LEGISLATIVE VS. PRACTICAL PROTECTION OF AN INTERTIDAL SHORELINE IN SOUTHEASTERN AUSTRALIA

Abstract

Harvesting of intertidal biota is a concern in many areas of the world. While the published literature is focused on reports of strong impacts of subsistence harvesting, recreational collection of biota can also have a strong effect. In either case, the management of these impacts is a major concern and is most often done by complete or partial closures of sections of coastline. This management method may require ongoing intervention, in the form of policing, education, or construction of barriers, and it is important to identify the effectiveness of these actions. We have previously shown that physical closure of a section of rocky coastline in southeastern Australia resulted in increased mean sizes of a range of intertidal molluscs collected for food and bait. The shoreline in question had legislative protection and mechanical barriers, and we present data that demonstrate that the mechanical barrier was a critical component. Removal of barriers resulted in changes in mean sizes and abundance of some gastropods over a period of 5 yr. The two most heavily harvested species, Turbo undulatus and Cellana tramoserica, showed reductions in mean size of ∼15%, relative to nearby areas that had been exploited for many years, while two less harvested species, Austrocochlea constricta and Nerita atramentosa, showed no changes following opening of the former protected areas. Three control (i.e., nonharvested) species, Bembicium nanum, Lepsiella vinosa, and Cominella eburnea, continued to show no differences between harvesting categories. Abundance of these gastropods, measured by catch per unit effort (CPUE), declined for the two harvested species over the 5 yr following opening of the protected shores. For Cellana, CPUE fell at sites in the reserve from 36% above exploited areas to similar values; for Turbo, CPUE values at the time of opening were 200–300% higher in the protected areas, but then fell to match values for exploited shores. These results show that legislative protection, which applied to the entire coastline, is ineffective in this section of the Australian coast, and effective protection requires physical barriers to exclude humans, or greatly increased enforcement.