Puget Sound harbor porpoise

Harbor porpoise (Phocoena phocoena) habitation of coastal waters exposes them to frequent interactions with fisheries, pollution, boat traffic and other anthropogenic threats. Many harbor porpoise populations throughout their range are in decline, while others show signs of recovery, with animals commonly sighted in some formerly abandoned portions of their range. Harbor porpoise were the most common cetacean in the inland marine waters of Washington State, including the Puget Sound, in the 1940s.

Harbor porpoise were a common year-round resident in the Puget Sound in the 1940s, but by the 1970s, they had disappeared from the Sound, and their numbers were greatly reduced in the Straits of Georgia and Juan de Fuca, and around the San Juan Islands. Some survey efforts were conducted to verify that there were no harbor porpoise within the Puget Sound, but prior to 2013, there were no dedicated small cetacean surveys providing complete coverage of Washington’s inland waters, including the Puget Sound.

The objective of this research was to determine whether detrimental effects possibly caused by toxic chemicals could be observed in Puget Sound marine mammals and marine birds.

Studies on birds and marine mammals from around the world indicate that environmental contaminants have adversely affected wildlife. This is especially well documented for stable chlorinated hydrocarbon compounds, such as DDT (and its major metabolite DDE) and polychlorinated biphenyls (PCBs), that occur at higher concentrations at higher trophic levels.

Aerial surveys were conducted off Oregon and Washington in the summer of 1991 to help determine the current abundance of harbor porpoise (Phocoena phocoena) in these waters. Effort in 1991 was increased from that in previous years' surveys to reduce the coefficient of variation around the estimated abundance and to cover regions that had not been surveyed in 1990.

Harbor porpoise (Phocoena phocoena) are considered to be a sentinel species throughout much of their range due to their sensitivity to a number of anthropogenic threats, including pollution, interaction with fisheries, boat traffic and sound. They also depend on healthy stocks of forage fish and squid to maintain their population. Harbor porpoise were the most common cetacean in the Salish Sea in the 1940s, and were seen year round in the Puget Sound.

As high trophic level, non-migratory marine mammals, harbor seals (Phoca vitulina) inhabiting the Strait of Georgia, Juan de Fuca Strait and Puget Sound (collectively referred to as the Salish Sea) in northwestern North America provide an integrated measure of coastal food web contamination.

In 2006, a marked increase in harbor porpoise Phocoena phocoena strandings were reported in the Pacific Northwest of the USA, resulting in the declaration of an unusual mortality event (UME) for Washington and Oregon to facilitate investigation into potential causes. The UME was in place during all of 2006 and 2007, and a total of 114 porpoises stranded during this period. Responders examined 95 porpoises; of these, detailed necropsies were conducted on 75 animals.