5 June 2007
A fish pass, which allows small fish to access one of the streams running into the Waikato River when water levels are low, has just been built at Bankwood Stream.
The sloping concrete channel with inset rocks, allows the fish to swim and climb up it to gain access from the river to Bankwood Stream at Swarbricks Landing, off River Rd.
The fish pass, a joint project between Hamilton City Council and NIWA (National Institute of Water and Atmospheric Research), has been funded by a $34,000 grant from Waikato Catchment Ecological Enhancement Trust.
NIWA studies showed that stream populations of small fish – smelt, common bullies, inanga, and banded kokupu – were absent or limited because access from the Waikato River was blocked at low river level. This was an issue because many indigenous fish spend part of their life at sea, and the Waikato River is their route between streams and the sea.
The pass has been designed to regulate the depth of water flow down the ramp to allow some fish, such as inanga to swim up the ramp, while still providing a shallow edge for fish such as the banded kokopu who prefer to travel along wetted margins. At the top of the ramp is pool which allows fish to rest before continuing their travel under River Rd and up Bankwood Stream itself.
The fish know the pass is there by sensing the current of the stream as they make their way up the banks of the Waikato River.
It's a first for the many streams flowing into the Waikato through Hamilton that have access problems. If monitoring shows it has been successful and fish numbers increase, similar fish passes will be installed at other sites. NIWA is also following up with improvements to the upstream habitats and there are plans for bank planting and installation of logs as cover.
NAME: Naomi Reynolds
DESIGNATION: Communication Advisor
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