Kerry Trayler brought along the skeleton of a pelican with fishing line around its beak to highlight the need to use biodegradable line, which can breakdown over time.
Dr Trayler also spoke about the importance of the rivers to the local Nyungar people, as well as how they are used for boating, swimming, transport, tourism, fishing, crabbing and prawning, and as the setting for fireworks.
She said shopping trolleys, batteries, plastic shopping bags, cans, fridges, tyres and glass bottles were all removed from the river, and algal blooms were the result of nutrients finding their way into the river from detergents, dog droppings and commercial fertilisers.
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READ NOWOther activities on the day included a visit from Kenyana Wildlife Rehabilitation Centre and the construction of a mobile garden with pallets, three grow-it-yourself cubbies and native bee houses. Upper school students learned about salinity and the macro invertebrates in fresh water while junior students had fun learning about waste with presenters from the Mindarie Regional Council.