Oceanographic characteristics at fish aggregating device sites for tuna pole-and-line fishery in eastern Indonesia

Abstract

The research was conducted to investigate the oceanographic characteristics at three traditional anchored Fish Aggregating Device (FADs) sites for tuna pole-and-line fishery in eastern Indonesia. The FADs locations, and sea surface temperature (SST) and chlorophyll-a (chl-a), salinity (sal), wave height (wav), wind (win) current (cur) were examined using a geographic information system (GIS). Relationships between Catch-per-Trip (CPT) with oceanographic characteristics (SST, chl-a, sal, wav, win and cur), were analysed using correlation and generalised additive models (GAMs) analyses. Correlation analyses was used in order to determine how strongly pairs of variables were related to one another, and generalised additive models (GAMs) were used in order to model relationships between Catch-per-Trip (response variable) and the oceanographic variables SST, chl-a, sal, wav, win and cur (predictor variables). Correlation analyses showed that significantly negative correlations were found in entire locations between SST and chl-a while in contrarily, the lowest correlation was found between CPT and chl-a. Furthermore, the GAM plots indicated that a positive association was observed between catch-per-trip and SST with approximately >26.5 °C, chl-a was <0,4 mg/m3, salinity was observed between>33 to < 34.5 (psu) for entire sites while wav was found at>0.23 for Sorong and >0,87 (m) in Larantuka and <0.64 in Pulau Bacan. Win variable had positive effects at>4.1 m/s in entire research sites while cur had a positive effect on CPT occurred at <56 (m/s) for entire locations. The GAM models showed that SST explains up to 20 % whereas chl-a explains as the lowest variable (up to 0.78 % of the deviances) in skipjack CPT relationships, and the addition of predictor variables resulted in an increase in the deviance explained. This research provides evidence that skipjack tuna CPT has relationship with oceanographic variables in eastern Indonesia.