Shark nets will go up around NSW beaches on Monday - but the NSW Greens say it's too early.

"The whale migration does not end for another two months so why are nets going in tomorrow?" Greens MP Ian Cohen said on Sunday.

Two weeks ago a baby humpback whale, dubbed Colin and then later renamed Colette, was euthanased after it was found motherless and starving in The Basin, inside Sydney's Pittwater.

Colette was nuzzling yachts in search of her missing mum and she was towed out to sea but soon returned.

Sea life experts determined she was suffering needlessly and euthanasia was the only way to put her out of misery.

Mr Cohen said shark nets could endanger whales and other marine animals such as turtles, dugongs and fur seals.

He said the environmentalists had called for a review of the state's shark net program at the Shark Summit in 2006, but nothing had eventuated.

"The Government should at least investigate whether or not the netting season can be shortened," Mr Cohen said in a statement.

"Even if the netting season was shortened, we should remember that nets are indiscriminate killers."

He said 82 people drowned last year along the NSW coast but there were no fatal shark attacks.

"Driving your car to the beach is more dangerous than sharing the water with sharks," he said.

Shark nets will be erected at beaches on the NSW coast, from Wollongong to Newcastle.

AAP