Exploris has been unable to rule out killing off the thousands of marine animals it cares for if Ards Council votes to shut Northern Ireland's only aquarium.
The licensing inspection, carried out by NIEA's wildlife team in July, clocked up 3,307 animals, the majority of which were marine invertebrates such as anemones and mussels. Fears have been raised by Marine Conservation Northern Ireland (MCNI) that the closure of the aquarium would mean a "mass slaughter" of hundreds of fish and other animals.
The marine pressure group also says that all juveniles born in captivity at Exploris are currently being culled as part of an ongoing scheme – a claim strongly denied by the aquarium and Ards Borough Council.
MCNI chairman Nigel Hamilton estimated more than 1,000 animals were put down in the past 10 years. His group had hoped to work with Exploris to reintroduce surplus rays and skate into Strangford Lough to boost stocks becoming increasingly scarce due to commercial fishing.
He said he had been told about the ongoing culling programme during a visit by MCNI representatives to the aquarium.
"There is now a very real danger that if closure is decided by council the juvenile ray and skate born in captivity – of which there have been thousands – will be terminated along with all other stock on display and in tanks behind the front of house," he said.
"This would amount to in excess of 20-30 species and amount to a planned massed slaughter of fish that have no commercial value but to be on display."
MCNI said Ards Borough Council needs to be responsible and inform people of the full process before any decision is made to close the aquarium.
"It's like going to a safari park – what do you do with the animals? You can't just put them down," Mr Hamilton said. "They need to make a decision and the decision needs to be informed."
However, Ards Borough Council and Exploris said it has never killed off juvenile fish. It said there are no surplus juvenile rays or dogfish because eggs are removed from fish and never hatch.
Exploris manager Helena Challinor said she couldn't comment on whether the existing stock would be put down if the tourist attraction is closed.
"Whatever happens, it's the welfare of the animals that we will be concerned with," she said.
An Ards Borough Council spokesperson said any surplus fish are either kept or shared with other facilities. "We don't kill fish stock," she said.
A NIEA spokesman said: "Pending the meeting's result, Exploris will forward a plan to NIEA detailing proposed arrangements for all the animals. There are no juvenile fish euthanised at Exploris."