Port Stephens residents are furious after hundreds of undersize dead fish and stingrays were dumped in the shallows of Jimmys Beach.
It's believed a net stretched between two boats was used to catch the fish, however unwanted and undersize species were then dumped at the eastern end of the beach last weekend.
It's thought a commercial fishing operator from outside the area may be responsible.
The Department of Primary Industries is investigating and says commercial operators who fail to immediately return non-target or undersize fish to the water during hauling operations face a maximum fine of $22,000.
