魚群探知機によるスケトウダラ産卵群の生態について
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概要
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The results of the investigation carried out by the present author on the behavior of the spawning pollack schools by means of Fish-Detector and other various fishing implements are summarized as follows: - (1) Schools of spawning migration are found distributed in various shapes of band, cloud, and nimbus. (2) The depth of migration is not decided by temperature, depth, and topography of sea-bottom: it is distributed over very wide limit. (3) Sexual segregation is found to exist, males inhabit upper layer and the other lower one. (4) Immature groups come to migration together with spawning groups, but they are separated from the latter staying in waters shallower than that in which the spawner inhabit.