Nippon Suisan Gakkaishi 65 (2), 167-174 (1999)

Seasonal Changes in Abundance, Length Distribution, Feeding Condition and Predation Vulnerability of Juvenile Japanese Flounder, Paralichthys olivaceus, and Prey Mysid Density in the Tottori Coastal Area*1

Shinpei Furuta*2

Seasonal changes in abundance, length distribution, food intake and condition factors of wild Japanese flounder juveniles, density of mysid as the main diet and stomach contents of 1 and 2-year-old group Japanese flounder as the main predator of flounder juveniles were studied in the Tottori coastal area in 1994. While the abundance in larger group of flounder juvenile decreased from the near shore nursery in early June, that for smaller group showed a rapid decrease from mid or late June. The equivalent size distribution for the smaller group was not found in the length frequency of juveniles which emigrated to the offshore nursery. This finding suggests that heavy mortality occurred in juvenile flounders in the nearshore nursery. Food intake and condition factors of juveniles decreased after mid June. Mysid abundance showed a rapid reduction coupled with decreases in food intake and condition factors of juveniles. Predation incidence of juveniles by 1 and 2 group flounders significantly increased in late June and kept high until late July. Based on these findings, a mechanism of mortality caused by starvation-induced predation was suggested.


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