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

A review of sterol markers for marine and terrigenous organic matter

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.

Sterols as ecological indicators

The lipid composition and biochemistry of freshwater fish.

1. 1. [1-14C]linolenic acid was injected into the rainbow trout, Salmo gairdnerii, ayu, Plecoglossus altivelis, eel, Anguilla japonica, red sea bream, Chrysophrys major, rockfish, Sebastiscus marmoratus, globefish, Fugu rubripes rubripes and prawn, Penaeus japonicus (molting stage D1″-D2), and the bioconversion of linolenic acid (18:3ω3) to highly unsaturated fatty acids such as eicosapentaenoic (20:5ω3) and docosahexaenoic (22:6ω3) acids was investigated. 2. 2. Linolenic acid was converted to 20:5ω3 and 22:6ω3 intensively in the rainbow trout, moderately in the ayu, eel and prawn, but slightly in the red sea bream, rockfish and globefish. 3. 3. These results were discussed in relation to the essential fatty acid requirements of the aquatic animals.

Relationship between essential fatty acid requirements of aquatic animals and the capacity for bioconversion of linolenic acid to highly unsaturated fatty acids.

Effects of dietary lipids, fatty acids. and phospholipids on growth and survival of prawn (Penaeus japonicus) larvae

Protein and energy requirements of nile tilapia, Oreochromis niloticus, fry

The requirements of essential fatty acids (EFA) for Tilapia zillii were examined by feeding diets with several types of lipids and with different levels of ω6 and ω3 fatty acids. The addition of 18:2ω6, 20:4ω6, 18:3ω3 and 20:5ω3 to the diet containing 12:0 as a basal lipid improved the weight gain of T. zillii. However, the growth-promoting effects of 18:2ω6 and 20:4ω6 were superior to those of 18:3ω3 and 20:5ω3. These data indicated that T. zillii requires ω6 fatty acids rather than ω3 fatty acids. The dietary requirement of T. zillii for 18:2ω6 or 20:4ω6 was found to be about 1.0% in the diet. In the groups of T. zillii fed with the EFA-deficient diets, the levels of 20:3ω9 and 18:1ω9 increased, but they were decreased by the supplementation of either 18:2ω6 or 20:1ω6. Also, the supplementation of 18:2ω6 to the diets increased the proportion of 20:4ω6 in polar lipids of Tilapia bodies, indicating that T. zillii probably converts 18:2ω6 to 20:4ω6.

/pdf/requirements-of-tilapia-zillii-for-essential-fatty-acids-4b9ptmqpoz.pdf

Shin-ichi Teshima

Papers

Relationship between essential fatty acid requirements of aquatic animals and the capacity for bioconversion of linolenic acid to highly unsaturated fatty acids.

Effects of dietary lipids, fatty acids. and phospholipids on growth and survival of prawn (Penaeus japonicus) larvae

Protein and energy requirements of nile tilapia, Oreochromis niloticus, fry

Requirements of Tilapia zillii for essential fatty acids.

Effects of coating and encapsulation of crystalline amino acids on leaching in larval feeds