Analysis of accumulation performance of differing set-net designs

Abstract

In order to determine the accumulation performance of differing set-net designs, catch analysis was conducted upon small scale set-nets of both the single-trap and double-trap type. Total catch per haul was significantly higher after the design change to the double-trap net. The ratio of catch per intermittent haul to successive haul was defined as the accumulation index, which was used as an index to evaluate set-net accumulation performance. The accumulation index was calculated as 1.10 for the single-trap net and 1.52 for the double-trap net for the total catch. For the dominant species such as jack mackerel Trachurus japonicus, total catch increased after the design change, as did the accumulation index. In contrast, for species such as Japanese barracuda Sphyraena japonica, total catch decreased after the design change, as did the accumulation index. For any dominant species, the catch per haul and the accumulation index tended to increase or decrease in a similar manner. These results suggest that for each dominant species, catch differences between set-nets of different designs can be attributed to changes in their accumulation performances.