New Zealand Journal of Zoology abstracts
Sensitivities of mosquitofish and black mudfish to a piscicide: could rotenone
be used to control mosquitofish in New Zealand wetlands?
KATE WILLIS
NICHOLAS LING*
The University of Waikato
Department of Biological Sciences
Private Bag 3105
Hamilton, New Zealand
email: nling@waikato.ac.nz
Abstract The comparative sensitivities of mosquitofish
(
Gambusia affinis) and black mudfish (
Neochanna diversus) to the
piscicide rotenone were investigated to determine whether it is feasible to use
rotenone to control mosquitofish in wetlands inhabited by mudfish. Mosquitofish
were exposed to four nominal rotenone concentrations (56, 79, 112, 158
ug.L
-1) and the time taken for 50% (ET50) and 90% (ET90) of
individuals to gasp at the water surface was recorded. Fish were removed from
the rotenone at this stage and placed in rotenone-free water to recover.
Mudfish were exposed to a single nominal rotenone concentration (100
ug.L
-1), and removed when hanging at the surface and gulping air.
The response time of mosquitofish decreased with concentration. Mean ET50
values were 158 and 26 min for 56 and 158 ug.L
-1 rotenone,
respectively. Mean ET90 values were 246 and 36 min, respectively. Mudfish were
approximately twice as sensitive as mosquitofish to 100 ug.L
-1
rotenone. All mudfish recovered following exposure to rotenone. The management
implications of the findings are discussed. We suggest that if rotenone were to
be used to control mosquitofish in wetlands, it could be applied in summer to
remnant standing water as repeated doses of 100-200 ug.L
-1.
Keywords mudfish; mosquitofish; rotenone; piscicide; fish
management; wetlands
*Author for correspondence.
Z99016
Received 14 May
1999; accepted 16 December 1999
PDF file of entire paper: medium quality (624K); (scanned from paper original: notes about this process)
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