Whale shark interactions with the tuna purse-seine fishery in the eastern Pacific ocean: summary and analysis of available data

The whale shark, Rhincodon typus is the world’s largest fish species, commonly exceeding 1000 cm total length (TL), with 1800 cm as the maximum length measured, but possibly reaching about 2000 cm TL (Compagno 2001; Stevens 2007). It inhabits all tropical and warm temperate ocean areas, and unlike almost all other sharks, feeds mainly on plankton (Compagno 2001). It is globally classified as “endangered” under IUCN Red List criteria (Pierce and Norman 2016), and since 2003 has been listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Appendix II (CITES 2017).

Interactions between whale sharks and the purse-seine fishery for tunas are known to occur in the eastern Pacific Ocean (EPO), although they are relatively uncommon. Observers of the Inter-American Tropical Tuna Commission (IATTC) and of the national programs that constitute the On-Board Observer Program of the Agreement on the International Dolphin Conservation Program (AIDCP), who are required aboard all large1 purse-seine vessels, collect data on these interactions.

This document provides a summary description of the types of data on whale sharks in the EPO available in IATTC databases, and some preliminary analyses of the data.