Implications of a zoned fishery management system for marine benthic communities

1. The impacts of trawls and dredges on marine benthic habitats and communities have been studied extensively, but mostly at small scales and over short time periods. To investigate the large-scale chronic impacts of towed fishing gears, zoned commercial fishery management systems allow comparison of habitats and communities between areas of seabed subjected to varying levels of towed-gear use. 2. The Inshore Potting Agreement (IPA) was implemented in 1978 to restrict the use of towed gears in inshore areas that had traditionally been used by static-gear (pot and net) fishers. We used scallop dredges to sample benthic communities at sites within and adjacent to the IPA area that had been subjected to four different commercial fishing regimes since the inception of the system. These were: (i) towed gears only, (ii) annual, seasonal towed-gear use, (iii) temporary towed-gear use but reverting to static-gear use 18-24 months prior to sampling, and (iv) static gears only. 3. There were no significant differences in the total species richness or biomass of benthic communities between sites under regimes (i) and (ii). There was significantly greater total species richness and biomass of benthic communities at sites under regimes (iii) and (iv) than at sites under regimes (i) and (ii). The benthic community biomass under regime (iv) was significantly greater than under all other regimes. 4. The IPA has maintained benthic species that are important for the settlement and survival of others. The cessation of towed-gear fishing for a period of greater than 2 years would be necessary for benthic communities in areas adjacent to the IPA to recover such that they were indistinguishable from areas where towed gears had not been used. 5. Synthesis and applications. Members of the fishing industry may object to the creation of permanent closed areas because harvestable stocks can move in space and time. This study indicates that zoned fishery management can allow some sectors of the fishing industry to retain access to fishery resources while protecting benthic species and habitats.