31 / 112
31
(far left, top) Shallow Channel causeway, showing Shallow
Channel on the left and Oyster Channel on the right (Photo
– Google Earth). Tidal flow has been blocked since the 1920s,
causing significant damage to seagrass beds, mudflats and fish
habitat. A large decline in shorebirds, fish species and overall eco-
system productivity has since occurred, a process which is being
reversed since the installation of a large double cell box culvert.
(far left, bottom) Recreational fishers enjoying the new culvert in
the Shallow Channel Causeway. Prior to the culvert being built
the area was not used by recreational fishers at all, a reflection of
the extremely low fish stocks present at that time. Photo credit:
Alan Cibilic, WetlandCare Australia
(left) Shallow Channel mudflats have been restored by the return
of tidal flows through the culvert. Photo credit: Alan Cibilic, Wet-
landCare Australia
improve ecological processes in the lower Clarence estuary. In 2006,
after years of consultation, geotechnical studies and extensive stake-
holder engagement, WetlandCare Australia initiated the installation
of a large doublecell box culvert. This design allowed the greatest
volume of tidal exchange and the best access for fish passage.
The completed culvert has dramatically improved connectivity be-
tween Shallow Channel and Oyster Channel for tidal flows and fish
passage. The once permanently-submerged sandbars and mud-
flats in Shallow Channel are now exposed at low tide and wading
birds have returned. Over time, sediment will be mobilised and
the channel structure reinstated. Nutrient and dissolved oxygen
levels are returning to normal, and the site no longer suffers de-
bilitating extremes of temperature. This has relieved the pre-
vious stresses on seagrass beds and other important aquatic
habitats, and vastly improved the overall ecological health of
Shallow Channel.
Fish passage has greatly improved, with recreational fishers
now regularly joining the active pelicans in Shallow Channel.
Numerous fish species including whiting, flathead, yellow-
finned bream, eel and mullet have benefited from the improved
fish passage and habitat at Shallow Channel. The value of the
area as a food resource for resident and migratory shore birds
such as pelicans, oystercatchers, terns, egrets, sandpipers and
spoonbills has also increased.