Megafauna interactions

Clive R. McMahon, Fabrice Jaine and Rob Harcourt

IMOS Animal Tracking Facility, Sydney Institute of Marine Science

Animals collecting hydrographic observations have advanced our understanding of the world’s oceans and the behaviour of its top predators. Technological advancements in instrument design, data compression and data transmission have made accessible data previously unavailable, but crucially important to oceanographic, climate and ecology studies. IMOS coordinates the collection and delivery of marine measurements collected by platforms deployed on animals from Australia’s marine estate into the broader Global Ocean Observing System (GOOS). These animal-borne observations are a cost-effective and complementary capability to for monitoring essential ocean variables (EOV), essential climate variables (ECV) and essential biodiversity variables (EBV). IMOS makes these quality-controlled observations freely available to the operational, research and industrial communities in near real time and in delayed mode. Here we describe in brief the procedures for (1) calibrating animal borne CTD profilers pre-deployment, (2) location quality control, (3) and real-time and delayed mode quality control of for vertical temperature salinity (T-S) profiles.

Fabrice Jaine, Phil McDowall, Francisca Maron, Charlie Huveneers, Rob Harcourt

IMOS Animal Tracking Facility, Sydney Institute of Marine Science

Over the last 15 years, the Animal Tracking Facility of Australia’s Integrated Marine Observing System (IMOS, www.imos.org.au) has collected data on the movements and presence of commercially and recreationally important aquatic species as well as species of conservation concern, using a continental acoustic telemetry network. Over 9,885 transmitters have been deployed on 154 marine species and tracked over a range of scales from hundreds of metres to thousands of kilometres. The receiver network includes a permanent array of IMOS acoustic receivers, complemented by hundreds of receivers owned and deployed by co-investment partners, with all resulting data centralised into a national database owned and managed by IMOS for the community. Much of this work has derived from, or been driven by, state fisheries agencies’ needs. In recent years, the IMOS Animal Tracking Facility has focused on optimising the continental tracking network to increase its relevance for fisheries management and opportunities to integrate with industry. As marine environments continue to change, understanding the occurrence and movement of marine species and populations will be crucial to effective and sustainable management. The IMOS Animal Tracking Facility plays a strategic role in coordinating efforts to monitor marine species of national relevance across jurisdictions.

Paul G. Thomson, Richard Pillans, Fabrice Jaine, Robert G. Harcourt, Michael D. Taylor, Charitha B. Pattiaratchi, Dianne L. McLean

Ocean Graduate School and The UWA Oceans Institute, The University of Western Australia

Subsea infrastructure of the oil and gas industry attracts commercial fish species as well as megafauna including sea lions, turtles, sharks and whales. Potential impacts of this attraction, whether positive or negative, are unknown. As a pilot study, we deployed acoustic telemetry equipment around offshore infrastructure to assess its effectiveness in detecting tagged marine animals and to gain insights into patterns of megafauna occurrence around these structures. Acoustic receivers were placed around four oil and gas platforms and on two remotely operated vehicles (ROVs) on Australia’s North West Shelf. Two whale sharks (Rhincodon typus) tagged in the World Heritage Ningaloo Reef Marine Park were detected at two platforms, North Rankin A and Pluto, located up to 340 km to the north. The shark at North Rankin A was detected infrequently and only 15 times over ~6 weeks. The shark at Pluto was detected each day of the 24-day deployment, in total 4894 times. Detections at Pluto platform were highest during the day, with peaks at dusk and dawn. Our study indicates that acoustic telemetry around platforms may be an effective method for understanding how marine megafauna utilise these structures. We recommend collaborating with industry to undertake receiver detection range testing to understand the effectiveness of the method. Furthermore, future studies should co-occur with tagging programs at sites like Ningaloo Reef and around the structures themselves to maximise the probability of detecting animals at these sites, thereby improving our understanding of how marine megafauna interact with these structures.

Luciana C. Ferreira, Michele Thums, Scott Whiting, Mark Meekan, Virginia Andrews-Goff, Catherine R. M. Attard, Kerstin Bilgmann, Mike Double, Fabio Falchi, Michael Guinea, Sharyn Hickey,  Curt Jenner, Micheline Jenner, Graham Loewenthal, Luciana Moller, Brad Norman, Kellie Pendoley, Ben Radford, Samantha Reynolds, Jason Rossendell, Tony Tucker, David Waayers, Sabrina Fossette

Australian Institute of Marine Science

As the use of coastal and offshore environments by humans expands, there is an urgent need for a better understanding of the exposure of marine megafauna populations to anthropogenic threats to direct management prioritization. Here, we document distributions of threatened and migratory marine megafauna using satellite telemetry data from 302 individuals of six species of shark, marine turtles, and whales. We assessed the spatial overlap between the distribution of these megafauna and multiple measures of anthropogenic activity (including shipping, industrial infrastructure, oil and gas exploration, commercial fishing and population density) to quantify the exposure of these taxa to potential anthropogenic threats. Management priority areas are identified as areas within species distributions with high exposure to cumulative threats and where risk assessments could be prioritized to inform scale-appropriate impact assessment processes and decision-making related to environmental management in Australia.

Stuart Corney

Institute for Marine and Antarctic Studies, University of Tasmania

In 2016 the Australian longline fishery for Patagonian toothfish on the Kerguelen Plateau experienced lower than average catch rates for most of the season (Apr – Nov). Catch rates dropped to about 50% of the 2011 – 2015 mean for the early months of the season and while partially recovering later, remained low throughout the year. A preliminary investigation concluded that the declining catch rates were unlikely to be caused by a decline in fish stock biomass, suggesting instead that it was related to a change in fish catchability driven by fish behaviour and environmental factors.

As a demersal species that lives on the shelf margins understanding the relationship between the environment and toothfish requires understanding sub-surface variability. This is difficult in the under-observed Kerguelen Plateau region and is made more difficult given the paucity of Argo floats that cross the plateau. Our solution was to draw upon the SRDL tags deployed on Southern Elephant Seals on the Kerguelen Islands. These data give uneven coverage of the region, but when combined with the assimilating CSIRO BlueLINK product they can provide information regarding subsurface changes on the plateau at depths relevant to toothfish.

Our results show a warming trend (0.17^oC per decade) and increase in kinetic energy (1.3 cm²/s² per decade) with a significant warming trend down to at least 1000m. We also seen evidence for a multi-year oscillation of warmer and cooler periods on the plateau that may impact on toothfish catchability.