Tag Archives: sea lice

Decline in salmon causes decline in cultural ecosystem services

Agriculture increases the supply of food supplied by an ecosystem, but often decreases its ability to supply other services.  The same appears to be true for salmon aquaculture.  In the Toronto Globe and Mail, Vancouver journalist Mark Hume reports Declining salmon runs blamed for wilderness tourism slump:

All along the B.C. Coast, wilderness tourism operators who run bear-viewing, whale-watching and sport-fishing resorts are reporting tough times because of declining salmon runs.

But the biggest impact may be occurring in the Broughton Archipelago, where Mr. MacKay operates, and where pink salmon runs have all but vanished, sending a shock wave through the region’s ecosystem.

“Some of the northern pods are just not here,” Mr. MacKay said yesterday. “And we’ve had three occasions [this summer] when we did not see any orcas at all. That’s pretty weird.”

He said northern killer whales visit the area during the summer months, collecting in big social gatherings where breeding takes place.

“When they get together like that it’s called Super Pod Day, and we will see over 100 dorsal fins out there at a time,” Mr. MacKay said. “That didn’t happen this year, for the first time since we’ve been collecting data, which is almost 30 years.”

Mr. MacKay said it’s not coincidental that the whales have vanished along with the salmon.

“It’s pretty simple. …What do you think these orcas eat?” he said.

Surveys by the Department of Fisheries and Oceans indicate pink salmon stocks have fallen to extremely low levels in the Broughton Archipelago. In Glendale Creek, a key indicator stream, there have been only 19,000 spawners counted this year, compared with 264,000 last year.

Pink salmon, which usually spawn in prodigious numbers, are a keystone species on the West Coast. Chinook salmon, the mainstay of the orca diet, feed on young pinks, while grizzly and black bears depend on spawning adult pink salmon to bulk up for hibernation.

Brian Gunn, president of the Wilderness Tourism Association, said the collapse of salmon stocks is threatening the survival of ecotourism businesses.

“The bear-viewing businesses, the whale-watching operations, they built up a lot of equity showing people these wild animals. Now the fish aren’t there and they are seeing their equity drain away. …If the salmon go, so does the wildlife, and so does the business.”

Mr. Gunn blamed the fish-farming business, saying a heavy concentration of net pens in the Broughton Archipelago has created sea-lice epidemics which kill young salmon.

How Salmon Farming Endangers Salmon

From Society for Conservation Biology’s Journal Watch Online:

Long-held suspicions that fish farms act as disease reservoirs for wild populations are well founded, according to findings published this week in Science. University of Alberta mathematical biologist Marty Krkošek and colleagues show that outbreaks of salmon lice Lepeophtheirus salmonis among wild pink salmon Oncorhynchus gorbuscha populations — the direct result of infestations within the open-net aquaculture pens the juveniles must swim past on their migration to the sea — can bring virtual extinction in just four generations. The pressure wild stocks are placed under by the disease risk from fish farms is much greater than that caused by over-exploitative harvesting: the very factor that prompted aquaculture in the first place. It’s surely time for a re-think on fish farming. Source: Krkošek M, Ford JS, Morton A, Lele S, Myers RA & Lewis MA (2007) Declining wild salmon populations in relation to parasites from farm salmon. Science DOI: 10.1126/science.1148744

Also see article in New York Times which quotes:

Ray Hilborn, a fisheries biologist from the University of Washington who was not involved in the study but is familiar with its findings, called the data persuasive and said they raised “serious concerns about proposed aquaculture for other species, such as cod, halibut and sablefish.”

“These high-density fish farms are natural breeding grounds for pathogens,” not necessarily limited to sea lice, he said in an interview. Dr. Hilborn noted, however, that the study involved pink salmon, not species like sockeye or chinook, which are usually larger and presumably less vulnerable to sea lice. Pink salmon are the most abundant salmon species in the northern Pacific.