European Carp, Turbidity and Algal Blooms

European carp, turbidity and algal blooms

Equipment

· Water sampling bottle (preferably on a pole)

· Turbidly tube

· Mobile phone or camera for photos

· Equipment to provide GPS coordinates

Background

Lake Mokoan was regarded as an excellent inland fishing location. Over time, introduced European carp became the dominant fish. They grow large and are bottom feeders. They strip the wetland bottom of plants including cane grass and suck up the mud to obtain food.

Large numbers of carp changes relatively clear water into very turbid water where light has poor penetration. With high nutrients dissolved in the water, there were seasonal outbreaks of blue-green algae. This very basic life form (similar to bacteria) produces powerful toxins. The toxins are very dangerous to humans and livestock.

The problem of carp only occurred when the Winton Wetland ephemeral wetlands became a permanent water reservoir. When Lake Mokoan was emptied, most of the carp were flushed out.

For the wetlands to recover:

1. It is essential that it remains as an ephemeral wetland, drying out most years so carp can’t re-establish

2. Carp exclusions grids prevent carp moving back from other areas in the catchment

3. Cane grass needs to be allowed to re-establish to restore the natural environment, create habitat and take up the excess nutrients.

With the exception of wide spread blue-green algae outbreaks throughout many waterways in 2016, there have been limited outbreaks since the decommissioning of Lake Mokoan has returned to being an ephemeral wetland.

Affect of blue-green algae on Lake Mokoan

https://www2.health.vic.gov.au/public-health/water/blue-green-algae-cyanobacteria

http://www.theage.com.au/articles/2002/05/10/1021002389836.html

http://rahogan.tripod.com/id42.htm

Introduced carp

http://www.csiro.au/en/Research/BF/Areas/Managing-the-impacts-of-invasive-species/Biological-control/Biocontrol-of-carp

http://www.theaustralian.com.au/news/inquirer/european-carp-public-enemy-no-1-in-the-murraydarling-basin/news-story/1e1c77892fa7f8dafc1cca6ddc1daac5

Turbidity

Turbidity is most easily measured using a turbidity tube

http://www.testkits.com.au/turbidity-tube/ (has video)

Past and current contributions of high turbidity in the Winton Wetlands can include:

· Presence of carp stirring up mud

· Thick layer of muddy sediment from the past introduction of carp

· Lack of cane grass (eaten by carp) to consolidate the mud

· Wind

· Runoff and erosion from further up the catchment.

Measuring change

· Finding out if the turbidity is similar around the different wetlands

· Lake Mokoan had very high turbidity. Is the turbidity still very high?

Examples of locations where turbidity could be measured

Outlet at Dam Wall 36°27'51" S 146°1'13" E

Duck Pond 36°24'5.11"S 146° 9'0.53"E

Boat ramp 36°26'37" S 146°3'36" E

Boggy Bridge Road 36°26'4" S 146°7'0" E

Proposed camping ground 36°30'3.24"S 146° 2'42.15"E

Data table

Describe main features of location, take a photo and annotate / GPS Coordinates / Turbidity measurement

Excluding carp

Locations of carp exclusion guards

Outlet at Dam Wall 36°27'51" S 146°1'14" E

Boggy Bridge Road 36°25'43" S 146°6'52" E

Measuring change

· Are the carp barriers still in place?

· What has been done to prevent turtles being trapped against the Boggy Bridge Road carp barrier?

Monitoring the carp exclusion barriers

Photograph and annotate the images to help answer these questions

How are carp being excluded from entering the wetlands from the drainage channel?

How are carp prevented from swimming into Green Swamp along Boggy Bridge Road?

What has been done to prevent a strong current trapping turtles against the carp barrier?