Microplastics in the gastrointestinal tract of the Pacific Sharpnose Shark (Rhizoprionodon longurio) in the Gulf of California, Mexico

Abstract

Microplastic (MPs: < 5 mm) ingestion has been recorded in Rhizoprionodon longurio, the Pacific sharpnose shark —a species of both commercial value and human consumption— around Santa Rosalia (Baja California Sur, Mexico). A total of 68 individuals were analyzed, revealing a 100% prevalence of MPs ingestion. Fibers and lines were the dominant types, comprising 92.8% of all MPs, with blue being the most common color (61.8%). These blue fibers/lines are commonly associated with fishing gear such as nets and ropes, as well as with synthetic textiles released from household laundry, suggesting multiple anthropogenic sources. Fragments were present in 69.7% of individuals in 2019 and 100% in 2024; while films (20%) and pellets (5.7%) were exclusively found in 2024. No statistically significant differences were detected in total MPs abundance between sexes, size classes (juveniles vs. adults), or sampling years (2019 vs. 2024). However, a significant increase in MP diversity was observed in 2024 (p = 0.036). These findings highlight the persistent and widespread exposure of R. longurio to microplastic pollution in Santa Rosalia area and underscore potential ecological and health implications especially for species of commercial importance.