Wild v Stocked Trout?

Needle Tubes and Tube Flies

The dangers of introducing farmed trout into wild waters

There appears to be widespread acceptance, among fishery managers and angling clubs throughout the U.K., that stocking wild rivers and lochs with farmed trout will improve the quality of the fishing on those waters, despite warnings from biologists that stocking with non indigenous farmed trout may often be detrimental to native stocks, migratory fish and the river and loch habitat in general.

I believe that there are very few circumstances where the introduction of farmed trout into a river or loch can be justified. Such an introduction may be necessary, for example, where a river is recovering from an incidence of severe pollution that may have wiped out the natural stock. In general, though, in a healthy river with a good stock of wild fish, artificial stocking is likely to be counter-productive and might, in the long term, have a serious, and perhaps irreversible, adverse effect on the river and its truly wild, and very valuable, fish stocks. There is likely to be pressure from a number of anglers who wish to catch bigger fish than their river or loch might produce naturally (and who are perhaps unaware of the damage that might be done to wild salmon and trout stocks by the introduction of farmed trout). There are, on the other hand, many anglers who would much rather catch wild trout on a wild fishery, even if the average size is a bit smaller. That is not to say that a river or loch should be neglected and left entirely to its own devices. The fishery and its wild fish stocks should be preserved and nurtured wherever possible. Habitat can be improved, spawning areas opened up, predators controlled, pollution prevented, professional advice sought - all paid for by the not inconsiderable sum which might otherwise be spent on artificial stocking. By encouraging voluntary catch and release, allowing for a reasonable number of trout for the pot, it should be possible, in many rivers and lochs, to maintain a healthy, self sustaining stock of wild trout. I think anglers are becoming increasingly receptive to the idea of catch and release. We realise how valuable, and fragile, our wild trout and salmon stocks are and I think most of us would be happy to limit the number of fish we kill for the sake of their survival. I must stress, though, that I am not in favour of total compulsory catch and release. We should all be able to take the odd fish for the pot. That, after all, is what the whole business of fishing is about.

As I understand it, there are some very good reasons to discontinue the stocking of wild waters with non-indigenous farmed trout:


The money spent on artificial stocking can be put to better use. A relatively small proportion of stocked trout might actually be caught by anglers, especially on rivers. Some might fail to adapt to the natural environment and die, some will fall prey to disease or predators, while others will swim downriver and out to sea, unlikely to return. I have read of one study, done on the River Dove by an Environment Agency scientist, which estimated that only 3% of stocked trout survived the winter. The money currently spent on the artificial stocking of our rivers might be better spent on habitat improvement etc., which would help maintain a self-sustaining stock of wild fish.


The environmental cost of fish farming, whether it be salmon farming on the west coast or inland trout farming, for both fishmonger and fishery, must be weighed very carefully. The fish farms pollute the environment. More importantly, though, it takes approximately 4 tonnes of fish protein to produce one tonne of farmed trout or salmon. A high percentage of the pellets used in the salmon farming industry, in particular, is derived from essential marine prey species like sandeels, hoovered from the sea by factory ships. While much of the fish protein and oil in trout pellet feed manufactured in the UK is, more sensibly, now derived from waste products of the fish processing industry, much of the content of imported pellet feed can still come from prey species. This is a criminally inefficient use of our fragile marine resources which, through the unnecessary depletion of an essential part of the marine food chain (the small prey fish like the sandeel), threatens essential stocks of sea fish like cod and haddock and game fish like salmon and sea trout, on which we depend for our sport, not to mention the many species of sea birds at risk of malnutrition through lack of sandeels.


Perhaps the most important worry about artificial stocking is the potential damage done to the wild stocks in the river - stocks of salmon, trout and sea trout. Stocked fish, particularly if stocked in numbers and sizes incompatible with the river or loch habitat, can represent one of the biggest threats to wild fish. The stocking of fish derived from a non indigenous source might, over a period of time, dilute the wild gene pool, which has adapted over millennia to the local conditions. Larger stocked fish tend to displace smaller wild fish. The stocked fish, however, are less likely to spawn successfully so that, when the wild fish have been forced out, there are fewer trout left to spawn successfully. More farmed trout are then required to supplement the ever decreasing stock of wild fish and the problem is compounded.


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