This week, the Department of Conservation released the New Zealand Sea Lion Species Management Plan 2009-14 (SMP) instead of a population management plan.
New Zealand sea lions were once found widely around the mainland coastline, but now the population of about 12,000 is restricted to a small presence on the Otago coastline, and most breeding occurs on the subantarctic islands.
Doc monitoring of pup production at the Auckland Islands indicates the population is declining.
Trust chairman Shaun McConkey, of Dunedin, said it supported the goals of the SMP but was disappointed with the decision by Doc to abandon the population management plan.
Under a population plan, sea lion bycatch limits would be set by the Conservation Minister but the species plan had no power to affect the limits, which were set by the Fisheries Minister, he said.
"With a decline in pup production of 50% in the last 10 years, current management strategies are obviously not working effectively."
The New Zealand sea lion should soon be classified as threatened due to its declining population, he said.
The current population was now below 10,000.
"A species management plan released now will not reflect either of these significant changes."
Green Party co-leader Metiria Turei said the decision to abandon the population plan left the species "high and dry, and moved it a step closer to extinction".
"It is bitterly disappointing that the Government has ditched one of the best tools we have in the law to protect a threatened marine mammal like the New Zealand sea lion."
The continued decline of the sea lion showed that the marine sanctuaries and reserves around its breeding grounds were insufficient, said Mrs Turei.
"We need a strong plan that will actually protect them."
Doc's research and development general manager, Kevin O'Connor, said the populations' downward trend was a significant concern.
Doc looked at introducing a population management plan but decided against the proposal, based on several concerns, he said.
The new information on the declining numbers and the upgrade in threat classification meant the models and data used for the population plan were out of date and no longer valid.
It was better to introduce a species plan that gave protection for five years rather than using an "outdated" plan which could be challenged, leaving the sea lions without protection, he said.
The SMP outlined work to help in the recovery of the sea lion during the next five years, including managing adverse human impacts, community relations initiatives, enforcement activities, and identified research priorities.
