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...

/pdf/metabolism-and-functions-of-lipids-and-fatty-acids-in-566zpmr4m0.pdf

Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

Many studies have recently described and interpreted the community structure and function of fishes inhabiting estuaries and other transitional waters in terms of categories or guilds. The latter describe the main features of the fishes' biology and the way in which they use an estuary. However, the approach has been developed by different workers in different geographical areas and with differing emphasis such that there is now a need to review the guilds proposed and used worldwide. The previous wide use of the guild approach has involved increasing overlap and/or confusion between different studies, which therefore increases the need for standardization while at the same time providing the opportunity to reconsider the types and their use worldwide. Against a conceptual model of the importance of the main features of fish use in estuaries and other transitional waters, this review further develops the guild approach to community classification of fish communities inhabiting those areas. The approach increases the understanding of the use of estuaries by fishes, their interactions and connectivity with adjacent areas (the open sea, coastal zone and freshwater catchments) and the estuarine resources required by fishes. This paper gives a global perspective on this categorization by presenting new or refined definitions for the categories, lists the synonyms from the literature and illustrates the concepts using examples from geographical areas covering north and central America, north and southern Europe, central and southern Africa, Australia and the Indo-Pacific.

/pdf/the-guild-approach-to-categorizing-estuarine-fish-3fkehy8ard.pdf

The guild approach to categorizing estuarine fish assemblages: a global review

Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme-producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.

Enzyme‐producing bacteria isolated from fish gut: a review

Comparative study of digestive enzymes in fish with different nutritional habits. Proteolytic and amylase activities

This review places the life-history styles of fishes associated with South African estuaries in a global context and presents a classification system incorporating all the major life-history categories for estuary-associated fish species around the world. In addition, it documents the early life histories of the major fish groups in South African estuaries, with particular emphasis on the differing modes of estuarine utilization by marine, estuarine and freshwater taxa. This review details factors influencing the ichthyofaunal community structure in South African estuaries. The availability of fish for recruitment into an estuary depends primarily upon the distributional range of euryhaline marine and estuarine species, with tropical and temperate taxa showing marked abundance trends. Within a particular biogeographic region, however, estuarine type and prevailing salinity regime have a major influence on the detailed ichthyofaunal structure that develops. There is an increasing preponderance of marine fish taxa when moving from a freshwater-dominated towards a seawater-dominated type of system, and a decline in species diversity between subtropical estuaries in the north-east and cool temperate systems in the south-west. Similar declines in fish species diversity between tropical and temperate estuaries in other parts of the world are highlighted. Fish assemblages in estuaries adjust constantly in response to changing seasons, salinities, turbidities, etc. Despite persistent fluctuations in both the biotic and abiotic environment, the basic ichthyofaunal structure appears to have an underlying stability and to be predictable in terms of the response of individual species to specific conditions. This stability seems to be governed by factors such as the dominance of eurytopic taxa within estuarine assemblages and the robust nature of food webs within these systems. The predictability arises from factors such as the seasonality associated with estuarine spawning cycles and juvenile fish recruitment patterns. These patterns, together with a well-documented resilience to a wide range of physico-chemical and biotic perturbations, appear to be an underlying feature of fish assemblages in estuaries around the world. In contrast to marine fish species, estuary-associated taxa have received little conservation attention. Apart from the designation of protected areas, the main direct means of conserving estuary-associated fish stocks include habitat conservation and controls over fishing methods, effort, efficiency and seasonality. Of these, the conservation of fish habitats, the most important, because healthy aquatic environments invariably support healthy fish populations. The use of estuarine sanctuaries for fish conservation is briefly reviewed, as well as the legislation governing the USA National Estuarine Research Reserve System (NERRS) and the Australian Marine and Estuarine Protected Area (MEPA) system. It is concluded that South Africa requires an expansion of the existing Estuarine Protected Area (EPA) network, as well as the upgrading of selected 'estuarine reserves' where fishing is permitted, into 'estuarine sanctuaries' where no exploitation of biological resources is allowed.

Ichthyofaunal assemblages in estuaries: A South African case study

Publisher Summary This chapter describes the alimentary canal and digestion in teleosts. It recognizes several types of teleosts on the basis of the different foods taken by them and their feeding habits: plankton feeders, herbivores, omnivores, carnivores, and specialists. The various degrees of specialization in feeding habits lead to the distinction of europhags, stenophags and monophags. Many cell types of the teleost digestive tract have been examined electron-microscopically, such as oral epithelial cells, chloride cells, scattered chemosensory cells, the cells of taste buds, intestinal goblet cells, and epithelium cells. Histo- and cyto-chemical techniques have been used in the study of the teleostean alimentary canal. Because the inner lining of this canal is mucified, emphasis is given to the mucus-secreting cells, which appear to contain either neutral or acidic mucopolysaccharides. In many teleosts, alkaline phosphatase and acid phosphatase activity has been detected in the brush-border of intestinal and cecal epithelia. Feeding rates have been measured by observing food intake under laboratory conditions with restricted or excess rations. The chapter discusses three methods by which the digestion rate in fish is estimated––namely, (1) by measuring the time interval between food intake and defecation, (2) by measuring the stomach contents at various time intervals after feeding, and (3) by using X-rays for observing the progress of digestion with time.

The Alimentary Canal and Digestion in Teleosts

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The Alimentary Canal and Digestion in Teleosts