Assigning shark fin origin using species distribution models needs a reality check

Abstract

The conservation and management of shark populations have become urgent issues to ensure the future health of our oceans [1]. There are many drivers of the decline of shark populations, with the demand for shark fins being one of the more important [2]. Understanding fin origin can help identify regions for improved management, and hence has been the focus of recent research (e.g. Fields et al. [3], Cardeñosa et al. [4]). In a recent Biology Letters article, Van Houtan et al.[5] contributed to this work using data on species composition of shark fins at four markets and species distribution models (SDMs) to predict the probability of fin origin. Their purpose was to address knowledge gaps in source and trade routes of shark products, which currently limit the effective allocation of management resources. While the broad concept behind their paper is novel, we disagree with the results and conclusions owing to flaws in methodology and interpretation.We fundamentally disagree with the central assumption of the paper that there is a direct link between species distribution and shark fin origin. This assumption relies on fisheries catch being equal through the distribution of a species, which we know is not true. Fishing effort that catches sharks is spatially

Emergent research and priorities for shark and ray conservation

“…Worm et al 2013). These models need to clearly acknowledge the limitations and biases related to the availability of source records and state associated output uncertainty to avoid yielding inaccurate distributions when extrapolated beyond the region of interest (Raoult et al 2021).…”

Narrowing the niche of shark fin harvests in the global ocean

“…In their Comment [1], Raoult et al challenge our use [2] of species distribution models (SDMs) to inform on the geographical origins of shark fins sold in global markets. This is despite our primary result that shark conservation should prioritize areas within the Exclusive Economic Zones (EEZs); a conclusion supported by independent biogeographic analyses [3,4], reconstructed global fishing effort and catch [5,6], and syntheses of biotelemetry data [7].…”