Local ecological knowledge and the historical context of marine apex predators near Islas Marías, México

Abstract

Many shark species and populations are threatened globally due to human actions. Monitoring and protecting these top predators is crucial to maintaining healthy marine ecosystems. However, for many habitats, long-term, historical datasets necessary to track population changes are lacking. This is the case of Islas Marías, México, where the presence of a prison hindered monitoring efforts for decades. In this paper, we addressed a knowledge gap about changes in shark populations through the synthesis of fishers’ local ecological knowledge (LEK). The compiled data allowed us to make a comprehensive list of the shark species diversity in the region. Fishers reported 15 species and one additional genus of sharks near Islas Marías. Overall, catch sizes and perceived abundance trends from 66 interviews suggest that populations of sharks near Islas Marías have been in decline since at least the 1960s. A thematic network analysis revealed that shark declines were attributed to environmental, social, and market factors. These results highlight the importance of fishers’ expert knowledge in reconstructing species population trends.