The SeaDoc Society is a program of the Wildlife Health Center at the UC Davis School of Veterinary Medicine.
Share 

Marine Protected Areas (MPAs)

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?
 
SeaDoc-funded scientists rolled up their sleeves and collected almost 1,000 samples of seal scat in the San Juan Islands. Detailed analysis of these samples revealed that herring make up nearly 60% of these harbor seals' diets, with their next favorite meals being salmon, pollock and cod-like fish. The seal's total menu, though, was surprisingly diverse, with seals chowing down on at least 35 species of fish! Still, through the entire first year of the study, less than 3% of samples contained rockfish bones. Case closed? Not so fast...
 
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:

(You can do these last two searches yourself by choosing "browse by species" or "browse by issue" from the Salish Sea menu at left.)

  • Share/Save

Using predator distributions, diet, and condition to evaluate seasonal foraging sites: sea ducks and herring spawn

Anderson, E. M., J. R. Lovvorn, D. Esler, W. S. Boyd and K. C. Stick. 2009. Using predator distributions, diet, and condition to evaluate seasonal foraging sites: sea ducks and herring spawn. Marine Ecology Progress Series 386: 287-302. Download PDF.

Using multibeam bathymetry to investigate marine geology and potential marine reserves in the San Juan Islands, Washington, USA

Tilden, J.E. and H.G. Greene. 2002. Using multibeam bathymetry to investigate marine geology and potential marine reserves in the San Juan Islands, Washington, USA. GEOHAB: Marine Geological Habitat Mapping, Moss Landing Marine Laboratories, CA. 70.

Using multibeam bathymetry and GIS to identify potential marine reserves in the San Juan Islands, Washington, USA

Tilden, J.E., H.G. Greene, T. Klinger, W. Palsson. 2002. Using multibeam bathymetry and GIS to identify potential marine reserves in the San Juan Islands, Washington, USA. 2002 Western Groundfish Conference, Ocean Shores, WA. 77 (World Meeting Number 000 5815).

Using multibeam bathymetry to investigate marine geology and potential marine reserves in the San Juan Islands, Washington, USA

Tilden, J.E. and H.G .Greene. 2001. Using multibeam bathymetry to investigate marine geology and potential marine reserves in the San Juan Islands, Washington, USA. Eos Trans. AGU, 82(47), Fall Meet. Suppl., Abstract OS12C-0436.

Two invaders achieve higher densities in reserves

Klinger, T., D. K. Padilla, and K. Britton-Simmons. 2006. Two invaders achieve higher densities in reserves. Aquatic Conservation: Marine and Freshwater Ecosystems: 16: 301-311. Download PDF.

Using multibeam bathymetry to characterize rockfish habitat in San Juan County, WA marine reserves, USA

Greene, H.G., J.E. Tilden. 2002. Using multibeam bathymetry to characterize rockfish habitat in San Juan County, WA marine reserves, USA. MEHP final report 5 plates, 21.

Using multibeam bathymetry to characterize rockfish habitat in San Juan County, Washington marine reserves

Greene, H.G. and J.E. Tilden, W.A. Palsson. 2003. Using multibeam bathymetry to characterize rockfish habitat in San Juan County, Washington marine reserves. Proceedings of the Georgia Basin/Puget Sound Research Conference, Vancouver, Canada, 2003.

Marine protected areas in the Puget Sound Basin: a tool for managing the ecosystem

Gaydos, J. K., K. V. K. Gilardi, and G. Davis. 2005. Marine protected areas in the Puget Sound Basin: a tool for managing the ecosystem. A SeaDoc Society Publication. 12 pp.. Download PDF.

Could the San Juan Islands National Wildlife Refuge serve to protect marine areas? Building on existing institutions and legal authorities to create marine protected areas

Don, C. 2002. Could the San Juan Islands National Wildlife Refuge serve to protect marine areas? Building on existing institutions and legal authorities to create marine protected areas. Coastal Management 30: 421-426. Download PDF.

The Salish Sea

Species & Issues

The SeaDoc Society

Hot Topics

For Scientists

Search


Sign up for our newsletter to get monthly updates on our activities and accomplishments.
  Required information:
* Email
  Optional information:

If you include your name and address we'll send you two free SeaDoc stickers so you can show people you care about healthy oceans. Plus you'll get hard copy versions of our Wildlife Posts six times a year.
First Name
Last Name
Address
City
State
Zip
Please send me reminders of SeaDoc events
I'm a SCUBA diver
 

Why our work matters

Healthy ecosystems support economic prosperity. The Salish Sea provides abundant natural capital that contributes substantially to the financial prosperity of the region. Unhealthy ecosystems cost money because we lose the opportunity to benefit from them. The Salish Sea's deteriorating health threatens our economic well being and quality of life. SeaDoc uses science to find solutions to the problems facing the fish, wildlife and people of the Salish Sea.

How you can help:

Make a donation: Most of SeaDoc's work is supported by private donations from people like you who care about the health of our coastal ecosystems. Your donation makes it possible for us to keep doing the science that will give us objective information about designing a healthy ecosystem that benefits both people and wildlife. Click here to learn more about donating to SeaDoc.

Adminstrator login | Sign up for our Email Newsletter | Make a Donation