DWER believes sandbar opening partly to blame for fish kill in Chapman River Estuary

A fish kill last week in the Chapman River Estuary is believed to have been partly caused by community members deliberately opening a sandbar, causing water levels to fall and salinity to rise in the river.

The deaths of about 1000 black bream and mullet were observed and it was reported to the Department of Water and Environmental Regulation on Friday, September 15.

DWER officers collected water samples to assess the dissolved oxygen, temperature and salinity in various locations along the lower estuary where the dead fish were seen.

The department said it suspected that digging out the bar and connecting the river to the ocean had caused water levels in the river to drop by about 1.5m.

As well, the opening of the sandbar had increased the volume of seawater entering the lower river system as a result of the frontal weather system earlier in the week, leading to a rapid rise in salinity and lower dissolved oxygen levels.

“The opening of the bar at the estuary of the river, can be considered by some to be a harmless activity, however, in this case we believe it has been one of the contributing factors in this fish kill incident,” DWER director regional services Don Cummins said.

“It is important for the health of the river system and for local aquatic species that the community do not interfere with the natural sandbar between the river and the ocean.”

People are asked to report any fish deaths to the Department of Fisheries Fishwatch on 1800 815 507.