Low nekton abundance in the western Bering Sea according to trawl survey data and model estimates

Low nekton abundance in the western Bering Sea according to trawl survey data and model estimates Complex trawl surveys were conducted in the upper epipelagic zone of the western Bering Sea and adjacent Pacific waters in the summer and fall seasons of 2002–2006. The abundance of small nekton (micronekton) was estimated using two independent methods: traditional trawling and a mathematical model of selective feeding by fish. According to the trawl data, total micronekton density varied from 1 to 158 (average 40) mg/m3 on the northwestern Bering Sea shelf and from 6 to 151 (37) mg/m3 in deep-water areas of the southwestern Bering Sea and adjacent Pacific waters. According to model calculations, micronekton density was higher—72–193 (141) mg/m3 on the shelf and 78–507 (228) mg/m3 in the deep-water part of the studied area. Both trawl and model data showed that small nekton on the northwestern shelf mostly consisted of larval and juvenile walleye pollock, as well as small fish species, such as capelin and Pacific sand lance. In the deepwater areas, mesopelagic fish and squid (northern lampfish, northern smoothtongue, and boreopacific gonate squid), which migrate to the surface at night, juvenile Atka mackerel, and shortarm gonate squid dominated among micronekton. The advantages and disadvantages of both the trawl and model methods for calculating the abundance of small fish and squid were considered. Comparison of abundance estimates for mass fish species, obtained through trawl and model methods, enabled us to analyze trawl catchability coefficients and propose a more differentiated division of micronekton into size classes than had been done earlier. A function that characterizes the dependence of the catchability coefficient (CC) on body length was offered for juvenile Atka mackerel. This equation can be also used for evaluation of CC for other fishes that have similar size and behavior. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Marine Biology Springer Journals

Low nekton abundance in the western Bering Sea according to trawl survey data and model estimates

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Publisher
SP MAIK Nauka/Interperiodica
Copyright
Copyright © 2009 by Pleiades Publishing, Ltd.
Subject
Life Sciences; Freshwater & Marine Ecology
ISSN
1063-0740
eISSN
1608-3377
D.O.I.
10.1134/S1063074009070050
Publisher site
See Article on Publisher Site

Abstract

Complex trawl surveys were conducted in the upper epipelagic zone of the western Bering Sea and adjacent Pacific waters in the summer and fall seasons of 2002–2006. The abundance of small nekton (micronekton) was estimated using two independent methods: traditional trawling and a mathematical model of selective feeding by fish. According to the trawl data, total micronekton density varied from 1 to 158 (average 40) mg/m3 on the northwestern Bering Sea shelf and from 6 to 151 (37) mg/m3 in deep-water areas of the southwestern Bering Sea and adjacent Pacific waters. According to model calculations, micronekton density was higher—72–193 (141) mg/m3 on the shelf and 78–507 (228) mg/m3 in the deep-water part of the studied area. Both trawl and model data showed that small nekton on the northwestern shelf mostly consisted of larval and juvenile walleye pollock, as well as small fish species, such as capelin and Pacific sand lance. In the deepwater areas, mesopelagic fish and squid (northern lampfish, northern smoothtongue, and boreopacific gonate squid), which migrate to the surface at night, juvenile Atka mackerel, and shortarm gonate squid dominated among micronekton. The advantages and disadvantages of both the trawl and model methods for calculating the abundance of small fish and squid were considered. Comparison of abundance estimates for mass fish species, obtained through trawl and model methods, enabled us to analyze trawl catchability coefficients and propose a more differentiated division of micronekton into size classes than had been done earlier. A function that characterizes the dependence of the catchability coefficient (CC) on body length was offered for juvenile Atka mackerel. This equation can be also used for evaluation of CC for other fishes that have similar size and behavior.

Journal

Russian Journal of Marine BiologySpringer Journals

Published: Jan 12, 2010

References

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