Effects of temperature on metabolic rate and lower dissolved oxygen tolerance of juvenile speckled peacock bass Cichla temensis.

Speckled peacock bass Cichla temensis is a popular sport and food fish that generates substantial angling tourism and utilitarian harvest within its range. This popularity and value make this species important for management and a potential aquaculture candidate for both fisheries enhancement and food fish production. However, little is known of optimal conditions in natural habitats which also are important for development of hatchery protocols for handling, spawning, and grow-out. Speckled peacock bass have been documented to have high sensitivity to extreme temperatures, but the metabolic underpinnings have not been evaluated. In this study, the effects of temperature (25, 30, and 35°C) on standard metabolic rate (SMR) and lower dissolved oxygen tolerance (LDOT) of juvenile speckled peacock bass (mean ± standard error total length: 153 ± 2 mm, and wet weight: 39.09 ± 1.37 g) were evaluated using intermittent respirometers after an acclimation period of 2 weeks. Speckled peacock bass had the highest SMR at 35°C (345.56 ± 19.89 mg O2 /kg/hr), followed by 30°C (208.16 ± 12.45 mg O2 /kg/hr), and 25°C (144.09 ± 10.43 mg O2 /kg/hr). Correspondingly, the Q10 , or rate of increase in aerobic metabolic rate (MO2 ) relative to 10°C, for 30-35°C was also greater (2.76) than from 25-30°C (2.08). Similarly, speckled peacock bass were the most sensitive to hypoxia at the warmest temperature, with a LDOT at a pO2 of 90 mmHg (4.13 mg/L) at 35°C compared to pO2 's of 45 mmHg (2.22 mg/L) and 30 mmHg (1.61 mg/L) at 30°C and 25°C, respectively. These results indicate speckled peacock bass are sensitive to temperatures near 35°C; therefore, we recommend managing and rearing this species at 25-30°C.