THE entire Geelong section of the Barwon River has been shut down due to an outbreak of blue-green algae.

Authorities yesterday extended the area of the river that is now closed from Buckley Falls to the Breakwater. Signs have been placed along these areas of the river.

Lake Connewarre and sections of the lower Barwon River also remained closed, while the river at Barwon Heads remains unsuitable for swimming, but is not closed.

The ocean beach immediately to the east of the river mouth has also been affected.

Parks Victoria district chief ranger Siobhan Rogan advised that contact with water should be avoided in areas where discoloured or greenish water, scum in the water or green algae were evident.

"Direct contact with water affected by blue-green algae could result in skin irritation and respiratory or hayfever-like symptoms," she said.

"The water could also affect animals, so pets should not play or swim in affected water as animals may try to groom away the algal residue."

Toxins produced by blue-green algae can accumulate in seafood and the advice is for anglers not to collect mussels, prawns or crabs from Lake Connewarre or the Barwon estuary.

However, Ms Rogan said people could still enjoy catching fish and boating in Lake Connewarre and along the upper and lower Barwon estuary by taking the following precautions:

REMOVE affected clothing and wash skin immediately if you come into contact with contaminated water;

REMOVE the guts and gills of all caught fish and clean them in uncontaminated water before cooking;

TAKE rubbish including internal organs of fish home to discard;

DO not cook the fish whole as this may distribute toxins from the gut to the fish flesh, making it unsafe to eat; and

WASH down water vessels with fresh water to avoid translocation to another site.

Swimming areas unaffected by the blue-green algae include the Geelong foreshore, all coastal locations from Geelong around the Bellarine Peninsula, including the Ocean Grove main beach, east of RAAF's Beach, and then west from Barwon Heads.

Sightings of blue-green algae can be reported to the DSE Customer Service Centre on 136 186.