Bj. Hicks et Rfg. Barrier, HABITAT REQUIREMENTS OF BLACK-MUDFISH (NEOCHANNA-DIVERSUS) IN THE WAIKATO REGION, NORTH-ISLAND, NEW-ZEALAND, New Zealand Journal of Marine and Freshwater Research, 30(1), 1996, pp. 135-150
Black mudfish (Neochanna diversus) were found at 39 of 80 sites in the
Waikato region, New Zealand, ranging from large wetlands to small swa
mpy streams. Of the sites with mudfish, 87% were dry at some time duri
ng summer. Sites with mudfish also generally had emergent and overhang
ing vegetation and tree roots, and showed low to moderate human impact
. Black mudfish coexisted at some sites with juvenile eels or mosquito
fish, but were absent from all sites with common bullies (Gobiomorphus
cotidianus) or inanga (Galaxias maculatus). Sites with mudfish had al
most exclusively semi-mineralised substrates or peat; only one site ha
d mineralised substrate. Geometric mean catch rate for the 39 sites wi
th mudfish was 0.70 fish per trap per night. Mean summer water depth w
as only 2.1 cm at sites with mudfish, compared to 22.6 cm at 41 sites
without. Winter and maximum water depths were also less at sites with
mudfish than at sites without mudfish. Mean turbidity was 11.5 nephelo
metric turbidity units (NTU) at sites with mudfish, but 21.3 NTU at si
tes without mudfish. Mudfish catch rates were negatively correlated wi
th summer water depth, winter water depth, disturbance scale rating, a
nd turbidity. A discriminant function model based on these variables s
uccessfully predicted 95% of the sites with mudfish. Habitat preferenc
e curves are also presented.