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Cid Harbour Research Finds Low Shark Numbers

Shark By Terry Goss, CC BY 2.5.jpg

By Terry Goss, CC BY 2.5

A study of sharks in Cid Harbour has turned up some surprising results.

Despite two serious shark attacks within a week of each other and a fatal attack in November, the study found the number of sharks in Cid Harbour in the seven days from December 13 was low.

Following those attacks in September and November 2018, The State of Queensland, acting through the Department of Agriculture and Fisheries, commissioned a scientific study to investigate the prevalence and behaviour of sharks in the Cid Harbour region.

The study was conducted between December 13 and 19 2018.

Several sampling methods were tested, including catch methods (single hook droplines, longlines), baited underwater video cameras (BRUVs), drones and acoustic and satellite
tracking.

Because of the bad weather brought in by Ex-Cyclone Owen, sampling by drones was not possible, due to reduced water and surface visibility. However, catch methods, BRUVs
and acoustic and satellite tracking provided useful information.

The report stated that "overall, results show that the number of sharks using Cid Harbour at the time of sampling were low".

"Catch rates from the shark control program that operated for a week in September 2018 were also low.

"Sharks caught/sighted were mostly tiger sharks, spot-tail sharks and tawny nurse sharks. Regarding tracking, ten acoustic receivers were deployed in the Cid
Harbour area, and five sharks were tagged with acoustic transmitters (four tiger sharks and one spot-tail shark)" it stated.  

Researchers fitted six sharks with satellite transmitters (four tiger sharks, one great hammerhead and one scalloped hammerhead shark).

So far, three of those sharks have been providing movement information, with data showing that all three sharks left Cid Harbour after being tagged, but remained in the general Whitsunday Islands region.

Surprisingly, no bull sharks, the marine creature thought to have been the one most likely involved in the three attacks in 2018, were caught or seen during the study.

By Michelle Price