Abstract: To reduce the bycatch rate of wahoo (Acanthocybium solandri), we collected the data (hook depth, temperature, salinity and chlorophyll-a concentration vertical profile, operating parameters and bycatch) by longlining surveys in waters near Cook Islands from September, 2012 to November, 2012. Stepwise regression was used to develop the hook depth calculation model. Statistics and clustering analysis were used to analyze the effects of depth and temperature on wahoo bycatch rate. The salinity and chlorophyll-a concentration range with high bycatch rate of wahoo was obtained based on the depth range with high bycatch rate of wahoo. Results show that the depth and temperature range with high bycatch rate for wahoo were 40.0~80.0 m and 26.0~28.0 ℃, respectively. The deduced salinity and chlorophyll-a concentration range with high bycatch rate of wahoo were 36.30~36.90 and 0.070~0.243 μg·L^-1, respectively. Results suggest that the hook should be deployed at the depth deeper than 80 m, temperature lower than 26 ℃, salinity higher than 36.90 and chlorophyll-a concentration higher than 0.243 μg·L^-1, to mitigate the bycatch of wahoo when fishing in waters near Cook Islands.