Preparations Underway for the Long Swamp Fish Study

Preparations Underway for the Long Swamp Fish Study

On Wednesday last week I headed out to Long Swamp, within Discovery Bay Coastal Park, to undertake some reconnaissance for the upcoming Aquasave (NGT) fish study – being funded by the Glenelg Hopkins CMA – which Nick Whiterod (our native fish specialist) will be coming down to undertake in the next month or so. I was checking the aquatic habitat and flow conditions at our proposed survey sites to help finalise specific site selection.The good news is that flows or standing water are present at all of the proposed sampling sites.

Most interesting to note is that the artificial outlet in the vicinity of White Sands now remains naturally closed, with a dune forming in front of the former outlet. This outlet was artificially cut by fisherman decades ago, but naturally closed a few years ago during the last drought. I first observed the swamp at White Sands just as the drought was breaking a couple of years ago when hiking the coastal stretch of the Great South West Walk (note: you can click on the images to enlarge them).

Long Swamp at White Sands in August 2010

Fast forward to last week – after a couple of above average rainfall years – and the Swamp at White Sands is undergoing some interesting changes. The standing water depth (particularly in the vicinity of the former outlet) has increased significantly, expanding the area of aquatic habitat at the site. These changes are very similar to those that have occurred in the vicinity of the artificial outlet of nearby Piccaninnie Ponds, since it was regulated to restore water levels in 2005.

Long Swamp at White Sands in July 2012

Coastal Wattle that had previously invaded the wetland edge has now been drowned by rising water levels, as the area of aquatic habitat recovers

The changes become more subtle as you head inland into Long Swamp, but they are still evident. It will be fascinating to compare the aquatic ecology (fish, frogs and crustaceans) of Long Swamp at White Sands where water levels are recovering to previous levels, with other sites in the system where a drying trend has been observed over recent years.

Inland of White Sands, this Cladium procerum (a long-lived wetland plant) welcomes the return of increased water depth, while the invading Coastal Wattle (a dryland species) behind it has been forced to retreat from Long Swamp.

Mark Bachmann