Adaptive significance of sex change in the stone loach (Nemachilus angorae)

Restocking fish species may be one way to overcome problems of overfishing or dwindling natural populations. To date, most restocking programs have failed. We believe that these failures are, in part, due to the sparse, uniform rearing environment that fails to teach the fish about heterogeneity. We report experiments in which the early rearing environment of juvenile cod were manipulated to generate experience of environmental variability. We manipulated two key variables; food and spatial cues. We found that manipulations to either or both of these cues had effects on a number of behaviours and produced fish that varied in terms of boldness, stress recovery and the speed with which they were able to transfer from a diet of pellet food to natural prey.