and the activity factors selected to estimate cost of activity. Changes in blubber conductivity and body composition had intermediate effects, while changes in water and air temperature and activity had little effect on model output. Comparing annual energy intake between a seasonally varying model","PeriodicalId":16669,"journal":{"name":"Journal of Northwest Atlantic Fishery Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69256652","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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