Temporal variation in fish communities on artificial reefs is stochastic and does not follow a traditional successional trajectory

The ecological succession of fish communities on offshore artificial reefs (ARs) may reveal ecosystem processes which underpin the sustainability of their fisheries. Traditional expectations suggest succession should consist of an initial colonisation by attracted planktivorous fish, followed by secondary species such as grazers and predators, developing finally to a relatively stable state. Yet the specific patterns of succession on ARs have not been quantified. Surveys of fish assemblages were conducted across 9 ARs in eastern Australia using multiple video techniques (baited remote underwater videos, remotely operated vehicles and drop cameras). Based on methodological and temporal differences, 7 of the ARs sampled were used for successional analysis. We found that fish communities on ARs change variably over time for up to 2 yr with no evidence of the expected traditional succession. All ARs showed continued community change and only 1 reef revealed a temporal increase in the number of species per sample and potential development to a stable community. Fine-scale monitoring revealed depth stratification of the fish community and establishment of smaller niche communities. Succession of fish communities on relatively small, isolated ARs is likely driven by stochastic connectivity to the surrounding natural reefs, oceanographic variation, the reef design and the known biases of observational methods.