Water Temperature and Practical Feeding Regimes Interact to Affect Growth, Enzyme Activities, and Histological Characteristics in Juvenile and Sub-Adult Chinese Mitten Crab (Eriocheir sinensis).

The Chinese mitten crab (Eriocheir sinensis) is commonly cultured using compound feed or iced fresh fish, but its performance may vary with water temperature and developmental stage. This 28-day indoor study evaluated the interactive effects of feeding regime and water temperature on growth, pooled survival (reported descriptively), apparent feed disappearance, tissue enzyme activities, and qualitative intestinal and gill histology in juvenile and sub-adult E. sinensis. Crabs were assigned to compound-feed or iced-fresh-fish regimes at 20, 24, 28, or 32 °C. Significant feeding regime × temperature interactions were detected for growth traits in both developmental stages. Under the present experimental conditions, the highest numerical juvenile body-weight gain was observed under the compound-feed regime at 28 °C, whereas the highest numerical sub-adult body-weight gain was observed under the compound-feed regime at 24 °C. Apparent feed disappearance was generally higher in the iced-fresh-fish regime but did not consistently correspond to greater growth. Linear mixed-effects models revealed tissue- and stage-specific enzyme responses, including significant feeding regime × temperature × time interactions for selected metabolic, ion-transport, and immune-related activities. Qualitative histological observations showed treatment-associated structural changes in the intestine and gill. Because the two regimes differed fundamentally in moisture content and nutrient density, our results reflect responses to commercial feeding practices rather than an evaluation of nutritionally equivalent diets.