What lurks beneath

The Mystery Creek lakes host a bevy of noxious swamp-things, according to University of Waikato pest management researcher Professor Brendan Hicks.

Labelled by the Department of Conservation as the “possums of the waterways”, the prolific red-finned fish known as rudd are an introduced species found in many Waikato lakes and ponds.

And the Mystery Creek lakes, potentially admired by thousands of Fieldays visitors every year, are teeming with them.

“They are an undesirable fish that is listed as an environmental threat in the Waikato Regional Council Regional Pest Management Strategy 2008-2013, which is still in force,” said Hicks.

“Any fish caught must be killed.”

Rudd are legally designated a noxious species outside the Auckland/Waikato Fish and Game region – inside it, they are a sport fish, albeit not a desirable one.

While they pose little threat to the native eel population of the lakes, their presence can be devastating for the fragile native aquatic flora, said Hicks.

“Because rudd are herbivorous, eating almost entirely a plant diet as adults, they are mostly an issue for the conservation of native water plants (aquatic macrophytes).”

So is there still hope for the Mystery Creek lakes?

Hicks, for one, is optimistic.

“They are attractive ponds that could have native plants and fish such as eels.

“The rudd could easily be eradicated, followed by restoration plantings of native water plants.”

He said rudd fishing is good sport for inexperienced anglers, but the flesh is said to be inedible.

As for the rudd themselves, Hicks urged compassion.

“The public should be sure to dispose of unwanted fish humanely – putting them in a plastic bag in the freezer overnight will euthanise them painlessly.

“This applies to rudd, goldfish, catfish, koi carp, tench, and perch that exist in the Waikato.

“Under no circumstances should they be put back into the water alive, or transferred to other water bodies.”