Characteristics of traditional dugong and green turtle fisheries in Torres Strait: opportunities for management. This data forms part of a PhD thesis which aimed to inform the development of management arrangements for the traditional dugong and green turtle fisheries in Torres Strait, and to provide an overall context for management at different special scales and investigating opportunities and challenges associated with co-management, particularly community-based monitoring.

This entry describes a GBRMPA Workshop Presentation on the status of dugong in the Torres Strait. Refer to the compiled report: Marsh, H.L. And Saalfeld. K. (1991) Status of Dugong in Torres Strait. In: D. Lawrence and T. Cansfield-Smith (eds) Sustainable development for traditional inhabitants of the Torres Strait region. Proceedings of the Torres Strait Baseline Study Conference. Kewarra Beach, Cairns, QLD, 19-23 November 1990. GBRMPA Workshop Series 16 : 187-194.

This project fills a critical information gap for dugong and turtle habitat management in the Torres Strait. It describes seagrasses in a recently identified data deficient region in northern Torres Strait that contains large dugong and turtle populations and is the subject of a proposed extension of the existing Dugong Sanctuary. The baseline assessments will form the foundation for ongoing monitoring, and provide essential information to the TSRA, Australian and Queensland governments for dugong and turtle management plans, complimenting dugong and turtle research studies in the region and building skills and capacity of Traditional Owners and Rangers.

The referenced report is presented in two sections. The first section reports on the results of a third survey of dugong distribution and abundance in Torres Strait conducted over four days in November 1996. The second section estimates the size of a sustainable dugong catch in Torres Strait using the Potential Biological Removal Method (PBR). The sustainability of the dugong fishery is then evaluated by comparing aerial survey estimates of the size of the dugong population in 1987, 1991 and 1996, and catch statistics from the Torres Strait Protected Zone (TSPZ) since 1991 in the context of current knowledge of dugong life history parameters.

Fishery Assessment Report (1994) on the Dugong Fishery in the Torres Strait. Compiled by H. Marsh and edited by the Southern Bluefin Tuna Fishery Stock Assessment Group, for AFMA: Marsh, H. (1995) The Torres Strait Dugong Fishery 1994, Fisheries Assessment Report, edited by the Southern Bluefin Tuna Fishery Stock Assessment Group. Australian Fisheries Management Authority, Canberra. 14pp.

This project will improve the accuracy of aerial survey estimates of the size and distribution of dugong and green turtle populations in western and central Torres Strait by: (1) collecting and analysing data on their movements and diving behaviour, and (2) estimating the proportion of turtles seen during aerial surveys that are the large female green turtles harvested by Indigenous hunters. These data will then be used to (re)estimate the size and distribution of the populations of dugongs and harvestable green turtles in Torres Strait by (re) analysing historical aerial survey data collected in 2001, 2005, 2006, 2011 and 2013.

This dataset describes seagrass at 34 individual meadows from surveys of Dugong and Turtle habitats in the North-West Torres Strait for November 2015 and January 2016. The data includes information on seagrass species, biomass, diversity, and BMI and algae percent cover. This meadow (polygon) layer provides summary information for all survey sites within the 34 individual seagrass meadows mapped in 2015-2016 with information including individual meadow ID, meadow location (intertidal/shallow subtidal/subtidal), meadow density based on mean biomass, meadow area, dominant seagrass species, seagrass species present, survey dates, survey method, and data custodian. ESRI and Landsat satellite image basemaps were used as background source data to check meadow and site boundaries, and re-map where required. The data described by this record is current as of 01/12/2016 for use in the Seamap Australia project. Newer versions of the data, additional 'point' data for 853 sites, and alternative download formats are available from eAtlas. http://eatlas.org.au/geonetwork/srv/eng/metadata.show?uuid=034ce816-0777-4bbd-aefc-8b73bd540245

This dataset shows (1) a raster spatial model of the distribution and relative density of dugongs (Dugong dugong) in the Torres Strait region based on an aggregate of 27 years (1987 - 2013) of systematic aerial surveys; and (2) a raster spatial model of the distribution and relative density of marine turtles (green turtles, Chelonia mydas) in the Torres Strait based on an aerial survey conducted in 2013. Aerial surveys were conducted using the strip transect method described by Marsh and Sinclair (1989). The survey region was divided into blocks containing systematic transects of varying length, which were typically perpendicular to the coast across the depth gradient. Tandem teams with two observers on each side of the aircraft independently recorded sightings of dugongs and marine turtles, including information on group size and calf numbers. Transects were 200 m wide at the water’s surface on either side of the aircraft. For the dugong spatial model, spatial data from all the aerial surveys in the region (1987, 1991, 1996, 2001, 2006, 2011, and 2013) were corrected for differences in sampling intensity and area sampled between surveys. For details on sampling intensities and areas, please refer to the reports and publications for each individual survey (list below). For the turtle model, spatial data were used from the survey conducted in 2013. The corrected data were then interpolated using universal kriging over the spatial extent of the aerial surveys. Planning units were 2km * 2km and were classified as low (1), medium (2), high (3) and very high (4) dugong/turtle density on the basis of the relative density of dugongs and turtles estimated from the models and a frequency analysis. Low density areas: 0 animals per square km; medium density areas 0.0015 - 0.25 animals per square km; high density areas 0.25 - 0.5 animals per square km; very high density areas > 0.5 animals per square km. Note: A project is currently under way (funded by AMMC) to create an integrated database for all aerial survey data which will host raw data. Limitations: The modelled abundance and distribution in this dataset shows the relative density of dugongs and turtles (areas where there are more or less animals). It does NOT show the absolute dugong and turtle density. The observations only count a small percentage of the total number of dugongs. Some dugongs will be missed by the observers in the survey plane (perception bias) and some dugongs will be diving and can't be seen due to water turbidity (availability bias). Corrections for these under estimates can only be estimated at the spatial scale of entire surveys (thousands of square kilometres) and so when they are allied to the dataset they are assumed to be constant over the entire survey area. However these correction factors would vary spatially and the absolute numbers of the dugongs at the fine scale of this dataset (in a small area) are unlikely to be accurate. Nonetheless, the relative densities among regions should be approximately comparable (H. Marsh, personal communication). Format: The spatial model is 794x680 pixels with a spatial reference of WGS84 UTM Zone 54S. The original dataset is stored in ESRI GRID format (60 KB), which was converted to a GeoTiff for use in the eAtlas (22 kB). The GeoTiff was then converted to a shapefile. Publications for aerial surveys in the Torres Strait: Marsh, H, Harris, ANM, & Lawler, IR. (1997) The sustainability of the Indigenous dugong fishery in Torres Strait, Australia/Papua New Guinea. Conservation Biology 11:1375-1386. Marsh, H, Lawler, IR, Kwan, D, Delean, S, Pollock, K, & Alldredge, M. (2004). Aerial surveys and the potential biological removal technique indicate that the Torres Strait dugong fishery is unsustainable. Animal Conservation 7: 435-443. Marsh, H.D., Hodgson, A., Lawler, I., Grech, A., & Delean, S. (2007) Condition, status, and trends and projected futures of the dugong in the Northern Great Barrier Reef and Torres Strait;