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Platypus:
year-to-year changes in abundance
in the Manning River
Platypus are only occasionally recorded underwater during the night-time surveying of fish. The resulting abundance data are quite variable, although moving-average trends appear to reveal responses to changing river flows.
These data are likely to provide a river-long perspective on platypus abundance given that they arise from twelve sites starting at the tidal limit and ending 54 km by river upstream (Cundle Flat).
High flows over the same time
(can scour & infill, as well displace fauna or encourage migration & breeding)
Flood impact??
There is a suggestion of a brief river-long impact on platypus caused by the major flood in June 2011. However, Dr Tom Grant surveyed platypus in the lower river and far upper estuary before and after the flood and found no changes in abundance. Water velocities are likely to be lower in the downstream end of rivers during floods: would this offset/reduce flood impacts on platypus there?
Low flows impact??
The reductions since 2014-15 are worrying and suggest platypus are susceptible to a run of low-flow events (reduced food supply, reduced habitat area, increased predation by foxes/dogs as they cross shallows or scurry up to burrows?).
Dwarf variant??
A very small individual recorded in the lower river.
At 20-25 cm TL this is considerably smaller than free-moving individuals recorded in other systems, even for the period of juvenile emergence later in summer (Grant pers. comm.).
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