Science & Data

Map and GIS data representing the regulated waters under Harbor Porpoise Take Reduction Plan for the Mid-Coast Management Area.

Map and GIS data representing the regulated waters under Harbor Porpoise Take Reduction Plan for the Massachusetts Bay Management Area.

Map and GIS data representing the regulated waters under Harbor Porpoise Take Reduction Plan for the Mid-Atlantic Regulated and Exempt Waters.

Map and GIS data representing the regulated waters under Harbor Porpoise Take Reduction Plan for the Cashes Ledge Closure Area.

Map and GIS data representing the regulated waters under Harbor Porpoise Take Reduction Plan for the Cape Cod South Closure Area.

Abundance of harbor porpoise (Phocoena phocoena) was estimated from data collected during vessel surveys conducted throughout the inland waters of Southeast Alaska. Line-transect methods were used during 18 seasonal surveys spanning 22 years (1991–2012). Estimates were derived from summer surveys only because of the broader spatial coverage and greater number of surveys during this season than during other seasons. Porpoise abundance varied when different periods were compared (i.e., 1991–1993, 2006–2007, and 2010–2012); however, persistent areas of high porpoise densities occurred in Glacier Bay and Icy Strait, and off the town of Wrangell and Zarembo Island. Overall abundance of harbor porpoise significantly declined from the early 1990s (N=1076, 95% confidence interval [CI]=910–1272) to the mid-2000s (N=604, 95% CI=468–780). This downward trend was followed by a significant increase in the early 2010s (N=975, 95% CI=857–1109) when abundance rose to levels similar to those observed 20 years earlier. Potential factors that could contribute to the downward trend were examined. The 2 regions with high densities of harbor porpoise (i.e., Glacier Bay and Icy Strait as well as Wrangell and Zarembo islands), that were consistently occupied by this species, and the different trend values of these 2 regions indicate that some fine-scale population structuring may exist for harbor porpoise inhabiting the inland waters of Southeast Alaska.

Yakutat Bay on the eastern Gulf of Alaska is a glacial fjord influenced by the activity of major tidewater glaciers at its head and is a region of high marine biodiversity. Two marine mammal species that live there year-round are the beluga whale, Delphinapterus leucas, and the harbor porpoise, Phocoena phocoena.

The harbor porpoise is among the smallest of the six porpoise species in the Family Phocoenidae, with an adult length of 1.4 m to 1.9 m (4.6–6.2 ft). They are rotund, have a stubby beak with small, spade-shaped teeth, and a triangular-shaped dorsal fin. In general, their dorsal surface is dark gray, becoming lighter gray on the sides, with a white underbelly. The sounds they make when breathing have earned them the nickname “puffing pig.” This species is rarely active at the surface but instead presents a low profile when surfacing and often travels alone. They generally forage on small, pelagic schooling fish in waters less than 200 m (656 ft) deep.