Improved Sampling of Rock Lobster populations in Merri Marine Sanctuary and the role of habitat in MPA assessments

Parks Victoria has an extensive monitoring program across the system of Marine Protected Areas, which provides a stronger evidence base to better inform management decisions. Rock lobster have been identified as one important... [ view full abstract ]

Parks Victoria has an extensive monitoring program across the system of Marine Protected Areas, which provides a stronger evidence base to better inform management decisions. Rock lobster have been identified as one important indicator of the health of subtidal reefs and the effect of poaching in the Marine National Parks and Sanctuaries. Rock lobster are surveyed as part of the Subtidal Reef Monitoring Program (SRMP), however it has been difficult to accurately sample rock lobster populations as part of this program as monitoring sites often don’t overlap with rock lobster habitat. A pilot project was established to trial the use of standardised fisheries methods for sampling southern rock lobster (Jasus edwardsii) (SRL) in the Merri Marine Sanctuary, with a subsequent study to establish the relationship with seafloor characteristics or biological assemblages and SRL populations. This study integrated ultra-high resolution multibeam echo sounder data, videography and scientific fishing data to assess SRL populations within Merri Marine Sanctuary (MMS) and surrounding waters. Study results indicate that the MMS supports a higher abundance of both under-size and legal-size lobster, with larger mean size and biomass. The association with seafloor characteristics, biological habitat and distance from MPA was tested using GLM models. The results indicated that the MMS has a significant effect on local SRL population size, including with variations in depth, slope, rugosity and distance from park taken into consideration. Additionally, more SRL were captured closer to the park suggesting the potential of a spill-over of SRL biomass into surrounding waters. This research informed on the effects of protection, seafloor characteristics and biological habitat on a localised SRL population. It was demonstrated that remotely sensed techniques, combined with scientific fishing approaches, can be used to evaluate: the effectiveness of MPA management; the role these MPAs might play as reference sites for fisheries management; and potential secondary benefits of MPAs to the rock lobster fishery.