Harbor Seal
New research from Alaska: Steller Sea Lions attacking Harbor Seals
A new paper just released in the Journal of Marine Mammalogy shows that Steller Sea Lion predation on Harbor Seals in Glacier Bay, AK could be responsible for the decline in Harbor Seals in that region.
While there is no evidence that Stellers are predating harbor seals in the Salish Sea region, it will be interesting to watch for this type of activity in the future.
In the Salish Sea, our Harbor Seal population is at carrying capacity and we are seeing more and more Steller Sea Lions in the region in the fall, winter and spring.
Harbor Seal Rehabilitation Study
Each year many stranded harbor seal pups are collected by marine mammal stranding networks and rehabilitated before being released to the wild.
But we don't know if these rehabilitation efforts really work.
A new SeaDoc study will try to find out if rehabilitated seals survive at the same rate as wild-weaned seals, if they have similar movement patters, and if they even remain in the Salish Sea.
It costs about $3,000 to rehabilitate a harbor seal pup. Rehabilitation rates have improved over time, to the point where the Wolf Hollow Wildlife Rehabilitation Center in San Juan County has a rehabilitation rate of 77%.
Our study -- funded by the John H. Prescott Marine Mammal Rescue Assistance Grant Program, the U.S. Federal Government, and private donations from SeaDoc supporters -- will monitor the movement and survival of 10 rehabilitated pups and 10 wild-weaned pups. By comparing the results from these two different populations, we'll be able to assess whether rehabilitation efforts are working they way we expect.
Pups are tagged with satellite transmitters as well as VHF tags on their flippers. This allows them to be tracked automatically by satellite with a backup tracking mechanism of local VHF tracking.
The satellite data network produces maps showing the seals' locations over time.
Multi-year harbor seal research
Three times each summer the SeaDoc Society and Cascadia Research visit Smith Island to survey the harbor seal population. Smith Island is part of the
San Juan Islands National Wildlife Refuge and is closed to the public. The visit consists of a count of live animals followed by a count of all carcasses. Scientists also try to count placentas to track birth numbers.
According to Sara Heidelberger, the third year veterinary student who necropsied this animal, this female seal was in good condition with a thick layer of blubber. Her teeth were deeply and evenly worn, suggesting she was relatively old. She had recently given birth. The team collected the skull for further study. Photos taken July 23, 2010.
What's the Deal with Rockfish and Seals?
Harbor seal populations have exploded nearly tenfold in the Salish Sea since the 1970s, while at the same time many rockfish species have plummeted. Some fishermen blame that on the increase in hungry seals. But coincidence is not science. So who ya gonna call?
In the second year, 12% of the samples contained rockfish remains, particularly in the winter when there are fewer salmon locally. With all the seals in the Salish Sea, those numbers could impact rockfish recovery. That doesn't mean, however, that we should start controlling seal populations: this study showed seals also have a taste for dogfish, another major fish predator. So fewer seals could mean more dogfish. The real answer is to remember that all parts of our ecosystem are tightly intertwined. Rockfish recovery depends upon ecosystem recovery, including salmon recovery, herring recovery and so on around the Sea.
More information on this topic:
- The original report on this study (so you can see what we've learned since the first round)
- The Puget Sound Partnership's resource page on rockfish.
- SeaDoc's comments on the proposed (12/2009) rockfish conservation plan by the WA Dept of Fish & Wildlife.
- All the info on our site about rockfish (automatic search)
- All the info on the site about predator/prey relationships (automatic search)
(You can do these last two searches yourself by choosing "browse by species" or "browse by issue" from the Salish Sea menu at left.)
Your best friend may not be so eco-friendly
Disturbing results came from a site in south Puget Sound where seals were not only infected with their own brand of Giardia, but also with a canine variety, which shows that diseases from our pet dogs are being transmitted to marine wildlife. Future studies will tell us what effect the dog Giardia is having on the seals, but for now it's an important wake-up call and reminder for everyone who cares about the oceans: The land and sea are intimately connected and even doing simple things like scooping your best friend's poop will help keep the ocean and its wildlife healthy.
Fishing gear-related injury in California Marine Wildlife
Canine Giardia in Harbor Seals
A recent study by the SeaDoc study demonstrates that harbor seals in the Puget Sound region carry their own type of Giardia, but in at least one location in South Puget Sound harbor seals could have been infected with a canine strain of Giardia. Many people are familiar with the cat parasite Toxoplasma gondii infecting and killing sea otters; this study suggests that dogs also could transmit their parasites to marine mammals and reminds us that what happens on land is intimately connected to what happens in the ocean.