Aucklanders have been urged to stop fishing at the Panmure Basin so the local pied shag population can be replenished.
Corine Hooper, who has looked after the protected bird population for eight years, raised the issue of overfishing and increased pollution with Maungakiekie-Tamaki local board chair Josephine Bartley.
Ms Hooper said she was once feeding 30 shags twice a day, and now she was feeding up to 10.
A dead baby shag was found in an estuary cleanup at the weekend and she suspected it died of starvation, Ms Hooper said.
"Any breeding birds, which is minimal, any young they produce is going to die unless they make some huge changes here."
Ms Hooper said the birds mated for life, so any loss would further devastate breeding lines which were desperately needed.
Ms Bartley met with Ms Hooper and said the problem was "serious".
She has asked the Ministry for Primary Industries to place a rāhui - or ban - on fishing in the area and is expecting a response on Monday, she said.
She would also raise it at a local board meeting on Tuesday to get the Auckland Council officers to investigate the causes of the depleting pied shag numbers.
"This is the effects of pollution and intensification and development and it's all showing up through the environmental effects, through the birds dying."
Meanwhile, Ms Hooper said she hoped people who fished in the area would understand if they were moved somewhere else.
"It's just about getting people to think twice before they put their rod down, is there anywhere else they could go and leave the estuary for the shags to rebreed and replenish the colony," Ms Hooper said.