Murky water lures vicious bull sharks
The sharks were spotted this week by NSW Department of Fisheries personnel under Missingham Bridge and at Mobbs Bay.
The areas are not closed and no signs have been erected, but the president of Surf Lifesaving Far North Coast, John Beasley, said anyone who swam in the river while the warning was in place would be putting themselves at risk.
"We don't want people to be scared, but they need to listen to the warning for their own safety," he said.
"At this stage we don't see a need to close the area, and we will put signs up if requested by the council.
"However, we are advising people not to swim or surf either side of the walls at the entrance of the Richmond River, or upstream towards the Ballina township."
The sightings come just a month after 16-year-old Wollongbar youth Peter Edmonds died after being attacked by what was thought to be a bull shark near Ballina's North Wall.
Peter received severe bites to his leg and died from a loss of blood on April 8, despite the brave efforts of his mate Brock Curtis-Mathew, who brought his friend ashore.
Only a couple of weeks before that, locals spotted about five bull sharks circling in the Richmond River under Missingham Bridge.
Mr Beasley said it was important people listened to the warning and not risk another shark attack.
While Ballina Jet Boat Rescue volunteers had patrolled the area since the sighting and not spotted the sharks, it was likely they were still nearby.
The rescue team would be patrolling throughout the weekend, Mr Beasley said.
He said there were several factors which had heightened the risk of the presence of sharks in the area.
They included dirty water flowing out of the Richmond River, some of which was from the heavy rain experienced in the region earlier this year.
The murky water made it difficult for swimmers to see what was beneath them in the water and enticed sharks, he said.
It was also mullet season, meaning sharks knew there would be mullet hanging around the mouth of the river so they went there to feed.
Ken Thurlow, CEO of ECOfishers, previously told The Northern Star bull sharks were a particularly nasty variety of the shark family.
He said they were aggressive and known to attack humans, cattle and dogs.
"They're totally non-selective in what they choose to eat," he said.
"And they are attracted to the murky water coming downstream from the heavy rains."
Swimmers and surfers should avoid entering the water until it is deemed safe to do so.
If you think you have sighted a shark, call 000 and contact the police immediately, or call Garry Meredith, Surf Lifesaving Far North Coast duty officer on 0414 777 099.