1. Are willows really such a problem ?  What's wrong with there being willows along our rivers ?

 

Willows are now considered one of Australia's worst environmental weeds; being among Australia's 20 Weeds of National Significance.  More than 30 willow species have been introduced into Australia and they are rapidly spreading and having major impacts on the health and flows of our rivers and wetlands.  Some of those impacts are:

 

Willows drop their leaves in autumn, breaking down in the water and changing water quality. This in turn impacts on river wildlife.

 

Willows are highly invasive, spreading from seeds, branches or twigs.  They can choke the waterways denying us the chance to enjoy our rivers (see photo at right), and out-compete native trees and shrubs along the banks.

 

Willows obstruct flows along rivers, sometimes changing the course of the river and accelerating soil erosion.

 

Willows shade rivers, sometime densely, and this can alter water temperature and disadvantage the breeding of fish and other native river species.

 

Willows 'drink' a lot of water - more than red gums that used to occupy the bank.

 

Willows overgrowing the Molonglo River near Canberra, ACT

 

 

 

Studies have shown that river reaches infested with willows have substantially less insects and wildlife.

 

To find out more follow this link to the Weeds Australia web site http://www.weeds.org.au/WoNS/willows/resources.htm

 

2.  Why carp are bad news for healthy rivers, wetlands and native fish

 

Photo taken by: Jason Higham

 

Carp are a highly adaptable invasive species, thought to have been introduced into Australia in the 1850-60s.  They are now widespread across the Murray-Darling Basin and some other areas of southern Australia.

 

They can live in a wide range of habitats, and tolerate a broad range of water temperatures, salinities and other water quality parameters.  In warmer areas they are fast growing and females start breeding at 2-3 years and males at 1-2 years.  They are prolific breeders in ideal environments.

 

Carp have few predators and they eat just about anything - plants, insects, seeds, algae, molluscs, other fish, shrimps etc

 

Carp will typically spend the cooler seasons in the main channel of rivers and then, if the opportunity exists, move into floodplain wetlands from spring through to autumn, where they will breed.  This presents an opportunity to reduce their populations.

 

Environmentally, carp are a pest because of how and what they eat.  They can reach large population densities in small areas and devastate the habitat by undermining aquatic plants, and muddying the water.  The latter then impacts on regrowth of plant species by denying them of light. 

 

Carp also compete with native fish for food and territory.  Today, native fish populations across the Murray-Darling Basin are thought to be at about 10% of their levels compared to pre-European times, and carp are seen as one reason for this drastic fall in numbers. 

 

Various new technologies are now available to reduce carp populations, and for each of its RiverSmart reach projects these will be considered.

 

3.  Why we need to allow native fish to bypass weirs and dams - coming soon

 

 

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