Estimating shark body sizes from fins as the future monitoring strategy for shark fin trade in Indonesia

Abstract

High market demand for shark products makes sharks more threatened due to targeted exploitation, bycatch and intensive utilisation. As the top producer and exporter of shark fins, Indonesia must have accurate and detailed trade data as well as proper monitoring of shark utilisation for implementing better management. This study aimed to estimate the body size of sharks based on their fin measurements. Data collection was done in one of the major shark landing sites at Tanjung Luar Fishing Port (Lombok, West Nusa Tenggara) during 2018-2020. Morphological measurements were taken for economically important and CITES-listed shark species, i.e. Sphyrna lewini, Sphyrna mokarran, Carcharhinus longimanus, Alopias pelagicus, Alopias superciliosus, Isurus oxyrinchus and Isurus paucus caught by both longlines and gillnets. Linear correlations were found in the relationships between body size (total length) and fin sizes (dorsal fin length, dorsal fin height and pectoral fin length), with variations among species. The results of this study will be useful for fishery and quarantine officers in predicting the body size of sharks caught from Indonesian waters and entering the fin trade, as an alternative approach in monitoring sharks as traded commodity, based on fin products. Keywords: CITES, Fins, Monitoring, Sharks, Threatened species, Utilisation