The effects of temperature changes on Totoaba macdonaldi larval development, growth, and respiratory rates.

Understanding the effects of environmental temperature on marine fish larvae is crucial for optimizing feeding regimes and promoting optimal development and growth from a zootechnical perspective in aquaculture practices. The present study investigated the impact of different rearing temperatures on development, growth, and oxygen consumption rates of Totoaba macdonaldi larvae. An open-flow seawater recirculating system was used in which larvae (150 specimens/L) were exposed in triplicate to four rearing temperatures (20, 24, 26, and 28 °C) for 24 days under standard larval rearing conditions. Larvae were sampled at 7, 12, 16, 20, and 24 days post hatching (DPH) to assess growth performance, survival, histological condition, and respirometry. At the end of the trial, the highest total length (TL) and body weight (BW) values were observed at 26 °C, with larvae displaying negative allometric growth in terms of TL and BW, similar to those reared at 24 and 28 °C. In contrast, larvae reared at 20 °C showed lower growth and an isometric growth pattern. No significant differences in Fulton's condition factor (K) were detected among treatments. Survival rates were the highest at 28 °C, while increased cannibalism at 26 °C was associated with elevated specific growth rates and thermal growth coefficients. Histological analysis revealed better structural organization in the gills and liver of larvae reared at 26 °C, whereas other treatments showed signs of inflammation. Respirometry results indicated that larvae reared at 20 °C had significantly higher metabolic rates. However, these differences diminished by DPH 20 and 24, likely reflecting developmental changes and phenotypic plasticity during the larval-to-juvenile transition. Based on physiological and metabolic indicators, a rearing temperature of 26 °C is recommended for T. macdonaldi larviculture.