A surprising discovery at Mount Burr Swamp

During a recent overnight stay at Mount Burr Swamp, water levels were close to maximum and I took the opportunity to set five fish traps to see what was about.

Checking the traps the next morning I was thrilled to find two tiny fish (pictured). Nick has confirmed the species as Southern Pygmy Perch (Nannoperca australis), a species recognised as vulnerable to extinction in the South East region, and another new record for the Mount Burr Swamp Restoration Reserve.

A juvenile southern pygmy perch caught in Mount Burr Swamp 30th October 2019.

We have known for some time that one species of fish, the nationally vulnerable Little Galaxias (Galaxiella toourtkoourt), occurs at Mount Burr Swamp. Little Galaxias have the rare ability to survive the dry phase in seasonal wetlands. Prior to NGT restoration, the dry phase at Mount Burr Swamp probably extended over several months through late summer and autumn, making it impossible for species requiring permanent water, such as Southern Pygmy Perch, to persist there.

Since restoration of the wetland water regime in August 2016, Mount Burr Swamp has not completely dried out. This appears to have enabled a population of Southern Pygmy Perch to establish. It is early days and we know very little about the abundance and age class distribution within the wetland, but finding juveniles is encouraging – it means the species is likely to have bred within Mount Burr Swamp.

The immigration path taken by Southern Pygmy Perch to reach Mount Burr Swamp remains something of a mystery. Despite several past surveys, the species has never been recorded in adjoining pristine wetlands within Marshes Native Forest Reserve. The nearest known population occurs in land-locked Lake Edward 6 km to the east. It is possible that a population within either the Bakers Range Drain or the Reedy Creek Drain, both of which Mount Burr Swamp is ultimately connected to, has dispersed upstream into the Reserve. However the nearest known location for the species within those drainage systems is approximately 20 km downstream. It is a testament to the tenacity of this tough little native fish that it has made it all the way to Mount Burr Swamp. We wish it all the best for a thriving future there!

Ben Taylor