MEPS 118:59-68 (1995)  -  doi:10.3354/meps118059

Influence of water temperature during the larval stage on size, age and body condition of a tropical reef fish at settlement

McCormick, M. I., Molony, B. W.

The effects of water temperature during the pelagic life-history phase on body characteristics at metamorphosis and settlement were examined for the tropical goatfish Upeneus tragula (Mullidae). Water temperatures were recorded daily at 2 stations on the northern Great Barrier Reef from April 1989 to May 1990. Temperature data were used to calculate an estimate of temperature history for individual newly metamorphosed goatfishes from 10 samples, collected at 5 stations across the northern Great Barrier Reef lagoon. Accounting for mean water temperature experienced during the larval phase reduced the within-sample variability in growth rates by 30%. There were significant negative relationships with mean water temperature for both standard length and age of fish at metamorphosis within and among samples. Adjusting for temperature history by analysis of covariance markedly changed the patterns of size at settlement among sampling stations. Use of a summation of daily water temperatures over the larval period of each fish as an estimate of physiological age (in degree-days) also changed the patterns of significance among sampling stations compared to patterns found using age (d) alone. These results suggested the importance of temperature in determining larval patterns of growth. An experiment examined the influence of water temperature on size, age, body composition and muscle development at settlement. Larval U. tragula were collected and placed randomly in 3 tanks at each of 2 temperatures, 25 and 30*C. Fishes were fed ad libitum and removed from tanks upon metamorphosis and settlement. Fishes in the 30*C water settled on average 2.8 d earlier than those in the 25*C tanks. The length, weight, muscle development and biochemical composition of fishes did not differ between temperature regimes. Together, the field and laboratory results suggest that relatively small changes in water temperature have the potential to greatly influence the patterns of variability seen in the age and size at metamorphosis in many tropical reef fishes. Developmental rate to metamorphosis appears to be more affected by water temperature than fish length.

Temperature . Reef fish . Metamorphosis . Larval duration . Developmental rate

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