Incidence of Odontocetes with Dorsal Fin Collapse in Maui Nui, Hawaii

Abstract

We examined the incidence of bent or collapsed dorsal fins of eight species of odontocetes observed in the nearshore waters of Maui Nui, Hawaii. Between 1995 and 2017, 1,312 distinctive individual odontocetes were photographically documented. Our photo-identification catalogs include 583 spinner dolphins (Stenella longirostris longirostris), 164 bottlenose dolphins (Tursiops truncatus), 132 short-finned pilot whales (Globicephala macrorhynchus), 253 pantropical spotted dolphins (Stenella attenuata), 82 false killer whales (Pseudorca crassidens), 70 melonheaded whales (Peponocephala electra), 15 pygmy killer whales (Feresa attenuata), and 13 rough-toothed dolphins (Steno bredanensis). Of these, two false killer whales (2.44% of catalog), two spinner dolphins (0.34% of catalog), and three pantropical spotted dolphins (1.19% of catalog) displayed major dorsal fin disfigurements. Both spinner dolphins and two of the spotted dolphins had multiple resights spanning several years, with one spotted dolphin having a 16-year span between resights. The two false killer whales with bent dorsal fins did not have any resights and were only sighted once throughout the study period. We also present the first progression of dorsal fin collapse after a significant injury to the leading edge of a spinner dolphin. Results from this research expand our knowledge on injuries to marine mammals and the survivorship of wild dolphins with dorsal fin injuries and contribute to the management of odontocetes in Hawaii, where interactions with fishing gear are a significant conservation issue.

Defining a common language to assess external deformities in free‐ranging cetaceans

“…Van Bressem et al 2007): anatomical malformations and physical impacts may indicate interaction with vessels (e.g. Barcenas‐De la Cruz et al 2018, Stack et al 2019); skin lesions may evidence disease and/or water pollution (e.g. Reif et al 2009, Taylor et al 2021); anomalous pigmentation can indicate congenital conditions leading to individuals being more susceptible to environmental stressors (e.g.…”

Acoustic deterrence to facilitate the conservation of pantropical spotted dolphins (Stenella attenuata) in the Western Pacific Ocean

“…The interaction between fishery activities and cetaceans has led to serious bycatch worldwide (Werner et al, 2015), raising an important issue on how to enhance the conservation on animals under serious threat. The victims include the pantropical spotted dolphins across the Pacific and Atlantic Oceans (Bradford and Lyman, 2015;Zhao et al, 2017;Stack et al, 2019;Carretta et al, 2020). The self-developed ADS system showed its potential to serve as a conservation tool for the pantropical spotted dolphins.…”

“…Stenella attenuata is primarily distributed in tropical and subtropical waters (Perrin and Hohn, 1994;Perrin, 2009). Interactions between fisheries and this species in and around Hawaiian waters have induced its serious entanglements with fishing gear (Bradford and Lyman, 2015;Stack et al, 2019;Carretta et al, 2020). Sixteen pantropical spotted dolphins were caught by accident during fishery activities in the Yellow Sea, China (Wu et al, 2015).…”