In this issue: Harbor porpoise questions answered, “Are sea stars recovering?” Divers needed for economic impact study, UC Davis gets high rankings, WDFW seeking comments from citizens, call for abstracts for Salish Sea Ecosystem Conference, Timothy Dwyer to speak on ocean exploration.
In the 1940s, harbor porpoise were considered one of the most frequently sighted cetaceans in Puget Sound, but by the early 1970s they had almost completely disappeared from local waters. Their numbers have since increased, but they remain a Species of Concern in the state of Washington. This in-depth profile looks at harbor porpoise in the Salish Sea, and was prepared by the SeaDoc Society for inclusion in the Encyclopedia of Puget Sound.
ABSTRACT: 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. Here we review the findings related to this event and how these compared to the years immediately before and after the UME. Relatively equal numbers among sexes and age classes were represented, and mortalities were attributed to a variety of specific causes, most of which were categorized as trauma or infectious disease. Continued monitoring of strandings during 4 yr following the UME showed no decrease in occurrence. The lack of a single major cause of mortality or evidence of a significant change or event, combined with high levels of strandings over several post-UME years, demonstrated that this was not an actual mortality event but was likely the result of a combination of factors, including: (1) a growing population of harbor porpoises; (2) expansion of harbor porpoises into previously sparsely populated areas in Washington’s inland waters; and (3) a more well established stranding network that resulted in better reporting and response. This finding would not have been possible without the integrated response and investigation undertaken by the stranding network.
Noren, S. R., D. P. Noren, and J. K. Gaydos. 2014. Living in the fast lane: rapid development of the locomotor muscle in immature harbor porpoises (Phocoena phocoena). Journal of Comparative Physiology B. December 2014, Volume 184, Issue 8, pp 1065-1076.
This study — based on harbor porpoise tissue samples collected from strandings, fishery bycatch, or observed killings by killer whales — looked at muscle development in juvenile harbor porpoises to understand how fast they mature into physically competent adults.
This is important because it shows that immature harbor porpoises can’t dive as well as adults and consequently have limitations on the kinds of habitat they can use. It brings attention to the concept that what might be okay for adult harbor porpoise (such as a certain level of boat traffic), might not be something that harbor porpoise calves can deal with as well as adults can.
Growing Up Underwater (the text of the postcard we mailed out)
A recent study by SeaDoc and Drs. S. Noren from UC Santa Cruz and D. Noren from National Marine Fisheries Service Northwest Fisheries Science Center (Seattle) used samples collected by the San Juan County Marine Mammal Stranding Network to measure diving capabilities in harbor porpoise, the Salish Sea’s smallest and most bashful cetacean. The results show that harbor porpoise achieve adult myoglobin levels by 9-10 months of age, and increased acid buffering as 2-3 year olds. This is faster than other cetaceans, which tracks with their earlier maturity and shorter lifespan. However, the study also proves that there is a period of time when harbor porpoise calves cannot keep up with the adults. This probably limits the habitat range and foraging of mothers and calves, leaving them vulnerable to habitat degradation.
SeaDoc and collaborators have recently undertaken a study to pinpoint harbor porpoise calving times so that we can further protect them at this delicate stage.
Some interesting facts about the study:
- This is one of the first studies to document muscle biochemistry development in dolphins and whales. It’s been done before with Fraser’s and bottlenose dolphins, but not with species resident in the Salish Sea.
- Specimens for this research were collected opportunistically from stranded harbor porpoises, from animals caught accidentally by commercial fishing operations, and from animals killed by killer whales. Collection was performed through the San Juan County Marine Mammal Stranding Network. This program is administered through the Whale Museum and NOAA and is composed of a huge number of very dedicated volunteers.
- Based on length, specimens were divided into 5 age classes, from fetus to adult.
- A prior study by Dr. Shawn Noren, et al. (2008) points out that “although cetaceans are born directly into the ocean, the behavior of cetacean calves may mitigate demands that may otherwise drive the maturation of muscle biochemistry. For example, cetacean neonates typically swim in echelon position (calf in close proximity of its mother’s mid-lateral flank), which lowers the effort required by the calf to move at a given swim speed. Cetacean calves are also nutritionally dependent on their mothers’ milk for prolonged periods (8–42 months depending on the species; for review see Evans 1987) so that the calves do not need to dive to meet their nutritional needs. The distinctly different swimming styles and diving requirements of cetacean calves, relative to adults, alleviate the demands of physical activity and exposure to hypoxia early in life.”
Learn more about harbor porpoise in the Salish Sea:
Harbor porpoise workshop: On February 7, 2013, the Pacific Biodiversity Institute, Cascadia Research Collective and the SeaDoc Society hosted scientists from Washington and British Columbia to determine the state of knowledge on harbor porpoises and coordinate ongoing research efforts. Read the statement identifying research needs.
Marine Science Lecture on harbor porpoise:
Cetaceans (dolphins and whales) are born into the aquatic environment and are immediately challenged by the demands of hypoxia and exercise. This should promote rapid development of the muscle biochemistry that supports diving, but previous research on two odontocete (toothed whales and dolphins) species showed protracted postnatal development for myoglobin content and buffering capacity. A minimum of 1 and 1.5 years were required for Fraser’s (Lagenodelphis hosei) and bottlenose (Tursiops truncatus) dolphins to obtain mature myoglobin contents, respectively; this corresponded to their lengthy 2 and 2.5-year calving intervals (a proxy for the dependency period of cetacean calves). To further examine the correlation between the durations for muscle maturation and maternal dependency, we measured myoglobin content and buffering capacity in the main locomotor muscle (longissimus dorsi) of harbor porpoises (Phocoena phocoena), a species with a comparatively short calving interval (1.5 years). We found that at birth, porpoises had 51 and 69 % of adult levels for myoglobin and buffering capacity, respectively, demonstrating greater muscle maturity at birth than that found previously for neonatal bottlenose dolphins (10 and 65 %, respectively). Porpoises achieved adult levels for myoglobin and buffering capacity by 9–10 months and 2–3 years postpartum, respectively. This muscle maturation occurred at an earlier age than that found previously for the dolphin species. These results support the observation that variability in the duration for muscular development is associated with disparate life history patterns across odontocetes, suggesting that the pace of muscle maturation is not solely influenced by exposure to hypoxia and exercise. Though the mechanism that drives this variability remains unknown, nonetheless, these results highlight the importance of documenting the species-specific physiological development that limits diving capabilities and ultimately defines habitat utilization patterns across age classes.
In this issue: Why do harbor seals swim upside down when foraging? Scientists close in on sea star wasting disease. Marine mammal video for kids. Salish Sea Conservation in Focus trip. SeaDoc’s newest collaborator is 6 years old. Harbor porpoise stranding update
Although the harbor porpoise is the most abundant and widely dispersed cetacean species in the Salish Sea, its probably one of the least well known. Believe it or not, we still know very little about their habitat preferences in the Salish Sea, if the population is increasing, decreasing or stable, how they are related to harbor porpoise outside of the Salish Sea, and even when and where they have their young.
We do know that Harbor porpoise are among the smallest of the cetaceans, reaching an average size of about 5 feet and 120 pounds. They can dive deep, more than 655 feet, but usually stay near the surface, coming up regularly to breathe with a distinctive puffing noise that resembles a sneeze.
On January 14th, 2014, John Calambokidis, a Senior Research Biologist at Cascadia Research Collective, shed new light on harbor porpoise in the Salish Sea. Calambokidis is a well-respected marine mammal biologist and has authored two books on marine mammals as well as more than 150 scientific publications. His work has been covered by the Discovery Channel and National Geographic TV specials.
The 2013-14 Marine Science Lecture Series is designed to inspire the general public and to highlight the amazing fish and wildlife of our region. Lectures are free.
The Lecture Series is presented by program partners The SeaDoc Society and YMCA Camp Orkila. It has been made possible through generous sponsorship by Tom Averna (Deer Harbor Charters), Barbara Brown, Audrey and Dean Stupke and West Sound Marina. Co- sponsors Barbara Bentley and Glenn Prestwich, Emmanuel Episcopal and Bill Patterson (Chimayo/Sazio).
Harbor Porpoises are the smallest cetacean (whale or dolphin) in the Salish Sea. They’re also the only year-round cetacean residents. Even the “Southern Resident” population of killer whales spends much of the year outside of the Puget Sound / Georgia Basin area. Because they’re here year-round, studying them reveals information about what toxins and diseases are in the water. Usually we don’t see much of harbor porpoises – they have only a short fin that hardly breaks the water when they breathe – but viewed from underwater you can see how curious and intelligent they are.
This video was filmed during the SeaDoc Society’s March 2014 board meeting and retreat, which took place at the Vancouver Aquarium.
At the 2014 North American Veterinary Conference, in Orlando, Florida, Joe Gaydos presented on Salmonella in wildlife. About 10% of the Salmonella outbreaks between 2006 and 2013 were caused by wild animals, and most of these were caused by reptiles and amphibians.
Salmonella infection can be prevalent in wild birds, and has been seen in many wild mammal species including white-tailed deer, raccoons, and river otters.
Relatively little is known about Salmonella in free-ranging marine mammals. It has been isolated from harbor porpoise (Phocoena phocoena), a killer whale (Orcinus orca), sea otters (Enhydra lutris nereis), northern elephant seals (mirounga angustirostris), California sea lions (Zalophus californianus), Northern fur seals (Callorhinus ursinus), and harbor seals (Phoca vitulina). Far more isolations have been made than actual documentation of disease. Salmonella Newport-associated septicemia has been documented in a harbor porpoise and a killer whale. Salmonella also has been isolated from marine birds such as Western gulls (Larus occidentalis). While one study found prevalence of Salmonella in 40% of California sea lion pups and 33% of northern fur seal pups on San Miguel Island, the prevalence in most marine wildlife populations is unknown but probably highly variable.
Download a copy of the paper: Salmonella in Wildlife by J. Gaydos
An estimated 1.2 million cases of salmonellosis occur annually in the United States (approximately 42,000 are laboratory-confirmed and reported to the Centers for Disease Control; CDC). Transmission comes primarily from contaminated food, water or contact with infected animals only some of which are wild animals. Of the 50 Salmonella outbreaks reported by the CDC between 2006 and 2013, only 5 (10%) were related to wildlife. These included the 2013 outbreak related to small turtles (Salmonella Sandiego, Pomona and Poona), two 2012 events associated with hedgehogs (Salmonella Typhimurium) and small turtles (Salmonella Sandiego, Pomona and Poona), the 2011 outbreak connected to Africa dwarf frogs (Salmonella Typhimurium) and the 2010 water frog-related outbreak (Salmonella Typhimurium).