Please see the Open Access paper Moore MJ, Mitchell GH, Rowles TK, Early
G (2020) Dead Cetacean? Beach, Bloat, Float, Sink. Frontiers in Marine
Science
https://doi.org/10.3389/fmars.2020.00333
Abstract: Variably buoyant, dead Cetacea may float, or sink and later
bloat to refloat if ambient temperature and pressure allow sufficient
decomposition gas formation and expansion. Mortality can result from
acute or chronic disease, fishery entanglement, vessel collision,
noxious noises, or toxicant spills. Investigators often face the
daunting task of elucidating a complex series of events, in reverse
order, from when and where an animal is found, and to diagnose the cause
of death. Various scenarios are possible: an animal could die at sea
remaining there or floating ashore, or strand on a beach alive, where it
dies and, if cast high enough, remain beached to be scavenged or
decompose. An animal that rests low on a beach may refloat again,
through increased buoyancy from decomposition gas and favorable tides,
currents, and wind. Here we review the factors responsible for the
different outcomes, and how to recognize the provenance of a cetacean
mortality found beached, or floating at sea. In conclusion, only some
carcasses strand, or remain floating. Negatively buoyant animals that
die at depth, or on the surface, and sink, may never surface, even after
decomposition gas accumulation, as in cold, deep waters gas may fail to
adequately reduce the density of a carcass, precluding it from returning
to the surface.
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