Artificial fish nurseries can restore certain nursery characteristics in marine urban habitats

Port areas are subjected to multiple anthropic pressures that directly impact residing marine communities and deprive them of most of their essential ecological functions. Several global projects aim to rehabilitate certain ecosystem functions in port areas, such as a fish nursery function, by installing artificial fish nurseries (AFN). In theory, AFNs increase fish biodiversity and juvenile fish abundance in port areas, but studies on this subject remain scarce. Thus, the present study aimed to examine whether the use of such AFNs could restore part of the nursery function of natural habitats by increasing fish and juvenile abundance, and by decreasing predation intensity compared to bare docks. Two years of monitoring on AFNs showed they hosted 2.1 times more fish than on control docks and up to 2.4 more fish juveniles. Fish community structures were influenced by both treatment (AFN and Control) and year of monitoring. In general, AFNs hosted a greater taxonomic diversity of fish than controls. The predation intensity around these structures was significantly lower in the AFNs than in controls. Part of the definition of a fish nursery was thus verified, indicating that AFNs might be an effective restoration tool. However, we also noted that total fish abundance and Young of the Year (YOY) abundance decreased in controls, possibly due to a concentration effect. Further detailed monitoring is necessary to distinguish between these effects.

Automated summary

Port areas are under multiple anthropic pressures that directly affect marine communities and deprive them of essential ecological functions. The use of artificial fish nurseries (AFNs) in these areas has the potential to restore part of the nursery function of natural habitats by increasing fish and juvenile abundance and reducing predation intensity. Two years of monitoring showed that AFNs hosted significantly more fish and fish juveniles compared to control docks. The taxonomic diversity of fish was also higher in AFNs, and predation intensity was lower. AFNs may be an effective restoration tool, but further monitoring is needed to understand potential concentration effects.