Determination of an optimum feeding rate (OFR; % body weight per day), defined as the rate at which growth is at a maximum in given rearing conditions, is a key component to establish optimal feeding management plans for culturing aquaculture species. In a variety of fish species with a wide range of body sizes, an OFR has been estimated on the basis of growth performance such as gain in weight and efficiency in feed utilization in response to graded feeding levels. Either analysis of variance (ANOVA) with multiple range tests (e.g., Hung & Lutes, 1987;Santiago, Aldaba, & Reyes, 1987) or regression models (e.g., broken-line model and quadratic model; Deng et al., 2003;Eroldoğan, Kumlu, & Aktaş, 2004) has been often practised by fish nutritionists to determine the estimate. Due to the limitation of ANOVA with multiple range tests that considers dose-response relationship between feeding rate and growth performance discrete, regression models reflecting that the relationship is continuous are reasonable to be tested (see
AbstractTwo feeding trials using different commercial feeds and different fish sizes were conducted to compare model performance of various regression models on the estimation of optimum feeding rates (OFR; % BW/day) for juvenile olive flounder. Six feeding rates ranging from 1% to 11% in trial I and another six feeding rates ranging from 1% to 6% in trial II were tested. Final body weight, weight gain, feed conversion ratio, condition factor, nutrient gains, and whole-body lipid and energy contents were significantly influenced by the feeding rates in both trials. The overall responses shown in trial I were generally comparable to those observed in trial II. In trial I, the OFR was estimated to be 7.3%, 5.7%, 9.8% and 10.2% by the one-slope straight broken-line, two-slope straight broken-line, quadratic broken-line and quadratic models, respectively. In trial II, the OFR was estimated to be 4.8%, 4.6%, 8% and 8% by the one-slope broken-line, two-slope broken-line, quadratic broken-line and quadratic models, respectively. Based on the model selection criteria (R 2 adj and AICc), the quadratic broken-line model was selected as the best-fit model in both trials. This model that describes the dose-response relationship best among the tested models can be recommended when determining an OFR.
K E Y W O R D Solive flounder, one-slope straight broken-line model, optimum feeding rate, quadratic brokenline model, quadratic model, two-slope straight broken-line model