Cane toads

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Approaches for monitoring effects of cane toads on aquatic fauna - fishes and invertebrates

Andrew Storey

School of Animal Biology (M092),
The University of Western Australia,
35 Stirling Hwy,
Crawley, WA 6009,
ph. (08) 6488 1482,
fax (08) 6488 1029,

A recent ecological risk assessment to predict the likely extent of impacts of cane toads on the fauna of Kakadu National Park (KNP) identified species of aquatic invertebrates and fish potentially at threat. However, few studies have detailed effects of cane toads on aquatic invertebrates and fish, with most information either observational or taken from incidental monitoring programs. Even in KNP, the rapid and extensive invasion of cane toads into the park, including into designated ‘control’ sites has complicated interpretation of their impact, with the established monitoring programs relying on detecting changes relative to pre-invasion baseline conditions. These interpretations are then further confounded by the inherent variability of tropical ecosystems.

With the approach of cane toads to Western Australia, the opportunity exists to establish a BACI (Before-After:Control-Impact) monitoring program in the East Kimberley, by selecting appropriate ‘control’ sites (i.e. located ahead of the advancing front or in inaccessible refuges), and by building on established baseline data sets.

Quantitative data on fishes and aquatic macroinvertebrates have been collected over the last five years, using standard methods, as part of various projects in the East Kimberley . River systems sampled, from east to west, include Sandy Creek , Keep River , Knox Creek, Lake Kununurra , lower Ord River , Parry Lagoon, and the Dunham, upper Chamberlain and Pentecost rivers. Data were applied to a range of outcomes, including determination of habitat preferences, environmental flow requirements, drought response, food web analysis and baseline monitoring for future irrigation developments. These data provide a solid foundation upon which a more comprehensive baseline may be built, and against which future changes associated with possible invasion by cane toads may be assessed.