Interactions between temperature and size on the growth, size heterogeneity, mortality and cannibalism in cultured larvae and juveniles of the Asian catfish, Pangasianodon hypophthalmus (Sauvage)

Temperature effects vary throughout the ontogeny, but are proportionally more variable during the early life stages than in older fish. The larvae of a few species have been studied but contrasting trajectories were observed, thereby making it difficult to predict how temperature impacts on the growth, survival and size heterogeneity in a particular species. This study examined these interactions in young [0.9 mg–1 g wet mass (WM)] Pangasianodon hypophthalmus, one of the most extensively cultured tropical fish. Fish were raised at five temperatures from 23 to 33 °C in a recirculated water system, fed in excess with a high-energy feed (Artemia then a formulated feed, >50% protein), and examined at 1-day (first feeding days) or 4-day intervals (older fish). The temperature that produced the fastest growth (T°opt) was 31 °C at the start of exogenous feeding (0.9 mg); it increased to 32.7 °C at 8 mg then decreased by 0.7 °C for each 10-fold increase of WM. Size heterogeneity was lower and survival was higher (70–85% from 0.9 mg to 1 g) when the temperature was close to T°opt. Comparisons with other species suggest that the slope of the relationship between T°opt and fish size has a strong latitudinal component, and may also reflect the fish sensitivity to oxygen.