Letting more salmon leap to reproduce naturally could ultimately benefit both nature & fishers…
First published 11.04.2012
An article published online yesterday [April 10, 2012] in the open-access journal PLoS Biology, by Taal Levi and co-authors from UC Santa Cruz and Canada investigate how increasing “escapement” (the number of salmon allowed by regulation to escape fishing nets to enter streams and spawn) can improve the natural environment in British Columbia and Alaska, leading to more salmon in the ocean and thus larger salmon harvests in the long term; “a win-win for ecosystems and humans”.
“Salmon are an essential resource that propagates through not only marine but also creek and terrestrial food webs,” says Levi who reflects on overfishing concerns and MSC certification.
I would concur… and extrapolate: the Alaska salmon fishing industry is indeed reliant on aquaculture operations to artificially boost/enhance salmon populations. 1-2 billion aquaculture/hatchery farmed salmon are released yearly into the wild to contribute to the total “wild” salmon harvest.
As I wrote earlier: those truly concerned about the conservation of this iconic species (rather than being firstly concerned about the economics – thus politics & marketing – of fishing) should perhaps consider not killing/harvesting salmon until the stocks and populations are truly “self-sustaining” (a condition defining a fish population under the Endangered Species Act).
For that, there would be one radical way: Do away with hatcheries… which may rightly be considered too extreme. An in-between solution would be to increase escapement and temporarily reduce harvests, as Levi et al. suggest; and – why not? – provide consumers with the (i.e. labelling/information) choice between ranched/enhanced/hatchery salmon vs. [truly] wild. This would probably prove unpopular in Alaska, but brings to the question: “Who decides what sustainable seafood is?”…
The Levi et al. team focused on the relationship between grizzly bears and salmon. Taal and his colleagues first used data to find a relationship between how much salmon were available to eighteen grizzly bear populations in British Columbia, and what percentage of their diet was made up of salmon.
“We asked, is it enough for the ecosystem? What would happen if you increase escapement—the number of fish being released? We found that in most cases, bears, fishers, and ecosystems would mutually benefit,” Levi said.
The relationship between salmon and bears is basic, Levi said. “Bears are salmon-consuming machines. Give them more salmon and they will consume more—and importantly, they will occur at higher densities. So, letting more salmon spawn and be available to bears helps not only bears but also the ecosystems they nourish when they distribute the uneaten remains of salmon.”
When salmon are plentiful in coastal streams, bears won’t eat as much of an individual fish, preferring the nutrient-rich brains and eggs and casting aside the remainder to feed other animals and fertilize the land. In contrast, when salmon are scarce, bears eat more of a fish. Less discarded salmon enters the surrounding ecosystem to enrich downstream life, and a richer stream life means a better environment for salmon.
In four out of the six study systems, allowing more salmon to spawn will not only help bears and the terrestrial landscape but would also lead to more salmon in the ocean. More salmon in the ocean means larger harvests, which in turn benefits fishers. However, in two of the systems, helping bears would hurt fisheries. In these cases, the researchers estimated the potential financial cost—they looked at two salmon runs on the Fraser River, B.C., and predicted an economic cost of about $500,000 to $700,000 annually. This cost to the human economy could help support locally threatened grizzly bear populations, they argue.
While these fisheries are certified as sustainable by the Marine Stewardship Council (MSC), the researchers suggest that the MSC principle that fisheries have minimal ecosystem impact might not be satisfied if the fishery is contributing to grizzly bear conservation problems.
The researchers believe the same analysis can be used to evaluate fisheries around the world and help managers make more informed decisions to balance economic and ecological outcomes.
Competing interests: The authors have declared that no competing interests exist.
Citation: Levi T, Darimont CT, MacDuffee M, Mangel M, Paquet P, et al. (2012) Using Grizzly Bears to Assess Harvest-Ecosystem Tradeoffs in Salmon Fisheries. PLoS Biol 10(4): e1001303. doi:10.1371/journal.pbio.1001303
Source: Public Library of Science pr & SeafoodIntelligence.com editorial comments
Click here to read the article in full:
On Twitter @Salmoskius:
Letting more #salmon leap to reproduce naturally could ultimately benefit both nature & fishers; in BC… & Alaska http://is.gd/EditoLevi #bears