"Mystique usually brings in coral, wood, rocks anything he can find. He's been bringing stuff to us for 10 years," Ms Shores said.
"He brings it in as an offering to us, to get praise, and because we give him a fish. If there is no fish in hand, he sits out in the water just beyond where we can reach."
Ms Shores said two other dolphins had started bringing similar gifts to shore in the morning, when volunteers fed the mammals.
"I think they thought they had done something wrong because there were no tourists to feed them," she said.
"They have been bringing more and more stuff in, and with [two] more dolphins [joining Mystique] bringing things in, it's a sign [they miss human interaction] because they know we wait for them to drop their stuff, praise them and feed them."
Dr Daniele Cagnazzi, a postdoctoral researcher at Southern Cross University's Marine Ecology Research Centre in Coffs Harbour, NSW, has previously studied the dolphins at Tin Can Bay.
He believes the idea of the mammals bringing gifts because they miss their usual attention and interaction with tourists is a human interpretation of complex dolphin behaviour.
"I have observed a male dolphin taking an object, such as a bottle or sponge, and swimming towards a female and trying to interact with that female," Dr Cagnazzi said.
"I am unsure how successful it is but I have observed a male and female moving away together afterwards.
"[Dolphin gift giving] is definitely interactive behaviour, but I never saw this behaviour lead to anything other than a social interaction between a male and female dolphin.
At the moment, the researcher said, the information wasn't available to know whether a dolphin enjoyed human interaction.
"With dolphin feeding, they are obviously attracted by the food but we don't know whether they enjoy the interaction with the people feeding them," he said.
Dr Cagnazzi said it was "very interesting behaviour", adding that dolphins were "intelligent and social animals".
"It would need to be investigated in more detail," he said.
Barnacles Cafe reopened on Thursday with revised operating hours.