Standardized CPUE for the winter-spawning stock of Japanese flying squid Todarodes pacificus caught by Japanese coastal squid jigging fishery
2016
Okamoto, S. (Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Kushiro, Hokkaido (Japan)) | Yamashita, N. | Kaga, T.
The objective of this study was to estimate the standardized CPUE of the winter-spawning stock of Japanese flying squid Todarodes pacificus by squid jigging fishery among the Japanese coastal fishing grounds from 1979 to 2013. We used monthly catch-and-effort data at each fishing port located on the Pacific side north of Miyagi prefecture (n = 1157). We modeled log (CPUE + delta sub(0)) using a generalized linear mixed model with normal distribution (delta sub(0): the constant minimizing '|skewness| + |kurtosis|' of the distribution of residuals). Explanatory variables in the model candidates were fishing year, month, port and their interactions. The year effect has reflected the interannual variability in the squid stock. Two candidates were selected by the Akaike information criterion (AIC) and Bayesian information criterion (BIC). As a result of cross-validation, the prediction accuracy of the model selected by AIC was better than that of the model selected by BIC. The model selected by AIC was the most complex model among all the candidates. We calculated the least squares mean and estimated the standardized CPUE using the model, as it is considered that the standardized CPUE corrects the relative biomass which is overestimated or underestimated by the nominal CPUE.
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