Assessing changes in Black Rockcod abundance and size

Despite having been protected from fishing in NSW since 1984, Black Rockcod are still caught (although must be immediately released), can die post-release from embolism, and are sometimes illegally taken. Long-term population monitoring is a high priority identified by the species’ recovery plan and the NSW Fisheries Scientific Committee.

In 2010, a broadscale baseline survey (81 sites) was undertaken in northern NSW and Lord Howe Island, followed by smaller surveys every four to five years. This hub project will repeat the initial baseline survey, contributing to a 13-year time series that shows whether Black Rockcod are increasing in abundance, becoming larger, and/or becoming more widespread. All these indicators can be used to assess the effectiveness of recovery actions such as marine protected area sanctuary zones.

Approach

The survey will apply methods established by the New South Wales Department of Primary Industries (NSW DPI), with two divers using stereo video cameras to enable accurate length measurements. This ‘timed swim’ method suits Black Rockcod surveys because it allows divers to thoroughly search habitats such as caves and overhangs. Key sites focus on populations in four NSW marine parks known to contain the highest Black Rockcod abundance (Port Stephens-Great Lakes Marine Park, Solitary Islands Marine Park, Cape Byron Marine Park and Lord Howe Island Marine Park).

The survey results will indicate whether Black Rockcod:

• are increasing in abundance at key sites through time;
• size structure now includes a higher proportion of bigger individuals (given they are protogynous hermaphrodites that change sex at a length of one metre and that none at near-to-expected maximum length have been recorded in surveys); and
• are becoming more widely spread on reefs in northern New South Wales and Lord Howe Island.
• Increases in these indicators will suggest recovery, whereas a lack of increase will indicate a lack of recovery. Increases in all three indicators will provide confidence that current management actions are leading to recovery of this threatened species.

Indigenous engagement: capacity building, training and employment

The project team will collaborate with several Indigenous organisations and build on existing partnerships established with the NSW Government. Sea-time experience and on-water training will be provided to four Gumbaynggirr and one Yaegl coxswain trainees. Bundjalung Arakwaal rangers will gain experience on survey vessels in Cape Byron Marine Park.

This capacity building is supported through NSW Marine Estate Management Strategy and coordinated through the Coffs Harbour and District Local Aboriginal Land Council (Garby Elders rangers program) and the Yaegl Local Aboriginal Land Council. Hours of work undertaken by the trainee coxswains are paid for through the NSW Marine Estate Management Strategy.

Opportunities will be sought to build shared understanding about reciprocal benefits of the project, and to develop appropriate research agreements and processes for communicating research findings.

Expected outcomes

The findings of this project will support decision-making under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and the New South Wales Fisheries Management Act 1994.

Commonwealth and state marine park managers and threatened species managers will have an improved evidence base for assessing the success of species recovery actions. This includes ensuring the effective protection of Black Rockcod in marine parks through sanctuary zones, management of hook and line fishing, and reassessments of population status and conservation listings.

Project location

Survey sites will be in northern NSW, Solitary Islands Marine Park, Port Stephens-Great Lakes Marine Park and Lord Howe Island Marine Park.