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The invasive fish research programme focuses on investigations into the distribution and abundance of pest fish such as koi carp (Cyprinus carpio), goldfish (Carassius auratus), and brown bullhead catfish (Ameiurus nebulosus). It also includes studies on the ecological effects of pest fish and on methods to improve capture efficiency and biosurveillance. Key equipment in this programme is a highly successful electrofishing boat (198KB pdf file). A 10MB pdf of a Powerpoint presentation is downloadable here.
The University of Waikato’s electrofishing boat on Lake Karapiro with (left to right) Dudley Bell driving, and David Hamilton and Brendan Hicks fishing.
Fish sampling in non-wadeable habitats
Brendan Hicks and Dudley Bell have developed New Zealand's first successful electrofishing boat specifically to fish non-wadeable habitats. The ability to catch pest fish in fresh water that is too deep for wading (1-3 m) is the key to determining the abundance, impacts, and biological effects of pest fish. Another major advantage of boat electrofishing is its time efficiency, with the ability to fish kilometres of habitat in a single day without the need for repeat visits. Further, quantitative fish capture is possible. With our on-board GPS unit we estimate the distance and area fished. We can then calculate density and biomass per unit area. Since its launch in July 2003 we have was used in over 100 locations in the North Island of New Zealand to catch over 20,000 fish (total weight over 5 tonnes). We have developed multiple-pass boat electrofishing to give removal population estimates (Hicks et al. 2006). Using this method, we have found that koi carp biomass in the Waikato region can reach 2,060 kg/ha.
Invasive fish surveys and fish removal from selected habitats
The electrofishing boat can used to remove koi carp from selected habitats of suitable size. Below is a selection of these fish surveys. Other surveys took place in the Waikato, Manawatu, Wanganui, and Mokau rivers, lakes Rotoiti and McLaren in the Bay of Plenty, and lakes in the lower Waikato basin.
Boat Electrofishing Survey of five Waitakere City ponds (read more)
Awatapu Lagoon pest fish survey (read more)
Boat electrofishing survey of Horseshoe Lake, Hamilton (read more)
Koi carp removal from Kauri Point ponds (read more)
Koi carp removal from pond at Apata (read more)
Koi carp removal from Hikutaia Cut (read more)
Koi carp removal from Waimapu Stream, Bay of Plenty (read more)
Reference
Hicks, B.J., M.W. Osborne, and N. Ling. 2006. Quantitative estimates of fish abundance from boat electrofishing. Pages 104-111(Download) (261KB PDF)
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