Author： Lilja Juha Keskinen Tapio Marjomäki Timo J. Valkeajärvi Pentti Karjalainen Juha
Publisher： Edp Sciences
E-ISSN： 1765-2952|16|3|185-190
ISSN： 0990-7440
Source： Aquatic Living Resources, Vol.16, Iss.3, 2010-03, pp. : 185-190
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Abstract
A 200 kHz digital echosounder (HTI) with two split-beam transducers was aimed horizontally to monitor the upstream migration activity of fish, from 24 April to 28 June, in Äijälänsalmi channel (mean width 35 m, length 700 m, and maximum depth 5 m) from large mesotrophic Lake Päijänne to small eutrophic Lake Jyväsjärvi. This study was part of a larger project which aims to analyse the movement of commercially unimportant fish species and reduce the abundance of these fish in L. Jyväsjärvi. Catch samples were collected with a trap net located immediately upstream from the acoustic beams. The most common species in the catch were roach (), perch (), bream (), ruffe (), and white bream (). The upstream migration of fish was correlated with water temperature ( = 0.40) with time lag of 1 d. In spring, L. Jyväsjärvi warmed faster than L. Päijänne, causing spawning migration from L. Päijänne to L. Jyväsjärvi. Clear diurnal rhythm in activity was observed. The migration rate through the channel peaked around dawn and dusk. Catch per unit effort of the trap net suggested that the peak of the spawning migration of different species was separate. Upstream migration was induced by the temperature difference between two lakes, and the activity of the migration was regulated by temperature changes and light rhythm.
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