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Using the Mud Crab (Scylla serrata) as an Indicator Species of the Effectiveness of Estuarine Marine Protected Areas

Paul Butcher, Steve Smith and Andrew Boulton

University of New England - National Marine Science Centre, ARMIDALE, AUSTRALIA

Theme: TH4

Marine parks have been formed to allow controlled access to users while conserving specific aspects of the environment. Marine park zoning, and in particular areas where fishing is excluded, has been seen as an effective way of managing populations which are vulnerable to overfishing. The Solitary Islands Marine Park is located on the mid-north coast of New South Wales. Some zoning schemes within the Park were allocated in the absence of adequate scientific data. The main objective of this study is to determine the effectiveness of estuarine marine park zones using abundance, gender, size-class and recruitment of mud crabs as indicators. This will be achieved by sampling mud crab populations in adjacent fished and unfished zoning sites in three estuaries (Sandon, Wooli and Red Rock). These estuaries will then be manipulated by providing fishing pressure (depletion) in currently-protected sites and protection in currently-fished sites. The Wooli River has two types of marine park zones providing for a variety of uses. The Sanctuary Zone has excluded fishing since 1991 whereas the Recreation Zone is heavily fished by recreational fishers. Mud crab populations have been sampled monthly in each zone from December 1998 using commercial wire traps. Each mud crab was tagged and assessed to determine carapace width and length, and gender type. The results so far suggest that the Sanctuary Zone in the Wooli River has been an effective management tool, as it contains significantly higher abundances and larger size-classes of crabs and provides a recruitment source into the fished Recreation Zone.