Canada Underwater World 2

A fici/ c ARCTIC CHARR Canada Underwater World 2 first cousin to the great fighting trout The most famous of the charrs, of F and the magnificent salmon, the course, is the eastern brook trout — arctic charr is a fish of distinguished Salvelinus fontinalis. This is probably ARCTIC family. In fact, to the uninitiated the dif- one of the best known fishes on the con- ferences between it and the other salmo- tinent since in the days before pollution CHARR nids are so slight as to be negligible — they swam in virtually every river and a scattering of light-coloured dots, a stream to the east of Saskatchewan. Not novel arrangement of teeth and a slight so widely known is the Dolly Varden variation in the bone structure of the malma — a crimson-spotted fish that—S. mouth. Yet to the knowledgeable, these was named in nineteenth century Cali- are the unmistakeable signs that say fornia after the brightly dressed heroine charr. of a Dickens novel. The Dolly Varden During much of the venerable history is found in rivers and streams all around of angling, the charr was considered the Pacific Rim, from California to little more than a poor relation to the Japan. Then there is the lake trout trout. Indeed, a noted American scien- namaycush — a giant which is sought—S. tist wrote in 1887 that "the English for trophies throughout the northern maintain, generally with a note of half of North America. And finally, in implied disparagement, that our eastern the cold, clear waters of the northern brook is not a trout at all, but a charr." hemisphere is the arctic charr The English were right in their facts, alpinus. —S. if not in their sentiments. Trout belong to a branch of the salmonid family Description called Salmo, whereas the eastern brook The arctic charr shares with the trout trout and arctic charr are both Salveli- and salmon a long, slender body and a nus: ergo, the charr is not a trout. But silvery coloration. The differences lie in if the fish has been denigrated for that the deep green or blue shading on the fact, it has also had its share of praise. back and upper sides, in the pale-edged One turn-of-the-century angler assured fins and sometimes in a scattering of his public that "nothing higher. .can small pink dots along and below the be said of a salmonid than that it is a lateral line. The arctic charr has very charr." fine scales, so deeply embedded that the Nineteenth century scientists, caught skin has a smooth, slippery feel. Unlike up in a classifying rampage, succeeded the trout, it has teeth only in the central in identifying some 31 separate sub- forward part of its mouth. Other differ- species of charr. Modern scientists, ences are less obvious, as in the boat- however, have preferred to ignore the shaped bone in the upper part of the minor idiosyncracies produced by vary- mouth. ing conditions of light, temperature and food among isolated groups. Today, in Distribution North America, there are only four The arctic charr is a most internation- types of charr that are recognized as true al fish, and one that has rejoiced in a species. wealth of names — red charr to the Brit- Figure 1. ish, saibling to the Germans, omble che- A rctic charr. valier to the French and ilkalupik to the Inuit. It swims in the circumpolar waters of Asia, Europe and North America — anywhere that the water is pure and cold. There are two principal groups of arctic charr, the one living entirely in fresh water, the other — the anadromous form — making annual migrations to the sea. Because of the plentiful food resources in the ocean, the second kind tends to be larger than its landlocked brother and of more importance in terms of fisheries. This form has lost its Underwater World 3 characteristic markings to take on an Using her fins, the female scoops out overall silvery sheen. a nest, or redd, in the loose gravel, little The landlocked charr is blocked more than a shallow depression about from the sea by some physical the length and width of her own body. barrier. It is found everywhere that the Here, she releases some of her 3,000 to sea-run charr is known, but also occurs 7,000 eggs at the same time that the male in smaller numbers much further to the releases the milt. Then, the female fans south. Thus, the arctic charr is known the gravel lightly back over the fertilized as a glacial relict in cold, deep lakes as eggs, usually in the course of digging far south as New England, Switzerland another nest nearby. This process is and Britain — in fact, it is the only charr repeated until the female is spent. in Europe. There appear to be few predators that live on charr eggs. In fact, with the Reproduction exception of the nine-spined stickleback, Most remarkable in the mature arc- the arctic charr is often the only species tic charr, particularly in the north, is of fish-eating fish to swim in a given the change in coloration that occurs as northern water. The spawning charr it approaches spawning condition. From itself will eat any eggs that are improp- silver, the body colour gradually erly covered in the nest, but no deliber- deepens to orange, through a range of ate excavation has been observed. It is reddish hues to bright red, and finally only when the young finally emerge as to deep vermillion. The leading edges of free-swimming fish that they come into the lower fins and a fold of skin under danger from predators — mainly their the upper jaw turn white, and the males own kind — and begin to suffer in the develop a protruding hook on the lower competition for food. jaw. The eggs incubate through winter at In colder regions, the charr spawns in temperatures of 0° to 2.2°C and hatch September or October — later if it lives some time in the first week of April, further south as a water temperature of though the timing will depend on light around 4°C is preferred. The spawning and water temperature at the specific female seeks out a suitable bed of gravel location. Temperatures above 8°C, at or broken rock, rather than silt where any time, will kill the eggs. The alevin, the eggs might suffocate. It will choose with a large food sac attached to their a stretch of river or lake bottom deep bellies, remain hidden in the gravel for enough to keep the eggs safe from the many weeks, only emerging as free- winter ice, or at the bottom of a rapid swimming fish or fry, when the food where ice does not form. reserves are used up. This occurs around the time of ice breakup — as late as mid- Figure 2. July in the most northerly regions — Traditional Inuit stone-weir method of fishing when their emergence coincides with the A rctic charr. renewed growth of plankton. Food The young fry is not much longer than 2 cm when it emerges from the gravel, and at first it feeds almost exclu- sively on small vegetation and tiny ani- mals. As the fish increases in size, however, its diet widens to include various insects, insect larvae and shellfish. Later, the adult charr is able to prey on any small swimming fish. After the age of four or so, when the sea-run charr migrates to the ocean, it has a much greater opportunity in terms of diet, and so tends to grow much larger than its lake-bound counterpart. Underwater World 4 It is not known what mechanisms control migratory behaviour, but it is thought that hormonal changes are touched off by changes in light intensity. Once in the sea, it is clearly the avail- ability of food that governs movement. When food is plentiful, the fish tend to remain near the mouth of the river from which they emerged. In times of scar- city, however, they move into offshore waters, sometimes travelling long dis- tances. Tagged charrs are frequently recovered 30 to 50 km from their river of origin, and some fish have made recorded journeys of up to 600 km. The record is 1,000 km. While in the sea, the charr from many different rivers meet and mingle, but when the time comes to return upriver, they tend in most cases to separate and return to the parent stream. In some in- stances, they even return to the exact spawning site of previous years. Growth The cold northern waters are not con- Figure 3. ducive to rapid growth. Even with its North American and global distribution of flexible eating habits and its fine adap- Arctic charr. tation to a cold environment, the charr I. Tree River The charr often does not eat in winter, grows slowly. At the age of one year, 2. Hall Lake when scale development begins, the 3. Salmon River when its metabolic rate slows in tune 4. Jayco River with a cooling environment. Rather, it charr is often less than 5 cm long. 5. Robertson River lives on the fat it has accumulated Growth rates vary greatly among indi- 6. Koukdjuak River during the summer, and growth is ac- vidual fish within a given habitat. How- 7. Sylvia Grinnell River cordingly limited during the cold ever, it is usual for a charr to reach full months. growth at two-and-a-half to three kilo- grams, or at about 12 years of age.

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