With the hot humid weather the Shoalhaven is experiencing this summer, residents are asked to be on the lookout for aquatic weeds. In particular, Salvinia and Water Hyacinth are of current concern in Shoalhaven.
Shoalhaven Water is currently carrying out a control program on Flatrock Dam to eradicate Salvinia (Salvinia molesta) that has reinfested the dam. Salvinia is a free-floating mat-forming fern from Brazil. With the right conditions, this plant can double in area in less than three days.
Dr Michael Roberts, Shoalhaven City Council's Manager Environmental Services stated "Salvinia can affect water quality by preventing light and oxygen from entering the water. This can impact on the natural processes within the waterway including aquatic life and recreational activities as the waterways can become unnavigable due to the dense mat it can form on the water."
Under the Biosecurity Act 2015 (NSW), Salvinia is a Regional Priority Weed. Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from properties and follow-up undertaken. The plant should not be bought, sold, grown, carried, or released into the environment.
Salvinia does not produce any seed and is only spread vegetatively by boats, canoes, trailers, vehicles, fishing equipment, animal e.g., birds, turtles, cattle, and people. Controlling Salvinia is difficult and expensive, due to the need to control every piece of the weed.
Water Hyacinth (Eichhornia crassipes) is also known to occur in the area. This plant can double in mass in five days under favourable conditions. Water Hyacinth reproduces by seed and each capsule from a single flower can have 300 seeds in it. These seeds are viable for up to 20 years. 'Daughter' plants are also produced vegetatively, and each plant can produce 2-4 daughter plants.
Water Hyacinth can reduce water quality, change water temperature, change water pH, lower oxygen levels and obstruct waterways. It is spread in much the same way as Salvinia.
"Water Hyacinth is an attractive-looking plant that can be very popular with fishpond and aquarium keepers. However, it can cause major environmental damage in our local waterways". Dr Roberts said.
Under the Biosecurity Act, there is a 'Biosecurity Zone' applicable for Water Hyacinth that includes the Shoalhaven. Within the zone, Water Hyacinth must be eradicated where practicable, or as much of the weed destroyed as practicable, and any remaining weed suppressed. Additionally, Shoalhaven City Council Biosecurity staff must be notified of any new infestations.
"We urge the community to report sightings of these weed species to Council so that the functions of the natural waterways in which they are found can be maintained." Dr Roberts said.
