Dietary lipids play important roles in the energy production processes of animal tissues and as the source of essential fatty acids (EFA). Besides these functions they do have other important dietary roles as carriers of certain non-fat nutrients, notably the fat-soluble vitamins A, D and K. Recent studies on EFA in fish have demonstrated that EFA requirements of fish differ considerably from species to species. On the other hand, the results of studies on the energy requirements of fish during recent years have indicated that in the carnivorous fish such as rainbow trout, eel, yellowtail and plaice which have limited ability to utilize carbohydrates of high mol. wt as an energy source, dietary lipids play an important role in this respect and have a sparing action on dietary protein.

Lipid nutrition in fish

Some aspects of the biochemistry of sockeye salmon (Oncorhynchns nerka) were investigated during spawning migration in the Fraser River, B.C. Studies included measurements of the activities of meta...

Sites and patterns of protein and amino acid utilization during the spawning migration of salmon

The basic pathways of intermediary metabolism that have been investigated so far in salmonid fish are very similar to those occurring in mammals and other animals, though important differences do exist with regards to the presence/absence and physiological importance of some pathways. Salmonids like many other fish, have relatively high dietary requirements for both protein and essential amino acids which in some cases are more than twice those of rat, chicken and pig (see reviews by Mertz, 1972; Cowey, 1975, 1979; Ogino, 1980). Carbohydrates are relatively poorly utilised by fish and the evidence suggests that proteins together with lipids are the major sources of energy (Atherton & Aitken, 1970; Pieper & Pfeffer, 1978; Cr6ach & Serfaty, 1974; Mommsen et al., 1980). This contrasts to the situation in omnivorous mammals where, under normal nutritional conditions, protein catabolism is of little significance in supplying energy whereas carbohydrates and lipids are important energy sources. Phillips (1969) has suggested that 70% of dietary calories in trout feed is from protein, thus a greater percentage of dietary protein is metabolised for energy, rather than utilized for body protein synthesis. Since the end produce of N-metabolism in teleosts is ammonia rather than the more energy costly urea or uric acid (as in mammals, birds and reptiles), fish do not derive the same amounts of energy from dietary constituents as do mammals and hence food protein may have a higher metabolisable energy than carbohydrates. The energy requirements of fish (being poikilothermic) are lower than mammals which expend much energy to maintain their body temperature. Since fish body temperature varies with the water temperature, then reaction rates and occurrence of some pathways within the fish are affected by the environmental temperature. This article is a somewhat brief attempt to describe aspects of the intermediary metabolism of amino acids, carbohydrates and lipids that have been reported for salmonids (predominantly).

Aspects of intermediary metabolism in salmonid fish

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Nutrient Requirements Of Fish

Partial or total replacement of fish meal by corn gluten meal in diet for turbot (Psetta maxima)

Effects of dietary energy level and dietary energy source on growth, feed conversion and body composition of turbot (Scophthalmus maximus L.)

In order to examine the effects of artificial diets at the tissue level, plaice (Pleuronectes platessa L.) were fed either high (50%) or low (20%) protein diets for several weeks and the total quantities of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein and phospholipid in their livers were measured. Alanine amino-transferase, aspartate aminotransferase, glutamate dehydrogenase and glucose-6-phosphatase activities in the livers were also measured. Similar measurements were made on the livers of wild plaice. The total amount of DNA in the livers of both cultured and wild plaice, of standard weight, did not differ significantly, irrespective of dietary history. In fish of standard weight, total hepatic RNA, protein and phospholipid levels were highest in the cultured fish fed high protein diet and lowest in the wild fish. These differences were related to dietary protein supply and environmental temperature. The total organ levels of the liver enzymes in plaice of equal weight were not significantly different in the cultured fish fed high and low protein diets. Wild-fish livers contained a smaller total amount of alanine aminotransferase, aspartate aminotransferase and glucose-6-phosphatase activity than did those of cultured fish. Total liver glutamate dehydrogenase activity was not significantly different in any of the fish examined. It is suggested that kinetic and allosteric factors may be more important in controlling protein metabolism and amino acid cat abolism in fish than total enzyme level.

Studies on the nutrition of marine flatfish. The effect of dietary protein content on certain cell components and enzymes in the liver of Pleuronectes platessa

Gametogenic asynchrony of mussels Mytilus in a mixed-species area: Implications for management

Comparison of DNA damage in plaice (Pleuronectes platessa) from two contrasting Scottish marine sites, utilising Comet assay cell preparation and electrophoresis undertaken at sea

Aileen M. Shanks

Papers

Effects of dietary energy level and dietary energy source on growth, feed conversion and body composition of turbot (Scophthalmus maximus L.)

Studies on the nutrition of marine flatfish. The effect of dietary protein content on certain cell components and enzymes in the liver of Pleuronectes platessa

Gametogenic asynchrony of mussels Mytilus in a mixed-species area: Implications for management

Comparison of DNA damage in plaice (Pleuronectes platessa) from two contrasting Scottish marine sites, utilising Comet assay cell preparation and electrophoresis undertaken at sea