The impact of carp on a rhizomatous macrophyte was examined in two consecutive years
using three outdoor aquaculture ponds with naturally established beds of Potamogeton
tricarinatus. Each pond was divided with wire fencing to form a carp (500 kg ha-1) and
control treatment. After 6 weeks, plant biomass had declined to the same extent in the
carp and control treatments, indicating that direct physical disturbance by carp was not
reducing the biomass of P. tricarinatus. In a second experiment, carp were added to two
of the same ponds when plants were regenerating after a 9-11 month drying period. After
8 weeks, P. tricarinatus biomass in the carp treatments was between one half and one
tenth of the biomass in the control treatments and one control treatment supported more
Najas tenuifolia than the paired carp treatment. The lower biomass of Potamogeton in
the carp treatments was a result of fewer shoots and less growth per shoot. Rhizomes
had been undermined in the carp treatment with less than 1% of plants growing from
rhizome compared to 36% in the control treatment. Accumulation of sediment into traps
was significantly higher in the carp treatments (2.5 to 77.5 times more than the control).
On average, carp resuspended 662 kg dry sediment ha-1 for each 100 kg ha-1 of carp or
6.6 times their wet weight biomass in dry sediments each day. Some implications of high
sediment resuspension are discussed. The research demonstrates that well anchored
macrophyte species can show tolerance to the physical disturbance associated with carp
benthic feeding, however, these same species are vulnerable during regenerating and
recruitment stages. It is suggested that anchorage is the most important factor for
determining plant tolerance to carp. The implications for aquatic plant and riverine
management are discussed, including the importance of excluding carp from newly
flooded wetlands and the role of carp in determining alternative stable states.
| Identifer | oai:union.ndltd.org:ADTP/219522 |
| Date | January 1999 |
| Creators | Swirepik, Jody, n/a |
| Publisher | University of Canberra. Resource, Environmental & Heritage Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | ), Copyright Jody Swirepik |
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