THE RESISTANCE AND ACCLIMATIZATION OF MARINE FISHES TO TEMPERATURE CHANGES. I. EXPERIMENTS WITH GIRELLA NIGRICANS (AYRES)

¹ Scripps Institution of Oceanography, University of California, La Jolla

The resistance of young Girella nigricans (Ayres) to low and to high temperatures and the changes of tolerance produced by acclimatization are examined in relation to temperatures in the natural habitat of the fishes.

The fishes were killed by moderately low temperatures well above 0° C., the lower limits of temperature tolerance being no more extreme, in comparison with normal environmental temperatures, than the corresponding upper limits.

The relationship between thetime (duration) of exposure to the test temperatures and the highest or lowest temperatures tolerated by 50 per cent of the experimental animals (upper or lower "median tolerance limits") is representable by smooth time-temperature curves of tolerance.

Acclimatization to different temperatures has a pronounced influence upon subsequent resistance to cold (hilling), as well as to heat, and upon the form of the respective time-temperature curves of tolerance.

Experiments on the rate of acclimatization corroborate the conclusion, based on earlier observations, that heat-resistance in fishes is gained rapidly after a rise of temperature and lost slowly after cooling.

Acclimatization to cold (i.e., increase of resistance to chilling) is relatively slow, and cold-resistance is lost no more slowly than it is acquired. Afterany given riseor fallof environmental temperature within the normal range, about 50 per cent of the total resulting change of cold-tolerance occurs in two days, and complete acclimatization (i.e., constant cold-tolerance) is apparently achieved in about twenty days.

Injury by chilling is no less important as a possible limiting factor in the distribution of marine fishes than heat-injury.

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