The NSW Department of Primary Industries has announced it is investigating the apparent slaughter of more than a dozen sharks at Fingal Head on the state's far north coast which has been described by anglers as "senseless".

Photographs of more than a dozen dead sharks left on a breakwall caused a stir on social media at the weekend.

The DPI said they were probably sliteye sharks which are subject to a five-fish bag limit.

A spokesman for the New South Wales Recreational Fishing Alliance and angling advocate Malcolm Poole said it was a worrying situation.

"As to why they're there, I'm perplexed as to why," he said.

"It is a senseless killing.

"(It was) highly unlikely to be a commercial fishing activity or anything to do with spear fishing.

"So once again, it is a concern."

A Banora Point woman, who snapped the photographs, said she did not realise the images would cause such a stir.

Laelia Gardner said she made the grisly discovery while walking on the breakwall with her father on Friday morning.

Ms Gardner said she was shocked to see the dead fish left to rot in the sun.

"I was just getting the word out there that it is wrong to do this," she said.

"Hopefully whoever did this will see that it is wrong and maybe educate themselves a little bit more to learn about how sharks are important to the ecosystem of the ocean."