Analysis of the effect of ENSO and IOD on the productivity of yellowfin tuna (Thunnus albacares) in the South Indian Ocean, East Java, Indonesia

Abstract

Abstract. Sambah AB, Noor’izzah A, Intyas CA, Widhiyanuriyawan D, Affandy DP, Wijaya A. 2023. Analysis of the effect of ENSO and IOD on the productivity of yellowfin tuna (Thunnus albacares) in the South Indian Ocean, East Java, Indonesia. Biodiversitas 24: 2689-2700. Yellowfin tuna (Thunnus albacares) is one of the fish that migrates through the Indian Ocean and is primarily caught in the south Java waters which are directly adjacent to the Indian Ocean. Fish abundance and migration are influenced by oceanographic factors, including climatic factors which affect annual and interannual variations, such as the Indian Ocean Dipole (IOD) and the El Nino Southern Oscillation (ENSO). This study aimed to determine the effect of climate anomalies on the productivity of yellowfin tuna in the Indian Ocean south of East Java, Indonesia. Data collection was carried out at Coastal Fishing Port of Pondokdadap East Java, involving 58 respondents consisting of fishermen with yellowfin tuna catches. The boundaries of the research area are at coordinates 110.9°-114.5° East Longitude and 8°-11° South Latitude. The data used in the analysis consisted of Sea Surface Temperature (SST) data, chlorophyll-a data, Nino 3.4 data, Dipole Mode Index (DMI) data, and yellowfin tuna catch data for the year 2017-2021. The results showed that of the fifteen GAM models, the combination of variables that most affected fish productivity was the distribution of chlorophyll-a and the ENSO phenomenon with values ??of AIC (1503.33) and DE (64.30%). Pearson correlation analysis showed that the IOD phenomenon was influenced by SST and chlorophyll-a, while SST and chlorophyll-a did not significantly influence the ENSO phenomenon. These results indicated that the phenomenon of climate anomalies and the oceanographic conditions in the waters indirectly affect fish productivity through the food chain process.

Implementation of the Pelagic Hotspot Index in detecting the habitat suitability area for bigeye tuna (Thunnus obesus) in the eastern Indian Ocean

“…This condition was supported by previous studies that found that the Southeast monsoon period from June to August associated with El-Niño and positive IOD events in the southern waters of Indonesia triggered the upwelling causing the nutrients, including the concentration of chlorophyll-a, to increase. The ENSO and IOD phenomena that occur in the EIO influence the existence of tuna through the dynamics of changes in the distribution of oceanographic parameters (Sambah et al 2023). The current trend figure describes the confluence of several currents flowing into this region such as ITF.…”

Role of environmental conditions in structuring the stock trajectory of Thunnus albacares, Th. alalunga and Th. obesus in the South Pacific Region

“…Environmental variation impacts on tuna resources can studied and quantified using models that incorporate environmental variables (Sambah et al, 2023;Taboada et al, 2023;Wang et al, 2023). These models normally require environmental data over decadal timescales, which are not always readily available and may not be always of reliable quality.…”