Fisheries-related traumatic shock deaths in pigmy sperm whales, Kogia breviceps

Abstract

The diagnosis of cetacean by-catch is more than ever under t}te scrutiny of tle scientific community. Although widely reported in certain species, the circumstances of fisheries interactions remain poorly documented and tie precise associated pathologi al processes are still lacking, especially for the species noi commonly identified to be interacting with fishing operations. We document here the stranding of threé Kogia in different regions of Spain (Canarias, Galicia y Asturias) between 1999 and 2001, and discuss the similarity of the clinical anã patholojical findings as indicative of a possible repetitive fisheries interaction. The th¡ee animals, young to adult maies, rtruã¿"¿alive and died shortly after beaching. External examination showed no obvious fisheries-i-nteraction-related marks, with the exception of rostral abrasions, and, in one case, penetrating incisions around the mouth. Full necropsies were routinely conducte4 and the tlvee Kogia were diagnosed úo present a traumatic shock due to cervical veÉebrae, and skull fractures with_ spread haemorrhages of the cervical region together with subdural, well-organisej haematoma compressing the temporal cortex. In addition to the shared traumã díagnosis, lung congestion, tracheal froth, subcutaneal crassicaudasis, and full urinary bladder were also found. The skull morphoiogy and bone texture of this species may help to understand the specifîcþ of the skull and vertebral fractures foúnd añãr a violent impac! without the beak fractures commonly described in other better-known by-caught species. In fact, the absence of á prominent roshum in this species may explain why Kogia is not usually reported entangl"d, and lacks the obvious consequent head fishing-line marks. The latter information, added to the time that the animals survived after the interaction, could have masked to some extent the usual evident fishing marks. Although not being the most obvious candidate for consideration as by-catch, the similarily of the clinical and pathological findings anL tne stranding in the same circumstances of tfuee animals of the same species in three different regions, suggest that this could ùe[illustate a diagnostic of fisheries interaction involvrngKogia sp.