Structural and social enrichment: effects on the morphology of a tropical hatchery fish

Abstract

Hatchery tanks offer conditions completely different from th e natural environment, with a high degree of environmental homogeneity. As a result, for some species, farmed fish can be morphologically distinct from their wild counterparts and the populations can be morphologically less diverse. To minimize the effects of the homogeneity, the environmental enrichment of tanks can be proposed as a way of resembling natural conditions. In this study we evaluated two types of enrichment: structural, which was performed by adding submerged logs (tree trunks) and artificial aquatic plants to increase environmental complexity; and social, which was accomplished by the simultaneous farming of two species in one pond to increase the degree of ecological interactions. The aim was to test whether social and structural enrichment o f hatchery tanks modifies the morphology and anatomical variability of curimba Prochilodus lineatus . The results showed that both types of enrichment led to morphological divergence, however social enrichment had a bigger effect, increasing morphological v ariability and diluting the effect of structural enrichment. Therefore, the simultaneous farming of two or more species can constitute a simple tool for hatchery fish management, to increase population morphological variability and potentially increase the chances for survival after release into the natural environment.