Ecosystem monitoring in different management zones within the Jurien Bay Marine Park - results of 2004 surveys.


Densities of fishes, macroinvertebrates, corals and plants on subtidal rocky reefs within the Jurien Bay Marine Park (JBMP) were surveyed at 42 sites in October and November 2004. At the time of survey, JBMP had been created but legislation to implement the zoning scheme and hence enforce fishing restrictions was not in place. Survey data obtained in 2004 thus represent baseline conditions. Monitoring surveys utilised the same underwater visual census techniques as used in monitoring programmes operating concurrently in Tasmania, New South Wales, South Australia and Victoria, forming part of a continental-scale study of the effectiveness of marine protected areas (MPAs). Twenty-five JBMP sites had been censused previously in 1999, 2000 and 2003, providing a detailed time series of baseline data. Following recommendations outlined in the 2003 report (Edgar et al. 2003), the monitoring program was considerably expanded in 2004 to encompass additional sites in the outer reef region and in inshore sanctuary zones, and data on rock lobsters were obtained from eight rather than four 50 m x 1 m transect blocks at each site. The flora and fauna at different sites generally exhibited a low level of change between years compared to variation between sites. With a few exceptions, the biotic composition of sites was generally 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. The exceptions were a lack of deep reef sites located in sanctuary zones (none are included in the zoning plan), and somewhat anomalous sanctuary zone sites in the north near Fishermans Island and inshore opposite Boullanger Island (south of Island Point) that could not be paired in other zone types. Regardless, data collected encompassed most of the range of variability within zones, allowing unambiguous analysis of change through time. Because a wide range of species have been examined, ecosystem shifts as well as changes in the abundance of targeted fishery species will be detectable following the protection of areas from fishing, other than ecosystem impacts caused by rock lobsters on deeper reefs. The selection of 14 sites within each management zone provides sufficient replication to detect biologically meaningful change for common species and species richness indicators. Any future change in species richness per site of 2 taxa would be evident as a significant effect, as would a doubling in rock lobster numbers within sanctuary zones relative to other fished 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 effects associated with such factors as climate change. We recommend: •Baseline data on algal and sessile faunal assemblages be obtained from sites 31, 33, 34, 40 and 41 as a high priority in 2005 •Surveys of fishes and mobile invertebrates be repeated on an annual basis, and surveys of plant assemblages be conducted on a biennial basis, until biotic changes associated with MPA protection stabilise •At least one sanctuary zone be extended to the outer reef region to fully protect the full range of biodiversity within JBMP. Additional sites within this new zone should then be monitored


Edgar G. J., Barrett N.S., Bancroft K., Brook J., Crane K




Tasmanian Aquaculture and Fisheries Technical Report Series

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