Abstract

Artificial reefs are widely used to provide additional habitat for fishes; enhancing diving and fishing. Artificial reefs often have higher densities of predators that could affect nearby natural reefs, but there are few quantitative studies on how these reefs interact. This study focused on Aquarius Reef Base (ARB), an underwater habitat offshore of the Florida Keys, and 14 natural reef sites spanning 4 habitats, on the surrounding Conch Reef to examine the spatial subsidy needed to support the artificial reef food web. Fish biomass at each habitat was quantified via fish surveys and species were organized into functional groups. Using Ecopath and additional parameterization from previous research, food web models were created for ARB and the natural reef habitats. ARB’s food web was found to have a large predator biomass with insufficient prey biomass to sustain the population, suggesting that these predators must forage on nearby natural reefs where the predator/prey ratio is smaller. Between 0.57km2 and 1.79km2 of natural reef is estimated to be a sufficient spatial subsidy for the large predatory biomass at ARB when the biomass, as determined by the seascape around the artificial reef, is added. We are unaware of other studies using Ecopath to determine spatial subsidy required by an artificial reef, and further studies are needed to expand this work to other artificial reefs that vary in size and fishing pressure. The management implications suggest that the placement of future artificial reefs needs to balance the aim with potential impacts on nearby natural reefs.

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