A whale shark has been continually tracked by satellite tag for 12 months in the far north of the Great Barrier Reef, according to researchers from the Biopixel Oceans Foundation, based at James Cook University in Cairns, Australia. Scientists say the monitoring is the longest period for which a satellite tag has remained active for a whale shark in the region.
The tracking is part of the Citizens of the Great Barrier Reef project, a collaborative initiative between businesses, NGOs and citizen scientists to survey and map the Great Barrier Reef in an effort to increase conservation efforts across the reef’s 2,300km extent.
Initial research for the whale shark monitoring project began in 2017, with the team searching for an aggregation of whale sharks believed to be driven to the area by plankton blooms caused by cooler waters upwelling against the reef.
‘Initially we thought finding an aggregation was like trying to find a needle in a haystack even though we were looking for the largest animals on the reef,’ said senior researcher Dr Adam Barnett. ‘However, by looking at historical records and oceanographic information we took a best guess at the timing and location, and it paid off.’
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Using a combination of spotter planes and drones, the tagging team located the animals using a tender from charter vessel Argo, and successfully tagged ten whale sharks. The researchers also identified that the aggregation was of mixed sex, which is unusual among whale shark aggregations.
‘Historically, whale shark satellite tags only last a few months but upon a shark called ‘Ali’ we have our first 12 month track,’ said Dr Barnett. ‘After leaving Wreck Bay [in the far north of the GBR], Ali swam out into the Coral Sea, up to New Guinea and now has returned to the location where we first tagged her. We are still hoping for a few more pings from Ali’s sat tag.’
The study also confirmed the presence of another large plankton eater, the Omura’s whale, which was only identified in 2003, despite growing to more than 10m in length. Using drones flown under special permits, the team observed the whales and their calves feeding on large blooms of plankton – only the second aggregation of Omura’s whales known to science, following a previous discovery in Madagascar.
‘The reason these large plankton feeders are showing up at these locations in the Far North of the Great Barrier Reef in the summer months is to feed on plankton,’ said senior researcher Richard Fitzpatrick. ‘During these summer months, upwelling events can occur bringing up cooler water from the depths and the associated plankton. It is really important for us to know when and where these events occur as it can identify areas of the reef that may be more resilient to climate change. We are using Whale sharks, Omura’s whale and even Manta rays to teach us about these upwellings.’
‘This is just the beginning of the research on these animals – now we know where to find them, we can start deploying more advanced technology and bring in other researchers from other disciplines such as oceanography and plankton specialists to learn more about these upwellings,’ added Dr Barnett.