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Under ice density and mobility of fish in winter-seining area of two Finnish lakes as revealed by echo-survey

Published online by Cambridge University Press:  15 September 2000

Juha Jurvelius ,
Juha Lilja ,
Esa Hirvonen ,
Raimo Riikonen  and
Timo J. Marjomäki
Juha Jurvelius
Affiliation:
Finnish Game and Fisheries Research Institute, FIN-58175 Enonkoski, Finland
Juha Lilja
Affiliation:
University of Jyväskylä, Box 35, FIN-40351, Jyväskylä, Finland
Esa Hirvonen
Affiliation:
Finnish Game and Fisheries Research Institute, FIN-58175 Enonkoski, Finland
Raimo Riikonen
Affiliation:
Finnish Game and Fisheries Research Institute, FIN-58175 Enonkoski, Finland
Timo J. Marjomäki
Affiliation:
University of Jyväskylä, Box 35, FIN-40351, Jyväskylä, Finland
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Abstract

The density and movements of fish under ice were studied with single-beam mobile surveys and fixed location split-beam surveys, as well as exploratory fishing in winter-seining areas of two shallow Finnish lakes during winter 1999. Fish schooled near the bottom during the day but the schools dispersed and fish ascended at night. Single and split-beam target strength distributions corresponded fairly closely with the length distribution of seine catch samples. Estimated fish densities were greater at night than in daylight. The swimming speed of smelt (Osmerus eperlanus) was 0.18 m·s–1 in daylight and 0.36 m·s–1 at night. The corresponding figures for vendace (Coregonus albula) were 0.11–0.17 and 0.05–0.08 m·s–1. Nights immediately before and after fishing were the best periods to estimate the effect of seining on fish density. The hydroacoustic fish density estimates at night corresponded closely with seine catches. We conclude that it is possible to estimate the effects of winter-seining by mobile under-ice echo-surveys and catch samples.

Keywords

echo-soundingvendacesmeltwinter-seiningfish migrations
Type
Research Article
Information
Aquatic Living Resources , Volume 13 , Issue 5: Shallow Water Fisheries Sonar , September 2000 , pp. 403 - 408
Copyright
© Elsevier, Inra, Ifremer, Cemagref, Ird, Cnrs, 2000

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