Settlement and recruitment of fish in mussel farms

Abstract

. Fish are thought to settle and recruit to shellfish and seaweed farms; however, there is little published evidence to support this assumption. Shellfish and seaweed farms increase structural complexity and epibiota productivity, which may attract settling fish larvae. In this study, fish settlement and recruitment patterns into 2 aquaculture habitats, mussel-kelp co-culture and mussel farm monoculture, were compared to 2 adjacent natural habitats, soft-sediment seafloor and rocky reef, within a settlement season. Standard monitoring units for the recruitment of fish (SMURFs) were used, as they are a common and reliable method for measuring temporal and spatial variability in fish settlement and recruitment among habitat types. The communities of fish species settling and recruiting to both sets of aquaculture and natural habitats were equivalent. This was most likely due to the artificial 3D structure of the mussel farm habitats functioning in a similar manner to the structural complexity of a rocky reef habitat. Further, there was indication that for at least the most abundant fish species, Fosterygion lapillum, the 2 aquaculture habitats were of sufficient quality to support growth from settlement to juvenile size classes (i.e. in mussel monoculture habitat 65% were newly settled in December, and 86% were of juvenile size class by February). Overall, these findings provide foundational quantitative evidence of the interactions that fish have with mussel farms and increases the understanding of restorative opportunities for aquaculture operations.