Zooplanktivory is a key process for fish production on a coastal artificial reef

Abstract

Artificial reefs continue to be deployed in coastal areas to enhance local fisheries. An important factor influencing the success of artificial reefs may be the provision of refuge for zooplanktivorous fishes, which use artificial reefs as a base to forage the surrounding zooplankton. A numerical model was developed to quantify this trophic pathway on a designed coastal artificial reef, using field-parameterised data for zooplankton biomass, current velocity, and the consumption rate and abundance of a reef-resident zooplanktivorous fish (Atypichthys strigatus). The model estimated that this species consumed 2.9 kg (1.0 g m-3) of zooplankton per day on this artificial reef, which represents only 0.35% of the total zooplankton biomass. The ability of this artificial reef to support 130 kg standing stock of this species suggests that the zooplankton pathway is a reliable mechanism for fish production. A second model explored the influence of reef size on zooplanktivorous fish densities and the supply of zooplankton required to sustain their consumption rate. As reef size increased, the ratio between the foraging volume and refuge volume declined, meaning that small reefs have lots of food and not much refuge, and large reefs can have lots of refuge but not enough food. This indicates that reef size can be manipulated to maximise fish abundance while avoiding food limitation. Reef size, shape, and orientation should be considered carefully during the planning of artificial reefs, as it can greatly influence the foraging of reef-resident zooplanktivorous fishes and thus influence the entire reef assemblage.