Use of historical data to assess changes in the vulnerability of sharks

Abstract

Shark populations have declined worldwide. However, the lack of data for most species makes it difficult to use conventional population assessments to estimate their status. The productivity and susceptibility analysis (PSA) has been recommended for elasmobranchs as it is a data-poor assessment that uses the best available information of the species and their fisheries to determine their vulnerability. A historical characterisation was performed to define the most important periods for the shark fishery in Campeche, southern Gulf of Mexico, and a PSA was conducted to determine the vulnerability of the eleven most important commercial shark species in each three periods. The periods were defined as: local commercialisation (1940–1979), when all species had their lowest vulnerability values, and Carcharhinus leucas, Negraprion brevirostris, and Sphyrna mokarran were classified as highly vulnerable; developed industry (1980–1998) when there was an increase of the fishing pressure, and most small species changed from low to moderate vulnerability and the large coastal sharks scored their highest vulnerability values; and declining industry (1999–2018), when all species had lower vulnerability values than in the developed industry period. However, Carcharhinus brevipinna, Ginglymostoma cirratum, N. brevisrostris, C. leucas, and S. mokarran were still classified as highly vulnerable and could be suffering the accumulative effects of decades of fishing pressure. This multidisciplinary approach serves to identify the most vulnerable species throughout the history of the fishery and to understand the vulnerability values within a historical context, avoiding the shifting baseline syndrome.