Assessing environmental effects on recruitment of Japanese common squid (Todarodes pacificus) in the Japan Sea using a biomass dynamics model
2005
Isoda, Y.(Hokkaido Univ., Sapporo (Japan)) | Bower, J.R. | Hasegawa, S.
Effects of variation in sea surface temperature (SST) on recruitment of the Japanese common squid (Todar-odes pacificus) in the Japan Sea were investigated using a biomass dynamics model. Two extreme cases where the spawner-recruit relationship approaches a linear form were examined: l) when the stock size is far below the carrying capacity, and 2) when the stock size is near the carrying capacity. For each case, we developed a recruit index estimated from the fishing mortality rate and catch data and proposed that annual changes in the indexes were due to environmental variation. Assuming that the true reproductive potential occurs somewhere between the two cases, years of good and poor recruitment were identified based on the indexes. Seasonal changes in SST around Japan during 1971-1995 were compared with changes that occurred in the indexes, and years of poor recruitment were found to correspond closely to years of lower than normal SST in winter and spring. Cold winters influenced by strong northwesterly winds were also associated with lower levels of recruitment.
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