World Wide Marine Mammal Strandings – Is it Species Specific and a Cause for Concern?

Askin Nesime1,3, Belanger Michael 2,3, Hill Eileen1,3, Wittnich Carin 1,2,3

(1) Department of Physiology, University of Toronto, MSB Rm 7256, 1 King’s College Circle, Toronto OntarioM8Z 3C2, Canada
(2) Department of Surgery, University of Toronto, MSB Rm 7256, 1 King’s College Circle, TorontoOntarioM8Z 3C2, Canada
(3) Oceanographic Environmental Research Society, 12 Burton Avenue, Barrie, OntarioL4N 2R2, Canada

Strandings of cetaceans and pinnipeds are evidence of marine environmental stress and continues to occur despite efforts to improve this environment. This study examined the global incidence of strandings over 4 decades. A stranding is defined as one animal found either dead/alive on the beach and/or trapped in man-made objects (e.g. nets, lines, etc).

Available stranding reports for cetaceans and pinnipeds from the United Kingdom (U.K.), California U.S.A., Florida U.S.A., and Queensland Australia were summarized in the table below.

In the U.K., the number of stranded marine mammals had a 5 fold increase over 14 years, in contrast California had a 2 fold increase, Florida had a 5 fold increase over 26 years while Australia had no change over a 4 year period. Based on geographical location, certain species had a greater number of strandings per year. For instance, in the U.K.

Harbour porpoises comprised 31% of strandings in 1990 and rose to 41% in 2003 with a spike of 47% in 1999. However in California, sea lions comprised 93% of all strandings both in 1990 and 2002. Strandings of Florida Bottlenose dolphins rose from 52% in 1978 to 73% in 2004.

Every geographical location had a dramatic rise in stranding numbers as well as a sharp increase in strandings of specific indigenous species. Despite current regulations to protect the marine environment, stranding numbers continue to grow and threaten marine mammal populations.