Catch statistics of commercial fishery are essential materials for fish stock assessment. However, the catch per unit effort (CPUE) estimated from the materials is subject to variations introduced from the non-static fisheries factors. These factors should be thoroughly recognized before the raw material could be properly used in the assessment. The present paper dealt with two commonly ignored factors occurred in the catch statistics of Taiwanese Atlantic albacore longline fishery: vessel tonnage and the kind of bait used. These two factors were found from the study to have obvious relationships with the Atlantic albacore CPUE: vessels with higher tonnage had lower albacore CPUE, and higher percentage of saury bait used might obtain higher albacore CPUE. Their effects were regarding to the shifting of target species of the fishery. Therefore, it is suggested that adjustments for the two factors should be made to the nominal statistics before the statistics being used in the assessment; unless the target species effect has somewhat been taken into account.