Effects of El Niño–Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean off Java

• Published in: Fishery bulletin (Washington, D.C.) Vol. 111; no. 2; pp. 175 - 188
• Main Authors: Syamsuddin, Mega L, Saitoh, Sei-Ichi, Hirawake, Toru, Bachri, Samsul, Harto, Agung B
• Format: Journal Article
• Language: English
• Published: National Marine Fisheries Service 01-04-2013
• Subjects: Marine; Marine productivity; Thunnus obesus; Indonesia; ISW, Indian Ocean
• ISSN: 0090-0656; 1937-4518
• DOI: 10.7755/FB.111.2.5

The effects of El Nino-Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean (EIO) off Java were evaluated through the use of remotely sensed environmental data (sea-surface-height anomaly [SSHA], sea-surface temperature [SST], and chlorophyll-a concentration), and Bigeye Tuna catch data. Analyses were conducted for the period of 1997-2000, which included the 1997-98 El Nino and 1999-2000 La Nina events. The empirical orthogonal function (EOF) was applied to examine oceano-graphic parameters quantitatively. The relationship of those parameters to variations in catch distribution of Bigeye Tuna was explored with a generalized additive model (GAM). The mean hook rate was 0.67 during El Nino and 0.44 during La Nina, and catches were high where SSHA ranged from -21 to 5 cm, SST ranged from 24 degree C to 27.5 degree C, and chlorophyll-a concentrations ranged from 0.04 to 0.16 mg m super(-3). The EOF analysis confirmed that the 1997-98 El Nino affected oceanographic conditions in the EIO off Java. The GAM results indicated that SST was better than the other environmental factors (SSHA and chlorophyll-a concentration) as an oceanographic predictor of Bigeye Tuna catches in the region. According to the GAM predictions, the highest probabilities (70-80%) for Bigeye Tuna catch in 1997-2000 occurred during oceanographic conditions during the 1997-98 El Nino event.