Movement patterns of winter flounder (Pseudopleuronectes americanus) in the southern Gulf of Maine: observations with the use of passive acoustic telemetry

Despite its recreational and commercial importance, the movement patterns and spawning habitats of winter flounder (Pseudopleuronectes americanus) in the Gulf of Maine are poorly understood. To address these uncertainties, 72 adult winter flounder (27–48 cm) were fitted with acoustic transmitters and tracked by passive telemetry in the southern Gulf of Maine between 2007 and 2009. Two sympatric contingents of adult winter flounder were observed, which exhibited divergent spawning migrations. One contingent remained in coastal waters during the spawning season, while a smaller contingent of winter flounder was observed migrating to estuarine habitats. Estuarine residence times were highly variable, and ranged from 2 to 91 days (mean=28 days). Flounder were nearly absent from the estuary during the fall and winter months and were most abundant in the estuary from late spring to early summer. The observed seasonal movements appeared to be strongly related to water temperature. This is the first study to investigate the seasonal distribution, migration, and spawning behavior of adult winter flounder in the Gulf of Maine by using passive acoustic telemetry. This approach offered valuable insight into the life history of this species in nearshore and estuarine habitats and improved the information available for the conservation and management of this species

Geographic and temporal patterns in size and maturity of the longfin inshore squid (Loligo pealeii) off the northeastern United States

Analysis of 32 years of standardized survey catches (1967–98) indicated differential distribution patterns for the longfin inshore squid (Loligo pealeii) over the northwest Atlantic U.S. continental shelf, by geographic region, depth, season, and time of day. Catches were greatest in the Mid-Atlantic Bight, where there were significantly greater catches in deep water during winter and spring, and in shallow water during autumn. Body size generally increased with depth in all seasons. Large catches of juveniles in shallow waters off southern New England during autumn resulted from inshore spawning observed during late spring and summer; large proportions of juveniles in the Mid-Atlantic Bight during spring suggest that substantial winter spawning also occurs. Few mature squid were caught in survey samples in any season; the majority of these mature squid were captured south of Cape Hatteras during spring. Spawning occurs inshore from late spring to summer and the data suggest that winter spawning occurs primarily south of Cape Hatteras

Holistic evaluation of management policies: What are the consequences of modified gear use on Georges Bank?

Georges Bank haddock is a recently recovered fish stock in the New England groundfish fishery. Due to federal constraints under the Magnuson-Steven Act, however, this stock cannot be optimally exploited due to the bycatch of other critical species in the New England groundfishery such as cod and yellowtail flounder which are overfished. The Ruhle trawl and Separator trawl are examples of recent advances in gear technology that have been shown to significantly increase haddock to bycatch ratios. This study models the groundfish fishery through a mixed stock yield model which incorporates technological interactions. We also develop a socio-economic model that quantifies the amount of employment and producer surplus associated with three trawl types. Our results explore policy situations regarding the use of the new trawls. By bridging the biological and socio-economic models, we are able to view the fishery as a system that more accurately represents stakeholder views. Our model shows that each trawl, when used exclusively, produces different optimum strategies and therefore an optimum management strategy would most likely include a combination of trawl types. Our results also support the logic of using modified trawls for haddock fishing trips in which bycatch is strictly regulated as the Ruhle trawl is able to maintain 80% of catches caught by a conventional trawl while reducing bycatch up to over 60%. This paper is a first step towards an aid for policy makers to examine fishery gear trade-offs and the resulting biological and socio-economic consequences of different management actions within the constraints of the Magnuson-Stevens Act

Mortality and movement of Yellowtail Flounder (Limanda ferruginea) tagged off New England

From 2003 to 2006, 44,882 Yellowtail Flounder (Limanda ferruginea) were captured and released with conventional disc tags in the western North Atlantic as part of a cooperative Yellowtail Flounder tagging study. From these releases, 3767 of the tags were recovered. The primary objectives of this tagging program were to evaluate the mortality and large-scale movement of Yellowtail Flounder among 3 stock areas in New England. To explore mortality, survival and recovery rate were estimated from traditional Brownie tag-recovery models fitted to the data with Program MARK. Models were examined with time and sex-dependent parameters over several temporal scales. The models with a monthly scale for both survival and recovery rate had the best overall fit and returned parameter estimates that were biologically reasonable. Estimates of survival from the tag-recovery models confirm the general magnitude of total mortality derived from age-based stock assessments but indicate that survival was greater for females than for males. In addition to calculating mortality estimates, we examined the pattern of release and recapture locations and revealed frequent movements within stock areas and less frequent movement among stock areas. The collaboration of fishermen and scientists for this study successfully resulted in independent confirmation of previously documented patterns of movement and mortality rates from conventional age-based analyses

An Interdisciplinary Assessment of Winter Flounder Stock Structure

Stock structure and management of winter flounder (Pseudopleuronectes americanus) was evaluated throughout its geographic range in the northwest Atlantic. Information on genetics, morphology, meristics, larval dispersal, life history traits, applied mark experiments and environmental signals was reviewed. Winter flounder in U.S. waters are currently managed as three separate units; Georges Bank, Gulf of Maine and Southern New England/Mid-Atlantic. Estuarine spawning, which likely plays an important role in reproductive isolation and population structure, appears to be obligate in southern New England, non-existent on Georges Bank and variable in the Gulf of Maine. Despite evidence for reproductively isolated estuarine groups, information from tagging, meristic analysis, and life history studies suggest extensive mixing, thereby supporting the current U.S. management regimen. In Canadian waters, winter flounder are managed as three units: western Scotian Shelf (NAFO Div. 4X), eastern Scotian Shelf (NAFO Div. 4VW), and the southern Gulf of St. Lawrence (NAFO Div. 4T). Genetic analysis and parasite markers indicate that these Canadian management units are distinct. However, examination of inshore and offshore winter flounder within division 4X suggests little interchange occurs between these groups. Several separate stocks probably exist within the 4T management area as well. Stock assessment and fishery management would likely benefit from stock composition analysis of mixed-stock fisheries of both U.S. and Canadian fishery resources

Changes in size and age at maturity of the northern stock of Tilefish (Lopholatilus chamaeleonticeps) after a period of overfishing

The modern fishery for Tilefish (Lopholatilus chamaeleonticeps) developed during the 1970s, offshore of southern New England, in the western North Atlantic Ocean. The population quickly became over exploited, with documented declines in catch rates and changes in demographic traits. In an earlier study, median size at maturity (L50) of males declined from 62.6 to 38.6 cm fork length (FL) and median age at maturity (A50) of males declined from 7.1 to 4.6 years between 1978 and 1982. As part of a cooperative research effort to improve the data-limited Tilefish assessment, we updated maturity parameter estimates through the use of an otolith aging method and macroscopic and microscopic evaluations of gonads. The vital rates for this species have continued to change, particularly for males. By 2008, male L50 and A50 had largely rebounded, to 54.1 cm FL and 5.9 years. Changes in female reproductive schedules were less variable among years, but the smallest L50 and youngest A50 were recorded in 2008. Tilefish are dimorphic, where the largest fish are male, and male spawning success is postulated to be socially mediated. These traits may explain the initial rapid decline and the subsequent rebound in male L50 and A50 and less dramatic effects on females. Other factors that likely contribute to the dynamics of maturity parameter estimates are the relatively short period of overfishing and the amount of time since efforts to rebuild this fishery began, as measured in numbers of generations. This study also confirms the gonochoristic sexual pattern of the northern stock, and it reveals evidence of age truncation and relatively high proportions of immature Tilefish in the recent catch

Eyes In The Sky: Linking Satellite Oceanography And Biotelemetry To Explore Habitat Selection By Basking Sharks

Background: Satellite-based oceanographic data products are a valuable source of information on potential resource availability for marine species. Satellite oceanography data may be particularly useful in biotelemetry studies on marine species that feed at low trophic levels, such as zooplanktivorous whales, sharks, and rays. The basking shark, Cetorhinus maximus, is a well-documented zooplanktivore in the western North Atlantic, yet little is known of its movements and spatial ecology in this region. A combination of satellite tag technologies were used to describe basking shark movements with respect to concurrent satellite-observed oceanographic conditions in order to test for selection of these environmental variables. Results: Satellite-linked ‘smart’ position only transmitting tags (SPOTs, N = 10) were used to assess horizontal movements, activity space, and habitat selection, while pop-up satellite archival tags (PSATs, N = 7) were used to describe depth preferences of basking sharks during summer and fall. The duration of SPOT tracks ranged from 5 to 45 days. Basking sharks used relatively small activity spaces in three focal areas off Massachusetts: Vineyard Sound, the Great South Channel, and Cape Cod Bay. These sharks appeared to select areas with shallow bottom depths, high primary production and chlorophyll concentrations, and steep surface gradients, but significant selection for these variables was only detected between mid-August and mid-October when the sharks were primarily located in Cape Cod Bay. Conclusions: Basking sharks in the southern Gulf of Maine during summer and fall focus their activities in discrete areas likely to support high primary and secondary productivity. Habitat selection may also be influenced by mating and social activity at times, but further research is needed to differentiate these behaviors from foraging activity. Satellite-based biotelemetry and oceanography are powerful tools that together can provide valuable new insights into habitat selection patterns of highly mobile marine species

Avoiding bycatch in U.S. Sea Scallop closed areas fisheries

Since 1999, the scallop fisheries have been granted access to closed areas on Georges Bank, and the access programs have been managed through individual vessel quotas for scallops, and a common-pool total allowable catch (TAC) for yellowtail flounder bycatch. The scallop resource is neither overfished and nor is overfishing occurring, but the yellowtail flounder resource is both overfished and experiencing overfishing according to criteria of U.S. fishery regulations. The yellowtail flounder bycatch TAC has forced early closure of these fisheries in more than half of these access fisheries. We present two programs designed in cooperation with fishermen and permit holders to avoid yellowtail flounder bycatch in these access fisheries, one in Closed Area II (CAII) in 2009 and the other in the Nantucket Lightship Area (NLA) in 2010. For both programs, we mapped the areas of scallop and yellowtail flounder densities and sent the density maps to permit owners and captains. In the second program, we implemented a daily system of captains transmitting daily yellowtail flounder catch and number of tows by area, analyzing the data, and sending messages to captains indicating low, medium, and high scallop densities per pound of yellowtail flounder by area. The 2009 CAII fishery closed three weeks after opening yielding only 61% of the scallop TAC. About 1/3 of vessels participated in the 2010 NLA voluntary reporting program. Observer data indicates that the scallop TAC will be caught for the first time in any closed area access fishery for the first time in the 2010 NLA fishery

Geographic extent of introgression in Sebastes mentella and its effect on genetic population structure

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Bycatch Avoidance Programs in Two New England (USA) Fisheries

We conducted similar bycatch avoidance programs in two New England fisheries: yellowtail flounder bycatch in the sea scallop closed area fisheries and river herring bycatch in the Atlantic herring and mackerel fishery. These species have different behavioral properties: sea scallops are sessile; yellowtail flounder are demersal with limited but unknown range. Herring and mackerel are pelagic species with wide spatial and temporal ranges; river herring are anadromous. Management actions also differed between the two fisheries. The sea scallop closed area fisheries were limited in time and space with hard quotas for each species. The herring and mackerel fishery was limited in large scale areas by hard quotas, without quotas for river herring. Fishermen were motivated to avoid river herring by strong conservation pressure, river herring are listed as a species of concern and under review for endangered species by the U.S. agencies, which designation would effectively close the Atlantic herring fishery. In the scallop fisheries, we mapped and updated densities for target and bycatch stocks through real-time monitoring and communicated hotspots with captains at sea. In the herring and mackerel fishery we identified densities through port sampling and communicated hotspots to captains at sea. We also reported environmental factors of river herring density such as depth to captains. Percent participation exceeded 75% in each fisheries with evidence of avoidance behavior in both fisheries. Yellowtail bycatch was sharply reduced in the scallop closed area fisheries with some reduction of river herring bycatch in the herring and mackerel fisheries