A HUMPBACK whale is the main suspect in a case where a shark net was damaged in Kirra.

Authorities replaced a section of the net soon after a section was found missing during a routine inspection yesterday.

Queensland Shark Control Program manager Jeff Krause said there was evidence that something large had encountered the net.

"We believe it was an adult humpback whale that struck the net overnight while heading south," Mr Krause said

"Whales do strike shark control equipment occasionally but this is the first time this season where a section of the net has been removed.

"It is possible that the whale may be trailing the missing section of net or it could have successfully freed itself."

Southern Cross University whale researcher Peta Beeman said shark nets and fishing nets are often not whale-friendly.

"Entanglement is a hazard for a humpback whale," Ms Beeman said.

"When I take photos I do see evidence they get caught up in nets.

"The whales do travel closer in to shore particularly on the southern migration."

Mr Krause said the nets served an important purpose.

"Nets and drum-lines are strategically placed off 85 beaches across Queensland to offer the best possible protection to swimmers, surfers and fishers.

"Regular patrols are conducted to ensure the equipment is in place and to check for any damage or entanglements," he said.

"If anyone spots a marine animal entangled in shark control equipment they should let us know immediately on the 24-hour Shark Hotline - 1800 806 891."