Lipids and their constituent fatty acids are, along with proteins, the major organic constituents of fish, and they play major roles as sources of metabolic energy for growth including reproduction and movement, including migration. Furthermore, the fatty acids of fish lipids are rich in ω3 long chain, highly unsaturated fatty acids (n-3 HUFA) that have particularly important roles in animal nutrition, including fish and human nutrition, reflecting their roles in critical physiological processes. Indeed, fish are the most important food source of these vital nutrients for man. Thus, the longstanding interest in fish lipids stems from their abundance and their uniqueness. This review attempts to summarize our present state of knowledge of various aspects of the basic biochemistry, metabolism, and functions of fatty acids, and the lipids they constitute part of, in fish, seeking where possible to relate that understanding as much to fish in their natural environment as to farmed fish. In doing so, it highli...

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Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

Flatfi shes are very accessible in the wild and hardy in the laboratory, thus many of the early studies of fi sh growth used fl atfi shes, especially plaice (Pleuronectes platessa) in the Atlantic and a number of species in the Pacifi c. As the science of fi sheries developed, so did the need to quantify the population structure and growth characteristics of the different fl atfi sh species. In fact, the importance of ageing fi shes and determining their growth rate was realised early in the last century (Allen 1916). Much of the early information on the aging and growth of fl atfi shes (primarily plaice) is referenced in Wimpenny (1953), Graham (1956) and Beverton & Holt (1957). Prior to the 1950s researchers had gained a fairly good understanding of the methods. A clear pattern of summer and winter growth was recognised in the otoliths, which were fi rst used in the late 1800s. Other bony structures such as opercular bones, the pectoral girdle and the concave faces of the vertebrae exhibited seasonal growth patterns (Cunningham 1905) but these were not as distinctive as those on the otoliths. The observation that a pair of rings may not delimit 1 year’s growth led to early verifi cation studies based on marginal increment analyses. Experimental work on plaice and fl ounder (Platichthys fl esus) showed that the seasonal pattern on both otoliths and scales was primarily driven by seasonal changes in water temperature rather than by variations in food availability. The use of otoliths for age estimation of fl atfi shes was not universal. Species differences slowly became apparent and methodological refi nements followed. Direct measurements of the growth of fl atfi shes were afforded by series of tagging and transplantation experiments, and laboratory or enclosure experiments (Johnstone et al. 1921). In all cases it was apparent that there was considerable variability in individual growth rates and that growth rates varied between areas. The widespread sexual dimorphism in growth with females growing faster and reaching larger sizes than males was also recognised (e.g. Johnstone et al. 1921; Bigelow & Schroeder 1953; Bagenal, 1955). The effects of gear selectivity and ontogenetic behavioural changes of fl atfi shes on the accurate estimation of age structure and growth rates were recognised, especially with the offshore movement of larger juvenile plaice from the nursery grounds and a general offshore movement with size and age. The possibility that fi shing pressure could make major changes to the age structure and growth of commercially exploited fl atfi sh populations was mentioned by Jones (1958), citing the prevalence of Rosa Lee’s phenomenon in plaice.

https://folk.uib.no/nfiag/nfiag/reprints/chapter7.pdf

Age and Growth

THE JOURNAL OF BIOLOGICAL CHEMISTRY: The Biochemical Behavior of LeadL I. Influence of Calcium, Phosphorus, and Vitamin D on Lead in Blood and Bone

Fatty acids have been used as qualitative markers to trace or confirm predator-prey relationships in the marine environment for more than thirty years. More recently, they have also been used to identify key processes impacting the dynamics of some of the world's major ecosystems. The fatty acid trophic marker (FATM) concept is based on the observation that marine primary producers lay down certain fatty acid patterns that may be transferred conservatively to, and hence can be recognized in, primary consumers. To identify these fatty acid patterns the literature was surveyed and a partial least squares (PLS) regression analysis of the data was performed, validating the specificity of particular microalgal FATM. Microalgal group specific FATM have been traced in various primary consumers, particularly in herbivorous calanoid copepods, which accumulate large lipid reserves, and which dominate the zooplankton biomass in high latitude ecosystems. At higher trophic levels these markers of herbivory are obscured as the degree of carnivory increases, and as the fatty acids originate from a variety of dietary sources. Such differences are highlighted in a PLS regression analysis of fatty acid and fatty alcohol compositional data (the components of wax esters accumulated by many marine organisms) of key Arctic and Antarctic herbivorous, omnivorous and carnivorous copepod species. The analysis emphasizes how calanoid copepods separate from other copepods not only by their content of microalgal group specific FATM, but also by their large content of long-chain monounsaturated fatty acids and alcohols. These monounsaturates have been used to trace and resolve food web relationships in, for example, hyperiid amphipods, euphausiids and fish, which may consume large numbers of calanoid copepods. Results like these are extremely valuable for enabling the discrimination of specific prey species utilized by higher trophic level omnivores and carnivores without the employment of invasive techniques, and thereby for identifying the sources of energetic reserves. A conceptual model of the spatial and temporal dominance of group-specific primary producers, and hence the basic fatty acid patterns available to higher trophic levels is presented. The model is based on stratification, which acts on phytoplankton group dominance through the availability of light and nutrients. It predicts the seasonal and ecosystem specific contribution of diatom and flagellate/microbial loop FATM to food webs as a function of water column stability. Future prospects for the application of FATM in resolving dynamic ecosystem processes are assessed.

Fatty acid trophic markers in the pelagic marine environment.

The lipid composition and biochemistry of freshwater fish.

Requirements, presentation and sources of polyunsaturated fatty acids in marine fish larval feeds

Requirement criteria for essential fatty acids

Optimising lipid nutrition in first-feeding flatfish larvae

Replicate groups of halibut larvae were fed to d 71 post-first feeding (PFF) either the marine copepod, Eurytemora velox, or Artemia nauplii doubly enriched with the marine chromist or golden algae, Schizochytrium sp., (Algamac 2000) and a commercial oil emulsion (SuperSelco). The fatty acid compositions of eyes, brains and livers from larvae fed the two diets were measured, and indices of growth, eye migration and skin pigmentation were recorded along with histological examinations of eye and liver. The docosahexaenoic acid [22:6(n-3); DHA]/eicosapentaenoic acid [20:5(n-3); EPA] ratios in Artemia nauplii enriched with the SuperSelco and Algamac 2000 were 0.4 and 1.0, respectively. The E. velox copepods were divided into two size ranges (125-250 and 250-400 microm) with the smaller size range containing the highest level of (n-3) highly unsaturated fatty acids (HUFA). The DHA/EPA ratios for the two size ranges of copepods were 2.0 and 0.9, respectively. The total lipids of eyes, brains and livers of larvae fed copepods had higher levels of DHA and lower levels of EPA than those of larvae fed enriched Artemia. The percentage of survival of the halibut larvae was significantly higher when copepods rather than enriched Artemia nauplii were fed, but larval specific growth rates did not differ. The indices of eye migration were high and not significantly different in larvae fed the two diets, but the percentage of larvae undergoing successful metamorphosis (complete eye migration and dorsal pigmentation) was higher in larvae fed copepods (40%) than in larvae fed enriched Artemia (4%). The rod/cone ratios in histological sections of the retina were 2.5 +/- 0.7 in larvae fed copepods and 1.3 +/- 0.6 in larvae fed enriched Artemia (P < 0.01). Histological examination of the livers and intestines of the larvae were consistent with better assimilation of lipid from copepods than lipid from Artemia nauplii up to 46 d post-first feeding. Thus, marine copepods are superior to enriched Artemia as food for halibut larvae in terms of survival, eye development and pigmentation, and this superiority can be related to the level of DHA in the feed.

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Natural Copepods Are Superior to Enriched Artemia Nauplii as Feed for Halibut Larvae (Hippoglossus hippoglossus) in Terms of Survival, Pigmentation and Retinal Morphology: Relation to Dietary Essential Fatty Acids

Effects of purified diets containing different combinations of arachidonic and docosahexaenoic acid on survival, growth and fatty acid composition of juvenile turbot (Scophthalmus maximus)

J.G. Bell

Papers

Requirements, presentation and sources of polyunsaturated fatty acids in marine fish larval feeds

Requirement criteria for essential fatty acids

Optimising lipid nutrition in first-feeding flatfish larvae

Natural Copepods Are Superior to Enriched Artemia Nauplii as Feed for Halibut Larvae (Hippoglossus hippoglossus) in Terms of Survival, Pigmentation and Retinal Morphology: Relation to Dietary Essential Fatty Acids

Effects of purified diets containing different combinations of arachidonic and docosahexaenoic acid on survival, growth and fatty acid composition of juvenile turbot (Scophthalmus maximus)