The current situation of marine debris in the stomach contents of cetacean stranding at Hokkaido ―Stranding Network Hokkaido―

Abstract

We conducted a research investigation with the aim of obtaining fundamental insights into the mechanism of plastic ingestion by cetaceans around Hokkaido. The study involved examining the stomach contents of cetaceans that had stranded in Hokkaido, specifically focusing on the occurrence and composition of plastic debris. Additionally, we sought to identify the prey species consumed by the cetaceans and analyze the correlation between the types of prey, feeding habits, and the prevalence of plastic debris. The ultimate goal was to unravel the mechanisms behind the incorporation of plastic debris by cetaceans and to gather basic information that could contribute to strategies for mitigating the impact. Among the cetaceans stranded in Hokkaido from 2012 to September 2023, significant plastic ingestion was observed in the family Ziphiidae. Examination of the stomach contents of Ziphiidae species, revealed a primary diet consisting of mesopelagic cephalopods, including Gonatidae species. This dietary preference suggests a potential relationship between their feeding habits and the ease of plastic ingestion in the marine environment.