Is artificial habitat diversity a key to restoring nurseries for juvenile coastal fish? Ex situ experiments on habitat selection and survival of juvenile seabreams

Man‐made infrastructures have become ubiquitous components of coastal landscapes, leading to habitat modification that affects the abundance and diversity of marine organisms. Marine coastal fish have a complex life cycle requiring different essential habitats. One of these habitats is known as a nursery, a place where juveniles can settle in large numbers, survive, and grow to contribute to the adult population. Nurseries are mainly found in shallow, sheltered zones and are thus particularly impacted by urbanization, notably by harbors. The vertical featureless structure of docks is very unlikely to be used by juveniles, which need complex habitats to find food and shelter from predators. Recent attempts to rehabilitate the nursery function in such environments by using artificial habitats have proven efficient in increasing juvenile densities. However, nothing is known about the survival of juveniles in these habitats, preventing any conclusions on the effectiveness of this means of restoration from being drawn. Here, we set up tank experiments to test the relationship between habitat preferences and the survival rate of two species of seabream when facing stalk‐attacking combers. Habitat choice was consistent with survival results, indicating that artificial habitats might not represent unintended ecological traps for juveniles. However, the artificial habitats' effect on survival was variable between species. Therefore, our results suggest that habitat diversity might be of prime importance to sustain juveniles of different species and stress the need for the development of diverse artificial habitats to counteract the effects of seascape homogenization.