Mr Mulcahy said he canoed on the river two or three times a week and discovered the rotting remains on the grass bank between the two rowing clubs on Valentine’s Day.
“As a boy I spent many an evening prawning with my father,” he said.
“We always poured the contents of the net on to a plastic sheet and once we were finished grabbing the prawns and extracting the rubbish we would drag the plastic and leftover net contents into the water.
“That avoids leaving a rotting pile of leftovers on the bank and removed some rubbish from the river.
“As an bonus, any prawn that you missed had a sporting chance of surviving so you could catch it next time.”
Mr Mulcahy said he was disappointed by the disregard some prawners showed for the environment, other river users and walkers.
“Prawners of today should show more respect for the river,” he said.