Risk of invasion
First-hand experience with the flows in a vertical slot fishway
|
A suite of freshwater fishes have been introduced to Australia. Unfortunately, many of them are considered pests. This is due to range of negative impacts they have on native fish species, and ecosystems in general. Key invasive species in Australia include European carp, Mosquito fish, Tilapia and oriental weatherloach. Trout species, despite forming the backbone of a multi-million dollar industry, are also a pest from an environmental perspective. Where these species are present, there are a range of documented impacts, including predation, competition, habitat degradation and harbouring and spreading disease. Once established, eradication is economically unfeasible in most cases, hence preventing introduction and establishment is a primary management objective. This study aimed to explore the invasive potential of a suite of feral fish in the ACT, by examining their intrinsic swimming performance.
This study has been accepted for publication in Ecology of Freshwater Fish |
Swimming speed |
Swimming performance trials (prolonged and sprint) were performed on numerous feral fish species from the ACT region. These included Gambusia holbrooki, Carrasius auratus, Oncorhynchus mykiss and Perca fluviatalis. Additionally, flow velocities at a fish passage structure (vertical slot fishway) in the lower Cotter River system were measured under a range of river discharges to examine the effect of river flow on likely by these invasive species. Data from other species and passage obstacles were included from Starrs et al. (2011) to allow for comparisons with the endangered Macquarie perch.
|
Invasion potential |
We found that the four species examined displayed a wide range of swimming performance abilities, with Gambusia holbrooki exhibiting the poorest swimming ability, while Oncorhynchus mykiss was the best. More generally however, swimming performance scaled well with body size, indicating that the introduction of large-bodied species will likely see the greatest rate of natural spread upstream. Comparisons to Macquarie perch revealed that the construction of barriers to impede feral fish invasion would likely create a passage obstacle to Macquarie perch. Preventing introduction is the key to ensuring the protection of Macquarie perch from the risks presented by Perca fluviatalis.
|
Relationship between fish size and swimming performance, and predicted probabilities of fish passage through a range of man-made and natural obstacles.
