PREFACE t the Bergen meeting of the International Council for the Exploration of the Sea in A- 1957, it was arranged that at the next meeting a symposium should be held on two aspects of salmon biology. The topics chosen were methods of tagging and the problems of stock replenishment either by natural or artificial methods. These topics are in fact related, for the success of the latter operations can often best be judged by techniques dealt with under the other heading. The symposium was held at Charlottenlund on 27. and 28. September 1958, and was well attended. The papers were well presented and discussions on them were informed and stimulating. The papers given are here published upon the recommendation of the symposium, which was accepted by the Salmon and Trout Committee and endorsed by the Consultative Com­ mittee. It is felt that they will be of value to biologists in many countries, and perhaps not only to those who are concerned with salmon research, for many of the problems dealt with have their applications to other fisheries as well. The reader may feel that the par­ ticular value of this symposium lay in its bringing together so many people from both sides of the Atlantic in a discussion of their common problems and the opportunity it afforded for a comparison of the methods and results obtained in different countries. In particular the inauguration of studies in population dynamics, especially in U.S.S.R. and Canada, opens up a field in which it is clear that further advances will yield great practical benefits. G. Nikolsky, Chairman. F. T. K. Pentelow, Rapporteur. n. (4) Freshwater Species of Salmon and their Significance in the Origin of the Salmonidae and Practical Fish Culture By N. I. K o s h in an d A. A. P r o t a s o v In 1948 Berg published two papers in which the from 1926 to 1932 served as the bases for these first attributed Caspian salmon to the subspecies of experiments. In December 1880 in Scotland young Salmo trutta and defined it as S. trutta caspius salmon, reared from artificially fertilized ova, were Kessler. In the second paper he considered Caspian planted into ponds. In 1884 ova and milt were salmon as S. salar caspius Kessler, but he added obtained from smolts from these ponds and successful that if the Caspian salmon is a genuine salmon artificial fertilizations were carried out. Some females (from S. salar) then it cannot be related to Caucasian had already matured in the ponds by December trout, as it is known that only males occur in the 1883 at the age of 3 years (Day, 1885; Berg, dwarf forms of salmon in the rivers, whereas both 1935). males and females are encountered amongst Cauca­ Six thousand young fish from two salmon (S. sian trout. He also considered that it was possible salar) caught in 1926, were obtained and used for for S. salar to penetrate into the Caspian Sea, for stocking ponds in Denmark in the spring of 1927. instance through the upper tributaries of the Petchora By the spring of 1930 all the males and some of the and the Kama (a tributary of the Volga). A. N. females had matured and artificial fertilization was Derzhavin (1956), on the other hand is of the carried out. In autumn of 1931 all the salmon in the opinion that the Caspian salmon originated from ponds were again mature and another artificial ferti­ the trout populating the rivers of the Caucasus, and lization was carried out. These salmon grew slowly he defined it as S. fario caspius Kessler. in the ponds and weighed about 1 kg. One female Caspian salmon migrate to the rivers for spawning. produced about 1,500 eggs. At the age of 5 years Within the territory of the USSR most of these the females hatched in 1927 reached 42 cm in length salmon enter the Kura river from November to and weighed 725 g (Otterstrøm, 1933; Berg, 1948). February with immature gonads which mature in 8 At the end of 1951 the yearlings that had been to 12 months (“winter” form of Berg, 1948). obtained as a result of artificial fertilization of the Females predominate in the catches of the “winter” “winter” forms of Caspian salmon were placed in forms and they may comprise more than 90% of the wooden tanks (2'5 mX0-7 mXO'6 m) for rearing total. Females make up about 60% of the catches of at the Chaykend experimental rearing station. the “spring” form. Rearing continued until November 1954. By the end The Mingechaursk dam, built in 1952, obstructed of the experiment 15 fish about 4 years old had the passage of salmon to the spawning grounds survived, of which there were 12 females and 3 males. which were situated in both the upper part of the The average weight of the fish was 394 g. Kura river and its outfall. Natural spawning areas It should be noted that the greater part of the were retained only in the basin of the Arax river reared males already had mature gonads by the end flowing into the Kura river below the Mingechaursk of 1953. dam. During rearing the salmon were generously fed Two salmon rearing stations were built and put with such different food stuffs as Enchytraeus, spleen, into operation in the basin of the Kura river (Azer­ fish meal, meat and bone meal, and blood. To arti­ baijan SSR) to preserve the resources of Caspian ficial (dead) food stuff rye flour was added. In salmon. Experiments were conducted at the Chaykend small amounts the salmon received tadpoles, gam- rearing station in order to obtain freshwater forms marids, maggots, earthworms, etc. of Caspian salmon, for the purpose of ascertaining In November 1954 artificial fertilization was carried their biological peculiarities, origin and improvement out with 12 tested females. The ova of 8 females of the rearing processes. The experiments carried were fertilized by the milt of 3 salmon males hatched out in Scotland in 1885 and 1886 and in Denmark in 1951, i.e., of the same age as the females. Four 43 II. (4) females were fertilized by the milt of four males system developed by VNIRO (a modernized type of hatched in 1952 and also reared in fresh water under the round Seetowne basin). artificial conditions. Altogether 12,360 eggs were ob­ tained from the 12 fertilized females or 1,030 eggs The average weight (g) of young in December 1956 Total number Average weight from each female. The average weight of the females Breeders was 250 g. As to their outward appearance the salmon in thousands of the young The experiment reared in fresh water resembled salmon more than Females hatched in 1951. 6 2.28 trout. Females hatched in 1952. 2.5 2.15 These experiments were continued in 1952 and Production 1953, Young fish of the “winter” form of Caspian Females of large salmon hatched in 1952 reached the smolt stage by descending salmon 175 2.26 November 1953. A small number of smolts were left at the experimental station for further rearing In January 1957, all the young salmon hatched under freshwater conditions and by 1. January 1954 in 1956 were planted into one round basin. By May there were 250 specimens of these young fish with 1957, out of 8,500, 7,000 had survived, a considerable an average weight of 20 g. During 1954 the young proportion being near the smolt stage. The final were reared in a wooden tank and they were also fed transition into the smolt stage was recorded in with various natural (alive) and artificial foods. January 1958. By the end of October 1954 the weight of these The weight of young salmon by the end of rearing young fish averaged 112 g. The greater proportion averaged 25 g. Some were partially tagged and released of the males had mature gonads and some of the into the Kura river. According to morphological females had also reached maturity. Experimental characters and colour, the smolts obtained from dwarf data show that 85% of the males and only 10 to females that had been reared in fresh water (the ova 15% of the females of Caspian salmon, reared in were fertilized by dwarf males) did not differ from fresh water, ripen at the age of 2+ years. All the smolts, obtained from the breeders of the “winter” males and females of Caspian salmon, reared in fresh form of descending salmon of the Kura river. water, were ripe at the age of 3+ years. In November Simultaneously with the above experiments similar 1954, the ova obtained from the females, hatched in experiments were conducted in 1956 and 1957 by 1952, were fertilized. The fertilized ova from the D. A. Panov at the Charnorechensk salmon rearing females hatched in 1951 and 1952 were put in the station (the Georgian SSR) on Black Sea salmon Shuster apparatus for incubation, whereas females (iSalmo trutta labrax Pallas). This salmon enters the in both years were separately stocked, according to rivers, flowing into the Black Sea, mainly from the age, into the ponds of the type of a “trout ditch”. Caucasian coast, for spawning. G. P. Barach holds These females were reared till the end of 1955. In that the Black Sea salmon and stream trout of the November 1955 the ova obtained from 11 females Caucasian rivers of the Black Sea (S. trutta labrax hatched in 1951 was fertilized with the milt of the Pallas morpha fario) make up a single stock (Barach, males (hatched in 1951, 1952, and 1953.) and reared 1952 and 1957).