Densities of fishes, macroinvertebrates, plants and corals on subtidal rocky reefs within the Jurien Bay Marine Park (JBMP) were surveyed in 1999, 2000 and 2003. These surveys utilised similar techniques to those used in Tasmania, New South Wales and Victoria during the same period as part of a wider-scale study of the effectiveness of marine protected areas (MPAs). Reefs investigated included moderately-exposed inshore reefs but not the deeper and more exposed outer reefs because no such reefs are included as sanctuary zones within the MPA zoning scheme. The flora and fauna at different sites generally exhibited a low level of change between years compared to variation between sites. With the exception of somewhat anomalous sites in the north near Fishermans Island, the biotic composition of sites was interspersed with respect to the three major MPA management zones – sanctuary, scientific reference and general use, with no zone possessing a predominance of one particular biotic assemblage type. Thus, data collected encompassed the range of variability within zones, allowing comparative analysis of change through time. Because a wide range of species have been examined, ecosystem shifts as well as changes in the abundance of target species will be detectable following the protection of areas from fishing. The selection of between 7 and 9 sites within each management zone appears to provide sufficient replication to detect biologically meaningful change for the species examined. Nevertheless, to restore a fully balanced design following slight changes to the management zone locations originally proposed, we suggest that an additional two sites in sanctuary zones are monitored in future. Additional sites should be located in the large sanctuary zone immediately south of Jurien Bay if reefs of sufficient size to encompass 200 m long transect lines can be found in that area, which is presently unmonitored. Analysis of the three years of baseline data indicated no significant differences between zones in number of fishes, macro-invertebrate or plant taxa per 50 m transect. These species richness variates were also similar between years for fishes and macro-invertebrates; however, minor differences in species richness of plants between years were evident, probably because observer experience affected how systematically across different management zones, hence should not affect detection of differences between zones. Once fishing restrictions pertaining to different management zones are adequately enforced, surveys should be repeated on an annual basis until differences between zones stabilise. Such a monitoring scheme would not only provide time-series information on trends in the abundance of species of interest in different management zones, but also information on indirect impacts of both rock lobster fishing and general recreational and commercial fishing on ecosystems, and regional changes associated with such factors as climate change. We recommend: • Surveys be repeated on an annual basis until biotic changes associated with MPA protection stabilise • At least one sanctuary zone be extended to the outer reef region to protect the full range of biodiversity within JBMP • Commencement of monitoring of the outer reef region • Commencement of monitoring at two additional sites in sanctuary zones, preferably within the large sanctuary zone located immediately southwest of Jurien Bay township.
Edgar G.J., Barrett N.S., Bancroft K.
Tasmanian Aquaculture and Fisheries Internal Report