Fish bioenergetics: (Fish and Fisheries 13. Series ed. T.J. Pitcher) Malcolm Jobling Chapman and Hall, London, 1994 ISBN 0-412-58090-X, 24.99 Hard cover, acid-free paper, pp. xiv + 309, 31 tables, 61 figures Author, species and subject indexes

Environmental drivers of Atlantic salmon behaviour in sea-cages: A review

Sublethal ammonia exposure of Nile tilapia (Oreochromis niloticus L.): effects on gill, liver and kidney histology.

Previous reviews of stress, and the stress hormone cortisol, in fish have focussed on physiology, due to interest in impacts on aquaculture production. Here, we discuss cortisol in relation to fish welfare. Cortisol is a readily measured component of the primary (neuroendocrine) stress response and is relevant to fish welfare as it affects physiological and brain functions and modifies behaviour. However, we argue that cortisol has little value if welfare is viewed purely from a functional (or behavioural) perspective—the cortisol response itself is a natural, adaptive response and is not predictive of coping as downstream impacts on function and behaviour are dose-, time- and context-dependent and not predictable. Nevertheless, we argue that welfare should be considered in terms of mental health and feelings, and that stress in relation to welfare should be viewed as psychological, rather than physiological. We contend that cortisol can be used (with caution) as a tractable indicator of how fish perceive (and feel about) their environment, psychological stress and feelings in fish. Cortisol responses are directly triggered by the brain and fish studies do indicate cortisol responses to psychological stressors, i.e., those with no direct physicochemical action. We discuss the practicalities of using cortisol to ask the fish themselves how they feel about husbandry practices and the culture environment. Single time point measurements of cortisol are of little value in assessing the stress level of fish as studies need to account for diurnal and seasonal variations, and environmental and genetic factors. Areas in need of greater clarity for the use of cortisol as an indicator of fish feelings are the separation of (physiological) stress from (psychological) distress, the separation of chronic stress from acclimation, and the interactions between feelings, cortisol, mood and behaviour.

Cortisol and finfish welfare

Water quality encompasses the water physical, biological, and chemical parameters. It generally affects the fish growth and welfare. Thus, the success of a commercial aquaculture project depends on supplying the optimum water quality for prompt fish growth at the minimum cost of resources. Although the aquaculture environment is a complicated system, depending on various water quality variables, only less of them have a critical role. One of these vital parameters is dissolved oxygen (DO) level, which requires continuous oversight in aquaculture systems. In addition, the processes of natural stream refinement require suitable DO levels in order to extend for aerobic life forms. The depletion of DO concentration (called hypoxia) in pond water causes great stress on fish where DO levels that remain below 1–2 mg/L for a few hours can adversely affect fish growth resulting in fish death. Furthermore, hypoxia has substantial effects on fish physiological and immune responses, making them more susceptible to diseases. Therefore, to avoid disease outbreak in modern aquaculture production systems where fish are intensified and more crowded, increasing attention should be taken into account on DO levels.

Fish response to hypoxia stress: growth, physiological, and immunological biomarkers.

Effect of chronic exposure to ammonia on growth, food utilisation and metabolism of the European sea bass (Dicentrarchus labrax)

Combined effects of water quality and stocking density on welfare and growth of rainbow trout (Oncorhynchus mykiss)

Effects of repeated hypoxic shocks on growth and metabolism of turbot juveniles

Influence of triploid status on salmon smoltification

The pollack Pollachius pollachius is a commercially important fish, considered as a candidate for aquaculture in France. Rearing attempts are promising (Suquet et al., 1996), and more information is required about its reproduction, to contribute to a better management of breeders for this species. This study was designed to examine the first maturity in pollack and the effects of conditions such as origin and delayed reproduction season, on gonad maturation, reproductive and growth performances of adults.

Annick Le Roux

Papers

Effect of chronic exposure to ammonia on growth, food utilisation and metabolism of the European sea bass (Dicentrarchus labrax)

Combined effects of water quality and stocking density on welfare and growth of rainbow trout (Oncorhynchus mykiss)

Effects of repeated hypoxic shocks on growth and metabolism of turbot juveniles

Influence of triploid status on salmon smoltification

Growth and reproductive performances of juveniles and sexually mature pollack Pollachius pollachius in different conditions