A pdf of the following paper is available from mmoore 'at' whoi.edu
Vet Pathol 46:536--547 (2009)
DOI: 10.1354/vp.08-VP-0065-M-FL
Gas Bubbles in Seals, Dolphins, and Porpoises Entangled and
Drowned at Depth in Gillnets
M. J. MOORE, A. L. BOGOMOLNI, S. E. DENNISON, G. EARLY, M.M. GARNER, B.
A. HAYWARD,
B. J. LENTELL, AND D. S. ROTSTEIN
Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA
025433 (MJM, ALB,
GE); Department of Surgical Sciences (Radiology), School of Veterinary
Medicine, 2015 Linden
Drive, Madison, WI 53706 (SED); Northwest ZooPath, 654 W. Main, Monroe,
WA 98272 (MMG);
NOAA Fisheries, Woods Hole, MA 02543 (BAH, BJL); College of Veterinary
Medicine & NOAA
Cooperative Center for Marine Animal Health, University of Tennessee,
2407 River Drive, Knoxville,
TN 37996 (DSR)
Abstract. Gas bubbles were found in 15 of 23 gillnet-drowned bycaught
harp (Pagophilus
groenlandicus), harbor (Phoca vitulina) and gray (Halichoerus grypus)
seals, common (Delphinus delphis)
and white-sided (Lagenorhyncus acutus) dolphins, and harbor porpoises
(Phocaena phocaena) but in only 1
of 41 stranded marine mammals. Cases with minimal scavenging and
bloating were chilled as practical and
necropsied within 24 to 72 hours of collection. Bubbles were commonly
visible grossly and histologically in
bycaught cases. Affected tissues included lung, liver, heart, brain,
skeletal muscle, gonad, lymph nodes,
blood, intestine, pancreas, spleen, and eye. Computed tomography
performed on 4 animals also identified
gas bubbles in various tissues. Mean6SD net lead line depths (m) were
92644 and ascent rates (ms21) 0.3
6 0.2 for affected animals and 76 6 33 and 0.2 6 0.1, respectively, for
unaffected animals. The relatively
good carcass condition of these cases, comparable to 2 stranded cases
that showed no gas formation on
computed tomography (even after 3 days of refrigeration in one case),
along with the histologic absence of
bacteria and autolytic changes, indicate that peri- or postmortem phase
change of supersaturated blood
and tissues is most likely. Studies have suggested that under some
circumstances, diving mammals are
routinely supersaturated and that these mammals presumably manage gas
exchange and decompression
anatomically and behaviorally. This study provides a unique illustration
of such supersaturated tissues. We
suggest that greater attention be paid to the radiology and pathology of
bycatch mortality as a possible
model to better understand gas bubble disease in marine mammals.
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