Population Structure and Seasonal Growth of the Protandrous Pandalid Shrimp Pandalus latirostris in Notoro Lagoon, Hokkaido

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Hokkai-shrimp, <I>Pandalus latirostris</I>, is one of the most important commercial species of shrimp in Hokkaido and eastern Russia, but its biology in only a few aquatic areas has been documented. We examined the population structure and seasonal growth of this shrimp in Notoro Lagoon, Hokkaido. The population consisted of three or four cohorts regarded as age groups. This shrimp generally matures as male at age-1 and then changes sex to female at age-2. In each age group, however, small proportions had sexual phases different from that of the majority, and their frequencies varied with age group. This shrimp grows from late-April to late-November, and the growth period is consistent with changes in water temperature in the lagoon. The critical water temperature for its growth was estimated at 4°C. We suspect that size-selective fishing potentially affects not only its growth rate but also its life history variation because it increases fitness of only small individuals.
日本水産増殖学会の論文