School's out: Thousands of dead fish wash up at north Auckland beach

Thousands of dead fish have startled residents at a north Auckland beach.

The washed up fish - identified by Auckland War Memorial Museum head of natural sciences Tom Trnski as anchovy Engraulis australis - lined the shores of the Stanmore Bay estuary on February 21, sparking fears of water contamination.

A video sent in by a resident shows just how many of the fish have washed up.

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A similar incident occurred at Stanmore Bay and Martins Bay, Mahurangi, in August 2009.

Auckland Council senior scientist marine environmental research and evaluation Dr Megan Carbines says a number of natural events could have caused the fish die off, including high temperatures, viruses and diseases.

"It may be as simple as predators such as kingfish or kahawai rounding up the [anchovies] on an outgoing tide," she said.

"Our advice is to report large shoal beachings such as this to MPI on 0800 80 99 66. MPI keeps a record of these reports and can look for similar events in the area that might warrant further investigation."

Those concerned about pollution in waterways can call the council's pollution hotline on 09 377 3107.