ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01374

ABSTRACT: Monitoring bycatch in fisheries is essential for effective conservation and fisheries sustainability. False killer whales Pseudorca crassidens in Hawaiian waters are known to interact with both commercial and recreational fisheries, but limited observer coverage across Hawaiian fisheries obscures the ability to assess bycatch. We build upon previous work and assess occurrence of fisheries interactions through photographic evidence of dorsal fin and mouthline injuries for 3 false killer whale populations in Hawai‘i. Photographs of injuries on dorsal fins and mouthlines collected between 1999–2021 were scored for consistency with fishery interactions (“not consistent”, “possibly consistent”, “consistent”). For individuals with both dorsal fin and mouthline photos available, the endangered main Hawaiian Islands (MHI) population had the highest rates of injuries consistent with fisheries interactions (28.7% of individuals), followed by the pelagic stock (11.7%), while no individuals from the northwestern Hawaiian Islands population with both types of photos had fisheries-related injuries. Some individuals from the MHI population were documented with multiple fisheries-related injuries acquired on different occasions, indicating repeated interactions with fisheries. Individuals first began acquiring injuries consistent with fishery interactions at an estimated age of 2 yr. Females were more likely to have fisheries-related dorsal fin injuries than males, but rates of fisheries-related mouthline injuries were similar between the sexes. Injuries consistent with fisheries interactions were acquired throughout the study period, indicating that this is an ongoing issue, not a legacy of past fishery interactions. Our results suggest that efforts to reduce bycatch and begin monitoring of fisheries that overlap the range of the endangered MHI population are needed.