Open Ocean Monitoring in the Chagos Archipelago
The designation of the Chagos Marine Reserve, and subsequent closure of the tuna fisheries, in 2010 represented a significant step in the conservation of pelagic predators such as tuna and sharks. Many of these species are internationally threatened and large no-take MPAs like Chagos offer unique refuges from exploitation. However, solid evidence of the benefits afforded to these species is difficult to provide, with a lack of baseline information on distribution, movement, population health indices and aspects of basic species biology.
Fantastic footage of Sandes’ Seamount taken on the Chagos 2012 expedition using BRUV technology
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Video Copyright: University of Western Australia
Pelagic environments are often remote making it hard to deploy human teams or monitoring equipment. The species themselves can pose problems for monitoring as their roaming behaviour and patchy distribution create a ‘needle-in-a-haystack’ effect. ZSL’s Marine and Freshwater team, in collaboration with the University of Western Australia (UWA), are attempting to tackle some of these problems by developing and adapting novel and existing technologies to better apply them to the pelagic environment through our Open Ocean Monitoring project.
Building on recent video-based surveys using Stereo Baited Underwater Video Systems (BRUVS) during the 2012 Chagos expedition, where more than 150 seabed areas were filmed as a baseline assessment, ZSL and UWA will be developing pelagic monitoring systems for similar analysis – Stereo Imaging System for Shark and Tuna Assessment (SISSTAS). With project partners that also include Oxford University and St. Andrews University, preliminary trials in Australia will guide recommendations for establishing long-term monitoring within the marine reserve.
Six project areas exist to tackle different elements of our knowledge and technology gaps with non-destructive methods:
1. Monitoring the big blue: Identifying key locations and methods for monitoring tuna and sharks. A range of potential predictors of the location of pelagic fish species exist, on which historical and new data will be collated to prioritise future sampling locations, including assessment of aggregation around seamounts and determination of tuna-dependent seabird foraging sites through satellite tracking.
2. Pelagic mobile species monitoring: With a focus on Yellowfin tuna and Blue sharks, abundance and size data will be collected using the SISSTAS. Strategically deployed in varying locations they will be paired with conventional BRUVS on the seabed for a comprehensive picture of the region.
3. Tagging: To identify residency behaviour and use of topographical features by the targeted species satellite tags will be attached to tuna and sharks to demonstrate their movement over a 6 month period.
4. Acoustics: Use of acoustic technology (sonar) will map fish biomass across areas of interest and validated using imagery data from the cameras. This will focus not only on larger mid-water fish, but also plankton and small pelagic fish biomass.
5. Oceanography: Tuna and sharks can be temperature sensitive and often prefer oceanic frontal systems, information long used in the fishing industry. This project will use oceanographic and remote sensing data in the focal regions to add layers to our understanding of potential movements.
6. Communications: Blogs, photographs and videos will all be used to document and publicise the project outputs. Peer-reviewed papers and articles are expected to exchange scientific and technological advances made.