Escaping farmed salmon pose risks

• Escaped salmon can be carriers of disease and parasites, which pose a threat to wild salmon populations.
• When the species farmed is native to an area there may still be an impact from escaped farmed salmon breeding with populations of wild salmon that are genetically adapted to specific streams.
• In British Columbia there is a greater danger arising from the fact that most of the salmon farmed are Atlantic salmon. Evidence exists that escaped Atlantic salmon can breed in BC's wild streams. The potential negative consequences of this could be dramatic.

How Many Farmed Salmon Escape?

The reported escapes of farmed salmon in BC between 1987 and 2001 fluctuates from one year to the next with the average being about 90,000 escapes per year for the period 1990-2000. Since the 1980's, salmon farms in BC have switched from farming pacific species to mainly Atlantic salmon. This is reflected in the escape figures, which are now predominantly made up of Atlantic salmon.

Of the 88 escape events that are known to have occurred, there is only one occasion where the farm operator attempted to recover the escaped fish, with limited success. Usually it is other members of the public that report their capture of any feral Atlantic salmon. The total number of marine Atlantic salmon captured in BC to date is 18,251. With 87 per cent of these being caught mainly by fishermen in the Broughton Archipelago, on the north east coast of Vancouver Island. There have also been an additional 1,295 caught or sighted in fresh water streams and lakes.

Once they have escaped their netpens, farmed salmon can travel great distances. A total of 556 Atlantic salmon have been caught in Alaskan waters to date. No salmon farms exist in Alaska and the nearest BC farm is over a thousand kilometers to the south. One Atlantic salmon was even caught in the Bering Sea.

The most disturbing catches and sightings of Atlantic salmon in BC have been those of freshwater juveniles produced by escaped Atlantic salmon breeding in the wild. On the north-east coast of Vancouver Island, a recent study found 153 such juveniles between 1998 and 2000. These were in the Adam, Amor de Cosmos and Tsitika rivers. The evidence that these juveniles did not escape from farms came from lab analysis of their scales. The rate of growth for the scales is related to how the salmon eat. On farms, where feeding is regular, scales grow at a more regular rate than in the wild where feeding is more random. In a fashion similar to the seasonal growth rings for a tree, the scales of wild or feral salmon also show growth rings. The lab results showed that the above juvenile Atlantic salmon had been born and bred in the wild. The above study, the first of its kind, states that they were only able to look at about one per cent of potential salmon rearing habitat. The total number of Atlantic salmon that could be breeding in BC's wild rivers is impossible to know at this time.

The Causes of Escapes

Growing salmon in marine open netcages exposes the farm operation to certain risks that can lead to escapes. The netpen system can be damaged due to storms, persistent sea mammals such as seals and sea lions that try to get at the fish, industrial accidents, and even sabotage. Farm operators must report the cause of the escape if they can, and more recently the BC government has decided to investigate the cause of escapes so that recommendations can be made to try and prevent others from happening.

At the moment, government data on the causes of the escapes is only available to us from 1988-1996. During that time, 1,078,368 farmed salmon escaped in B.C., and of these, the exact cause of escape was known for 1,021,702. The causes can be categorized as follows:

To be clear, the above breakdown is given with respect to the number of salmon that have escaped, not the number of escape events. The more salmon escape, the greater their impact on the environment. In terms of environmental impact then, the two most important causes of escape are weather and industrial accidents. When ranking the causes of farmed salmon escapes, authors will not always specify whether their ranking is with respect to number of salmon or number of events. Numbers given with respect to number of events do not accurately reflect the level of environmental impact.

Trends in Number of Escaped Salmon

In a recent B.C. government press release, the following comparison was made:

"In 1999, 0.3 per cent of farmed salmon were reported to have escaped, compared with 3.7 per cent in 1990. This decline can be attributed largely to the development of improved containment and harvesting technology and to better farm practices."

What wasn't made clear in the press release is that the percentage quoted refers to the tonnes of salmon escaped compared to the total tonnage produced that year. It wasn't mentioned that between 1990 and 1999, farmed salmon production in B.C. tripled. So the percentage quoted for 1999 tells us very little about any change in the total number of individual salmon that escaped from farms between those two years. In terms of environmental impact, the more individual farmed salmon escape, the greater the impact. The numbers quoted by government are perhaps more of an issue in terms of economic impact to the industry.