Salmon
River Otter Diet and Predation Project
In 2012, SeaDoc is funding a River Otter diet and predation study by Monique Lance of the Washington Department of Fish & Wildlife.
The study aims to describe the diet of river otters and investigate the potential effect they have on rockfish and salmon populations in the San Juan Islands.
Rockfish and salmon are currently listed under the Federal Endangered Species Act. Because of the dramatic decline in these species over the past several decades, Marine Protected Areas have been created to assist in their recovery.
However, little attention has been paid to how predators respond to increased prey densities. Therefore it's important to investigate the diet of potential predators.
Otter scat samples were collected in the spring, summer and fall of 2008 on Fidalgo, San Juan and Orcas Islands. The scat samples have been cleaned and invertebrates in them have been identified. The project now allows for the analysis of fish remains in the scat, as well as examinations of spatial variation among the project sites and temporal variations through 2008. Data will also be compared to diet data from Alaska and British Columbia. The project will also compare diet among various predators, including harbor seals and Steller sea lions.
Photo by Michael Ransburg: Creative Commons license.
Elwha Dam Removal
Joe Gaydos serves as a governor appointed Commissioner and science and technical advisor to the Northwest Straits Commission.
He shared this from the Northwest Straits Commission meeting on May 20, 2011:
At the meeting today, we heard a great presentation by Dean Butterworth of the National Park Service on the removal of the Elwha Dams, scheduled to begin this September.
This will be a major national and international event.
The three main reasons for removing the Elwha Dam and Glines Canyon Dams from the Elwha river are:
- To benefit salmon and sea-run trout; both dams were built without provision for fish passage and you can still see salmon pooling below the dams, blocked from spawning.
All 5 salmon species as well as 3 species of anadromous trout (steelhead, bull trout and cutthroat) used to inhabit and/or spawn in the Elwha river.
Before the dams, fish could access over 70 miles of streams and freshwater. Since the dams, only the lower 5 miles of the river remain for spawning.
Note: in addition to benefitting salmon and trout, allowing these fishes to re-inhabit 65 miles of freshwater will benefit the riparian habitat as well as over 130 species of animals.
- Dams also block the movement of sediment from the river from moving into the Strait of Juan de Fuca (about 18-20 million yards of sediment are thought to exist trapped behind the dams).
- A giant push by the Lower Elwha-Klallam tribe for full restoration of the Elwha River ecosystem.
To date, there have been numerous studies to direct the removal of the dams as well as on-the-ground work to help open up an area where there will eventually be another delta at the mouth of the Elwha river.
As September draws near and for the next several years in the future, this huge ecosystem restoration story will be talked about all over the country and the world. We'll keep you posted with updates.
Don't miss these two very cool animated visualizations of the removal of each dam.
Note: Some images are static, others are animated. Click on the image to start or advance the slideshow.
More info at http://www.nps.gov/olym/naturescience/elwha-faq.htm
Beaver & Salmon Lecture Recap
On February 8 SeaDoc hosted Greg Hood from the Skagit River System Cooperative for a talk on Beaver, Salmon, and restoration of tidal habitat. We recorded audio and video of this event: see below for links.
Removal of dams on Olympic Penninsula to help salmon
The removal of two dams on the Elwha River near Olympic National Park is anticipated to help restore salmon runs in this area. Five different species of salmon use this river, which as been dammed since 1917.
For details on the project and the expected benefits, see the Elwha dam removal page at the Olympic National Park site or an article in the Sequim Gazette.
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.)
Here's a video (aimed at kids) that gives a behind-the-scenes look at how this kind of research is done.
Species of concern within the Salish Sea Marine Ecosystem: changes between 2002 and 2008
Persistent Organic Pollutants in Chinook Salmon (Onchorhynchus tshawytscha): implications for resident killer whales of British Columbia and Adjacent Waters
When Food Can Kill: Salmon and Killer Whale Populations
A study published in Environmental Toxicology and Chemistry explains the process by which threatened and endangered killer whales in the waters of northwestern North America become contaminated with persistent organic pollutants, particularly polychlorinated biphenyls (PCBs), that are present in chinook salmon, their primary food source.
Two years of this study were funded as part of the SeaDoc Society's competitive grants program.
Two main observations were made. First, nearly 100% of the contaminants in chinook salmon were acquired while they lived in the ocean. Second, southern killer whales are contaminated with higher concentrations of chemicals because 1) they eat more salmon than their northern counterparts and 2) southern salmon have higher levels of contaminants than northern salmon because the southern waters are more contaminated than the northern waters. In fact, PCB concentrations in southern salmon were almost four times those in northern salmon.
It is known that salmon can lose as much as 80% of their lipid (fat) stores as they journey back to their natal streams. Salmon stop eating during this time and draw energy from their lipid stores. Thus, they are less nutritious to whales than they would be otherwise. Furthermore, southern salmon were found to have lower lipid content than northern salmon. Whales therefore eat larger amounts of salmon and consequently are exposed to larger amounts of chemicals in the salmon. Southern whales, in particular, consume as much as 50% more salmon to compensate for the fact that their food is, per unit, less nutritious.
Salmon paradoxically help killer whales (food) and harm them (contamination). This study is important because it illustrates the increasing amount of damage to fragile ecosystems that occurs as industries continue to dump waste into rivers and oceans.
To read the entire review, Persistent Organic Pollutants in Chinook Salmon (Oncorhynchus tshawytscha): Implications for Resident Killer Whales of British Columbia and Adjacent Waters (Vol. 28(1):148–161), visit http://www.allenpress.com/pdf/ENTC_28.1_148.pdf
Scientists try to uncover the dangers to Killer Whales
When seven resident killer whales that frequent inland waters of Washington went missing this year, there was no shortage of suspects.
SeaDoc Society convenes meeting to discuss Orca deaths
Read more about the meeting in a Kitsap Sun article by Christopher Dunagan.
