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

UHART, MARCELA; LOIZAGA DE CASTRO, ROCÍO; D´AGOSTINO, VALERIA; HEREDIA, FEDERICO; FIORITO, CARLA; COSCARELLA, MARIANO ALBERTO; CHALCOVSKY, AILEN; ALZUGARAY, LUCIA; DI MARTINO, MATIAS; RIMONDI, AGUSTINA; GRANDI MARIA FLORENCIA; GARCÍA NÉSTOR ANÍBAL; DURANTE, CRISTIAN; SUEYRO, NICOLAS; MARCHESSI, CONSTANZA; NOVACOVSKY, GABRIELA; BUONO, MONICA; POLLICELLI, DEBORA; MCALOOSE, DENISE; MORÉ, GASTÓN; CRESPO ENRIQUE ALBERTO; DEGRATI MARIANA; VALES DAMIÁN GUILLERMO; FERNANDEZ, SANTIAGO; SANTO, MARCELO; DANS SILVANA LAURA; SOSA DROUVILLE, AILIN; LUCENTI, AGUSTÍN; KROCK, BREND; GALLO CALDERÓN, MARINA

Otro; Scientific Committee International Whaling Commission SC/68A/E/08; 2019

ABSTRACTWe report on the investigation of a mass stranding of 68 short-beaked common dolphins (Delphinus delphis) that occurred in GolfoNuevo, Península Valdés, Argentina in March 2018. Twenty-one of the stranded dolphins were returned alive to the sea, while 47animals died. Dead dolphins included all ages, with more males than females (29 males and 18 females). The cause of deathinvestigation reported here is restricted to 15 adult individuals and one fetus on which a full set of diagnostics was prioritized due tolimited funding. Our results demonstrate that the death of 16 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 condition and had no external evidence of injuries.Infections by Morbillivirus, Influenza A virus, Sarcocystis spp., Toxoplasma gondii, or Neospora caninum, as well 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 of exposure to PSP toxins in short-beaked common dolphinsfrom the Argentine Sea. At present our results are insufficient to assess whether PSP toxin exposure played a role in the death of thestranded dolphins. Notwithstanding, the full documentation and investigation of the most commonly reported pathogens and toxinsinvolved in cetacean mass strandings allowed us to clear the most relevant health differentials and suggests areas for future study.Additional potential hypothesis related to factors known or speculated to cause cetacean mass strandings are currently being exploredwithin the ecological context at the time of the event.