Growth and Activity of Juvenile Mosquitofish: Temperature and Ration Effects

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Abstract
The effects of constant temperatures (10, 15, 20, 25, 30, and 35 C) and ration size on the growth rates and activity of juvenile mosquitofish Gambusia affinis (mean wet weight, about 20 mg) were measured in laboratory experiments. On ad libitum rations of Tubifex spp. worms, food-consumption rates of mosquitofish were very high, ranging from 7% dry body weight/day at 10 C to 83%/day at 35 C. Growth increased from 0% dry body weight/day at 10 C to 21%/day at 30 C and declined slightly at 35 C. Gross efficiencies (100 growth/food consumption) increased from 0 at 10 C to a peak of 28% at 30 C and declined slightly at 35 C. On reduced rations (20% of dry body weight/day) maximum growth rates occurred at 25 C. Weight loss of starved fish varied from 1.5%/day at 10 C to approximately 13%/day at 35 C. Fish activity increased significantly with temperature and was generally highest at intermediate feeding levels. Received August 30, 1982 Accepted June 7, 1983