Effect of hauling and soaking time of stationary lift nets on fish aggregation using a hydroacoustic monitoring approach

This study aimed to determine the effect of hauling and soaking time of stationary lift nets on the pattern of fish aggregation in the Banyuasin waters, South Sumatra, Indonesia using a hydroacoustic monitoring approach. The fish aggregations were monitored using the SIMRAD EK-15 single beam (200 kHz) during hauling, and the transducer was mounted on the side of the fishing gear. Furthermore, data were collected before (17:00–23:59) and after midnight (24:00–05:00) at four different soaking times (S1, S2, S3, and S4). The data obtained were then analyzed using pairwise comparisons (nonparametric tests). The pairwise test (p = 0.25 > 0.05) showed that there was no significant difference between the acoustic mean densities obtained before and after midnight (292.2 and 178.9 g/m3), but the total values for both periods varied widely (6,797 and 3,507 g/m3). Dunn’s post hoc tests (p = 0.001 < 0.05) revealed that there were significant differences in the acoustic mean densities between S1 (1–16 min) and S2 (17–32 min). Based on the results, the optimum soaking time was 17–32 min, which was recommended for improving the effectiveness of the stationary lift nets. Furthermore, fish aggregation began to spread out of the catchable area when the soaking time was over 32 min.