Deeper water fish and benthic surveys
in the Lord Howe Island Marine Park: February 2004

Recommendations

The benthic communities of the hard and soft seafloors identified on the shelf appear quite rich and to be well represented in the Commonwealth Sanctuary Zone east of Lord Howe Island. These habitats should be investigated more closely at finer taxonomic resolution to determine their biodiversity. This would place their conservation value in context with the shallow water habitats of this seamount and the habitats of other seamounts to the north and regionally. This could be achieved in suitable sea conditions with remotely operated vehicle (ROV) and a high-resolution digital still camera. The still camera should be mounted to drop and take photographs with flash illumination in a vertical plane above the substrata, whilst the ROV provides a controlled perspective at wider horizontal and vertical scales. The Lord Howe Island Marine Park Manager has a suitable ROV and support vessel and efforts should be made to coordinate State and Commonwealth interests to utilise this resource. The unreliable weather dictates an opportunistic approach employing on-site resources.

Due to the constraints of bad weather, no work was undertaken in the Sanctuary Zone south of Balls Pyramid and we can provide no information on its habitats. The work around South East Rock in the proposed State Sanctuary Zone identified numerous hard corals but the spatial extent of this habitat and the species composition of its inhabitants should be addressed by ROV surveys at suitable spatial scales.

There is scant knowledge on the status of populations of endemic marine fauna and flora, but the small size of the shelf habitat on the rises means that the fine-scale description of their abundance and distribution is a tractable problem with appropriate survey techniques. If the habitat preferences of animals such as endemic fishes can be ascertained, then the geographical extent of the various habitats favoured by such fish could be mapped with a towed camera array. Other species of interest to the island consumers, like kingfish, rosy jobfish and redfish, might be counted directly in the complex shelf slope depths using a combination of hydroacoustics ground-truthed with towed camera array (with lights).

Baited video techniques are also useful in these habitats, provided that appropriate lighting and an acoustic-release system are used. The existing BRUVS design could be used more intensively on the shelf, where the problems associated with snagging of hauling ropes and sinking of buoys in strong currents can be managed. The fish fauna of the gorgonian gardens on the deeper slopes and shelf break should be described with this combination of techniques. BRUVS could also be used to monitor the effectiveness of the Sanctuary Zones.

The Galapagos whaler shark, Carcharhinus galapagensis, was numerically abundant and ubiquitous. Its close association with oceanic shoals, including marine reserves north of Lord Howe, indicate that it may be well catered for in terms of habitat protection. From a scientific viewpoint, there are intriguing questions concerning the food webs supporting such a large biomass of sharks, and the location of predator aggregations in the deep, dark waters of the shelf drop-off. Some charter operators proposed to us that these predators are intercepting the schools of ommastrephid arrow squid that move across the shelf break between dusk and dawn. They also mentioned the role of seasonally occurring schools of slimy mackerel (Scomber australasicus) as a food source for kingfish, and that these schools had declined in the past decade. Slimy mackerel schools (but no squid) were seen on some towed videos.

Underwater footage from this rapid ecological assessment was shown in the full island community hall to members of the local community, Lord Howe Island Board, NSW Marine Park manager, charter boat operators and visitors to the island. This use of video footage is a useful conduit to trigger ownership of future studies by islanders. Our presentation prompted the park users to volunteer their own conclusions and sharpened our interpretations by making comment informed by their experience. Future studies should capitalise on the use of video tools to help the islanders and park users “own” new research and management plans, and further promote their involvement.

December 18, 2008