By Annabel Boyer
The need to prevent shark attacks on swimmers and surfers while also protecting these top-order predators has led researchers and authorities to try a new approach. The emphasis has moved from deterring sharks to detecting, to inform people of their whereabouts.
These measures are being used in concert with more traditional deterrents such as enclosures and barriers. The logic is that if people know where sharks are, they can stay out of the way – leading to better protection of both people and vulnerable shark population
Sharks are high-profile inhabitants of the marine environment, yet much about their movements is unknown. Research into the movement patterns of dangerous species of sharks – where they swim and why – is providing valuable information on how to minimise interactions between sharks and humans.
Recent projects have focused on two key areas: interactions with ocean-based activities including aquaculture and fishery operations in South Australia, and interactions with recreational beach users in NSW.
In 2003, an FRDC-funded workshop with South Australian aquaculture operators and a broad range of other stakeholders identified the White Shark (Carcharodon carcharias) and Bronze Whaler (Carcharhinus brachyurus) as the species of greatest concern to operators.
A more recent FRDC project, led by Paul Rogers at the South Australian Institute of Research and Development (SARDI), is mapping the movements and whereabouts of White Sharks and Bronze Whalers in and around South Australia’s Spencer Gulf and the eastern Great Australian Bight. The results of the project will inform discussions around the use of marine areas and aquaculture zoning regulations.
The Australian Southern Bluefin Tuna Industry Association (ASBTIA) ranches Southern Bluefin Tuna (SBT) in the waters off Port Lincoln on the Eyre Peninsula. It has supported research into shark movement patterns to better evaluate and address concerns from the broader community about the potential whereabouts of dangerous shark species. A key concern has been whether activities such as aquaculture draw more sharks to an area.
Claire Webber, research and liaison officer with the ASBTIA, has assisted on the project. She says interactions with sharks do happen in the aquaculture leases in the Lower Spencer Gulf, although not often.
By mapping how the movements and habitats of these species overlap with human activities such as swimming, surfing, fishing, aquaculture and diving, researchers hope to learn whether human activities attract sharks or if the patterns observed are part of typical seasonal and ecologically driven movement phases.
The tracking project has used data from previous satellite and acoustic tracking of White Sharks and Bronze Whalers, combined with anecdotal information from fishers and aquaculture operators, to identify the best locations to set up acoustic receiver arrays.
The arrays detect the passing of sharks fitted with acoustic tracking devices, which is then linked with information about the individual shark detected, such as size, sex, residency and movement patterns.
Chosen locations included Australian Sea Lion and Long-nosed Fur Seal breeding colonies, Snapper habitats, possible deep-water migration pathways and offshore reefs, as well as selected inshore and offshore fish farm sites and inactive aquaculture sites.
As well as acoustic transmitters and acoustic-release receivers, dorsal fin-mounted satellite tags and miniature pop-up satellite archival tags were used to track sharks over large distances, including migrations across the Great Australian Bight to the Indian Ocean.
Paul Rogers says advances in the durability and sophistication of these technologies is making remote research into these highly mobile pelagic predators more feasible and provides clear direction for future research. GPS technologies coupled with oceanographic sensors help to understand more about how sharks use their habitats.
For example, pop-up satellite archival tags can be pre-programmed before deployment to monitor water temperature, depth and light intensity, latitude and longitude and time of day, for up to six months. This in turn provides researchers with the ability to understand the behaviours of these animals over time frames that were previously not possible.
When a shark is detected by an acoustic receiver or satellite, coinciding environmental information is also logged, including time of day, month, water temperature, depth and ocean colour, which gives researchers an indication of things such as the presence of nutrients in the water column or the presence of warm or cold eddies.
Much of the environmental data comes from the Integrated Marine Observing System (IMOS), which collects information on water temperatures, ocean chemistry and other variables (see breakout).
“Once we have collected the tracking data we match it up to these valuable environmental data streams to explain why the sharks are likely be using those areas,” Paul Rogers says.
This information is being used to unpick patterns that explain when and where apex predators, including sharks, tuna and their prey are likely to be at certain times, and this can be incorporated into predictive modelling. These types of models can help predict the potential impacts that multiple marine users in relatively small areas can have on sharks and, in some cases, the reverse impact of sharks on other users.
The project involved deployment of 66 electronic tags on White Sharks up to five metres in length and 24 Bronze Whalers up to 2.5 metres in length between 2013 and 2015. Paul Rogers says there were some surprising results.
“One of the key findings was that more White Sharks stayed longer in the Neptune Islands Group Marine Park than any other site or site type they visited,” he says. Activities such as cage diving and fishing occur in the marine park and the area also has a significant Long-nosed Fur Seal colony, where more than 3000 pups are born every year.
He says at most other sites and site types, including seal colonies, Snapper habitats and deep-water contours, tagged White Sharks visited briefly and then moved on quickly
“This latter movement strategy was what we expected from these highly migratory predators, given their need to keep moving in order to feed their large appetites,” Paul Rogers says.
The project also identified temperature and seasonal patterns linked to the movement of sharks in and around the Spencer Gulf.
Bronze Whalers were recorded in the Spencer Gulf in summer and autumn but moved offshore for winter. White Sharks, which are endotherms and can regulate their own body temperature, preferred to use the cooler waters in the Gulf through autumn, winter and spring and rarely visited the Gulf in summer.
The project also found that most aquaculture operations in the Spencer Gulf were not in the main shark travel pathways, which were identified for White Sharks as deep-water Gulf and shelf habitats.
Paul Rogers says the findings are a positive result for aquaculture operators. “The data indicated low shark residency in natural foraging areas and regions used by that industry. White Sharks are regular visitors to deep-water offshore island habitats that are also valuable abalone fishing areas. We are currently working with the abalone industry to develop innovative safety solutions for their divers.”
Claire Webber says the SBT industry has worked hard to improve its practices over the past 20 years, including efforts to reduce any likely attractions for sharks. For example, any dead fish in pontoons are removed daily and pontoon nets are well maintained to keep the SBT in – and other marine animals out.
To help operators on those very rare occasions when they encounter a shark in a SBT pontoon, the SA project developed best practice guidelines with industry in order to safely release the animal.
In addition to mapping and managing shark interactions, the SA project also included a stakeholder survey on attitudes to aquaculture and other marine issues, and analysis of media reports.
Respondents included stakeholders likely to have an interest in aquaculture zoning discussions: natural resource managers, local government, surfing, recreational and commercial fishing and aquaculture. The survey included semi-structured interviews and media analysis, and found no strong link in the perceptions of those surveyed between sharks and aquaculture. Seals and marine protected areas were issues of greater concern.
Those surveyed were, overall, supportive of new aquaculture developments, and the survey findings will be used to develop communications materials and build confidence in the process around aquaculture zoning discussions in SA.
In NSW, the Department of Primary Industries (DPI) has developed SharkSmart, a program designed to reduce the number of interactions between people and sharks, specifically White Sharks, Tiger Sharks (Galeocerdo cuvier) and Bull Sharks (Carcharhinus leucas). The focus is on detection and deterrence – increased awareness that changes the behaviour of swimmers and surfers.
In 2013, the NSW DPI first released SharkSmart as a free smartphone app to provide the public with information about the location of sharks and beach safety information. In 2015, a major upgrade to the app included dynamic, real-time information about the location of tagged sharks. This generates alerts from area surveillance about potentially dangerous sharks near swimmers and surfers. It also provides maps of shark sensor locations and shark barriers and enclosures along the NSW coast.
Shark alerts are also provided on the @NSWSharkSmart Twitter account.
A community engagement officer with NSW DPI, Kim Wolfenden, says the app is being continually improved. The most recent upgrades allow users to filter alerts to specific beaches and set the times they would like to receive them. The app has already been downloaded more than 20,000 times.
“We receive a lot of positive feedback that people can access this real-time data. This information has also shown that millions of us share the waterways with sharks every day, with only a very small number of encounters,” she says.
The locations of tracking receivers are strategic, taking in some of the state’s most popular beaches. Other surveillance methods include aerial surveillance using helicopters and drones.
Twenty sensors or listening stations along the NSW coast are part of the IMOS national array and they can detect sharks that swim within 500 metres. Once a shark has been detected, information is relayed to DPI shark scientists, validated and then sent to beach authorities and the public.
Twenty-five SMART (Shark Management Alert in Real Time) drumlines are also set up, designed to catch but not kill sharks. Once a shark has been caught it can be relocated.
“During the recent NSW summer school holidays, 525 potentially dangerous sharks were seen and reported by helicopter crews and 46 shark sightings were made by drones, of which 26 were considered as potentially dangerous,” Kim Wolfenden says.
An important function of the community engagement program is to improve awareness about shark movements, recognising that sharks are migratory and do not always appear at the same place and the same time every year.
The data gathered from tagging sharks is also allowing DPI scientists to review shark movements over the longer term to help develop a predictive tool for places and times of increased shark numbers.
The Integrated Marine Observing System (IMOS) provides national research infrastructure and facilities around Australia to improve understanding of our ocean territories.
Its animal tracking facility has deployed
a large number of surveillance arrays around the country to track sharks and other creatures. There are 16 arrays deployed by IMOS in collaboration with several partner organisations, with more than 2000 receiver stations.
The animal tracking database has already accumulated more than 65 million detections and is used in collaborative research that has involved more than 170 Australian and international researchers to date.
FRDC Research Codes: 2002-040, 2014-020
Paul Rogers, firstname.lastname@example.org
Integrated Marine Observing System, www.imos.org.au