Reproductive Success in Fish Stocks Can Be Reproduced by Environmental Factors Alone
This study showed that reproductive successes (RPS) in fish stocks could be reproduced using only environmental factors. As the environmental factors, the monthly Arctic oscillation index and Pacific decadal oscillation were used. The RPS of 12 stocks harvested around Japan were reproduced. The results were as follows: the fitness between observed and reproduced RPS, and the number of the independent variables necessary for reproducing the RPS differed by stock. However, the fluctuations of RPS
... could be reproduced using only the environmental factors. These results support the validity of the mechanism proposed by Sakuramoto regarding the factors that drive the fluctuation in RPS. That is, the fluctuation in RPS occurs due to conditions determined by environmental factors, and is not a density-dependent effect. been considered only a perturbation factor. However, Sakuramoto   showed that the RPS of Pacific stock of Japanese sardines and Pacific bluefin tuna could be reproduced using only environmental factors. The model did not assume a density-dependent effect. As the main environmental factors, the sea surface temperature in the Kuroshio extension area was used for the former stock, and the monthly index of Arctic Oscillation (AO) and Pacific Decadal Oscillation (PDO) were used for the latter stock. The aim of this paper is to investigate whether or not the mechanism proposed by Sakuramoto   could be adapted to other stocks. That is, whether RPS could be reproduced using only environmental factors. In this study, only AO and PDO by monthly index were used as the environmental factors, and we attempted to reproduce the RPS for 12 stocks harvested around Japan. The stocks investigated were: 1) Pacific stock of Chub mackerel (Scomber japonicus); 2) Tushima warm current stock of Chub mackerel; 3) Pacific stock of Blue mackerel (Scomber australasicous); 4) East China Sea stock of Blue mackerel; 5) Pacific stock of Alaska pollock (Teragra chalcogramma); 6) Northern Sea of Japan stock of Alaska pollock; 7) Pacific stock of Japanese sardine (Sardinops melanostictus); 8) Pacific stock of Japanese anchovy (Engraulis japonicus); 9) Autumn-spawning group of Japanese common squid (Todarodes pacificus); 10) Winter-spawning group of Japanese common squid; 11) Northern Sea of Japan stock of Arabesque greenling (Pleurogrammus azonus); 12) Pacific stock of Splendid alfonsino (Beryx splendens).