Investigation of a mass stranding of 68 short-beaked common dolphins in Golfo Nuevo, Península Valdés, Argentina

UHART, M.; CRESPO, E.A.; GRANDI, M.F.; LOIZAGA DE CASTRO, R.; DEGRATI, M.; GARCÍA, N.A.; D'AGOSTINO, V.; VALES, D.; DURANTE, C.; HEREDIA, F.; FERNÁNDEZ, S.; SUEYRO, N.; FIORITO, C.; SANTO, M.A.; MARCHESSI, C.; COSCARELLA, M.A.; DANS, S.L.; NOVACOVSKY, G.; CHALCOVSKY, A.; SOSA DROUVILLE, AILÍN; BUONO M.; ALZUGARAY L.; LUZENTI A.; POLLICELLI D.; DI MARTINO M.; KROCK B.; MCALOOSE D.; RIMONDI A.; GALLO CALDERÓN M.; MORÉ G.

Otro; International Whaling Commission Scientific Committee; 2019

We report on the investigation of a massstranding of 68 short-beaked common dolphins (Delphinus delphis) that occurredin Golfo Nuevo, Península Valdés, Argentina in March 2018. Twenty-one of thestranded dolphins were returned alive to the sea, while 47 animals died. Deaddolphins included all ages, with more males than females (29 males and 18females). The cause of death investigation reported here is restricted to 15adult individuals and one fetus on which a full set of diagnostics wasprioritized due to limited funding. Our results demonstrate that the death of16 dolphins assessed in this study was not due to obvious human effects (e.g.bycatch) or underlying pathologies, as all animals were in good body conditionand had no external evidence of injuries. Infections by Morbillivirus,Influenza A virus, Sarcocystis spp., Toxoplasma gondii, or Neospora caninum, aswell domoic acid (DA) toxicity were ruled out as ethiologies in this event.Notably, results on exposure to paralytic shelfish toxins (PSP) were the onlyinvestigated cause of death found positive. This is the first documentation ofexposure to PSP toxins in short-beaked common dolphins from the Argentine Sea.At present our results are insufficient to assess whether PSP toxin exposureplayed a role in the death of the stranded dolphins. Notwithstanding, the fulldocumentation and investigation of the most commonly reported pathogens andtoxins involved in cetacean mass strandings allowed us to clear the mostrelevant health differentials and suggests areas for future study. Additionalpotential hypothesis related to factors known or speculated to cause cetaceanmass strandings are currently being explored within the ecological context atthe time of the event.