Smolt Stage Research Articles

Etude histophysiologique des corpuscules de stannius de Salmo salar L. au cours des diverses etapes de son cycle vital

Correlation between functional activity of the corpuscles of Stannius with phases of the life cycle of Atlantic Salmon ( Salmo salar L.) was inferred from a study of histology and cytology of these organs. The corpuscles appeared very active in smolts. However, there was a difference between pseudosmolts in a storage phase and smolts in a secretory phase, elaboration of the secretory material occurring probably during the smolt stage. Corpuscles of adult anadromous salmon appear completely inactive, while those of reproductive adults, especially males, appear very active. The corpuscles of mendeds have a characteristic structure; they contain degenerative zones formed by holocrine dissolution of certain cellular islets. We believe that these corpuscles have a secretory cycle and that the mode of secretion alternates between a more usual merocrine phase and a holocrine phase.

Effects of Tagging and of Fin-clipping on the Survival and Growth of Atlantic Salmon Between Smolt and Adult Stages

Rates of recapture of Atlantic salmon marked as naturally produced smolts in the Northwest Miramichi River, New Brunswick, were 2.9 for tagged and 3.9% for fin-clipped grilse and 0.7 for tagged and 1.8% for fin-clipped larger salmon. There are indications that survival to the adult stage is much higher for unmarked smolts than for tagged or fin-clipped fish. Length measurements of 117 tagged, 607 fin-clipped, and 301 unmarked grilse taken above tidehead in the Northwest Miramichi showed that those entering freshwater early in the season were smaller that those entering later. Tagged grilse were shorter than fin-clipped grilse which returned at the same time, and the fin-clipped grilse were shorter than unmarked ones. Rates of increase in size among tagged, fin-clipped, and unmarked grilse during the season of return to freshwater (June through October) did not differ significantly.

The non-protein nitrogensous constituents of the muscle of parr and smolt stages of the atlantic salmon ( Salmo salar)

1. 1. The non-protein nitrogenous constituents of the muscle of the parr and smolt stages of the atlantic salmom have ibeen examined. 2. 2. There is a significantly greater amount of non-protein nitrogen in the muscle of smolt than in that of parr. This increased quantity of non-protein nitrogen in smolt muscle is almost wholly due to its higher content of creatine. 3. 3. Parr muscle had a higher taurine content than that of smolt. 4. 4. These differences excepted, the same nitrogenous substances are present in similar quantities in muscle of the two stages. 5. 5. The free amino acid fraction of the muscle of these young freswater stage is compared with that of the muscle of adult, marine fish.

Atlantic Salmon Production in Cove Brook, Maine

Egg deposition by Atlantic salmon, Salmo salar Linnaeus, at Cove Brook, Maine, in 1955 was estimated at 226 eggs per 100 square yards. In 1956, the estimated egg deposition was 293 per 100 square yards. Standing crops of young-of-the-year averaged 20 per 100-square-yard unit in the summer of 1956 and 33 per unit in 1957. Yearlings numbered 26 to 34 per unit in 1956, 12 to 15 per unit in 1957, and 14 to 18 per unit in 1958. Known smolt production per year class averaged 3 migrants per 100 square yards. Survival of midsummer young-of-the-year to the migrant smolt stage was estimated at not less than 5.3 percent. Survival of smolt to mature, returning adults may be as high as 3 percent.

Sodium Regulation in the Blood of Parr and Smolt Stages of the Atlantic Salmon

THE sea-ward migration of the salmon (Salmo salar) which coincides with the parr-smolt transformation, involves the solution of important osmotic and mineral regulation problems by the fish. The lack of tolerance for salt water at the parr stage has been noted previously1. However, neither the capacities for mineral regulation of this stage nor their probable shift in the smolt have been subjected to an analysis, made more desirable by the fact that, like the endocrinological changes which occur at the same time2, they may be causally connected with migration itself3.

単眼性のサケ稚魚に見られた異常体色に就いて

In this paper the author has described on the external morphology of deformed chum salmon parr (Oncorhynchus keta) with aberrant body coloration. Moreover, the histology of some endocrine glands and melanization of skin were observed. 1. The author thought that this monstrosity belongs to “Synophthalmia bilentica” in WERBER's classification, because it was under the condition of the approachment of both eyes, poor development of upper jaw, protruding of lower jaw, and uniting of nostrils which lie in the apex of head. The atrophy of each fins and the delaying of differentiation of visceral organs were recognized. 2. Although the parr marks (lateral bars) and other dark spots were not founded, while the body coloration of this synophthalmic chum salmon parr shows pallor like as in the metamorphosing smolt stage salmon. The epidermis of synophthalmic fish is thicker and also the melanization is denser than those of normal parr stage fish. As the melanin granules not exist in the melanophores, so that these granules do not controlled by adrenergic nerves. Furthermore, there are no scales in body sides. Thus the origin of body color between synophthalmic parr and metamorphosing smolt salmon differs with each other. 3. The deformation and retardation of development of forebrain, chiefly hypothalamus, pituitary gland, saccus vasculosus and pineal body were recognized, on the contrary the hind brain was no changed. The histology of the thyroid gland appeared to be in the condition of hypofunctioning figure. 4. The author has discussed on the origin of development of these abnormalities.

A study of the melanophore-concentrating effect of mammalian thyroid extract in rainbow trout.

THE only clearly recognized function of the thyroid gland in fishes and amphibians is that of the control of metamorphosis. An actively functioning thyroid gland or its equivalent in increased concentration of thyroid hormone in the body has been shown to be necessary for the transformation of the larval into the adult stage in a number of amphibians and several teleosts. However, since not all fishes pass through a larval stage, it may be said that the role of the thyroid gland in the body economy of this class of vertebrates is still largely unknown.1 Recent studies by the author (Robertson 1948, 1949) on the transformation of the parr to the silvery smolt stage in rainbow trout have revealed two manifestations of increased activity of the thyroid gland in this species of fish: one is the deposition of a thick layer of guanine crystals on the scales which gives the trout a silvery appearance;

The Reintroduction of Atlantic Salmon into Tributary Streams of Lake Ontario

Abstract Experimental plantings of Atlantic salmon (Salmo salar) fry were made in Duffin Creek, Ontario County, each year from 1944 to 1948. From 1945 to 1947 a large part of the creek was planted uniformly at a density of one fry per yard, regardless of local stream conditions. Each of these uniform plantings was followed by a study of the survival and distribution of the salmon during life in the creek. Populations were estimated by the use of a one-man hand seine. Each of the three uniform plantings resulted in the same pattern of survival over the stream system and showed the comparative suitability of various stream types for rearing salmon. Unsedimented gravelly riffles were found to be necessary for a high survival of newly planted fry. Subsequent survival to the smolt stage in areas not characterized by lethal summer temperatures was largely dependent on suitable habitats to accommodate the fish as they become larger. Capture of smolts during the spring of 1948 showed that at least 2 percent of th...

Production of the silvery smolt stage in rainbow trout by intramuscular injection of mammalian thyroid extract and thyrotropic hormone

Production of the silvery smolt stage in rainbow trout by intramuscular injection of mammalian thyroid extract and thyrotropic hormone

Cyclical Abundance and Birds versus Salmon

American mergansers and belted kingfishers that eat large parr, particularly during the low water of dry summers, fulfilled the prediction (based upon statistics) that the periodic scarcity of Atlantic salmon is due to a factor operating on the salmon when near the smolt stage. One year's bird control more than doubled the number of descending smolts and correspondingly increased the sea catch of salmon related to the experimental river, as demonstrated by the occurrence of fish marked as smolts in the river. Bird control may thus remedy periodical scarcity. This serves to explain the favourable influence on numbers of fish that man's presence has been observed to have.

Sea Movements of Canadian Atlantic Salmon Kelts

Salmon related to various rivers of eastern Canada were tagged and liberated after spawning, by the Department of Fisheries in various years from 1913 to 1936. Analysis of the recaptures shows varied movements, the differences from river to river and for the one river from year to year being seen as due to differences in the environment. When liberated in or even outside the estuary, they may enter and ascend the river while still in the kelt condition, if suitable freshets occur.As kelts and as clean fish in both first and second years after liberation, they are principally found in the estuary, distinctly more riverward than the virgin fish. However, when swept out of the estuary, as occurs in a river like the Margaree and, if return is difficult, their distribution will differ but little from that of the virgin fish.A pronounced zone of river influence in the sea is seen as holding the salmon to the locality near the river mouth, as for the Saint John river of New Brunswick. With an indistinct zone, more or less of the salmon wander to other regions, largely in correspondence with water movements.The length of time between successive spawnings is found to correspond with the time between the smolt stage and first spawning and to be related to sea temperature during the spring and summer.