Flow as a disturbance agent: fish responses to serial flooding in a hydrologically-variable dryland river system, Australia

Presentation cancelled by author

Flow as a disturbance agent: fish responses to serial flooding in a hydrologically-variable dryland river system, Australia

(Oral)

Glenn Wilson
wilson@biology.sdu.dk

Ecosystem Management, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia Present address: Department of Biology, University of Southern Denmark, Odense M, 5230, Denmark, Denmark

DOI: 10.17011/conference/eccb2018/108200

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Lowland rivers are one of the most prominent freshwater ecosystems globally, yet are also one of the most imperiled from expanding human settlements, agriculture and water resources capture. Many countries are implementing environmental water programs to help offset the ecological impacts of human activities. While these rely on knowledge of ecological responses to flow variability, their strength lies in access to data from as wide a range of hydrologies as possible, and both natural and managed events.

I examined shifts in fish assemblage structure and recruitment across a lowland distributary network in Australia's northern Murray-Darling Basin. Sampling during 2011 and 2012 coincided with a small flow pulse followed by two large flood events. It was hypothesized that assemblage structure would vary significantly over time but that abundances of all common species would respond in a similar (positive) manner to flooding.

Assemblage structure varied substantially among sites at the beginning of the season, particularly following the initial, small managed release. However, assemblages had a far greater similarity following the two floods, although began to diverge again by winter. Native species displayed varying responses to the flood events in their recruit abundances. Juvenile carp gudgeons declined markedly in abundance after the first large flood and were absent following the second large flood. However, spangled perch (Leiopotherapon unicolor) and bony herring (Nematolosa erebi) showed a generally positive response to both floods in their recruitment. Recruit abundances for the exotic carp Cyprinus carpio) increased by up to 55,000% following the initial large flood, yet were nearly absent following the second flood. Size-structure data for the exotic goldfish (Carassius auratus) indicated a similar pattern to that of carp.

These findings confirm the general adaptation of indigenous aquatic species to local flow conditions, including highly variable discharge rates and large floods - albeit that species with a greater lentic preference (carp gudgeons) may be impacted by larger events. Further, they indicate the corresponding potential for a disconnect between exotic species and local climatic variability despite the broader colonisation success in these taxa.

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INTRO:
Changes in fish assemblage structure in response to floods were examined in dryland river sites accross Australia's northern Murray-Darling Basin. Fish assemblage structure varied greatly between sites at the beginning and toward the end of the flood season but became more similar at the height of the season. Juvenile carp gudgeons declined in abundance after flooding, yet spangled perch and bony herring increased in abundance. Exotic carp and goldfish increased in abundance after the first flood but were nearly absent after the second flood. The observed patterns demonstrate the better adaptation of native species to local flow conditions, however lentic native species are less well-adapted to flood events.
MERITS:
Interesting and novel research. The topic is well introduced and the findings are clear yet concise.
CRITIQUE:
I would have liked a bit more detail on the nature of the sites and the experimental design but recognise this is difficult to convey in an abstract
DISCUSSION:
Useful research looking at the variation in resiliance and adaptation to different hydrological regimes. The data was from 2011 and 2012 so it would be interesting to find out in future research if any changes in population structure have occured over time and how they may be predicted to change in the coming years.

- - -
INTRO:
The study aimed to assess how the fish community of a lowland rever reflect to the flood event, in context of disturbance. Results indicated, that non-indigenous species may benefit from the recorded disturbance events (floods).
MERITS:
The positive relation of disturbances (or alterations in disturbance regimes) and biological invasions is a known phenomenon and hotspot in invasion biology, therefre results of this study could be interesting for scieentific community.
CRITIQUE:
In my opinion the adaptation of native species to local environmental conditions/factors within their range is evident and do not need to highligt it in you abstract. Much more interesting topic, the potential invasion - distubance connection should be better "discussed".
DISCUSSION:
This study will be interesting mostly for invasion ecologists, therefore I suggest to take it into consideration, throughout your discussion section

Flow as a disturbance agent: fish responses to serial flooding in a hydrologically-variable dryland river system, Australia

Presentation cancelled by author

Flow as a disturbance agent: fish responses to serial flooding in a hydrologically-variable dryland river system, Australia

(Oral)

Glenn Wilson wilson@biology.sdu.dk Ecosystem Management, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia Present address: Department of Biology, University of Southern Denmark, Odense M, 5230, Denmark, Denmark

SEE PEER REVIEW

SEE PEER REVIEW

Glenn Wilson
wilson@biology.sdu.dk

Ecosystem Management, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia Present address: Department of Biology, University of Southern Denmark, Odense M, 5230, Denmark, Denmark