Environmental Engineering Reference
In-Depth Information
2004). Application of pheromone technology is well advanced for sea lamprey but
is also being investigated for round-goby (Murphy
et al
. 2001), goldfi sh, and com-
mon carp (Sisler 2005) although no teleost pheromone system has yet been fully
elucidated and fi eld tested (Sorensen and Hoye 2007).
Fish pathogens
The release of species-specifi c pathogens (parasites, bacteria, viruses) for control-
ling invasive fi shes is currently only experimental. In Australia, limited success in
controlling European perch has been achieved by the unintentional introduction
of epizootic haematopoietic necrosis (Langdon and Humphrey 1987). Species-
specifi c viral agents such as carp herpes virus (CyHV-3) offer some potential to
signifi cantly reduce common carp biomass (McColl
et al
. 2007) but this disease is
not universally lethal, highly temperature dependent (Gilad
et al
. 2003), and the
likely outcome is some degree of immunity and population recovery. Moreover the
widespread importation or application of such a virus would encounter signifi cant
opposition in those countries where common carp are a legitimate and highly val-
ued ornamental species. Indeed, most research on koi herpes virus worldwide is
targeted at combating this disease in captive ornamental koi.
Habitat modifi cation and restoration
Many invasive fi shes typically thrive in degraded aquatic habitats and may actually
cause habitat deterioration by encouraging eutrophication or increasing turbidity
through sediment resuspension. Reversing the declining quality of aquatic habitats
is unlikely to result in eradication of invasive species but may signifi cantly reduce
their impacts. For example, impacts of
Gambusia holbrooki
on a native Australian
frog were found to be diminished in ponds that retained extensive riparian and
littoral vegetation affording refuge for frogs and tadpoles, respectively (Hamer
et al
. 2002). Riparian revegetation increases stream shading, reduces sediment
and nutrient loading, and may improve the habitat for native species over exotics.
Harris (1997) argued that river restoration, including catchment management,
fl ow allocation, pollution abatement, habitat reconstruction, and the restoration
of connectivity, should form part of an integrated management strategy for com-
mon carp in Australia. Such a strategy has the potential to reduce carp impacts and
restore indigenous fi sh populations but must be exercised with extreme caution
and thorough species knowledge to ensure that any restoration efforts do not make
matters worse rather than better.
Immunocontraceptive control and genetic modifi cation
The induction of triploidy in fi sh using heat, cold, electrical or pressure shocks,
or chemicals, has been commonly used to produce sterile, fast-growing fi sh for
aquaculture (Tiwary
et al
. 2004) and to reduce the likelihood of breeding in fi sh
released for biological control. However, the physiology of triploid fi sh is poorly
understood (Maxime 2008) and some sterile triploids routinely reproduce by
