Physiological performance in aquaculture: Using physiology to help define optimal conditions for growth and environmental tolerance

Abstract

In commercial fish aquaculture, it is crucial to ensure that environmental rearing conditions are adequate, if not optimal, for fish growth, welfare and profitability. In recirculating aquaculture systems (RAS), where environmental conditions can be tightly controlled, targeting these optima may be important in offsetting high costs. However, truly optimal conditions for growth are rarely defined in the literature. In net-pen aquaculture, site selection permits some control over the most relevant parameters; however, it is clear that changes in environmental conditions, such as sub-optimal temperatures, hypoxia and algal blooms, are increasing in frequency and duration, often unpredictably. Thus, an understanding of how changes in relevant environmental parameters affect growth and physiological performance is vital for the selection of strains that may be more resistant to these and other unpredictable changes. In this chapter we provide a physiological framework based upon the “Fry paradigm” for defining optimal values of temperature, salinity and water velocity for fish growth and performance, and the impact of hypoxia and gill damage. We consider these parameters in isolation, but also in combination as they often co-vary in the culture environment. Furthermore, we promote the use of stress tolerance tests to predict the ability of fish to withstand changes in their environment that may arise due to unforeseen circumstances. Finally, we review the various assays that can be used to quantify physiological performance during changes in these environmental parameters.