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BLACK MUDFISH

(Neochanna diversus)

Below is a report compiled by Dwayne Walsh .

Endangered Species:  Conservation and Preservation of the Black
Mudfish of the Hikurangi swamp.

The Black Mudfish (Neochanna diversus) is one of four species of the
genus Neochanna  is one of two genera that make up the family
Galaxidae.  The Black Mudfish was most probably relatively widespread
south of Auckland, and in the Waikato district where it is commonly found in swamps, drains and wetlands.  It was also probably widespread
through out the Northland region in pre-European times in the many Kauri
swamps and wetlands , however due to the reclamation of many of these areas the black mudfish has become an endangered species.

Neochanna diversa  is now found in very few localities in the Northland
region these include Kauri gumfield swamps around Northland, the
Otaikarairangi swamp in Hikurangi and also near Wellsford.

Habitat requirements:

Little is known about the habitat requirements of the black mudfish
Like many native fish, they have a very secretive nature and most
people are unaware of their very existence.
Therefore much of the information used in this report is from research
undertaken in Waikato.
They prefer shallow cool water of acid conditions.  Extensive trapping was carried out in 1993 by Barrier, who found that 87% of the sites where
black mudfish were located , dried up completely in the summer months.
This suggests they are obligate occupiers of seasonally dry areas of
wetlands(Dean;1995)  This appears to be a survival adaptation as these
fish do not compete well with other types of freshwater fish, for example
native fish as well as more recently introduced species such as mosquito fish (Gambosia affinis)  Another study in the Waikato found that the
mudfish inhabit very shallow waters with a pH range of 4.5 - 7.0 with
very little dissolved oxygen.  However the range of levels of DO was from
0.69 to 7.8mg/L , this was during Sep 93 and Oct 94 and mudfish were caught at all sites in reasonable numbers.

The Hikurangi Swamp was once very extensive covering several thousand
hectares.  Only two areas of any size remain of the swamp totalling
approx. 300Ha.  Until recently no examination had been carried out by D.O.C .  Recently two mudfish in the Northern end of the swamp were found and these were the first that had been seen here in over 30 years.

Northland Polytech students in the Freshwater

Copyright©1998Department of Environmental Management

Following field work surveys and research into other black mudfish (Neochanna diversus) studies, the freshwater ecology class at Northland Polytech completed an assignment based on exploring management strategies for this species in the Otakairangi Wetland Reserve.

What follows is an edited version of the main strategies suggested and the rationale for beginning active management of this population of black mudfish.

All the mudfish species are endemic to New Zealand, and thus have an intrinsic conservation value. They should be seen to be as important as other endemic species which currently receive substantial amounts of the conservation budget for protection. As less anthropocentrically attractive species their management has been put on hold for too long and so they deserve long overdue attention.

There are certain legal responsibilities indicated which require protection of black mudfish, eg:

• N.Z.’s biodiversity strategy - a consequence of signing the international biodiversity agreement at the 1992 Rio convention
• the RMA Section 6c - protection of significant habitats of indigenous fauna
• conservation of this species is Category C (which should be reviewed)

The three known black mudfish populations in Northland are fragmented and two (Hikurangi and Kerikeri/Ngawha) are insecure. The current debate re whether these are genetically differing species needs to be clarified. If they are in fact separate species, they become even more vulnerable and important. However, if they are not separate species, their geographical isolation suggests further speciation is in process. Recognition of this species should enhance its biodiversity importance.

It is suggested that the protection of this population is in fact relatively easy, in comparison with other major endangered species programmes. That is, there is little or no need for costly pest and predator eradication measures. It has been suggested that the mudfish may be able to co-exist alongside possible competitors such as mosquito fish (Hicks, 1996). However this suggestion is based on limited data, therefore the ecological interactions of mudfish and mosquito fish need further study as a priority (see Monitoring section).

The population is already partially "protected" by the fact that its habitat is DoC owned reserve. Protection of the habitat is suggested as the best way of protecting the species.

This habitat of course has its own intrinsic values and importance as an ecosystem. As such any maintenance or enhancement would most likely also benefit many other flora and fauna species. The conservation status of freshwater fish in general needs to be addressed. The anomally of the RMA specifically affording protection to habitats of trout and salmon, while native fish species as a group have no formal protection is ludicrous.

Therefore a campaign to raise the conservation status of important wetland habitats alongside the status of freshwater fish species, especially the mudfish, would achieve a dual purpose.

It has now been established that the black mudfish is present in the Otakairangi Reserve; therefore there is a need to act NOW!

MANAGEMENT STRATEGIES:

The need for more information about the species and this population in particular, has been highlighted as a high priority. Monitoring and survey work could be sponsored by DoC with minimal expenses helping a student to research:

• investigation of appropriate monitoring techniques - a priority to ensure accurate data
• the temporal questions surrounding how much water the fish need & for how long, are crucial . This is also related to the questions of the future "drying rate" of the wetland, and the ecological relationships of the mudfish & mosquito fish & eel species
• habitat parameters: water quality, nutrient run-off etc, effects of drainage, demographic data / recruitment success etc.
• this could be combined with research into other successful wetland management systems and maintaining contact with other experts and working groups to share knowledge.

• investigate the feasibility of various ways of stabilizing and regulating the water table levels, eg. blocking drains running through the reserve, while enabling neighbouring farmers to continue maintenance of pasture
• get engineers’ reports on above systems, weirs, gates, stopbanks as buffer zones etc
• create mudfish habitat via digging holes similar to gumholes in northern habitat where it is reported (Richard Parrish, pers. comm.) the mudfish are reasonably abundant. Site these appropriately to ensure connecting waterways, minimise risk of invasion by competitors and predators.

Take back management of adjacent DoC owned land to create a buffer zone around the current reserve. Suggested future management ideas:

• plant in appropriate wetland vegetation (ensuring plant provenance) to extend and enhance habitat. This also acts as a filter for agricultural pollutants, run-off etc.
• use this area as an education resource base, eg interpretation centre, information kiosk etc.
• create ponds and lakes, to extend wetland habitat and provide habitat for other threatended species, eg Brown teal, crakes, bittern etc. This could possibly be included in the water level regulation system.
• investigate funding to buy adjacent land as it becomes available to further extend habitat and/or buffer zone.

Considerable possum sign was noted in the reserve, and it is suggested that a management strategy for these pests would a) enhance the general ecosystem and b) be a good PR exercise in regards to the neighbouring landowners.

Various weed species were also noted. A detailed survey to determine species and their extent is necessary. The drains running through and around the reserve are probably a major source of infestation, thus closing or diverting those drains would help stop reinfestation.

There is concern re the amount of gorse present, and its possible effects on mudfish habitat through nitrogen fixing and nutrification.

The most efficient time for weed control would be in the summer when drain water levels are lower.

Care should be taken to avoid chemical sprays which have a residual effect on the soil.

• once aware and educated, the public can become a strong and effective lobby group, ie pressuring for more funding etc.
• it fosters a sense of self responsibility and care, and furthers the education and advocacy through networking
• takes advantage of local knowledge - environmental, historical, cultural etc.
• can provide a large proportion of costs, labour, support etc through involvement similar to the Limestone Island Committee and the Karori Reserve coalition, thus taking pressure off DoC’s limited resources.

This was identified as very important, especially in raising public awareness of the species, but also the value of wetlands as ecosystems. It was seen to be particularly important to educate landusers in the vicinity, on the effects of their activities.

Further suggestions:

• produce an education programme including video, merchandising (stickers etc), a mudfish aquarium etc to promote the mudfish cause.
• investigate the possibility of a long term strategy of linking the Otakairangi Reserve with one or more of the nearby kiwi bush areas. Work towards obtaining legal tenure or access to these kiwi areas and promote both as an educational resource package.
• promote Otakairangi Reserve as a whole ecosystem education resource, including: raised boardwalks, hides and shelters for unobtrusive wildlife observation and ecosystem experience, interpretation centre, etc.

• a detailed survey of the reserve is required to ascertain accurate data on flora and fauna, habitat quality etc. It should include aerial photos.
• boundary fencing must be secure.
• continued monitoring would build on existing data and guage the effectiveness of strategies put in place. Such strategies should be open to review if proving less effective than desired or anticipated.
• use knowledge and experience (positive and negative) gained elsewhere, eg Whangamarino Swamp.
• investigate the feasibility of establishing further populations of this species elsewhere to protect and enhance species diversity and lessen the chance of catastrophe wiping out the existing population.

The arguments above all point to some crucial research questions which should be pursued and that initial management of the habitat should be undertaken.

It is clear that the conservation status of the black mudfish at Otakairangi Reserve, and the habitat itself has been underrated historically. This must be addressed now with some urgency.

We should also take into account the apparent strong El Nino weather patterns we are now entering, and the implications for the winters of 1998 &’99. With the presumed drying trend in the Otakairangi wetland because of agricultural drainage, the implication of a one in 100 year dry period could be very serious if not fatal. A contingency plan is warranted to deal with a 100 year drought event.

BARRIER, Rhys (et al). 1996. Habitat requirements and aerial respiration in the black

mudfish. NIWA Water & Atmosphere #4(3) 1996 : 14-17.

DEAN, Tracie Lee. 1995. Environmental physiology of aquatic and aerial respiration

in the black mudish (Neochanna diversus, Stokell, 1949). Waikato University

(unpub. thesis).

HICKS, B.J. & BARRIER, R.F.G. 1996 Habitat requirements of black mudfish

(Neochanna diversus) in the Waikato region, North Island, N.Z. NZ journal of

marine & freshwater research. 1996 : Vol. 30 : 135-151.

McDOWALL, R.M. 1990. New Zealand freshwater fishes. Auckland : Heinemann.

YOUNG, David. 1996. In search of mudfish. Forest & Bird (Feb 1996) : 14-17.

This paper was a compilation of student work from the 2nd year Freshwater Ecology Class.

Tutor:

Vince Kerr

Sue Bell

Colin Bishop

Jorg Breker

Tania Carter

Lorna Douglas (editor)

Wendy Holland

Jackie Kearns

Trish Routley

Nikki Sharma

Annette Vollmer

Dwayne Walsh

Copyright©1998Department of Environmental Management