Trends in the Sri Lankan Longline Tuna Fishing Effort (2015-2019): A GIS-Based Spatial-Temporal Analysis

Abstract The Fishing industry play a major role in socio-economic context of Sri Lanka. Even though, there is a significant potential to develop the fishing industry in country, the current economic performances of the industry are not satisfactory due to poor management mechanisms. It is essential to implement sustainable management approaches in order to achieve socio-economic and environmental sustainability. The analysis of the spatial and temporal distribution of fishery resources is an important step toward sustaining the resources. However, acquiring data about the distribution and spatiotemporal allocation of catch and fishing efforts in commercial marine fisheries remains challenging. This study aims to investigate the distribution pattern of the longline tuna fishery and identify sustainable fishing grounds in Sri Lanka. The study uses the fisheries data from VMS and logbook between 2015 until 2019, obtained from the Department of fisheries and aquatic resources. The socio-economic data were collected from thirty multiday boat fishermen covering the south, west and east coasts using a semi-structured questionnaire. The study is based on Geographic Information System (GIS) and descriptive statistical analysis. The results of the GIS-based analysis show high variations in catch and catch per trip distribution patterns by years and seasons. Hotspots of fishing efforts, catches (quantity) and catch per trips (CPT) were identified. The results show the areas of clusters with high CPT values increased slightly after 2016. The hotspots map show that there is strong seasonal influences in the concentration of fishing efforts and catches. The socio-economic results confirm that Sri Lankan longline fishers predominantly use traditional ecological knowledge (TEK) to determine their potential fishing zone. Natural signs such as birds, floating, group information, and extreme oceanographic conditions such as waves, wind, and currents were the main factors that longline fishers use to decide where they will go fishing. The effective visualization and communication of identified and mapped seasonal, and annual as well as persistent and sustainable fishing grounds maps to stakeholders and managers may provide a great opportunity to sustainable management of fisheries in Sri Lanka. Moreover, the study shows the importance of integrating TEK to understand the fishers behavior in space and time and to support sustainable management of the fishery system