Update from the North West Shoals to Shore Research Program No Images? Click here Informing the sustainable development of Australia's North West marine estate Welcome to the quarterly newsletter from the North West Shoals to Shore research program. Produced by the Australian Institute of Marine Science, this bulletin provides updates on activities within the three-year program. In this edition:
What's happening?World First Marine Noise Experiment a SuccessThe Australian Institute of Marine Science has conducted the first real-world seismic experiment to determine the effects on fish and pearl oysters. The experiment, using the seismic vessel, the BGP Explorer, surveyed two sites off the northwest of Western Australia over ten days in September. The experiment, which has taken the collaborative efforts of more than 100 people 12 months to design and coordinate, could help to clarify some issues around marine noise. “This was always going to be a complex experiment and a great challenge in the planning,” AIMS Project Science Leader Dr Mark Meekan said. “I’m happy to say all went well and we can look forward to getting results that we can be confident in, and that could provide some science-based answers to the questions about the effects of seismic surveys on pearl oysters and fish.” What is Seismic Noise?Seismic surveys are used to produce images of the various geological layers and their location beneath the earth’s surface. The seismic vessel tows an array of airguns that use compressed air to produce acoustic energy. Sound waves penetrate the seabed and, depending on the depth and characteristics of the geological layers, are reflected back at different time intervals and intensity. Targets for Research and Study AreaPearl Oysters (Pinctada maxima)Western Australia’s pearling industry, valued at about $67 million in 2014, is largely based in Broome. It is the second most valuable fishing industry in the State after rock lobster. The offshore site selected for the pearl experiment was relatively close to Broome, 35 kilometres to the west, in 20 to 35 metres water depth. With the support of the Pearl Producers Association and the Paspaley Pearl Company, the AIMS study set out more than 10,000 pearl oysters in groups of about 1200 at different distances of up to six kilometres from the seismic vessel operation. After being exposed to the seismic sound, the pearl oysters were brought back to shore where some were sent to the laboratory and some were sent to grow out to determine if the sound has had any effect on their condition and growth. Others were seeded to test if exposure to seismic sound affects the ability of the oyster to produce market quality pearls. Demersal FishCommercial fisheries, which focus on demersal species across northern WA, are the most valuable finfish sector in the State, estimated to be worth more than $12 million annually. Red emperor were chosen as one of the key species for the study both because of their popularity as a commercial and recreational target and because of their resilience to being tagged and returned to the seabed. The experiment site for the fish study was located 90 kilometres off the Pilbara coast, between Karratha and Port Hedland, in an area that has been closed to fishing since 2002. Researchers tagged 390 red emperor, which are commercially important and an indicator species for other demersal fish. The AIMS team are tracking the fish via an array of 96 acoustic receivers as well as using BRUVS© (Baited Remote Underwater Video Systems) to document their movements before, during and after exposure to the seismic sound. Mapping the Experiment SiteA significant part of the field work program involved preliminary studies ahead of the seismic vessel run to map out the experiment areas. The mapping work was conducted by acoustic scientists Dr Miles Parsons from AIMS and Associate Professor Rob McCauley from Curtin University (left), who is leading the analysis of the sound produced by the seismic survey. Threatened species of the North West projectTurtles spend 40 days at nesting beaches before migrating to foraging groundsTwenty hawksbill turtles and 20 green turtles were fitted with satellite transmitters at their nesting grounds early in the breeding season in order to get a first glimpse of the Western Australian population’s inter-nesting behaviour and migration to foraging grounds. The inter-nesting period is the period of time that marine turtles stay around the nesting beaches, when they come ashore about every two weeks to lay eggs. The results show that the turtles spent on average 40 days in and around the nesting beaches and up to 84 days before migrating to their foraging grounds, which are mostly further north. During the inter-nesting period, the core area that the turtles use is roughly 10 km2 (red areas on the maps above) around their nesting beaches, with hawksbills resting on the reef edge in between nesting events and greens staying nearer to the nesting beach. The hawksbill turtles nested every 13 days laying three clutches of eggs over the nesting season, while the greens laid five clutches every 18 days. It’s the first time that these parameters have been recorded for hawksbill and green turtles in WA and the results are in line with estimates from Queensland and around the world. On the horizonFunding provided by Quadrant Energy as part of Good Standing Agreement commitments. |