The relationship between the temperature requirements of some fish species, using published data for growth optima, final preferences and lethal limits were examined. A good correlation was found and it is suggested that the data established gives a good estimate of the temperature promoting maximum growth. Determinations of final preferenda are easily conducted in the laboratory and could therefore be used to give rapid assessments of optimum growth temperatures of potential culture species. The practical application of such measurements is discussed.

Cannibalism is a frequent phenomenon in fish, especially in culture environments where fish are unable to escape predation via habitat segregation or migration. Not all cultured fish species start to exhibit cannibalism at the same age or size, nor is cannibalism equally intense in different species or life stages. Predator to prey size ratios vary substantially between species and life stages, chiefly because cannibalism is governed by gape size limitations and allometric growth of mouthparts. The development of sense organs, hard body parts, swimming and escape capacities in both the predator and the prey also influence prey size selectivity. The dynamics of cannibalism are influenced by these, as well as by environmental, factors that have effects on feed intake, growth depensation and facilitate or complicate the displaying of cannibalistic behaviour. Knowledge about cannibalistic behaviour and the logistics of cannibalism along with environmental enhancement are prerequisites for the mitigation of cannibalism in aquaculture. Also, within the context of strain selection, it is of importance to determine whether cannibals are natural-born killers or just lottery winners. These factors are discussed, chiefly as they apply to intracohort cannibalism. In addition, guidelines are suggested for cannibalistic risk assessment, and methods for mitigation of cannibalism are discussed.

Following feeding, the rate of oxygen consumption of fishes increases to a peak and then slowly declines to the pre-feeding level. Many factors have been shown to influence the magnitude and duration of post-prandial oxygen consumption and these include quantity and/or quality of ration and environmental temperature. The effects of the various factors are described and the phenomenon of the post-prandial increase in metabolic rate of fish is discussed in relation to work with other species of animals.

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