Research shows need for restoring salmon population key to orca recovery
November 9, 2011
VANCOUVER – In a paper published today in PLoS ONE, researchers reveal the energetic needs of killer whales for Chinook salmon in the Salish Sea. This important information underscores how recovery planning for both species needs to factor in just how many salmon the killer whales require. A healthier whale population could mean increased competition between fisheries and killer whales, resulting in more pressure on wild salmon stocks.
“If the aim on both sides of the border is to not only stop the decline of killer whale populations but also help increase their numbers, then we have to ensure that the salmon they require are there when they need them,” says Dr Rob Williams, who led the work at University of Washington when he served as Canada-US Fulbright Visiting Research Chair.
The researchers modeled killer whale prey requirements based on information gathered from captive killer whales, and data from historic live-capture fishery and whaling records worldwide. Along with information from wild killer whales and knowledge of salmon, they were able to estimate how many salmon are needed to maintain and recover this killer whale population
“Our research indicates that southern resident killer whales easily consume 100,000 Chinook each year, and depending on their winter diet, their requirements could easily be double that,” says co-author Erin Ashe. “A nursing female needs to eat 42% more to meet the needs of her and her calf – it’s an incredible amount of salmon.”
The orcas need for salmon will mean increased competition between the whales and the commercial, recreational and aboriginal salmon fisheries. For instance, a U.S. recovery goal for the killer whales over the next 28 years implies a 75% increase in salmon intake. In BC, the average fisheries catch of Fraser River Chinook is 18,000 fish, with another 300,000 fish entering the spawning grounds. It is possible the orcas will need 12% to 23% of available Fraser River Chinook in the region from May-September.
Currently, government agencies in the US and Canada are holding workshops to consider reducing fishing quotas to leave more salmon for the whales. However, the authors note that feeding the whales does not have to come exclusively from reduction in fisheries quotas. “Rebuilding wild salmon populations for killer whales could include marine habitat protections to safeguard salmon from a growing list of new health threats, such as sea lice and infectious salmon anemia,” says Dr. Martin Krkosek, assistant professor at the University of Otago and coauthor of the study.
“If we make decisions to protect our wild salmon from the stresses caused by disease, pollution and habitat loss, it will mean more fish for the whales, and for us,” say Christianne Wilhelmson, Executive Director, Georgia Strait Alliance. “The key to doing this is to manage the waters of the Salish Sea as a whole and not one species at a time.”
Oceans Initiative (www.oceansinitiative.org)was formed in 2007 to provide the cutting -edge science needed to protect biodiversity and threatened marine wildlife in the face of critical environmental challenges. We advance conservation and knowledge through on-the-water field studies in remote wilderness, innovative analyses and collaboration and engagement with the global community.
Formed in 1990, Georgia Strait Alliance (www.GeorgiaStrait.org) is the only citizens’ group working to protect and restore the marine environment and promote the sustainability of Georgia Strait, its adjoining waters and communities, the place where 70% of British Columbians live, work and play.
Download full publication here http://dx.plos.org/10.1371/journal.pone.0026738
For more information:
Dr. Rob Williams, Marie Curie Research Fellow, University of St Andrews and co-founder Oceans Initiative (rmcw@st-andrews.ac.uk rob@oceansinitiative.org; cell: +1 206 300 2856)
Erin Ashe, PhD candidate, University of St Andrews and co-founder Oceans Initiative (ea84@st-andrews.ac.uk erin@oceansinitiative.org cell: +1 206 947 2249)
Marty Krkošek, Assistant Professor, University of Otago, martin.krkosek@otago.ac.nz
Christianne Wilhelmson, Executive Director, Georgia Strait Alliance, office: 604 633 0530, cell: 604 862-7579