The Southern black drum Pogonias courbina was an important marine fisheries resource, but due to overexploitation, it is now considered vulnerable by the IUCN. They are widely distributed in the Southwestern Atlantic Ocean, and as such, are exposed to a wide range of temperatures. Despite this, their temperature tolerance range is still unknown. Critical thermal maximum (CTmax) has been widely used to explore fish acute thermal warming tolerance. Nevertheless, these results are directly influenced by the temperature at which fish are reared before the trial. The present study aims to determine the influence of short-term acclimation temperatures (Tacc) on the CTmax of juvenile P. courbina.
In the experiment, 180 fish per tank (3.1±0.6g) were randomly distributed in four recirculating aquaculture systems (RAS) with different temperatures (29.2±0.3; 31.3±0.3; 33.1±0.2; 35.0±0.4). Each RAS had temperature control (heater or chiller), constant aeration, mechanical and biological filtration to ensure good water quality. During the trial, the fish were fed four times a day with commercial feed. After 12 days, nine individuals (three at a time) were randomly sampled with a net and transferred to 16 L glass tanks with a heater, thermometer, and aeration to avoid stratification. The aquarium was previously filled with water from the ‘original system. The temperature ramping-up rate was set at 0.3 °C min− 1. Once each fish lost equilibrium, the temperature was recorded.
The general CTmax of P. courbina was 40.3±0,9°C. Fish CTmax was linearly correlated with temperature (p<0.01). All CTmax were statistically different (p<0.01) and ranged from 39.2°C for fish acclimated at 29°C to 41.4°C for fish kept at 35°C (Fig 1.). These findings provide useful information on the upper water temperature limit for juvenile P. courbina. This report can help fish farmers establish appropriate conditions to produce this emergent aquaculture species.