Norsewood's longfin eel population at The Wop Wops Wetland Park took a dive in the early hours of yesterday when a number of them were taken.
Phil Grant, chairman of KuiKui Charitable Trust, caretakers of the Wop Wops, said at 4.30am yesterday the endangered longfins were taken.
He said heard a vehicle drive in but thought it was the Norsewear staff getting sock orders made up for CD Fieldays.
The fishermen left 15 minutes later.
Grant was uncertain as to how many eels remain, but said there were not very many.
"The other day there were about 20 or 30 there but yesterday morning there were only two or three. From marks on the limestone path it looked as though between six and 10 could have been taken, but it's hard to tell."
He said they had noticed a decline in eel numbers recently, but the creek was low and the eels sought out deep holes when this happens.
"It's sad to have lost these longfins, but its pretty low to scoop them out of the creek from the spot were they are hand fed."
On the positive side, Grant said the eels will naturally replenish.
"They each have their own territory and you do see those spot filling up."
For Grant the main issue was trespassing. Access to the eels is through his property.
"The wetland park is open during the hours the Natural Clothing shop is open which is from 9am till 5pm, but we realise that for some families they can't get to see them until after 5 but that's not the issue.
"It's the people who turn up after dark. They think it's their right to take the eels. If I hear anyone I will go out and see what's happening."
He said the eels did not belong to the Wop Wops.
"We can't or won't stop people from taking them for food from either side of the park. But we are going to trespass those who do it on our property."
Grant says the trust is going to invest in surveillance equipment.
"We want families to be able to go into the park after hours, but we will be watching who comes and goes more closely."
In a Facebook post Grant asked locals to keep an eye out as well.
"If you get offered a feed of eel, question where they came from please."
Grant said there were other fishing spots in the area that were teeming with eels.
"People just need to throw a line out and they can catch eels easily."
Grant said the trust was monitoring the situation and it may have to gate the site and perhaps look at charging people to visit because of the cost of the security measures that will have to put in place.
The Wop Wops Wetland Park is an ongoing conservation project that aims to help the native New Zealand longfin eel and educate communities about them. The site was established in 2013.