A report released by commissioner Dr Jan Wright recently shows the native longfin eel is on a ''slow path to extinction''.
Her findings were partly based on Otago Regional Council research on freshwater fish numbers, including eels.
Council water resource scientists Matt Dale said longfin eels were found in most of Otago's coastal rivers that were open to the sea, as well as the tributaries of the Clutha, downstream of the Roxburgh dam. However, as shown in the commissioner's report, there was a drop in the number of young longfin eels across Otago, he said.
The Clutha hydro dams had prevented longfin eels from accessing ''about one-third of their potential habitat in Otago''.
''The dams also kill most adult eels that try to migrate downstream.''
As longfin eels took more than 80 years to grow to maturity, they had to evade eel fishermen at least 10 times, so the odds of them surviving to maturity were minimal.
The eel was being ''managed to extinction'' by Government agencies responsible for their protection and a lack of action after this report would be ''wilful negligence'', he said.
''Closure of the fishery, essential if the species is to survive, will have little impact on the total catch of eels, given that shortfin eel will still be available.''
He believed the only way ''sustainable exploitation'' of eels could occur was if either the South or North Island's fisheries were permanently closed to fishing.
Dunedin freshwater fish specialist Dr Terry Broad, who did his PhD on longfin eels, said the problems had been around for at least 10 years.
He agreed bans on commercial fishing were needed but long-term it might only be needed on areas below dams as above them eels were ''doomed to die''.
''They're in a goldfish bowl. That is not protecting them.''
Mr Broad believed there were more than 20 fishermen with quotas for eel in Otago.
Forest and Bird last month presented a 5000-plus petition to Parliament calling for a moratorium.
''New Zealand has already lost too many native species to extinction, and we must not lose another,'' Forest and Bird's advocacy manager, Kevin Hackwell, said.
''They are of particular significance to Maori, both as a cultural icon, and for their value as a source of kai.''
The commissioner's report was a well-considered scientific document that served as yet another major red flag to the minister, who needed to act urgently, before it was too late, Mr Hackwell said.
''The longfin eel will not survive without an immediate moratorium. The species' fate is in the minister's hands.''
Commercial eel fishermen spokesman Bill Chisholm said the commercial eel fishery supported more than 100 jobs and $10 million in export earnings.
Longfin eel stocks were recovering, mainly due to the enhancement efforts of commercial and customary fishermen.
''The report appears to ignore this,'' Mr Chisholm said. ''All the issues about eel harvesting were addressed a decade ago by joint committees of commercial and customary fishermen, and longfin eels are now responding positively to the measures they implemented at that time.''
Recommending that commercial eel fishermen ''go bust'' while eel habitat is threatened by ''hydro dammers, water abstractors and polluters is ridiculous''.
They questioned Doc's ability to manage longfin eel habitat, saying its ''advocacy for eel habitats has been ineffectual at best'', Mr Chisholm said. The Ministry for Primary Industries (MPI) and the Department of Conservation (Doc) welcomed the report.
Doc director-general Al Morrison and MPI deputy director Scott Gallacher said staff would work together to address the report's recommendations.
''We take our responsibilities for this species very seriously, and welcome any insights the Parliamentary Commissioner can offer,'' they said.
''We will take the time to digest the PCE's recommendations, and we will work together in reviewing and responding to them.''
• Found only in New Zealand, mostly in rivers and lakes.
• Grow up to 2m long.
• Can weigh more than 20kg.
• Can live to 60 to 80 years.
• Named because its top (dorsal) fin is longer than its bottom fin.
• Are usually dark brown to grey black.
• Eat ''live'' food such as insect larvae, worms and water snails.
• Bigger eels feed on fish and even small birds.
• Hunt at night by smell.
• Breed only once, at the end of their life.
• Leave New Zealand to travel 5000km to the tropical Pacific to spawn.
• Females lay millions of eggs and the larvae reach New Zealand by drifting on ocean currents before taking an eel shape to enter fresh water.
• On average, males migrate at age 23; females at 34. Adults never return as they die after spawning.
• South Island allowable catch of longfin and shortfin eels combined 539 tonnes North Island allowable catch of longfin eels 170 tonnes
Parliamentary Commissioner for Environment found longfin eels are on a path to extinction because of.-
• Loss of habitat.
• Extermination campaign in the 1950s.
• Dam building.
• Commercial fishing.
• Suspension of commercial catch of longfin eels.
• Increased protection.
• Independent specialist peer review panel to reassess the science.