|
|
|
 |
SPEAKER SERIES 2011-2012
The Puget Sound Chapter of the American Cetacean Society Speaker Series does not meet during the months of July, August, & December. 21 September 2011 - Film Showing
|
|||||||
 |
| Harlequin duck by Alan Fritzberg |
Growing up surfing in Baja California and Southern California, Nacho Vilchis has spent most of his life in or around the Pacific Ocean. Nacho completed his undergraduate studies at the University of San Diego, his first graduate program at the Universidad Catolica de Chile, and earned his Ph.D. from at the Scripps Institution of Oceanography in La Jolla California. He's spent thousands of hours surveying underwater in kelp forests in California and Chile, and months at sea studying tropical and temperate seabirds in open oceans off the Hawaiian archipelago, Clipperton atoll, Malpelo Island and the Galapagos Islands. Currently, he is doing his residency in the Pacific Northwest as a post-doctoral fellow with the SeaDoc Society, investigating long-term trends of marine birds in the Salish Sea.
We are taking a closer look at two very different harbor porpoise populations. One in Southeast Alaska and the other in Greater Puget Sound. Marilyn Dahlheim, a wildlife biologist with National Marine Mammal Laboratory's Cetacean Assessment and Ecology Program, will present her findings from studying Southeastern Alaska. Brad Hanson, an ecologist with the Northwest Fisheries Science Center will talk about the increases in harbor porpoise abundance in our waters.
Marilyn Dahlheim is a wildlife biologist with the National Marine Mammal Laboratory's Cetacean Assessment and Ecology Program. Marilyn has conducted research on several cetacean species in places ranging from Mexico to the Arctic with a primary focus on abundance estimation, distribution, and movements. In 1989, she initiated studies in Southeast Alaska on cetacean biology and ecology, studies which have continued each year to the present. In particular, she has been involved with long-term studies on Southeast Alaska killer whales; she has published several papers addressing abundance, stock structure, contaminant levels, and dietary preferences of killer whales from this region. Recently, she has been working on population studies of harbor porpoise and Dall's porpoise in Southeast Alaska.
Before joining NMML in 1978, Marilyn worked at Marine World (Redwood City, California) with captive killer whales and bottlenosed dolphins. Between 1974 and 1978, she worked as a biologist/acoustician at the Naval Undersea Center in San Diego. She received her B.S. and M.S. in biology from San Diego State University. Her master's degree reported on signature information in the calls of captive killer whales. She obtained her Ph.D. at the University of British Columbia. Her dissertation was titled "Bioacoustics of the Gray Whale."
 |
| Harbor Porpoise (Phocoena phocoena) on map of North America's NW Coast Uko Gorter |
'Abundance and Trends of Harbor Porpoise (Phocoena phocoena) in Southeastern Alaska inland waters'
Marilyn E. Dahlheim1, Alexandre N. Zerbini12, Janice M. Waite1, and Amy S. Kennedy1
1 NOAA Fisheries, Alaska Fisheries Science Center, National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, Washington, 98115-6349, USA
2 Cascadia Research Collective, 218 ½ W 4th Ave., Olympia, Washington, 98501, USAIn 1991, researchers from the National Marine Mammal Laboratory (NMML) initiated harbor porpoise studies aboard the NOAA R/V John N. Cobb with survey coverage throughout the inland waters of southeastern Alaska. Between 1991 and 1993, line-transect methodology was used to: 1) obtain population estimates of harbor porpoise, 2) establish a baseline for detecting trends in abundance, and 3) define overall distributional patterns and seasonality of harbor porpoise. Three surveys were carried out each year spanning spring, summer, and fall. Annual surveys were continued between 1994 and 2005, however only two trips per year were conducted; one either in spring or summer and the other in fall. Although standard line-transect methodology was not used, all cetaceans observed were recorded. During this 12-year period, observers reported fewer overall encounters with harbor porpoise. Although this raised concerns, our confidence in these data was low due to lack of quantification of effort, variable number of surveys per year, differences in methodology, and other factors that could influence these counts (i.e., differences in mean group sizes by season or year, differences in survey coverage and duration, and given that focal studies were aimed at humpback whales and killer whales). To fully assess abundance and population trends for harbor porpoise, we once again employed line-transect methodology during our cruises in 2006, 2007, and 2010.
Harbor porpoise abundance and trends were examined for the entire study area and selected sub-areas of historical porpoise concentrations. Results show an overall decline of harbor porpoise in southeastern Alaska inland waters. An inspection of the regional estimates indicate that harbor porpoise abundance and trends vary by area with a more pronounced decline observed in the southern range of the survey area near Zarembo and Wrangell Islands and Frederick Sound. The reasons for the negative trends are not well understood and could include bycatch, a change in prey distribution, a decrease in survival or a shift in distribution due to habitat degradation, predation, or a combination of these factors. It is noteworthy that a greater decline was observed in areas where gillnet and purse-seine fisheries exist.
Brad Hanson joined the Northwest Fisheries Science Center in April of 2003. Previously, Brad worked as a Wildlife Biologist at the National Marine Mammal Laboratory in Seattle, WA. Brad received a Ph.D. from the University of Washington where he worked on the development of improved tag attachment systems for small cetaceans. He also holds an M.S. in Fisheries from the University of Washington and a B.A. in Zoology also from the University of Washington.
Brad is an ecologist and is currently studying foraging and habitat use of Southern Resident killer whales and health assessment of harbor and Dall's porpoises.
Return of Harbor Porpoise to Puget Sound: Recent Increases in Abundance
Brad Hanson, John Calambokidis, Steven Jeffries, Jessie Huggins, Candice Emmons, Marla Holt, Dawn Noren, and Eric Ward
Harbor porpoise were reported to be the most commonly observed marine mammal in Puget Sound in the 1940s. Although little information on their status is available from the next three decades, by the mid-1970s when greater attention began to be paid to marine mammal distribution and abundance in this region, harbor porpoise appeared to have all but vanished from the main basin and south Puget Sound. A paucity of anecdotal reports, sightings during surveys, or strandings over the following two decades appeared to confirm that this species had essentially disappeared from this area. While the reasons for their disappearance are unclear, several anthropogenic factors could have been responsible including mortalities in gillnet fisheries, impacts of contaminants, noise, and the degraded state of Puget Sound.
However, in the 2000s, numerous anecdotal reports and a few strandings were documented in the main basin and south Sound. By 2009, multiple groups of harbor porpoise were being sighted throughout the year in a number of areas of Puget Sound including south of the Tacoma Narrows where historical records from the 1940s reported them as common. Recent systematic boat surveys of the main basin indicate that at least several hundred and possibly as many as low thousands of animals are now present.
While the reasons for this recolonization are unclear, it is possible that changing conditions outside of Puget Sound, as evidenced by a tripling of the population in the adjacent waters of the Strait of Juan de Fuca and San Juan Islands since the early 1990s, and the recent higher number of harbor porpoise mortalities in coastal waters of Oregon and Washington, may have played a role in encouraging harbor porpoise to explore and shift into areas like Puget Sound. The return of harbor porpoise to these regions of Puget Sound provides encouraging evidence that many of the underlying ecosystem components, e.g., forage fish populations, are functioning at a level sufficient to support these and other top predators. With their return to Puget Sound increased strandings of harbor porpoise have also been recorded in this area, indicating that a number of threats to the long-term viability of this population may still exist.
January's Speaker Series meeting was cancelled on account of dangerous driving conditions.
