Will fencing floodplain and riverine wetlands from feral pig damage
conserve fish community values?
Abstract
Installation of feral pig (Sus scrofa) exclusion fences to conserve and
rehabilitate coastal floodplain habitat for fish production and water
quality services remains untested. Twenty-one floodplain and riverine
wetlands in the Archer River catchment (north Queensland) were surveyed
during post-wet (June-August) and late-dry season (November-December) in
2016, 2017 and 2018, using a fyke net soaked overnight
(~14-15hrs) to test: 1) whether the fish assemblage are
similar in wetlands with and without fences; and 2) whether specific
environmental conditions influence fish composition between fenced and
unfenced wetlands. A total of 6,353 fish representing twenty-six species
from 15 families were captured. There were no wetland differences in
fish assemblages across seasons, years and for fenced and unfenced
(PERMANOVA, Pseudo-F <0.589, P<0.84). Interestingly
the late-dry season fish were far smaller compared to post-wet season
fish: a strategy presumably in place to maximise rapid disposal
following rain and floodplain connectivity. In each wetland a calibrated
Hydrolab was deployed (between 2-4 days, with 20min logging) in the
epilimnion (0.2m) and revealed distinct diel water quality cycling of
temperature, dissolved oxygen and pH (conductivity represented
freshwater wetlands), which was more obvious in the late-dry season
survey because of extreme summer conditions. Water quality varied among
wetlands in terms of the daily amplitude and extent of daily
photosynthesis recovery, which highlights the need to consider local
conditions and that applying general assumptions around water quality
conditions for these types of wetlands is problematic for managers.
Though many fish access wetlands during wet season connection, the
seasonal effect of reduced water level conditions seems more
over-improvised when compared to whether fences are installed, as all
wetlands supported few, juvenile, or no fish species because they had
dried completely regardless of the presence of fences.