Planning of egg stock assessments according to reproductive characteristics of Japanese anchovy
2006
Tsuruta, Y.(National Abundantly Productive Sea Promote Association, Tokyo (Japan))
In order to enhance the accuracy of the Egg Production Method applied for Japanese anchovy with a relatively long spawning season and short time interval between spawning episodes, the effect of daily change in developmental stage of ovary on gonosomatic index was discussed. Moreover, the effect of water temperature, food ration and population density on batch fecundity and spawning frequency was formulated definitely in reared anchovy. As a result, the best sampling time of adult female is about 1800 hour just before the beginning of spawning. The number in a batch fecundity per gram body weight changed about 33 ind. per one centigrade and 38 ind. per one percent of food ration respectively. Population density also affected exponentially on the number in a batch fecundity. Therefore, it was necessary to carry out the investigation of food environment and school size of anchovy at the same time.
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