| The invasive
algae didymo has been found in the Arahura
River north of Hokitika.
The Department of Conservation says it is concerned
it could be spread to more rivers and might impact on endangered
native whio/blue ducks.
The didymo cells have been found in samples
taken near the mouth of the Arahura River in a DOC didymo survey.
Didymo has previously been confirmed in the Buller, Haast
and Kakapotahi Rivers, bringing the number of rivers infected on
the West Coast to four.
The department and MAF Biosecurity New Zealand
are reminding people to 'Check, Clean, and Dry' their gear between
waterways to prevent the spread of didymo to other rivers and areas
in the catchment.
DOC Acting Hokitika Area Manager, Judy Brennan,
said the find of didymo in the Arahura River was very disappointing
and concerning. "While the long term effect on invertebrates
and whio is unknown, didymo can form dense mats which may affect
invertebrate populations. Invertebrates are a food source for whio".
The Arahura is a popular recreational river,
as well as having significant cultural importance to Maori. We are
appealing to people kayaking, fishing or carrying out other activities
in the area, particularly the Arahura, to make sure they 'Check,
Clean and Dry' their gear between waterways.
"Trampers are asked to avoid contact with
Arahura River water and as the track runs alongside it they won't
need to cross it. If any boots, socks or other gear are put in the
river then these should be cleaned afterwards using 'Check, Clean
and Dry' procedures before being put in any other waterway. Wherever
possible, trampers should use bridges to cross waterways.
"People recreating in the Arahura river
have an essential role to play in preventing the spread of didymo
within area and helping to protect the areas' pristine rivers, freshwater
biodiversity and native blue ducks. Kayakers need to be very vigilant
with following procedures for cleaning gear, especially when they
are kayaking different catchments.
MAF Biosecurity New Zealand didymo response
manager Chris Bicknell said the find highlighted the need for every
fresh waterway user, no matter where they are, to 'Check, Clean
and Dry' their gear between waterways.
"Individual water way users have a crucial
role in slowing the spread of didymo and other aquatic pests. 'Check,
Clean, and Dry' is our best defence.
Information on didymo and approved cleaning
methods can be found on the MAF Biosecurity New Zealand website:
http://www.biosecurity.govt.nz
The DOC didymo survey on the West Coast, in
conjunction with a MAF Biosecurity New Zealand didymo survey, is
testing for didymo in about 20 rivers. Rivers being surveyed include
those considered to be at high risk of didymo infestation or which
have high biodiversity values.
Didymo is tested for using conical shaped drift
nets that are placed in a river. Water is filtered through the net
and material is collected at the end of the net in a small plastic
jar. Samples are examined using a compound microscope at 40 and
100 x magnification. Didymo cells are a distinctive shape and can
be readily distinguished from other diatom species. Any samples
identified as having didymo in them are sent to NIWA for verification.
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