Project 8.3 'Significance of no-take marine protected areas to regional recruitment and population persistence on the Great Barrier Reef'

Led by: Professor Geoffrey Jones, James Cook University

Our recent four-year MTSRF project demonstrated significant export of larvae of the inshore coral trout species (Plectropomus maculatus) from existing no-take marine reserves (green zones) in the Keppel Island group on the Great Barrier Reef (GBR). In addition, no-take reserves were shown to make a disproportionately large contribution to recruitment in fished areas (blue zones) at this location. These significant findings were revealed by a unique combination of genetic analysis of parent-offspring relationships and biophysical dispersal modeling. While these previous results provided crucial support for green zones as an effective conservation and fisheries management tool, the scale over which reserves benefit fisheries through recruitment subsidies and the degree to which reserves contribute to long-term population persistence have yet to be evaluated. To understand how marine reserve networks function in a larger conservation and fisheries framework, it is vital to extend the study beyond the Keppel Island group and to include the more important commercially exploited coral trout species (P. leopardus). The expansion of the project will permit us to describe patterns of dispersal on larger regional scales and to assess how marine reserves contribute to population persistence over future generations.

The overall goal of this project will be to apply genetic parentage analysis and biophysical modeling, to assess larval dispersal patterns, demographic connectivity and levels of recruitment subsidies from green zones at a regional scale. The project will employ meta-population modeling to extend predictions over multiple generations. Specifically, our target objectives are to:

Provide empirical estimates of recruitment subsidies for both P. maculatus and P. leopardus over a >200 km scale on the southern GBR, quantifying larval retention within and connectivity among inshore (Keppel Islands, Percy and Duke Islands) and offshore reefs (Capricorn-Bunker Group);
Refine the existing biophysical model for this region to take account of new information on coral trout larval behaviour, larval sensory abilities and availability of critical recruitment habitat to better predict regional recruitment patterns; and
Compare observed patterns of larval dispersal from parentage studies and predicted patterns of larval dispersal from the biophysical model, and use both approaches to evaluate strengths and weakness of the existing marine reserve network for the target species.
Develop spatially explicit meta-population models that incorporate real data on larval dispersal to evaluate the effects of reserve network design, differential production in reserves and fishing pressure outside reserves on long-term population persistence.

Project objectives at a glance (Year 1)

Develop a new set of hyper-variable microsatellites for P. maculatus and P. leopardus for examining parent-offspring relationships. If possible, test parentage assignments from hatchery-reared P. leopardus.
Carry out field studies on hatchery-reared P. leopardus larvae of different ages to quantify depth preferences, swimming speed and orientation, and habitat selection.
Refine the existing biophysical model to apply new information on coral trout larval behaviour, fix discrepancies in reef locations, modify reef detection distance and incorporate knowledge of suitable recruitment habitat.
Conduct sampling of tissues of adult and juvenile P. maculatus and P. leopardus from green zones in the Keppel Islands, selected Percy and Duke Islands and a sub-set of the Capricorn-Bunker reefs (including Masthead, North Reef and One Tree). If possible, supplement sampling from recreational and commercial catches from blue zones.

Specific objectives and intended outputs of this Project are detailed in the NERP TE Hub Multi-Year Research Plan.

Project Factsheet