Becker, A., Lowry, M., Taylor, M. and Folpp, H., 2017. Assessment of the Sydney offshore artificial reef.  NSW DPI Fisheries Final Report Series No. 155 (PDF 3.5 MB), 103p.

Summary

The Sydney offshore artificial reef was the first deployed in offshore waters of NSW. The Department of Primary Industries, in partnership with academic institutions, undertook a detailed pre-deployment planning phase, and following placement of the structure, conducted a series of scientific monitoring programs, lasting up to 4 years. Outcomes of the research projects have been published in the peer reviewed literature; however the objective of this report was to bring both the planning and post-deployment research together in a single document, highlighting the procedures undertaken by DPI when deploying reefs.

Planning of the artificial reef was comprehensive; this report details the constraint mapping exercise, risk analysis and environmental assessment conducted by DPI. Information such as this is normally difficult to access, yet the approach taken by DPI can be considered ‘best practice’, by publishing this information it is hoped other agencies may adopt similar methods.

Post deployment research primarily focused on the response of fish. A 4 year monitoring program using stereo-BRUVs revealed that the fish assemblage on the artificial reef underwent significant temporal change, but remained distinct from nearby natural reefs. However, it still harboured species of key recreational importance at sizes available for recreational harvest. Pelagic fish have a close spatial association with the structure, and recreational species were observed in the water column around the reef. Acoustic telemetry showed benthic fishes had high residency on the reef, but at times moved to nearby natural reefs and further afield.

Use of the artificial reef by recreational anglers was monitored using shore based cameras. Fishing effort at the reef was significantly greater than comparable large estuaries from where comparable effort data is available. The numbers of fishers using the reef showed seasonal patterns, with less effort during winter periods.

Finally, modelling the productivity on the reef showed that zooplankton was by far the greatest contributor to this production. This work also revealed that simply increasing the size of a structure may not simply increase the biomass of zooplankton feeding fishes, as this simply increases refuge area, not the foraging zone required by these fish to feed.