Coping styles in farmed fish: consequences for aquaculture

Individual differences in physiological and behavioural responses to stressors are increasingly recognised as adaptive variation and thus raw material for evolution and fish farming improvements including selective breeding. Such individual variation has been evolutionarily conserved and is present in all vertebrate taxa including fish. In farmed animals, the interest in consistent trait associations, that is coping styles, has increased dramatically over the last years because many studies have demonstrated links to performance traits, health and disease susceptibility and welfare. This study will review (i) the main behavioural, neuroendocrine, cognitive and emotional differences between reactive and proactive coping styles in farmed fish; (ii) the methodological approaches used to identify coping styles in farmed fish, including individual (group) mass-screening tests; and (iii) how knowledge on coping styles may contribute to improved sustainability of the aquaculture industry, including welfare and performance of farmed fish. Moreover, we will suggest areas for future research, where genetic basis (heritability/epigene tic) of coping styles, and the neuroendocrine mechanisms behind consistent as well as flexible behavioural patterns are pinpointed as central themes. In addition, the ontogeny of coping styles and the influence of age, social context and environmental change in coping styles will also be discussed.European Commission under the 7th Framework Programme FP7-KBBE [265957

Intrasaccular injection of aminoglycosides: a novel method for temporary damaging fish inner ear hair cells

Fish models are increasingly being used for hearing research investigations. Aminoglycoside antibiotics that are used for damaging the inner ear hair cells can have systemic side effects leading to death of study animals. This study aimed to compare two methods: i) systemic (intravenous) and ii) local (intrasaccular) gentamicin administration for induction of inner ear hair cell damage in the Atlantic cod, Gadus morhua (L.). Hair cell damage was assessed using scanning electron microscopy; hair cell density, prevalence of immature hair cells and kinocilia length were measured. Gentamicin-treated fish were compared with control and sham fish. Intravenous gentamicin led to dose-dependent mortality caused by nephrotoxicity. The only visible effect after treatment was more immature hair cells and shorter kinocilia, the effect on hair cell density was equivocal. Following intrasaccular gentamicin treatment, fish mortality was negligible, and hair cells were damaged regardless of dose. Here, we observed decreased hair cell density, high prevalence of immature hair cells, and significantly shortened kinocilia. Conclusion: intrasaccular injection is preferable to intravenous injection of gentamicin for the study of ototoxicity in the Atlantic cod

Effects of carbon dioxide and pH on growth and risk of IPN in Atlantic salmon

Infectlous pancreatlc necrosls (IPN) Is a virus dlsease that has been an Increaslng problem for Norweglan salmon farmlng lndustry. A major question is whether there Is a causal link between reduced water quality due to Intensive production and Increased frequency Of IPN-outbreaks. In the present study, we have examlned the effects of longterm exposure to three dlfferent concentrations of carbon dloxlde (CO2) and low pH on growth and susceptlbllity to IPN virus in Atlantic salmon

Aminoglycoside antibiotics and the sensory hair cells of inner ear and lateral line system in the Atlantic cod, Gadus morhua: effects on fish hearing threshold

The aims of the present study were to investigate: a) the potential involvement of the fish lateral line system in hearing at 250 Hz and b) the possible regeneration of the inner ear hair cells in the Atlantic cod (Gadus morhua). The inner ear and lateral line system of the Atlantic cod were inactivated using ototoxic aminoglycoside antibiotics by injection (gentamicin) or bath (gentamicin and streptomycin), respectively. Hearing thresholds were measured in the fish using the Auditory Brainstem Response (ABR) technique at 10, respectively 17 - 20 days following antibiotic treatment. Results were compared between groups of individuals i) with inner ear damage, ii) with lateral line system altered, iii) placebo (immersion in fresh sea water) and iv) control. The sound stimuli applied were series of 2000 five-cycle (2-1-2) 250 Hz tone bursts delivered using a Brüel & Kjær (Nærum, Denmark) loudspeaker. ABRs were measured using a filter set at 30-3000 Hz, a gain of 100 000 and visual interpretation using the Bio-Logic AEP software. Sound stimulus level was reduced until threshold was attained. To check the tissue status of the inner ear and lateral line system, hair cells from sensory maculae were visualized using scanning electron microscope (SEM). Ten days after treatment, hearing thresholds of placebo and lateral line damaged cods did not differ from controls fish (p = 0.387 and p = 0.095, respectively), whereas the fish that received intravenous gentamicin injection had significantly elevated hearing thresholds compared to controls (p < 0.0001). SEM analyses further demonstrated that, 10 days following antibiotic treatment, cod inner ear hair cells were damaged, as well as lateral line hair cells and more particularly in the case of canal neuromasts. There was no hearing effect or microscopic tissue damage in untreated fish. From the 17th day after treatment, ABR measurements showed that some of the gentamicin treated fish had regained hearing thresholds comparable to the control cods (p = 0.535), and this was associated with an apparent regeneration of hair cells in the sensory maculae of their inner ear. This study indicates a capacity for inner ear hair cell regeneration in Atlantic cod, and illustrates the advantages of the ABR-method for investigation of fish hearing after intervention on the inner ear, and during the hair cell regeneration process. The present work further suggests that the lateral line system is not involved in cod hearing at 250 Hz

A multi-disciplinary framework for bio-economic modeling in aquaculture: a welfare case study

This article summarizes the framework that translated data from multiple disciplines into a bio-economic decision tool for modeling the costs and benefits of improving fish welfare in commercial aquaculture. This decision tool formed the basis of a recent EU research project, BENEFISH which was funded via the European Commission's Sixth Framework (FP6) initiative. The bio-economic decision model can incorporate biological data, productivity data, micro (farm) and macro (industry) level economic data, and consumer marketing and business to business data. It can identify areas for potential added value that might be achieved by improving fish welfare across a range of species and husbandry systems within European aquaculture. This article provides a brief overview of the minimum data requirements for successfully modeling the bio-economic impacts of improvements in farmed fish welfare using the model developed during the BENEFISH project. It also highlights potential bottlenecks and the minimum prerequisites for each potential data set to be used for successful modeling