CBER's invasive fish research programme

Hikutaia Cut pest fish removal

The Hikutaia Cut (NZMG 2742152E 6430934N) is 10 hectares in size with a maximum depth of 3 m. It was constructed as a floodway but was never connected to the adjoining Waihou River. It is located on the eastern edge of the Hauraki plains north of Paeroa and has no permanent surface inflows or outflows. However, during periods of high water, there are outflows into the nearby Waihou River. Water quality in the Hikutaia Cut is excellent, with visibility in excess of 3 m. There are well established populations of exotic and native fish species including perch tench, goldfish, koi carp and eels. There are extensive beds of macrophytes covering approximately 95% of the lake bed. In 2000, an eradication attempt was undertaken by an independent contractor on behalf of Environment Waikato to eliminate koi from the Hikutaia Cut using nets. If you have Google Earth, click here to go to the site location. This opens best with Mozilla Firefox browser.

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Figure 1. Hikutaia Cut looking north-east to the Kaimai Ranges. Photo: Brendan Hicks.

Boat electrofishing surveys of Hikutaia Cut were undertaken in August 2003 and March 2006. The August 2003 electro-fishing covered an area of 2400 m2 in 27 minutes and resulted in a total of 70 fish, including koi carp, tench, perch and goldfish. A large number of eels were also sighted but not captured. There were two size classes present for the tench (37–144 mm FL), perch (125–377 mm FL) and koi carp (196–530 mm FL), while goldfish ranged in size from 90 to 157 mm FL. Of particular interest was the large number of koi and tench missing pectoral and pelvic fins, indicating high predation pressure from perch and tench.

 

Koi

Perch

Tench

Goldfish

Total

Number of fish

19

23

19

9

70

Total Weight (g)

9742

5144

310

420

15676

Mean Weight (g)

513

224

16

47

-

Kg/ha

37.5

19.8

1.2

1.6

60.1

Table 1. Results of boat electrofishing Hikutaia Cut 19 August 2003

The Hikutaia Cut continues to have viable populations of pest fish despite eradication efforts carried out in 2000. The two boat electrofishing surveys carried out in 2003 and 2006 both found adult and juvenile individuals of koi carp, perch and tench; adult specimens of brown bull head catfish were also captured during 2006. There does appear to have been a significant reduction in fish biomass between 2003 and 2006 but further surveys are needed to confirm this. The Hikutaia Cut is also a prime candidate for a large scale eradication effort; it is easily isolated from the Waihou River and the high water quality means it can be easily electrofished.

 

Koi

Perch

Tench

Goldfish

SF eel

Catfish

Inanga

Total

Number of fish

28

30

23

43

48

2

3

177

Total weight (g)

15764

5556

234

3649

2977

423

13

28616

Mean Weight (g)

563

185

11

85

62

211

4

-

kg/ha

1.6

0.60

0.02

0.36

0.3

0.042

0.001

2.923

Table 2. Results of boat electrofishing Hikutaia Cut 6 March 2006.

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Figure 2. Fish from Hikutaia Cut, Waihou River system. Koi carp are to the left and top, European perch of a range of sizes are in the centre, goldfish occupy the right of the picture, and tench, including young of the year, are just above the ruler at the bottom.