Rainbows: good or bad?
Simon Cooper sees different shades of the argument
RAINBOW TROUT EXCITE STRANGE passions in chalkstream fishers. Some loathe them with a passion, the catch-record books containing such entries as, “Lovely day spoilt by too many (expletive) RAINBOWS.” Others delight in the reel-screaming exuberance of our North American imports. So, as a humble fishery manager, how do I straddle this divide? Well, it’s worth acknowledging from the outset that rainbow trout are not entirely new to the United Kingdom, with the first stock arriving in 1859. I’m not sure when they found their way into the chalkstreams, but I suspect, with river owners of that time being particularly innovative, it wasn’t long afterwards. The fish were common by the early part of the last century in the River Test. An extract from a 1926 catch book, which hangs on the wall of The Grosvenor Hotel in Stockbridge, records that in July an unnamed angler caught 24 fish: 10 brown trout and 14 rainbow trout. By way of a brief diversion, the same record book belies the belief that the inter-war years were a Valhalla of huge fish and dry-fly purists. Our man caught all his fish on wetflies (Alexandra, Red Palmer and Teal & Silver), an average weight of 1lb 13oz for the browns and 10oz for the rainbows. The reasons most commonly cited for stocking Oncorhynchus mykiss is that they are great fighting fish and offer sport when Salmo trutta is idling his way through the dog days of summer. I can’t possibly disagree with the first assertion. I suspect the second is a riverine myth. The real dirty secret is cost. Rainbows are half the price of browns, so you either save money or get twice the bang for your buck. The case against stocking rainbows seems to me more emotional than practical. They are not, whichever way you cut it, native to the British Isles. If man disappeared tomorrow, rainbows would all but vanish from our island within the space of a decade. That would have applied even in the days when we stocked diploid fish, that is to say fish capable of reproduction. For reasons not really understood they rarely breed and we’ve never had brown-rainbow crosses. Today, all stocked fish are triploids, that is to say sterile fish, and extinction would happen even faster. Triploids are, by the way, created at the fertilised ova stage when the eggs are subjected to huge pressure in a diving air cylinder, which forces the egg to retain a chromosome that is normally ejected during egg development. Hence a triploid has three chromosomes, a diploid two. I do have time for the tradition argument: chalkstreams are synonymous with brown trout, the habitat managed for the past two centuries towards the goal of fly-fishing for our native quarry. But on the other hand, in doing so we have gradually driven out a multiplicity of native fish species that would have otherwise shared the river space. And – this is a philosophical question – at what point does the import become the native? We don’t regard rabbits as anything other than native but they are only here thanks to the Romans. For more than half the time the River Test has been regarded as hallowed water, rainbows have been part of the mix. I think we can be reasonably certain that the founding father of modern dry-fly fishing, Frederic Halford, came across them (he died in 1913) and I don’t recall him fulminating against them. They even have official sanction. The Environment Agency doesn’t list rainbow trout as non-native; it allows them the same classification as brown trout. When you apply for a trout stocking licence the EA is not primarily concerned with the species, it cares about size and quantity – the biomass, matching the volume of fish to the volume of water. There doesn’t seem to be a habitat issue; the two types generally co-exist in harmony. Rainbows: good or bad? They don’t do harm. They cost less. On certain waters the fishing will be improved. But, and it is a big “but”, they don’t really belong. There is a comparison to the shooting world where pheasants (origin: China) are no more native than rainbows, so some shoots have entirely abandoned them, focusing on rearing the native English partridge, which is smaller, faster and harder to hit. These estates are flourishing: there has to be a lesson there. Yes, you perhaps won’t have such a big bag at the end of the day. The sport may have been tougher. But you have been part of something special. People appreciate authenticity. We go fishing to get back to nature. We expect to catch something that is natural. It may be time to say goodbye to rainbows.
“We fish to get back to nature. We expect to catch something natural”
An entry for 1926 in the catch book of the Grosvenor Hotel.