Feeding ecology and microplastic contamination of juvenile scalloped hammerhead sharks (Sphyrna lewini) in the Gulf of California

Leony Michèle Kristin Malthaner

Microplastic ingestion is an ever-increasing threat for marine fauna, leading to an array of possible negative impacts. The scalloped hammerhead shark (Syphrna lewini) is a critically endangered and circumglobally found apex predator, whose vulnerability to microplastic ingestion is yet unknown. In this study we inspected the gastrointestinal tracts of 22 juvenile S. lewini captured in the Southern Gulf of California, revealing that every specimen contained synthetic particles. A total of 984 synthetic particles of various colour were isolated, with the majority being fibers (95.43%). Our results suggest that no significant difference in microplastic count, colour composition and diet exists between sharks of different sex, size or season, suggesting that microplastic is ubiquitously available to this species in large amounts throughout the year. However, FT-IR spectrometry yet must reveal the functional groups of the identified particles in order to allow for better identification of the origin of the high microplastic load and possibly unraveling pathways of ingestion in S. lewini. This study provides a first insight into microplastic ingestion in this apex predator, yet another factor that needs to be taken into consideration for the further conservation of this charismatic species.