Evidence of a Singular Cause of the Vaquita’s Steep Decline: Bycatch

A recently published paper provides etiological analyses of eight vaquita deaths in March and April 2016–2018. Nutritional state, lesions, biotoxins and levels of contaminants in fat were considered. Injuries to the seven vaquitas found dead (the eighth animal was the healthy adult female that died after being live-captured in November 2017) were consistent with entanglement in monofilament nets or ropes. The authors were able to exclude persistent organic pollutants and biotoxins as sources of mortality in this critically endangered species, and their findings reconfirm that incidental mortality in illegal fishing gear is the sole factor driving the vaquita ever-closer to extinction.