Salmon Facts

Hatching flies dance on the water and the salmon ‘parr’ feed on every available morsel of food to come their way. Another freshwater winter still lies ahead when food will again be at a premium and the small parr must be everwatchful for herons and a host of other hungry predators.

Given survival and a bit more luck, at the end of a two-year sojourn in the upland streams the Salmon Running the gauntlet of nets, pollution, traps and starvation, the salmon achieves feats of saltwater and inland migration that awe its hunters and fascinate those who study its lifestyle The Atlantic salmon (Salmo salar) is one of the most mysterious fish in the world. Considered by many to be the king of fish, its reputation as a fighter, its great stamina and unusual life-cycle is still fascinating despite our increased knowledge.

Egg fertilization

The salmon egg or ‘ova’ is generally laid by the parent hen fish in November and December. Scooping out a hollow or ‘redd’ in the stones she quietly lays her eggs while an attendant male covers them with milt. Fertilization of the covered eggs takes place fairly quickly and it is not long before the female uses her broad tail to cover the fragile eggs with loose stones. Unless disturbed, or subjected to excessive floods, the eggs are safe from predators and silting and it will only now be a matter of approximately 90 to 120 days before the new life is born.

The salmon starts its life as a minute egg—the size of a small pea—nestling under loose stones and gravel in the upland waters of the classic salmon rivers or small Highland burns. Approximately 12 to 15 weeks following fertilization, depending on water temperature, a minute fish or ‘alevin’ will emerge from the egg. It is then sustained for the next six weeks on a small yolk-sac attached to the underside of its body, Once this has been absorbed, the fish must fend for itself. It is now at this crucial stage that many mortalities can occur.

Once the yolk-sac is absorbed the initial problem for the infant salmon or ‘fry’ is that of finding food. Early spring can be cold and cheerless. Natural food in many upland, acid streams will be at a premium and the salmon faces the first battle for survival. Sadly, the ravages of nature will kill off a large number of young parr slowly acquires a silvery coat. It is now fast approaching the ‘smolt’ stage. With the first warming of the upland waters—frequently in May—the smolt will instinctively drop downstream to the estuaries and the wide open sea. This too is fraught with predators and pollutants in the lower reaches of many rivers. Further losses will occur, and only a few will attain the sanctuary of the deep sea.

Sea-going migrations

Today, we know some of the seagoing migration routes which British salmon take. It is known, for instance, that many go to the rich feeding grounds off the coast of Greenland. Also, once at sea, a smolt is known to increase its weight by 15 times in less than a year. Thus a small, insignificant fish of five or six ounces can quickly become one of five or six pounds. At this stage of its development it is known as a ‘grilse’ and is capable of reproduction and of making its way back to the river of its birth. Depending on circumstances, however, many of the fish will continue to rove the seas for another year. This may enable them to double or treble their weight and thus reach maturity. A great deal depends on water temperatures and availability of food; but a two-year sea life salmon should reach 8-10lb. Some salmon, staying up to five years at sea, reach weights of 30 or 40lb and more.

Many of our migrating salmon go north. Some are reputed to go under the Arctic ice—which, mercifully, protects them from the destructive tactics of the commercial fishermen to which they often fall prey.

At some stage in their sea journeys the salmon will develop the overpowering urge to come back to the rivers of their birth, find a mate and reproduce the species. Salmon behaviour in this respect is not uniform and a great deal will depend on the individual river from which the salmon have originally come. On such rivers as the Tweed, Tay, Spey, Dee, Wye and Eden—a lot of fish return in the early spring. Some rivers will, however, have fresh fish in January, but it is little more than speculation why fish enter one river then and others in summer or autumn. Not all salmon are destined to spawn in November or December. What induces spring-running in one salmon and an autumn return in another still remains a mystery.

The salmon’s trials begin

History provides a lot of clues of when salmon are likely to enter a specific river system. On most rivers of the British Isles the first trial the fish must undergo is to run the gauntlet of the various netting and trapping systems operated in or near the estuary. Sustained high water in the rivers during the early months will ensure good passage for the fish with minimal loss to the commercial operators. At times of low water the fish tend to rove the estuaries waiting for adequate flows and may thus be more likely to suffer capture by the nets on every ebb and flood of the tides. Of course it makes sense for man to crop this valuable resource; but it also demands responsible behaviour from those who take the crop. Unfortunately, the high price of salmon encourages the illegal element and the species will continue to be in jeopardy until greater protective measures are introduced.

Shortly before entering the river, the salmon ceases to take food, though the reason for this is unclear.

Some authorities say that salmon lose all desire for food and that, as a result, the stomach occludes and the fish become incapable of digestion. Others claim that nature causes the gut to atrophy so that food cannot be taken anyway. Whatever the real reason, there is little doubt that salmon in freshwater do not feed in the full sense of the word. Living in freshwater the salmon suffers a slow deterioration. But even if the salmon did show a desire to feed in freshwater, few of our classical salmon rivers contain sufficient food to sustain them anyway. Certainly on capture in freshwater, nothing is ever found in the salmon’s stomach. On entering the river the salmon is beautifully arrayed with a bright silvery mantle—an object of power and beauty, in its prime for both sporting and culinary purposes. Apart from an unidentified spasmodic disease known as Ulcerative Dermal Necrosis (UDN), the next predator in the chain is the angler. But, as the fish do not feed in freshwater, angling is a very ineffi-cient method of catching them. There is no known bait that will in-duce them to feed, but there are several lures which will, on occasion, induce salmon to take them into their mouths for sufficient time to become hooked. Many fisheries de-mand a high standard of sportsman- y. fAnglers’’

On their first entry into fresh-water the salmon may be lethargic or active depending on water temperature alone. Cold water induces sluggish response from the fish. Most will be content to move slowly and to stay in the lower reaches of the classic rivers.

Angling tactics involve making the lure or bait move slowly and at a good depth; but there is always the chance of sport with fresh-run fish. Within 48 hours of their entry into freshwater, the parasitic sea lice will begin to drop from their host. There is no specific time for sea lice to stay alive in freshwater, for they have been known to survive under laboratory conditions for up to seven days. Most anglers accept the 48-hour theory, so it is assumed that when a fish is caught with sea lice on it, it is as fresh as possible.

As water temperatures rise, and always provided there are adequate river flows, the fish will be induced to run quickly through the lower beats and into the middle and upper reaches. Here they may be induced to take small flies or lures fished near the suface and they can be much more active. Sometimes it is possible to catch them 50 miles upstream of the estuary with sea lice still on them, but there can be no hard-and-fast rule. Only long ex-perience of a specific river over the seasons will give a clue as to where the fish might be and when.


Despite these movement patterns, there comes a time when all the salmon requires is to be left in peace and quiet. Most will settle up in pools and known lies for long periods throughout the summer. Joined by laterrun fish or small summer grilse, most will ignore the flies and lures offered by anglers. While the stock of fish in the pools gradually increases, the salmon will slowly be burning up energy and losing body weight and girth. By November the salmon having sur-vived the wiles of man and nature will be a sorry-looking creature. The flesh will have wasted away to provide the essential milt and ova which it will shed on the redds. Males will compete with other males for the best spawning places and the most ‘attractive’ partner. Some redds will be overcut and nature will also exact a high toll. Following the spawning act, many of the female salmon will drop back into quiet water and recover.

Many male salmon, however, will stay near the redds and fight off other intruders. Many will succumb and die; but, unlike the Pacific salmon, which dies following spawning, there will be many survivors slowly dropping back downstream as spawned salmon or ‘kelts’ to return to the sea once again. Here, many of these weak and emaciated kelts will fall to marine predators such as seals, and only a few will survive to make the journey again and repeat the act of spawning.