Aramoana residents are concerned at a dramatic drop in nesting yellow-eyed penguins in the area this year.
The breeding area north of Keyhole (or Bear) Rock has just one breeding pair and overall numbers are down in Otago-Southland from 491 pairs in 2012 to about 160 this season.
Aramoana Conservation Trust chairman Bradley Curnow said there was a multitude of issues that could have contributed.
''It's really sad. We can't see what would cause such a catastrophic event on land,'' Mr Curnow said.
Predator traps, no diphtheria and no evidence of dogs ripping up nests meant it was probably an issue out at sea.
''We have very little understanding of what happens in the ocean,'' Mr Curnow said.
''It's probably not in the colony that's the problem. It's frustrating and depressing.''
Two weeks ago, Aramoana locals, members of the Yellow-eyed Penguin Trust and the Department of Conservation completed their second annual nest search and discovered the solitary nest.
''We think that six [nests] is pretty ... good.''
Kaitiaki for Otakou runanga and Yellow-eyed Penguin Trust member Hoani Langsbury said he and the trust were ''significantly concerned''.
''There aren't the numbers around any more. If we hadn't been doing the work in the past, we wouldn't have what we have now,'' he said.
Mr Langsbury said he was ''not confident'' the numbers would recover significantly, as numbers were also down on previous years in the sub-Antarctic islands. In the past, if breeding numbers were down on the mainland, they were usually up in the subantarctic islands, but this was not the case this season, he said.
''We just don't know what this season will bring.
''At the moment, we have no idea.''
Doc coastal Otago biodiversity ranger Mel Young said nest numbers in the region were at their lowest since 1990.
Penguin communities would work closely over the coming months to manage any detrimental events that may affect penguin survival, she said.
Breeding adults had been hit hard over the past three years, including by a marine-based toxic agent, starvation, diphtheria and barracouta attacks.
''Every bird is important and we are doing our utmost at each site.''