He also said the filleting was wasteful of much of the fish.
Mr Edwards said the snapper limit for recreational fishers was nine per fisher but any suggestion the snapper in the photos had been poached and were intended for sale were "pure speculation".
"What is of concern is that we haven't been notified of these incidents. We would like the public to report anything they see directly to us," Mr Edwards said.
The issue of dumped fish frames was raised in late December by Labour list MP Shane Jones, who was "disgusted and hacked off" to find a number of filleted carcasses in a stream near his Waimate North home.
He was affronted not just by the pollution of a normally clean waterway but also by the waste at a time when many families struggled to put food on the table.
Mr Jones said he doubted the culprits were Maori, for whom fish heads were a delicacy. The majority of fish eaters in New Zealand eat only the fillets.
In September, about 100 filleted dogfish carcasses were dumped at the Onerahi boatramp.
Six men, who appeared to be Pacific islanders, had been seen late one night bringing in a boat laden with the small sharks, also known as lemonfish and rig.
The men spent a couple of hours filleting them, afterwards dumping the carcasses at the bottom of the boat ramp.
There is no limit on the size of small school sharks but the allowable take is 20 per person per day. A fisheries officer said there were no compliance issues in the Onerahi incident.
"In this case, we can't just presume there were too few people fishing for the size of the catch or that the mesh was the wrong size, and there's no reason to believe this rig was caught to be sold," the officer said.
Mr Edwards urged anyone finding a large number of dumped fish frames or any other suspicious fishing or shellfish activity to call the hotline, 0800 4 POACHER (0800 476 224).