Evaluation of the effects of temperature on gastric evacuation and the associated mathematical models in different sizes steelhead trout (Oncorhynchus mykiss)

Abstract

Steelhead trout ( Oncorhynchus mykiss ) of four different sizes (27.06 ± 4.27, 75.99 ± 10.48, 140.21 ± 22.08, and 224.72 ± 31.20 g) were cultured for two weeks at four different temperatures (8 °C, 12 °C, 16 °C, and 20 °C) to evaluate the effects of temperature on gastric evacuation (GE) and the associated mathematical models. The wet and dry mass within the stomach contents of the steelhead trout were assessed at predetermined postprandial times (0, 6, 12, 18, 24, 36, and 48 h) by serial slaughtering, and the GE models were fitted. After selecting the optimal GE model for each trout group, we used curve and 3D surface fitting to analyze the effects of temperature, size, and their interaction on GE based on the 80% dry-mass evacuation time (D80) under the optimal model. The results indicated that the dry-mass fitting model could reflect the GE more accurately than the wet-mass fitting model, and both temperature and size had significant effects on the GE model and gastric evacuation rate (GER) of steelhead trout. With increasing size and temperature, the GER initially increased, followed by a decrease. The GER of two size groups (27.06 and 224.72 g) reached its maximum at 19.22 °C and 18.40 °C, respectively. A 3D surface model “Rational Taylor” was selected to calculate the appetite recovery time of any combination of steelhead trout in the range of 25–250 g and 8.0–20.0 °C. The results of this study provide theoretical information that can be used in selecting intelligent feeding strategies for Salmonidae aquaculture production. • Temperature and size can significantly influence the gastric evacuation (GE) model and GE time of steelhead trout. • The dry-mass GE model can more accurately reflect the conditions of GE. • The GE rate showed a trend of first increasing and then decreasing with increasing temperature or body length. • The optimal model of two-factor interaction on the appetite recovery time of steelhead trout was obtained.