Historical Catch Estimate Reconstruction for the Pacific Ocean based on Shark Fin Trade Data (1980-2016)
This paper describes a methodology to estimate silky shark catches in the Eastern and Western Central Pacific Ocean by all fleets based on a characterization of the global shark fin trade. Catch estimates using this method have been used in ICCAT blue and shortfin mako assessments, IOTC blue shark assessments, and the previous WCPFC assessment of silky sharks. Estimates were constructed using four steps. First, estimates of the number and biomass of silky shark represented in the global shark fin trade in 2000 were reconstructed using triangular distributions in a WinBUGS model. These estimates were then adjusted using annual imports into Hong Kong for 1980-2016. Figures were then further adjusted based on the diminishing share of Hong Kong’s shark fin trade as compared to the total global trade in recent years. Finally, these adjusted annual global estimates were scaled in a number of ways (by ocean area (km2), by tuna and tuna-like species catch, and by longline effort) to represent potential shark catches in the Eastern and Western Central Pacific Ocean. It is important to note that these estimates capture only a portion of the potential silky shark catches (i.e. only those sharks’ whose fins are internationally traded).