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STUDIES ON THE GROWTH OF TROUT, SALMO TRUTTA FROM FOUR CONTRASTING HABITATS
Author(s) -
THOMAS J. D.
Publication year - 1964
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1469-7998.1964.tb04510.x
Subject(s) - trout , salmo , brown trout , biology , helminths , ecology , productivity , larva , habitat , fishery , fish <actinopterygii> , zoology , macroeconomics , economics
An ecological investigation was undertaken at four contrasting stations on three river systems in West Wales, namely the Teify, the Rheidol and the Pysgotwr, with a view to evaluating the effect of ecological factors, particularly the helminth parasites, on the growth of the trout. When compared with the larger, faster growing trout from the two stations (A and B) on theTeify the slow‐growing trout from the other two stations (C and D). located in each of the more acid rivers, were characterized by a lower specific growth rate, a more restricted growing season, a lower condition factor, less fat on the pyloric caeca and earlier maturation of the gonads. The diet of the smaller, slow‐growing trout contained e smaller proportion of large, readily accessible food and seemed to be more adversely influenced by the effect of floods and the onset of winter than was the case with trout at the other stations. There was no evidence that poor growth of trout in the more acid streams wm due to the effect of helminth parasites. Of the thirteen species of helminths encountered in the trout at Stations A and B only three occurred commonly at Stations C and D and the only demonstrably pathogenic helminths, namely the acanthocephalan Neoechinorhynchw tutili and the plerocercoid larva of Diphyllobothrium were conspicuously absent. The growth of the trout appeared to be a function of several components of the ecosystem. Favourable productivity indices include a pH of approximately 7 or more, a high ionic and calcium content, a large area of depositing substratum, a low susceptibility to sudden flooding, a favourable temperature regime (Brown, 1946 c), a rich growth of algae and phanerogams. a wide variety and high density of animals including those of a large size and high accessibility and finally a rich fauna of helminth parasites particularly nematoda and acanth6cephala.