A web-based combined nutritional model to precisely predict growth, feed requirement and waste output of gibel carp (Carassius auratus gibelio) in aquaculture operations

Aquaculture nutritional models play a vital role in the management of fish culture operations. This study reported a combined nutritional model constructed based on the data from several fish farms and published studies in order to predict the growth, feed requirement and waste output of gibel carp (Carassius auratus gibelio) and the web-based model service platform. This combined model comprised a growth model, a feed requirement model and waste (nitrogen and phosphorus) output model. The performance of different growth models and the growth trajectory of gibel carp were analyzed based on growth data obtained from two fish farms in Jingzhou, Ningbo (China) and published studies. The least squares method was used to optimize the growth coefficient within each growth stanza and to choose the best fit of growth model, which was the thermal-unit growth coefficient (TGC) model. Three growth stanzas of gibel carp in its life cycle were found by using TGC model, which were from firstfeeding (1 g) to 13.5 g (Stanza 1); from 13.3 to 175.5 g (Stanza 2); and > 175.5 g (Stanza 3). Feed requirement of fish in different growth stages were determined by digestible energy requirement (DEreq), estimated based on the summary of recovered energy (RE), basal metabolism (HeE), heat increment of feeding (HiE), and urinary and branchial excretion (UE+ ZE). Nutrient mass balance method was used to estimate waste output when the different growth stages of gibel carp was fed with different diets. The combined model was developed as a web-based service which could be obtained freely online. The design and implementation of the program which included three layers, i.e., front user side, application layer and data storage, were also reported in the current study. The user interface, functionalities of the application layer and database design were outlined. The service could be accessed by any browser and mobile device, providing a convenient tool for fishery management for farmers, farm managers and researchers in academia. The validation of the predicted body weight and feed conversion rate (FCR) showed that the current combined model has a great reference value in estimating the growth, feed requirement and waste discharge in gibel carp farms. The web-based model service could be an effective tool for benchmarking the growth performance, providing differentiated production, reducing feed waste, increasing economic benefits, and evaluating aquaculture pollution in different gibel carp culture operations.