Aerial shark patrols of the NSW coastline are "inefficient and expensive", a government report says.
A Department of Primary Industries report found there were "serious concerns" about the efficiency of aerial shark-spotting after less than one shark was sighted per 100 kilometres flown in a 2012-13 helicopter trial period.
This included an instance of aerial surveillance failing to spot a shark that bit a surfboard in Dee Why despite a flight over the area within 30 minutes of the incident last December.
The patrol failed to spot any animals within a 33-kilometre radius of Dee Why, the report into the Shark Meshing (Bather Protection) Program found.
Despite the department's claim that flights "enhance bather safety" by providing an early warning, the report found this incident implied the "ineffective nature" of aerial surveys.
"The results of the various studies undertaken over several years to date raise serious concerns about the utility of aerial beach patrols as an early-warning system for sharks," it said.
The department defended a decision to extend the program until 2014-15, saying that "further research" into its efficacy would continue into the 2013-14 season.
The latest helicopter trial began on December 21 and covers 51 beaches from South Wollongong to Stockton, north of Newcastle.
These twice-daily flights on 47 days are funded by $200,000 that the government committed annually to the aerial observation program.
A department spokeswoman said the funding covers "many aspects" in addition to the helicopter trial, including observation flights and research into the use of drones.
"Aerial observation flights are also used to collect data to inform other aspects of the program such as beach visitation rates, sightings of target versus non-target species, and checking location of nets," she said.
Scientists will take part in aerial patrols for the first time this year to help identify shark species and improve data reliability.
Money for the aerial program comes at the expense of an initiative to monitor the efficiency of shark nets.
Trained observers were present for only 131 of the 719 net checks by contractors due to reduced funding.
More than 100 animals were entangled in shark nets during the September 1 to April 20 season, including endangered species and non-target sharks.
Only 34 were released alive, including two humpback whales and eight of 70 sharks captured.
The department's independent Fisheries Scientific Committee expressed its concern about the funding cuts, saying claims that nets made beaches safer was "unsubstantiated".
More scientific data "would provide crucial information in the assessment of public safety and the efficacy of nets in preventing shark attacks," its said.
The department spokeswoman said there had been only one fatal attack on a netted beach since the shark net program began in 1937.