Wetland fauna restoration
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Before the Sanctuary valley was cleared and the stream dammed, there would have been limited wetland habitat. However, the two old water reservoirs provide us with the opportunity to develop wetland habitats and release a range of aquatic species that would be appropriate to this area.
We assumed that the aquatic fauna to be restored in the Sanctuary should be characteristic of the southern lowland North Island. A list was generated of species known from this area before human settlement and those that have become naturally established since then.
This list includes 32 species of birds (of which 12 are now extinct), two amphibians (of which one is extinct), and approximately ten fish (of which one is extinct).
When the Sanctuary was first established, seven species of birds (two shags, two gulls and two ducks) used the lakes and two species of native fish (banded kokopu and short-finned eels) have been identified in the Sanctuary since then. Two exotic fish species, brown trout and perch are also found in the Sanctuary and are a priority for eradication before any new species of native fish can be released.
Aquatic Birds
The lakes, streams and wetland provide a variety of habitats that are attractive to a range of aquatic birds.
Nineteen aquatic birds have been identified as suitable for the Sanctuary. A number may self-introduce when the habitat is right, but others will need to be transferred.
The first waterfowl releases have occurred: brown teal, shoveler, and New Zealand scaup. These birds have been sourced from captive breeding programmes. Further releases of shoveler will be required before these birds are successfully established at the Sanctuary. As the wetland and lake habitats improve, the second wave of releases could include: Australian coot, grey teal and grey duck.
Some species, such as dabchick, marsh crake and spotless crake have never been transferred and techniques may need to be trialled first. Source populations will also need to be identified before transfers can be effected.
Frogs
Only two species of native of frogs (that may have been found in the Sanctuary) are regarded as semi-aquatic, and one of these is extinct. The Maud Island frog was introduced to the Sanctuary in 200x - these frogs are mainly land-based.
Fish
Any fish species introduced to the Sanctuary should be:
- able to breed in a small landlocked eco-system; or
- be able to climb through the predator-proof fence; or
- be able to be caught and transferred over the fence to complete their migration (in or out of the Sanctuary).
Eight species including longfinned eel, several species of bully and several species of galaxiid have been identified as meeting the criteria for release in the Sanctuary. However, before any native fish are released into the Sanctuary, exotic fish need to be successfully eradicated and habitat evaluated for the new species. You can view some species of native fish in the fish tank and display at the lower lake.
Invertebrates
The quality of stream water in the Sanctuary is very high and there is a good diversity of freshwater invertebrates present, especially in the streams of the upper valley. Two new species of water beetle have been discovered in the Sanctuary.
Any introductions of wetland invertebrates must be done with caution to protect existing species. The introduction of the wetland invertebrates is an unknown science so any transfers will be carefully evaluated and monitored, and are unlikely to be undertaken until the exotic fish have been eradicated.