b>Illegal spreading of pest species not uncommon
I have seen at times different fish introduced to Western Springs Lake to clear the lake weed. On a recent visit there seemed to be a large number of what appeared to be catfish under the narrow bridge on the western arm near the zoo. I wonder what species they are, how many were introduced, when they were inserted and when they will be taken away (I wonder how may that are released are recaptured too). John Paynter, Auckland.
Matt Bloxham, senior freshwater adviser with Auckland Council's biodiversity team, says that in New Zealand there is a culture of people spreading pest fish to waterways illegally, and Western Springs is an example.
Only two species of fish have been released legally into Western Springs (both by New Zealand Waterways Restoration): grass carp and silver carp, neither of which can breed naturally in New Zealand. Grass carp were introduced to control aquatic pest weeds, because they feed exclusively on plants. No other species of fish in New Zealand has the ability to control aquatic pest weeds. A small number of silver carp were introduced into the lake as they consume aquatic algae.
Koi carp have been introduced illegally, along with rudd, goldfish and brown bullhead catfish. All, with the exception of goldfish, are considered pest species and are unwanted because of the harm they cause to native wildlife and/or water quality. People caught displaying, releasing, spreading, selling or breeding unwanted organisms without an approval under the Biosecurity Act are liable, on conviction, to a fine not exceeding $100,000 or imprisonment for a term not exceeding five years, or both.
