There is growing awareness and concern on microplastics pollution in marine environments. Seagrasses are among the most productive shallow water ecosystems, serving a diverse assemblage of fish and invertebrates. Sediment and benthic animal samples collected from small islands at Spermonde archipelago confirmed the presence of microplastics with different levels of contamination. The occurrence of microplastics for up to 28.29% and 25% of contamination level in sediments and benthic animals, respectively, clearly indicated an alarming state of the microplastics pollution in rich and productive shallow water seagrass ecosystem of tropical seas. Moreover, all positively contaminated microplastics of benthic animals are for human consumption and therefore pose threats for microplastics transfers which may facilitate pathways for a wide spectrum of organic pollutants entering the food web and affecting human health.
Large pelagic fish (LPF hereafter) is an important group of fishes targeted by local fishermen in the Indonesian Fisheries Management Area-713 (IFMA-713). This IFMA includes the Makassar Strait, Flores Sea, Bali Sea, and Gulf of Bone. The objective of this study was to identify the preferred oceanographic conditions based on LPF fishing grounds in the study area. The experimental fishing was conducted from April to September 2018 by using local commercial fisheries (pole and line and purse seine). The fishing base of pole and line vessels operating in the Gulf of Bone was at Murante fish landing site, Luwu Regency, South Sulawesi. On the other hand, the fishing base of purse seine vessels operating in the Makassar Strait was at Siddo fish landing site, Barru Regency, also in South Sulawesi. Oceanographic factors such as sea surface temperature (SST), sea surface chlorophyll-a (SSC) concentration, and depth were derived from satellite data. The LPF fishing grounds were analysed and visualize using Geographic Information System (GIS) techniques. Based on the results, LPF distributions tended to be the highest in specific oceanographic conditions, including SST of 30.0 - 31.0 °C and SSC of 0.20 - 0.30 mg.m−3. They were mostly found in nearshore and offshore areas (maximum depth of about 2,000 m). The selected oceanographic factors played an important role in explaining the LPF fishing grounds. This information could be used for spatial prediction of potential LPF fishing zones in relation to the fish distribution and abundance during the Southeast monsoon in the IFMA-713.
Skipjack tuna is an important fishery species, targeted by purse seine and handline fisheries in Makassar Strait. Fish distribution patterns are markedly influenced by several underlying oceanographic factors. This study aimed to assess the relationship between skipjack CPUE and some oceanographic variables, and map out the distribution pattern of this fish in the study area during January-May 2018. To meet these objectives, we combined satellite data of sea surface temperature (SST) and chlorophyll-a concentration (chl-a) with catch data. We used generalized additive models (GAMs) to explore skipjack abundance in relation to the oceanographic conditions and we employed the gravity centre of fishing ground movements to map the fish distribution pattern. Results indicate that SST and chl-a significantly influenced skipjack tuna CPUE. The fish schools were mostly located in the eastern Makassar Strait. In January skipjack schools were initially in Majene offshore waters and moved to Mamuju waters in February. The skipjack schools returned to the border area between Polman and Majene waters in March and then made a continuous migratory journey to the south-western areas of Barru and Pare-pare offshore waters in April. In May, the skipjack tuna returned to concentrate in southern areas of Majene waters. We proposed that the fish schools followed a clock-wise distribution movement pattern where the habitat displacements may have a link with the dynamic ranges of preferred oceanographic conditions (habitat hotspots). It is likely that these areas provide good feeding opportunities for skipjack tuna.
The aims of this study were to compare skipjack catch between FAD and free school fishing grounds and to describe the effect of the oceanographic factors on either skipjack tuna Fish Aggregating Device (FAD) or free school. We used a field survey method for collecting the skipjack catch and the fishing positions for both near FAD and free school areas. Remotely sensed satellite data of sea surface temperature (SST) and chlorophyll-a concentration (Chl-a) were also used to extract the oceanographic data corresponding with both the fishing locations. To find out the vital oceanographic factors, we examined the characteristics of the oceanographic variables and skipjack catch using t-test. Results indicated that the fishing operations of skipjack tuna at FAD tended to locate areas of relatively higher Chl-a than at free school locations. We also found that skipjack tuna catch was higher near the FAD than the other area, where the Chl-a was the most significant factor that affected the difference. This study suggests that the number of skipjack tuna FAD in the coastal waters of Bone Bay should be calculated accurately to ensure and support the tuna fishing management in that study area.
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