Response to a fish kill at Port Geographe Marina

At a beach on the marina’s western side, around 20 blue swimmer crabs were reported to be immobile but able to wave their nippers, along with a slow-moving eel-like fish. A dead flounder was also reported by one caller. Dead crabs were reported on a subsequent visit.

DPIRD believes this fish kill was most likely due to decreased dissolved oxygen levels within the canal caused by a combination of high water temperatures, a build-up of decomposing seagrass and seaweed and a temporary disturbance of this decomposing material during maintenance dredging in the marina.

Maintenance dredging to increase flushing of the marina is required annually to maintain safe vessel passage by removing marine sands and decomposing seagrass and seaweed accumulates after winter storms. It also helps maintain navigational safety of the entrance channel. DoT has a dredge management plan and completes environmental monitoring during dredging operations to assist in reducing the risk of affecting aquatic life within the marina, while also improving access.

While the fish kill appears to have passed, the risk of further fish kills in the marina remains high with the very warm weather and the continued dredging. If further kills occur, people are urged to stay safe around fish kills by following general Department of Health advice:

• not to swim in areas of water with large numbers of dead and decomposing fish because they may contain high levels of bacteria and have an objectionable odour;
• not to fish in water with large numbers of dead fish;
• temporarily not to collect or consume fish from the waters near a fish kill;
• not to collect and use dead fish for bait or consumption because of the risk of high levels of bacteria; and
• not to allow pets and other animals to come into contact with dead or decomposing fish either in the water or on shore.

Our officers have been trained to collect fish and water samples using appropriate safety equipment and methods. The best way the public can help is by reporting fish kills to FISHWATCH on 1800 815 507. This is a 24/7 reporting service. Tell us where and what you saw, including numbers of dead fish and, if possible, the species affected. And, if you have GPS coordinates and/or photographs, that will also assist DPIRD’s investigation.