scholarly journals Nursery areas of juvenile northern rock sole (Lepidopsetta polyxystra) in the eastern Bering Sea in relation to hydrography and thermal regimes

2014 ◽  
Vol 71 (7) ◽  
pp. 1683-1695 ◽  
Author(s):  
Daniel W. Cooper ◽  
Janet T. Duffy-Anderson ◽  
Brenda L. Norcross ◽  
Brenda A. Holladay ◽  
Phyllis J. Stabeno
Keyword(s):  
Bering Sea ◽  
Resource Selection ◽  
Large Scale ◽  
Gulf Of Alaska ◽  
Nursery Area ◽  
Eastern Bering Sea ◽  
Middle Domain ◽  
Nunivak Island ◽  
Near Shore ◽  
Unimak Island

Abstract Age-0 and age-1 northern rock sole were collected over large-scale areas of the eastern Bering Sea in the summers of 2003, 2008 and 2010. Age-0 presence was poorly predicted by a published resource selection model developed for the Gulf of Alaska, and the failure of that model may have been caused by oceanographic features in the eastern Bering Sea. Where a front (inner front) separated the well-mixed coastal domain from the stratified middle domain, age-0 fish were less abundant and occurred at fewer stations in the nearshore, thermally mixed coastal domain than expected by the Gulf of Alaska model. In contrast, where the inner front was not established, age-0 fish were present in the highest densities in nearshore and thermally mixed waters. North of Unimak Island, the same hydrographic pattern that inhibits the formation of the inner front also likely transports larvae near shore. Age-1 densities were highest in the coastal domain, and age-0 length decreased with distance from shore, suggesting northern rock sole move shoreward after settlement. Juvenile northern rock sole were abundant in a nursery area between Nunivak Island and Cape Newenham in a warm period (2003), but were almost completely absent in cold periods (2008 and 2010), leading to the hypothesis that climate variability limits the utility of this nursery area during cold periods.

Individual and colony-specific wintering areas of Pacific northern fulmars (Fulmarus glacialis)

2010 ◽  
Vol 67 (2) ◽  
pp. 386-400 ◽  
Author(s):  
Scott A. Hatch ◽  
Verena A. Gill ◽  
Daniel M. Mulcahy
Keyword(s):  
Bering Sea ◽  
Gulf Of Alaska ◽  
Fulmarus Glacialis ◽  
Northern Bering Sea ◽  
Eastern Bering Sea ◽  
Deep Waters ◽  
Pribilof Island ◽  
Wintering Areas ◽  
Satellite Transmitters ◽  
Northern Fulmars

Seabird mortality associated with longline fishing in the eastern Bering Sea occurs mainly from September to May, with northern fulmars ( Fulmarus glacialis ) comprising the majority (60%) of the bycatch. Along the west coast of North America, winter dieoffs of fulmars may be increasing in frequency and magnitude, the most severe on record being a wreck that peaked in October–November 2003. We deployed satellite transmitters on fulmars from the four main Alaska colonies and tracked individuals for up to 2 years. Fulmars from Hall Island (northern Bering Sea) moved to Russian coastal waters after breeding, while Pribilof Island fulmars (southeastern Bering Sea) remained relatively sedentary year-round. Birds from Chagulak Island (eastern Aleutians) preferred passes between the Aleutian Islands in winter or foraged widely over deep waters of the central Bering Sea and North Pacific. Fulmars from the Semidi Islands (western Gulf of Alaska) migrated directly to waters of the California Current. Individuals from St. George Island (Pribilofs) and Chagulak were consistent in the places that they visited in two successive winters. The Pribilof Islands population is most affected by winter longlining for groundfish, whereas the Semidi Islands colony sustains most of the natural mortality that occurs off Washington, Oregon, and California.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

2008 ◽  
Keyword(s):  
Bering Sea ◽  
Stock Assessment ◽  
Gulf Of Alaska ◽  
Pressure Change ◽  
Fishing Effort ◽  
Aleutian Islands ◽  
Anoplopoma Fimbria ◽  
Eastern Bering Sea ◽  
Mean Size ◽  
Longline Fisheries

<em>Abstract.</em>—This report summarizes biological, fishery, and survey information on giant grenadier, <em>Albatrossia pectoralis</em>, in Alaskan waters. Catch estimates of giant grenadier in Alaska for the years 1997–2005 have averaged over 16,000 metric tons (mt), and most of this catch has been taken as bycatch in longline fisheries for sablefish, <em>Anoplopoma fimbria</em>, and Greenland halibut, <em>Reinhardtius hippoglossoides</em>. The giant grenadier catch is all discarded, and none of the fish survive due to the pressure change when they are brought to the surface. Most of the catch is from the Gulf of Alaska. Data from bottom trawl and longline surveys in Alaska indicate that giant grenadier are extremely abundant in depths 300–1,000 m, and it appears this species is very important ecologically in this environment. Greatest abundance is in the western Gulf of Alaska, eastern Aleutian Islands, and in some areas of the eastern Bering Sea; abundance declines in the eastern Gulf of Alaska. Relative abundance of giant grenadier is much higher off Alaska than off the U.S. West Coast. Fish in the eastern Bering Sea and Aleutian Islands were consistently larger than those in the Gulf of Alaska. Mean size of females was larger in shallower water, and decreased with depth. Females and males appear to have different depth distributions, with females greatly predominating in depths less than 800 m. Although sex composition of giant grenadier caught in the fishery is unknown, nearly all the fishing effort is believed to be in waters less than 800 m, which indicates females are disproportionately harvested. Because of the great abundance of giant grenadier in Alaska and the relatively modest catch, overfishing of giant grenadier does not appear to be a problem at present. However, because information on the population dynamics of giant grenadier is very sparse, and because of the 100% discard mortality, the disproportionate harvest of females, and the general susceptibility of deep-sea fish to overharvest, fishery managers should monitor this species closely if catches increase in the future.

scholarly journals Implications of a warming eastern Bering Sea for Bristol Bay sockeye salmon

2011 ◽  
Vol 68 (6) ◽  
pp. 1138-1146 ◽  
Author(s):  
Edward V. Farley ◽  
Alexander Starovoytov ◽  
Svetlana Naydenko ◽  
Ron Heintz ◽  
Marc Trudel ◽  
...  
Keyword(s):  
Bering Sea ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Pacific Salmon ◽  
Bristol Bay ◽  
Eastern Bering Sea ◽  
New Information ◽  
Energy Stores ◽  
Overwinter Mortality ◽  
Dependent Processes

Abstract Farley, E. V., Starovoytov, A., Naydenko, S., Heintz, R., Trudel, M., Guthrie, C., Eisner, L., Guyon, J. R. 2011. Implications of a warming eastern Bering Sea for Bristol Bay sockeye salmon. – ICES Journal of Marine Science, 68: 1138–1146. Overwinter survival of Pacific salmon (Oncorhynchus sp.) is believed to be a function of size and energetic status they gain during their first summer at sea. We test this notion for Bristol Bay sockeye salmon (O. nerka), utilizing data from large-scale fisheries and oceanographic surveys conducted during mid-August to September 2002–2008 and from February to March 2009. The new data presented in this paper demonstrate size-selective mortality for Bristol Bay sockeye salmon between autumn and their first winter at sea. Differences in the seasonal energetic signatures for lipid and protein suggest that these fish are not starving, but instead the larger fish caught during winter apparently are utilizing energy stores to minimize predation. Energetic status of juvenile sockeye salmon was also strongly related to marine survival indices and years with lower energetic status apparently are a function of density-dependent processes associated with high abundance of juvenile sockeye salmon. Based on new information regarding eastern Bering Sea ecosystem productivity under a climate-warming scenario, we hypothesize that sustained increases in spring and summer sea temperatures may negatively affect energetic status of juvenile sockeye salmon, potentially resulting in increased overwinter mortality.

scholarly journals Spatio-temporal distribution of euphausiids: an important component to understanding ecosystem processes in the Gulf of Alaska and eastern Bering Sea

2016 ◽  
Vol 73 (8) ◽  
pp. 2020-2036 ◽  
Author(s):  
Kirsten A. Simonsen ◽  
Patrick H. Ressler ◽  
Christopher N. Rooper ◽  
Stephani G. Zador
Keyword(s):  
Primary Production ◽  
Bering Sea ◽  
Gulf Of Alaska ◽  
Additive Models ◽  
Trophic Levels ◽  
Production Model ◽  
Trawl Survey ◽  
Large Spatial Scale ◽  
Eastern Bering Sea ◽  
Abundance And Distribution

Abstract Euphausiids (principally Thysanoessa spp.) are found in high abundance in both the eastern Bering Sea (EBS) and the Gulf of Alaska (GOA). They are an important part of these cold-water coastal and pelagic ecosystems as a key prey item for many species, including marine mammals, seabirds, and fish, forming an ecological link between primary production and higher trophic levels. Acoustic-trawl (AT) survey methods provide a means of monitoring euphausiid abundance and distribution over a large spatial scale. Four years of AT and bottom-trawl survey data (2003, 2005, 2011, and 2013) were available from consistently sampled areas around Kodiak Island, including Shelikof Strait, Barnabas Trough, and Chiniak Trough. We identified euphausiid backscatter using relative frequency response and targeted trawling, and created an annual index of abundance for euphausiids. This index has broad application, including use in the stock assessments for GOA walleye pollock (Gadus chalcogrammus) and other species, as an ecosystem indicator, and to inform ecological research. We then used generalized additive models (GAMs) to examine the relationship between relative euphausiid abundance and potential predictors, including pollock abundance, temperature, bottom depth, and primary production. Model results were compared with an updated GAM of euphausiid abundance from the EBS to determine if the factors driving abundance and distribution were consistent between both systems. Temperature was not a strong predictor of euphausiid abundance in the GOA as in the EBS; warmer temperatures and lack of seasonal ice cover in the GOA may be a key difference between these ecosystems. Pollock abundance was significant in both the GOA and the EBS models, but was not a strongly negative predictor of euphausiid abundance in either system, a result not consistent with top-down control of euphausiid abundance.

scholarly journals Schooling pattern of eastern Bering Sea walleye pollock and its effect on fishing behaviour

2009 ◽  
Vol 66 (6) ◽  
pp. 1284-1288 ◽  
Author(s):  
Haixue Shen ◽  
Martin W. Dorn ◽  
Vidar Wespestad ◽  
Terrance J. Quinn
Keyword(s):  
Instrumental Variables ◽  
Bering Sea ◽  
School Size ◽  
Principal Component ◽  
Walleye Pollock ◽  
Fishing Vessel ◽  
Eastern Bering Sea ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Spawning Areas ◽  
Unimak Island

Abstract Shen, H., Dorn, M. W., Wespestad, V., and Quinn, T. J. 2009. Schooling pattern of eastern Bering Sea walleye pollock and its effect on fishing behaviour. – ICES Journal of Marine Science, 66: 1284–1288 Walleye pollock (Theragra chalcogramma) form persistent midwater and near-bottom schools in the daytime during the winter spawning season in the eastern Bering Sea (EBS). Two spawning areas in the EBS, north of Unimak Island and near the Pribilof Islands, are the main fishing grounds. To study the schooling pattern of pollock and its effect on fishing behaviour on these two fishing grounds, a principal component analysis with instrumental variables was carried out using acoustic and observer data from 2003 and 2005. Significant differences between the school descriptors distinguished the schooling patterns among areas and years. The harvester, that is to say, the fishing vessel and its crew taken together, searched for fish aggregations, which were caught in a different manner when the schooling pattern changed. School density had a greater effect than school size on fishing behaviour. Aggregations were less dense in 2003 than in 2005, and the harvester tended to fish with longer tows, at higher speeds, when it encountered less dense aggregations.

Distribution of population-based indicators across multiple taxa to assess the status of Gulf of Alaska and Bering Sea groundfish communities

2005 ◽  
Vol 62 (3) ◽  
pp. 344-352 ◽  
Author(s):  
Franz J. Mueter ◽  
Bernard A. Megrey
Keyword(s):  
Bering Sea ◽  
Gulf Of Alaska ◽  
Population Based ◽  
Fishing Effort ◽  
Frequency Of Occurrence ◽  
Catch Per Unit Effort ◽  
Eastern Bering Sea ◽  
Trawl Fishing ◽  
The Status ◽  
Commercial Species

Abstract Ecosystem-based approaches to fisheries management require researchers and managers to take into account effects of fishing on other components of the ecosystem, including non-commercial species. Currently, stock assessments in the Northeast Pacific are limited to the most important commercial species, little being known about the status of non-commercial species. Nevertheless, standardized bottom-trawl surveys conducted in the eastern Bering Sea (EBS) and Gulf of Alaska (GoA), although primarily designed to assess commercial species, provide valuable information on the abundance, distribution, and mean weight of numerous taxa. Using a novel statistical approach and survey data for the years 1993–2003, we examined trends in catch per unit effort (cpue), frequency of occurrence, and mean weight of individuals for each taxon. Time trends were computed as the slope of a linear regression of each indicator on year, and were summarized separately for the eastern and western GoA and for the EBS. Within each system, trends were further compared between commercial and non-commercial taxa. Simulations were used to obtain reference distributions for the expected distribution of slopes across many dependent populations. Observed distributions of trends were compared with simulated distributions, suggesting that more taxa than expected showed a decreasing trend in cpue in the EBS, but not in the GoA. These trends likely resulted from low groundfish productivity in the EBS during the 1990s. At the same time, the frequency of occurrence of significantly more taxa than expected increased in the EBS and, to a lesser extent, in the western GoA. Increases in frequency of occurrence were much more common among non-commercial, invertebrate taxa, and may be a response to reductions in trawl fishing effort during the 1990s.

scholarly journals Examining the ecological role of jellyfish in the Eastern Bering Sea

2019 ◽  
Vol 77 (2) ◽  
pp. 791-802 ◽  
Author(s):  
James Ruzicka ◽  
Richard D Brodeur ◽  
Kristin Cieciel ◽  
Mary Beth Decker
Keyword(s):  
Bering Sea ◽  
Gulf Of Alaska ◽  
Forage Fish ◽  
Eastern Bering Sea ◽  
Gadus Macrocephalus ◽  
Northern California Current ◽  
Capelin Mallotus Villosus ◽  
Northern Pacific ◽  
Negative Impacts

Abstract Within the Eastern Bering Sea, the jellyfish Chrysaora melanaster has fluctuated widely over recent decades. We examined the role of C. melanaster as an ecosystem-structuring agent via application of ecosystem models representing inner-, mid-, and outer-shelf regions of comparable areal coverage. Chrysaora melanaster utilize 1% of total mid-shelf consumer production, or 1/4th the energy required by forage fish (capelin Mallotus villosus, Pacific herring Clupea pallasii, age-0 Pacific cod Gadus macrocephalus, age-0 walleye pollock Gadus chalcogrammus). Model simulations show the impacts of C. melanaster are broadly distributed across consumer groups with increasingly negative impacts with higher jellyfish biomass. Age-0 pollock represent the greater part of the forage fish biomass, and observed pollock biomass during low jellyfish years (2004–2007) was significantly greater than during high jellyfish years (2009–2014). However, sensitivity among consumer groups to observed jellyfish variability is small, within 5% of baseline (2004–2015) conditions. Estimates using similar models for the Coastal Gulf of Alaska (CGoA) and Northern California Current (NCC) suggest large differences in the role of scyphozoans among northern Pacific shelf ecosystems. Only 0.1% of total summer consumer production is required to support CGoA Chrysaora, while the coastal NCC population uses 19%.

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