Integration of broodstock replenishment with community-based management to restore trochus fisheries

• Department of Agriculture, Forests, Fisheries and Meteorology, Samoa
• Fisheries Department, Vanuatu
• Department of Fisheries, Western Australia, Australia

The marine topshell Trochus niloticus, commonly called trochus, is a large conical-shaped herbivorous marine snail that occurs on shallow tropical reefs in the Indo-Pacific region. It is sought after for its shell, which possesses a thick mother-of-pearl layer that makes it useful for making buttons, inlays and ornaments. Trochus is an economically valuable resource for indigenous and artisanal fishers in the Indo-Pacific region. Since the 1920s, the species has been translocated to almost every island group in the Pacific Ocean. This extensive translocation has resulted in the establishment of substantial fisheries in many locations. However, the translocations did not always result in stock enhancement and sometimes had low success rates.

Research on the effectiveness of strategies for restocking trochus indicated it was feasible to use broodstock seeding as a tool to re-establish stocks on depleted sites or suitable sites where trochus are absent. To enhance the outcome and to ensure the success of broodstock stocking, community involvement is essential, operating in tandem with community-based management strategies such as customary marine tenure (CMT) in Vanuatu, village-based fisheries management in Samoa, and cooperative management arrangements involving traditional owners in the Kimberley region of Western Australia.

The project used broodstock seeding in tandem with community-based management strategies to facilitate the establishment of effective breeding populations of trochus on depleted reefs in Australia (Kimberley), Samoa and Vanuatu. The ultimate goal was to provide a simple framework to allow each responsible agency to implement a nationally coordinated and strategic stock management plan for establishing the respective trochus fisheries sustainably - through broodstock reseeding, the application of CMT and/or the establishment of marine protected areas (MPAs).

After first consulting local communities the country coordinators compiled a list of communities and reefs to be involved in the trochus broodstock seeding. They then held scoping meetings with the participating communities and government agencies to develop CMTs for the reefs involved. The CMTs were dependent on existing management arrangements, the customary practices of the community, and their plans and capabilities for management.

Country coordinators appointed a community coordinator for each participating community, and established management plans to initiate MPAs for sustainable fishing of the enhanced trochus stock as populations showed signs of replenishment.

The project team worked with community members to collect broodstock from the nearest reefs with healthy populations or purchased broodstock from nearby nations. In each country, three to four reefs received broodstock and a similar number of reefs were left untouched as controls.

The team monitored broodstock and controlled reefs, assessed the wild stock density and checked if populations of adults had become established on the reefs. They then identified within each reef site the habitat that appeared best for juvenile settlement and established plots for surveying juveniles. At regular intervals the team used strip transects to census the abundance of juvenile trochus and determine if recruitment had occurred.

The project team worked to successfully establish a framework for community consultation and involvement in activities to enhance broodstock seeding of trochus. The key to the success was the consultative approach taken by project staff and on-going training, negotiation, engagement and involvement of communities in the seeding work.

A major output was the establishment of MPAs at the Australian and Vanuatu project sites. In Samoa the project assisted in strengthening the community involvement in community-based fisheries management (CBFM). Whilst the Pacific island nations are familiar with the application of CMT and MPAs for coastal resources management, this is the first time an indigenous group in Australia has participated and fostered the establishment of MPAs to protect its natural resources.

In attempting to enhance stock on selected reefs, the results clearly indicated that MPAs are highly effective in protecting and enhancing the existing trochus fishery. The efficacy of MPAs is likely to be assisted on reefs where sufficient numbers of adult broodstock and favourable currents result in good levels of intrinsic recruitment. Additionally, in the Kimberley, where very strong tidal currents occur, extrinsic recruitment may affect trochus densities on adjacent reefs. Hence, the location of MPAs should take into consideration the possible impacts of both intrinsic and extrinsic recruitment.

The project team found that MPAs established in juvenile habitats can improve the density of adult trochus in adult habitats, providing the areas are closed for sufficiently long periods to allow the carrying capacity of juvenile areas to be met and thus allow migration to occur. It was found that the variability in trochus densities within and between treatments affected the capacity to detect changes, despite improvement on some reefs.

In Vanuatu MPAs were highly effective in protecting seeded broodstock and allowing recruitment to proceed. The researchers recorded enhancements in all broodstock seeding when compared with the control sites. Towards the end of the project, adult density in seeded sites has reached harvestable number.

In Samoa, broodstock were sighted in two of the three seeded sites in relatively low numbers, and were recorded both in and outside the survey areas. They were observed to move against the current and were believed to have moved rapidly out of the survey sites, but it was too early to report on sighting of juveniles in seeded reefs.

Ongoing support was provided to the Samoan and Vanuatu nodes of the project. They received training in field survey techniques, site selection, data analyses and interpretation, and hatchery activities. In Australia, seven staff from Kimberley Aquaculture Aboriginal Corporation (KAAC) and three students from Broome TAFE received training through their participation in field surveys. Additionally, all nodes applied the concept of using community coordinators as the focal point for training and interaction between project staff and communities. The capacity of community coordinators was strengthened and their understanding of the project work enhanced through this interaction.

Ongoing in-country dissemination of results continued during the course of field work. All three countries are now briefing the communities involved in the project work through regular meetings and participation in the project field work. In the Australian node, KAAC disseminated project information via its quarterly KAAC Newsletter, which is available on its website: www.kaac.org.au.