HR: 10:45h
AN: NB22B-02    [Abstracts]
TI: Flow Permanence Controls Fish and Invertebrate Assemblages at Multiple Spatial Scales in a New Zealand Gravel Bed River
AU: * Kelly, D J
EM: d.kelly@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research, PO Box 8602, Riccarton, Christchurch, New Zealand
AU: Scarsbrook, M
EM: m.scarsbrook@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research, PO Box 11 115, Hillcrest, Hamilton, New Zealand
AU: Larned, S
EM: s.larned@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research, PO Box 8602, Riccarton, Christchurch, New Zealand
AU: Fenwick, G
EM: g.fenwick@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research, PO Box 8602, Riccarton, Christchurch, New Zealand
AB: Intermittent flows are a natural feature of many alluvial plain rivers of New Zealand, however water abstraction and climatic variability can greatly affect both the duration and spatial extent in loss of surface flows. We have initiated a long-term study on the Selwyn River, Canterbury, with the aim of determining how interactions between natural flow variability and water abstraction control invertebrate and fish communities through variation in flow permanence. River discharge along the 40 km study section is simultaneously controlled by runoff from the foothills and groundwater levels along the plains, with permanence ranging from 100% at both the runoff dominated upper reaches and groundwater dominated lower reaches, to <10% in the middle reaches. During contiguous flow, invertebrate assemblages formed two distinct groups characterized by contrasting life histories: a univoltine/semivoltine group at the top and bottom of the river where flow permanence exceeds 80%, and a multivoltine group in the central reaches where flow permanence ranges from 10 to 75%. Distinctive fish assemblages characterized upper and lower portions of the river, possibly reflecting impairment of dispersal across intermittent middle reaches. Only relatively small numbers of fish dispersed into intermittent middle reaches, with the greatest fish densities at sites with >80% flow permanence. Results of our study indicate that changing flow permanence leads to spatial and temporal patchiness in habitat availability, with significant consequences for biodiversity and ecosystem function.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1842 Irrigation
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly