Fish were also reported, by other sources, at Maitai Bay and Karikari Beach late last week.
Some of the fish found at Tokerau were described by locals as fresh, as were some seen by Mr Osborne a week later, making it unlikely that they all came from the same source.
Others at both locations had clearly been dead for some time.
Mr Osborne said the fish he saw were exclusively snapper, ranging from legal size to around 3.6kg. He saw no evidence that they had been hooked or suffered net damage.
"There was nothing to suggest they had been thrown overboard from a boat, but given that there were no other species I can't think of any other explanation. It's a bit of a mystery," he said.
"We saw hundreds of them, but I imagine that all up there would have been thousands," he added.
Whatever the cause, a reliably productive fishing spot had that day yielded just one snapper, smaller than the legal minimum.
Meanwhile, further angry contributions have been made to Facebook following the discovery earlier this month of a pile of snapper frames on 90 Mile Beach and dozens of empty paua shells at Tauroa, none of the latter reportedly being of legal size.
There is no defence for taking excess or undersized paua, but anyone who had fish frames they didn't want might go to www.freefishheads.co.nz to be put in touch with someone who would appreciate them, one incensed local said.