WA beachgoers are not being told the size of sharks that swim past satellite receivers because authorities fear idiots will try to get a closer look at sharks they believe to be small and safe.

Satellite receivers are a growing method of informing the public of shark threats, with eight to be added off the South West and south coasts this summer to complement 20 off metropolitan beaches.

Authorities are worried about the expanding network's ability to provide an unprecedented road map for the location of sharks lingering in areas for prolonged periods.

The West Australian has heard anecdotal reports that amateur wildlife hunters fashioned a makeshift shark cage out of security screens during a cluster of electronic notifications off Perth's northern beaches last summer.

Asked directly about the shark cage story, the Department of Fisheries declined to comment.

Shark response unit manager Lisa Clack confirmed details of tagged sharks were kept out of alerts because of fears the information would be misused.

"We don't want people making value judgments about risk, based on the size or species of sharks," Ms Clack said.

“The Department of Fisheries does not release information about specific sharks, as all of the sharks tagged as part of this program are potentially dangerous.

“The important information is that there has been a detection.”



In October last year, tagged sharks triggered electronic receivers off Ocean Reef and

Mullaloo beaches more than 50 times in little over more than a week.

About 140 of the 326 sharks tagged off WA are great whites, but other species including bronze whaler, tiger and grey nurse sharks have also been fitted with electronic receivers to help map their movements.

Fisheries has spent the winter refining the network’s data management and messaging system, which sends almost instant notification of a tagged shark to Surf Life Saving WA’s Twitter and Facebook feeds.

While the feeds often includes the size of the shark spotted by the Westpac helicopter patrol, recreational boaters or Water Police, the detail it is not contained in the Fisheries’ electronically-generated alerts.

A 3m bronze whaler was spotted from the Westpac helicopter off Quinns Rocks yesterday morning. A similar sized shark of the same species was also spotted at Point Picquet in Dunsborough.