CPUE standardization of Chinese longline fishery for targeting bigeye tuna, Thunnus obesus in the Indian Ocean
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Key Words: CPUE standardization  GAM  GLM  bigeye tuna  Indian Ocean
Author NameAffiliation
DAI Xiao-jie 上海海洋大学 海洋科学学院 
MA Chao 上海海洋大学 海洋科学学院 
TIAN Si-quan 上海海洋大学 海洋科学学院 
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Abstract:
      Generalized Linear Models (GLM) and Generalized Additive Models (GAM) were used to standardize catch per unit fishing effort (CPUE) of Chinese bigeye tuna (Thunnus obesus) fishery in the Indian Ocean. In CPUE standardization, nominal CPUE was treated as the dependent variable and three groups of affected variables were considered: spatial variables (longitude and latitude), temporal variables (year and month) and environmental variables (temperature at various depths, salinity at various depths and Sea Level Height). The results indicated that the standardized and nominal CPUEs were similar and showed the same trends in spatio temporal distribution. The CPUE increased with year and high CPUE usually occurred in 42°E-60°E, 85°E -90°E, 15°S-5°S and 10°N-15°N. Both the results of GLM and GAM showed that the longitude was the most important variable affecting CPUE, which could explain 17.3% and 23.81% of the deviance,respectively. The effects of latitude, the interaction terms of longitude and latitude, year, temperature at 317 m depth and temperature at 381 m depth on CPUE were also apparent. GLM tended to be more appropriate than GAM in the analysis of CPUE standardization in this study.