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Reared and wild fish: how do they compare?
Blaxter, J.H.S. (1976). Reared and wild fish: how do they compare?, in: Persoone, G. et al. (Ed.) Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 1. Research in mariculture at laboratory- and pilot scale. pp. 11-26
In: Persoone, G.; Jaspers, E. (Ed.) (1976). Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 1. Research in mariculture at laboratory- and pilot scale. IZWO: Wetteren. ISBN 90-6281-001-2. 620 pp., more

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Document type: Conference paper

Keyword
    Marine/Coastal

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  • Blaxter, J.H.S.

Abstract
    This paper reviews the comparisons which have been made between reared and wild fish of the same species, and includes some recent results on herring. Generally, selection pressure is higher in the wild and density higher in the hatchery. Work on salmonids has shown that wild fry swim better but are less aggressive than hatchery fry, which has implications for stocking streams. Hatchery salmonids often have a higher fat content despite their normal high protein diet. There may also be parental effects -the eggs of wild females being different in biochemical content from reared females. Marine fish rearing is likely to be financially successful only for luxury species. Nutritional studies are less advanced and there is little likelihood of attempting to re-stock the sea from hatcheries. Reared plaice have shown very poor survival when released into the sea due to their lack of normal avoidance responses. Other species will not take their normal food after a long time on artificial diets. Crowding in flatfish hatcheries leads to abnormal colouration and fin-biting, and size hierarchies are evident in many species. Allometric growth may be abnormal in herring leading to very high condition factors, while the snout may be very foreshortened with neoplasms in the head region. As with salmonids the fat content of marine fish from hatcheries can be very high with low ash content as a result of poor ossification. The problem of whether reared fish can be used for deducing events in the field is discussed.

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