Ecological role and productive potential of a ∼30 years artificial reef - Southeastern Brazil

Artificial Reefs (ARs) increase the heterogeneity of areas that previously had homogeneous unconsolidated substrate, favoring the survival of juvenile fish by providing more anti-predation refuges. The efficacy of ARs to increase the abundance of fish and decrease the impacts of fisheries depends on their functionality as either attractors or producers of fish biomass. The present study sought to elucidate on the potential production role of a reef complex installed on the northern coast of Rio de Janeiro in 1996 besides the well-known attraction potential. Specifically, we aimed to compare the structure and composition of the ichthyoplankton community along a distance gradient from the ARs (0–1000 m). A total of 1941 ichthyoplankton specimens were sampled on dry and rainy seasons, including 13 families, 8 genera, and 11 species. During the rainy season, higher abundance of fish larvae was collected near the ARs, while in the dry season, ichthyoplankton was concentrated at greater distances from the reef complex. In both periods, fish eggs were mostly collected <100 m from the ARs. Newly hatched larvae predominated at 1000 m distance, mainly during the rainy season. The number of larvae in the pre-flexion stage was predominant at 0 m, mainly during the rainy season. The presence of eggs and the predominance of pre-flexion larvae in areas closer to the reef modules indicate that this reef is an important spawning site for various fish species. The results reinforce spatial distribution characteristics of fish larvae in the ARs area, also suggesting that these structures initially acted as fish attractors but are now functioning as biomass producers for some species, including commercial ones. The ARs, being no-fishing zones, can be an effective tool both for fisheries management and biodiversity conservation.