Devastated director John Reuhman claims he was offered a $75,000 bribe to keep quiet about the move.
"It's absolutely unbelievable. It's gut wrenching. I am numb.
"We will have to put down most of the animals. The animals can't be released, they are our friends, they can't fend for themselves in the wild and are the innocent victims of Port Marlborough's cold, callous approach."
The centre attracts about 51,000 people a year and brings in $4.75 million in visitor spend annually.
The centre is currently home to 117 native animals.
Port Marlborough chief executive Rhys Welbourn says the port is focused on helping EcoWorld rehome its animals.
The move would be done in consultation with Department of Conservation wildlife experts and MPI as required, he says.
But Reuhman says the centre was effectively served a "death sentence".
"In effect EcoWorld [was offered] the nominal sum of $75,000 for EcoWorld's multimillion dollar, purpose-built aquarium building on the condition that ... all of these termination arrangements secret.
"It's now total destruction. No kindness, no compassion, no goodwill, no empathy at all. It's heart-breaking after 20 years of dedicated work."
The centre leases an area of land between a council-owned carpark and the Edwin Fox Visitor Centre.
Reuhman says the aquarium had plans for expansion and had been led to believe there would be no problem.
Welbourn says support is being offered to the centre and its staff following the end of the aquarium's 10-year lease.
"Some time ago Port Marlborough and Ecoworld discussed a possible extension of the lease. However, Ecoworld sought different terms that were not acceptable to Port Marlborough and this has been consistently conveyed to Ecoworld.
"Therefore the lease has come to an end in accordance with its agreed terms. We are now trying to help the business vacate its premises, and assist with the sustainable rehoming of the aquarium's marine-life and other animals."
But Reuhman has hit back at the claims, saying he was given "strong indications" from Port Marlborough that the lease on the Picton foreshore would be renewed.
He says leaked confidential conversations indicate the site is needed to use as temporary offices as part of the $400 million joint Port Marlborough Kiwirail port redevelopment.
The building would then be repurposed as an Envirohub and museum, he says.
Welbourn has ruled that out and says the end of the lease is unrelated to neighbouring infrastructure work for KiwiRail's ferry service that is currently underway.
"Following the expiry of the lease it is important for us to consider other uses for the land that deliver better cultural, environmental and economic benefits for the region and the community as a whole.
"We will be working with our community and mana whenua to identify options for the future."
Reuhman says he refuses to let the centre fold and is in talks with a lawyer.
"This leaves EcoWorld with little option but to have most of the animals put down with six highly-skilled people losing their jobs.
"This is a David and Goliath battle. We are now going all out to save the animals and save EcoWorld Aquarium and Picton Cinemas."
- Marlborough Weekly