Why are large white sharks attracted to North Coast waters?
NORTH Coast surfers and swimmers, if you would rather not know what lurks underneath, you will be forgiven for not reading on.
There have been white shark detections at Evans Head and at Ballina in recent days, and we are not talking about baby sharks.
These are top of the food chain apex predators, ranging from 3-4m at Evans Head and 4-5m at Ballina.
What exactly brings them to our waters?
Southern Cross University marine biologist Danny Bucher identified a range of factors including food, water temperature and fish breeding season.
"One thing we did know before all the tagging work started is we do tend to see great whites in local waters in winter, over the cooler months," Dr Bucher said.
"The tagging work is generally confirming that.
"Great whites are spending more time further north the colder the water gets down south.
"Our winter water temperatures are similar to summer water temperatures in Melbourne."
Fish activity brings predators close to our shores.
"This time of year we see the mullet runs start," Dr Bucher said.
"We see bream and a lot of lower estuarine fish spawning around the mouths of estuaries."
Winter means breeding season for many fish in North Coast waters. Their offspring relies on plankton, and there is an abundance of plankton in early spring.
"There's a lot of action happening in winter," Dr Bucher said.
"Fish want to release their eggs, so they hatch out in time to feed on the plankton.
"As winter starts, fish start breeding, you see a greater aggregation of fish, and sharks following the fish into shallower waters."
Whales are also migrating north, but whales do not necessarily attract the big sharks.
"Their prevalence coincides with whale migration, whether that's the primary driving force I don't know," Dr Bucher said.
As for the 2m dolphin found with massive shark bites at New Brighton Beach in April, Dr Bucher said it is possible it was eaten while it was dead or alive.
"Sharks, like any predator, will take the easiest option," Dr Bucher said.
"In saying that I have seen footage of a tiger shark taking a live dolphin in Newcastle.
"Do they take old, sick, young and weak more often than healthy animals? Yes."