Grass carp will be released into North Otago irrigation
canals next month - just the second time the fish have been
released in the South Island.
The North Otago Irrigation Company this week received
approval from the Department of Conservation to release carp
into its Otago and Canterbury canals, near Smillies Rd, to
control the growth of aquatic weeds.
North Otago Irrigation chief executive Robyn Wells said using
grass carp was the ''most environmentally elegant'' solution
to control weeds, which could block screens and cause
problems with pumps.
Grass carp ''have extremely specific spawning and rearing
requirements and the establishment of a wild population is
extremely unlikely'', according to the National Institute of
Water and Atmospheric Research.
The only other time grass carp were released in the South
Island was 10 years ago at Lake Hood.
Ms Wells said the fish would be supplied and managed by New
Zealand Waterways Restoration Ltd of Auckland, which would
transfer the stock from an aquaculture farm in Nelson to the
canals next month.
''Our first step now that we have approval is to implement
the appropriate steps to ensure the carp stay within our
canals and do not get pulled into our pumping equipment, by
installing mesh on all inlets and outlets prior to the fish
''Once released and established, the expectation is that the
fish will reduce the weed volumes by two-thirds, which will
mean that our employees will be moved to more cost-effective