REACTIONS OF MARINE FISHES TO TEMPERATURE GRADIENTS

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Abstract
An apparatus is described whereby a steep horizontal temp. gradient can be maintained, without the presence of vertical gradients, for the study of the reactions of fishes. Girella nigricans (Ayres) and other active marine fishes showed marked selection of temps. which were relatively high in comparison with their normal environments. While acclimatization was found to influence selection, the effect was, at most, slight and temporary, the selected temp. being to a large extent independent of past experience. The fishes tended to avoid rapid changes of temp., but quickly became adapted to new temps. Selection in the exptl. gradient is indicative of the relative stimulative or injurious effects of given rapid changes of temp., and not of the nature of "optimal" conditions or habitat preference.