Predicting catch trend of Triggerfish (Canthidermis maculata) and Indian scad (Decapterus russelli) in the Indian Ocean using environmental conditions.

Abstract

Since the introduction of multi-day fishing boats to the Sri Lankan fishing fleet, the use of ring nets to harvest fish resources gathered around flotsam has grown in popularity. Ring net catches included fish species that are not commonly caught in other fishing methods such as gillnetting and longlining. These species are found near moored or natural Fish Aggregating Devices (FADs). To ensure the sustainable use of pelagic fish resources and develop reasonable and effective management strategies, it is essential to comprehend the reasons behind their spatial and temporal variability. Understanding the connections between fish spatial distribution and environmental variables is critical for fisheries management and conservation. In this context, the present study was carried out using remotely sensed satellite data from 2016 to 2019 on the 30- day means of sea surface temperature (SST), chlorophyll-a (Chl-a), and water current velocity (WCV) in the Indian Ocean to examine potential fishing grounds of Indian scad (Decapterus russelli) and triggerfish (Canthidermis maculata), primarily caught by using ring nets. Present findings indicate that Indian scad preferred SST, Chl-a, and WCV ranges of 27.5-29.5 °C, 0.1-0.37 mg/m3, and 0.01-0.35 m/s, respectively. An analysis revealed that triggerfish species preferred SST ranges of 27.5-29.1 °C, Chl-a ranges of 0.1-0.4 mg/m3, and WCV ranges of 0.055-0.25 m/s. Most of the catches were reported within the EEZ throughout the year and, the Arabian Sea, the Bay of Bengal, and the Southern Ocean, Sri Lanka were the primary fishing grounds for the species throughout the months and seasons. The northeast monsoon (NEM) produced most of the catches rather than the southwest monsoon (SWM). During the period of SWM, most catches were recorded within the EEZ while most of the catches during the NEM period were observed in the Bay of Bengal and the Southern Ocean, Sri Lanka. The present study concludes that environmental conditions directly influence the fishing grounds of Indian scad and triggerfish, and Ring net fisheries are directly impacted by the variability of oceanographic conditions. Present findings help aid in reducing fishing costs and time spent for searching fish during fishing activities, as well as decision-making for sustainable fisheries management.