Environmental variability in the early rearing environment generates behaviourally flexible cod: implications for rehabilitating wild populations

The release of hatchery-reared fishes for restoring threatened and endangered populations is one of the most controversial issues in applied ecology. A central issue has been to determine whether releases cause extinction of local wild populations. This may arise either through domesticated or non-local fishes hybridizing with wild fishes, or through inappropriate behavioural interactions; for example, many hatchery fishes show exaggerated aggressive and competitive behaviour and out-compete wild counterparts. The impact of the impoverished hatchery environment in shaping behaviour is only now receiving attention. Attempts to counteract hatchery-related behavioural deficiencies have utilized intensive training programmes shortly before the fishes are released. However, we show here that simple exposure to variable spatial and foraging cues in the standard hatchery environment generates fishes with enhanced behavioural traits that are probably associated with improved survival in the wild. It appears that fishes need to experience a varying and changeable environment to learn and develop flexible behaviour. Using variable hatchery rearing environments to generate suitable phenotypes in combination with a knowledge of appropriate local genotypes, rehabilitation of wild fishes is likely to succeed, where to date it has largely failed

Effects of turbidity on the spontaneous and prey-searching activity of juvenile Atlantic cod (Gadus morhua)

Increasing turbidity in coastal waters in the North Atlantic and adjacent seas has raised concerns about impacts on Atlantic cod (Gadus morhua) using these areas as nurseries. A previous experiment (Meager et al. 2005 Can. J. Fish. Aquat. Sci. 62, 1978–1984) has shown that turbidity (up to 28 beam attenuation m−1) had little effect on the foraging rate of juvenile cod. Although this was attributed to cod using chemoreception in conjunction with vision to locate prey, foraging rates may also be maintained by increased activity. Higher activity, however, is energetically costly and may offset benefits from increased foraging return

Does female nuptial coloration reflect egg carotenoids and clutch quality in the Two-Spotted Goby (Gobiusculus flavescens, Gobiidae)?

Summary 1 - Carotenoid-based ornamentation has often been suggested to signal mate quality, and species with such ornaments have frequently been used in studies of sexual selection.2 - Female Gobiusculus flavescens (Two-Spotted Goby) develop colourful orange bellies during the breeding season. Belly coloration varies among mature females, and previous work has shown that nest-holding males prefer females with more colourful bellies. Because males invest heavily in offspring during incubation, the evolution of this preference can be explained if colourful females provide males with eggs of higher quality.3 - We tested this hypothesis by allowing males to spawn with &lsquo;colourful&rsquo; and &lsquo;drab&rsquo; females and comparing parameters including egg carotenoid concentration, clutch size, hatchability and larval viability between groups. We also investigated relationships between egg carotenoid concentration and clutch quality parameters.4 - Eggs from colourful females had significantly higher concentrations of total carotenoids than drab females, and photographically quantified belly coloration was a good predictor of egg carotenoid concentration. 5 - Colourful females produced slightly larger clutches, but female belly coloration was not related to any measure of clutch quality. In addition, there were no significant relationships between egg carotenoids and clutch quality. Females with high levels of egg carotenoids spawned slightly earlier, however, possibly because they were more ready to spawn or because of male mate choice.6 - Our results call into question the generality of a causal link between egg carotenoids and offspring quality.<br /