When salmon run in from the sea, they lose the desire and ability to eat. Why, then, does a fly or worm attract a bite? Does the response date back to river feeding in early life? Salmon fishermen deduced before the scientists that salmon do not feed in freshwater, for every time they gutted a fish, no food was found in its stomach.
Furthermore, no salmon river has sufficient food stocks to support a ravenous run of feeding salmon for any length of time. The sad sight of the stale red salmon caught after a few months in the river and the emaciated kelt which may have spent a year there are further evidence of the failure to feed when compared with the silver salmon fresh-run from the sea. The reasons are unclear. Popular opinion is divided between a physical change which makes the fish unable to digest food, and a psychological change in which the salmon simply goes off its food. The evidence sounds conclusive, until we ask why salmon are caught by anglers in freshwater! Any explanation must be prefaced by the fact that we know next to nothing about our native salmon. We do know that the young salmon hat-ches from an egg in a river bed and develops into a parr (a small fish resembling the related brown trout, but with dark perch-like bars down its flanks). The parr feeds on a diet which includes flies, larvae, worms and crustaceans. After two years, when it weighs 4-6oz, it turns silver and as summer approaches it heads for the sea as a smolt. It heads for the Arctic Circle and feeds voraci-ously on the rich stocks of crustaceans and herrings in the icy waters of the Arctic Ocean.
After a period of one to five years at sea, the fish returns to spawn in the river where it started life. The navigational powers of the salmon are remarkable and it is exceptional for an adult salmon to be found in the wrong river. It is thought that the fish can recognize the scent or taste of the water of its native river.
From these facts, we assume that the salmon has highly developed in-nate behavioural patterns—it must have a memory, without the powers of reasoning.
The majority of salmon taken on baits have been in their native rivers for less than a month. If we analyze the types of bait with which such fish are caught, we will see that each one provides a strong memory link; tstrong enough to trigger a reflex action associated with the fish’s former feeding habits. The main baits on which salmon are caught in freshwater include the fly, the Artificial flies can also be mustered into categories: the sunk-line lure, the floating-line fly and the dry fly. Sunk-line lures are roughly the shape of small fish, often up to 4in long and bearing absolutely no resemblance to any fly. These lures trigger off the fish’s instinct to seize at food. Flyfishing with a sunk line for salmon may be described as a difficult way of spinning, but is often practised when spinning is banned.
Floating line flies are fished close to the surface. The size of fly is often small, resembling tiny fish or a fly. Anyone who has seen a salmon rise to such a fly knows the automatic, almost mesmerized way the fish rises. I attribute this reaction to the fish’s memory of having fed on hundreds of such fish and fry.
Both salmon and sea trout will take a dry fly from the surface of the water, although it is insignificant as a regular bait for salmon. The dry fly is an imitation of a natural fly. The taking of a dry fly must stem from a ‘memory’ of eating flies as a parr.
The theory which asserts a form of territorial aggression as an explanation for salmon and sea trout taking baits is, I believe, confounded by the success of a tiny dry fly in provoking a response.
The Devon minnow, varying in length from 2”3in, is a magnificent imitation of a small fish. Its spinning motion causes the same reflex feeding reaction as a sunk line lure, and I have caught countless salmon on them, and on many occasions the bait has been taken with tremendous ferocity.
Prawns and shrimps, as part of the salmon’s regular diet at sea, are plausibly explained as successful freshwater baits once we accept the theory of feeding reflexes. Worms no doubt spark off memories of early life in the river.
Loss of interest
A point in favour of the feeding-reflex theory is that salmon will most often take a bait within the first few casts. After that, they seem to lose interest and are best left alone for a couple of hours. This is explained by the feeding-reflex theory; the instinctive reaction is sharpened by the element of surprise and afterwards becomes dulled.