Bioenergetic growth model for the yellowtail kingfish (Seriola lalandi)

Abstract

The culture of Seriola species is well established in Japan and is an emerging industry in many other temperate regions around the world. Despite many studies on the growth, physiology and nutritional requirements of yellowtail kingfish, the complex interactions between nutrition and environmental impacts are still being investigated. Here, we present a theoretical bioenergetic model for yellowtail kingfish bringing together the current knowledge of this species growth, metabolism and other aspects of its physiology. We solve the energy budget of yellowtail kingfish using existing theoretical equations to represent all energy gains and all metabolic costs and parameterising them with published data obtained when rearing yellowtail kingfish. Our model predicts growth as a function of suitable temperatures for yellowtail kingfish (18–27 °C) and estimates the rate of feed ingestion as well as the effect of diet on feed conversion ratio (FCR). Our model can be used to estimate energy and protein retention, nutrients loads into the ecosystem, and how these outputs change through diet manipulation at specified weight classes. We demonstrate how to use our model to predict improvements to FCR and include a simulation example showing results from shifting from a high protein-low fat diet for juveniles (0 to 500 g) to a low protein-high fat diet for adult fish (500–1000 g). Excretion of dissolved nitrogen and the consumption of oxygen through fish respiration are highest at the optimum temperature for growth. When fed a diet of 45% protein and 20% fat, our simulation shows that a constant biomass of 1000 kg of fish at a constant optimum temperature of 22.8 °C, excretes 153.1 kg of nitrogen year -1. For the same diet composition and temperature, oxygen consumption decreases from 19.9 to 10.2 kg day−1 for 1000 kg of fish weighing 50 g and 1.5 kg, respectively. Our model is useful to investigate complex interactions of metabolism for the culture of yellowtail kingfish in a commercial setting and allows predictions for changes that could improve production.