Fish have adaptive responses to certain thermal conditions, causing changes in metabolic processes, which can be evaluated in their biological performance and physiological state. Striped bass (Morone saxatilis) in mariculture is exposed to various environmental factors, among which temperature stands out, which varies throughout the year. In the present study, the growth and hematological profile of striped bass were evaluated at different acclimation temperatures, this will allow highlighting the influence of this factor on the health and welfare of the species.
Twelve 430l tanks were used, connected to an open flow seawater system, with a 200% water replacement, where acclimation temperatures were established (16, 19, 21 and 24°C), in triplicate. In each of the tanks, 17 juvenile striped bass with an average weight of 29.4 ± 3.6 g were placed. The water temperature for the 16° and 19°C treatments was controlled with Aqua Logic chillers, and for the 21° and 24°C treatments, 1000W titanium heaters with regulating boxes were placed. The fish were provided with 3mm EWOS food, with 54% protein and 14% lipids, which was provided twice a day, to apparent satiety. For blood collection, the fish were anesthetized with clove oil at a dose of 0.05ml/l. Subsequently, using a 13 x 0.4mm syringe, the blood sample was taken from the caudal vein. Fish handling and blood procedures were performed following the guidelines of Institutional Committee for the Care and Use of Laboratory Animals of CICESE.
After 45 days, survival (S) was 100% in all treatments. Fish acclimated to a temperature of 24°C had significantly (p <0.05) better performance in productive parameters (Table 1), such as final weight (FW), weight gain (WG), specific growth rate (SGR), and thermal growth coefficient (TGC), compared to 16, 19 and 21°C. In relation to hematological values (Table 2), significant differences (p <0.05) were observed between treatments in hemoglobin (Hb), white blood cells (WBC), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). The results indicate that fish at a temperature of 24°C show greater growth, compared to 16, 19 and 21°C. The high concentration of Hb in fish acclimated to 16°C could be related to the lower energy expenditure in this thermal condition associated with the decrease in metabolic activity. Higher values were also observed in MCH and MCHC in fish acclimated to 16 and 19°C. This study contributes to establishing the hematological reference values for the species and could be used as indicators of its health status.