Environmental aspects of tuna catches in the Indian Ocean, southern coast of Java, based on satellite measurements

Abstract

The present work seeks to assess the relationship between daily Sea Surface Temperature (SST) and thermal front (Gradient Magnitude method) using AMSR-E, daily Sea Surface Chlorophyll-a (SSC) using MODIS, and daily long line (LL) bigeye (BG), albacore (ALB), yellowfin (YF), and southern bluefin (SBF) tuna catch data expressed as catch per unit effort (CPUE), which was calculated as the number of fish caught by 1000 hooks in 1° latitude by 1° longitude square grid, and integrated into a month of fishing activity for the period of March–December 2010 in South Java (Indian Ocean). Results obtained showed evidences of non-linear relationships between catch yields and environmental data. BG and ALB show largest CPUE values which occurred mainly in the area with SSTs of 26 – 27 °C and SSCs of 0.15 – 0.3mg/m3. CPUEs appear to be “randomly” dispersed and have a slight positive (negative) correlation with SSC (SST) i.e., 0.33 (−0.38) but not with GM values i.e., −0.02. The weak correlation between CPUE, SST, SSC and GM lead to assume that CPUEs might be linked to other influential parameters that are not assessed in the present study but are needed to give complete prediction of potential fishing ground areas, knowing that the length of observation period is less than 1 year.