Retained levels of dietary α-, γ- and δ-tocopherol in tissues and body fluids of Atlantic salmon, Salmo salar, L.

The purpose of this study was to describe the relationship between dietary supplementation and concentration of γ- and δ-tocopherol (TOH) in tissues of Atlantic salmon, Salmo salar , L., when α-TOH was fed at a constant level. Post-smolt Atlantic salmon (230 g) in duplicate tanks were fed a fish-meal-based diet with 250 g kg⁻¹ lipid. Different combinations of RRR -tocopherylacetate preparations were added to give the following levels of TOH (mg kg⁻¹) in diets 1–4, respectively: 150α; 150α+ 100δ; 150α+ 50γ+ 50δ; 150α+ 100γ+ 100δ. The concentrations of γ- and δ-TOH in most tissues were directly proportional to the feed concentrations. Exceptions were γ-TOH in erythrocytes, spleen and kidney and δ-TOH in heart muscle, where the intercept with the y -axis was significantly different from zero. The relative retained levels of α-, γ- and δ-TOH in most tissues were similar to their biological activities in mammals. An exception was muscle and adipose tissue, where γ- and δ-TOH were retained at rates of 70–90% and 20–35% compared with α-TOH, respectively. α-TOH was retained to a greater extent when α-TOH was fed alone than when γ- and δ-TOH were added to the diet. Fish growth was significantly correlated to total dietary TOH concentration. The data suggest that turnover of tocopherols in Atlantic salmon is similar to that in mammals, i.e. that discrimination between the tocopherols is mediated through competition for a tocopherol-binding protein in the liver, and consequently that α-TOH is preferentially secreted in very low density lipoprotein. Muscle and adipose tissue appear to be supplied with tocopherols from chylomicrons that have not yet been exposed to the hepatic discrimination mechanism.     

International management of Atlantic salmon, Salmo salar L., by the North Atlantic Salmon Conservation Organization, 1984–1994

Abstract  The development of distant water fisheries at West Greenland and in the Northern Norwegian Sea during the 1960s and, more recently, in the Faroese zone, led to the establishment, in 1984, of the North Atlantic Salmon Conservation Organization (NASCO). This paper summarizes the progress made in the 10 years since this Organization was established towards achieving its goals of conservation, restoration, enhancement and rational management of salmon, Salmo salar L., stocks. Agreements on regulatory measures have reduced the proportion of the total catch taken by the distant water fisheries and, in the case of the West Greenland fishery, management is now firmly based on scientific advice. The stability created by these regulations has allowed NASCO to address the broader areas of conservation called for under the Convention and international action has been taken to address a number of threats to the resource, including the impacts of aquaculture, introductions and transfers, and fishing in international waters by non-contracting parties. These actions are described and the paper concludes that NASCO has a significant role to play in the future, both through continued regulation of the fisheries and by promoting international cooperation to address these broader threats to the resource.     

Reproductive strategies in Atlantic salmon, Salmo salar L.

Abstract. Life-history strategies are means by which animals solve the problems of successful reproduction in varying environments. Their development patterns are consequences of responses to the opportunities the environment offers them. Understanding them requires an understanding of the way they evolved, their ontogenetic development, their physiological control, and their adaptive value. The present paper views the salmonids as marine fishes, which have radiated into fresh water through using river beds as protected spawning grounds. It also takes the view that the maturation process has priority over somatic growth in fish, and that it has already been initiated by the time of first feeding. Its completion is environmentally dependent, and can be arrested annually. Whether or not it will be arrested depends on the status of the energy stores of the individual at particular critical times of year. This mechanism has adaptive value both for immediate reproductive success — adequate energy to provision the next generation — and for later overwinter survival, ensuring that if energy stores are inadequate for reproduction they are spared. Atlantic salmon show variation in their reproductive patterns, and examples are given from laboratory and aquaculture experiments to demonstrate some environmental controls which result in these variations. A hypothetical model is presented to account for the operation of these controls.     

Nocardiosis in tank-reared Atlantic salmon, Salmo salar L.

Nocardiosis is an infection caused by aerobic Gram-positive, branching, filamentous rods of the genus Nocardia . The organism is resident in both soil and plants ( Austin & Austin 1993 ; Frerichs 1993 ), and is closely related to Mycobacterium spp. Nocardiosis caused by Nocardia asteroides and N. seriolae (previously N. kampachi ) has been reported in several finfish species, both freshwater and marine. The first reported incidence was recorded by Valdez & Conroy (1963) in neon tetras, Hyphessobrycon innesi (Myers), and subsequently in other fish species, some of commercial significance including rainbow trout, Oncorhynchus mykiss (Walbaum) ( Snieszko, Bullock, Dunbar & Pettijohn 1964 ), brook trout, Salvelinus fontinalis (Mitchill), ( Campbell & MacKelvie 1968 ) and yellowtail, Seriola quinqueradiata (Temminck & Schlegel; Kubota, Kariya, Nakamura & Kira 1968 ). Despite two of these incidences occurring in salmonids, infection by Nocardia spp. in Atlantic salmon, Salmo salar L., has not previously been reported.     

Carbohydrate nutrition in Atlantic salmon, Salmo salar L.: growth and feed utilization

Five groups of Altantic salmon, Salmo salar L., (80 g postsmolt) were fed moist diets containing increasing levels of starch from 0% to 31% and concomitant decreasing levels of protein. The results showed that feeding a diet containing 22% lipid with no starch or a starch inclusion higher than 22% exerts negative effects on growth and feed utilization. A starch inclusion above 9% resulted in decreased starch digestibility, while protein digestibility was not influenced by the dietary starch content. Undigested starch is suggested to affect lipid digestibility in the same manner as dietary fibre. The reduced digestibility by high levels of dietary starch led to increased loss of particulate matter to the environment. Taking into account feed utilization and environmental aspects, the present experiment suggests that a diet containing approximately 9% starch is optimal.     

Aquaculture: The legal framework: Bruce H. Wildsmith. Emond-Montgomery Ltd., Toronto,Canada, 1982, 313 pp. U.S. $ 45.00, ISBN 0-920-722-08-3

In the present communication the gross symptoms of severe riboflavin deficiency are reported as observed in six experiments conducted with four independent stocks of rainbow trout fry and fingerlings. Unlike other reports on salmonids, ocular opacities were infrequently observed, and neither their rate of incidence nor their severity was related to dietary riboflavin content. Compared with both satiety-fed and pair-fed controls, riboflavin-deficient trout exhibited lethargy, apparent muscular weakness, reduced appetite and growth rate, severe fin erosion (all fins), rapid opercular movements, light greenish-yellow skin coloration and high mortality rate. These symptoms, although due to riboflavin deficiency per se, are nonspecific. As the cataracts produced by others in riboflavin-deficient trout appear to be a specific, diagnostic symptom, it is important to identify those conditions which can preclude their development in riboflavin deficiency.     

Technology for cultivation of Atlantic salmon, Salmo salar L.: problems and possibilities

Abstract. The concept of farming Atlantic salmon, Salmo salar L., beyond smolt stage in sea water started in Norway and Scotland in 1967–1968, using natural enclosures or sea water ponds. Cage culture has since 1969 developed to be the dominating method. Atlantic salmon is cultivated in more than nine countries with a production of 235400t in 1990. Incubation of eggs, hatching, first feeding and smolt production have to a large degree been standardized. Various types of incubator systems and holding units are briefly presented and discussed. There has recently been a trend to move ongrowing cage farms from inshore and sheltered waters to more open and offshore locations. The various types of cages and supplemental equipment for the two options are compared and evaluated. The offshore trend is a more expensive and difficult technology than existing inshore farming methods. Sea enclosures and net enclosures are less attractive. There is new interest in pump ashore systems. Large land-based farms have been built in six countries with varying success. The amounts of water required are enormous and constructions costs are high, but running costs are comparable to cage culture. Great improvements have taken place for both smolt farms and pump ashore farms in treatment of water, use of heat exchangers, filtration of water, disinfection, aeration, oxygenation, photoperiod and light control, automatic feeding, internal transport, handling of fish and surveillance and control systems for fish and water. The problems and prospects of farming are discussed in relation to new and old technology.