May 2017: Silkwood field studies

About the MRR

1. What is a Mark, Release, Recapture (MRR)?

MRR studies are commonly carried out by ecologists to estimate population dynamics of insects, fish and other animals, or to monitor how far a species has moved and how long they live. Our MRR in Innisfail aims to better understand the behaviour of male Aedes aegypti mosquito. Our MRR study in Innisfail aims to better understand the behaviour of male Aedes aegypti mosquito.

This will involve releasing male Aedes aegypti mosquitoes only (males don't bite) that have been marked with a dye. The mosquitoes will be released in small identified neighbourhoods and then recaptured through a network of traps to see how far they have flown from the release point, in what time and if they have mated with local female Aedes aegypti in that time.

[CSIRO logo appears on screen with text: monitoring mosquitoes in Innisfail]

[Animation of a map of Australia appears on screen with three places labelled Cairns, Innisfail and Townsville. A small section between Cairns and Townsville is marked out with a white line, the dot that Innisfail sits at with another text box saying Cassowary Coast]

[Image changes to show an aerial shot of Innisfail, buildings can be seen either side of a river and connected by a bridge. An animated mosquito flies in from the right above a text box: mosquitoes love tropical climates]

[Image changes to show a line graph indicating the average rainfall and temperatures of each of the months. Text reads: … like Innisfail where it’s wet and hot]

[Image changes to show a shot of the main street, lined with shops and parked cars. Text reads: … and some love to live around people]

[Image changes to show two CSIRO staff members walking the streets together. Text reads: we’ve been studying mosquito numbers since November 2015]

[Image changes to show a small map of Innisfail and surrounding areas appear on the right hand side. Text reads: through a network of traps]

[Image changes to show the male CSIRO staff member seated with another male at an outdoor table and chair setting. Text reads: - thanks to Innisfail residents and business owners]

[Image changes to show the CSIRO staff members setting a trap. Text reads: the GAT trap attracts females ready to lay their eggs – emptied weekly]

[Camera pans out to show more of the extensive trapping system being set by the two CSIRO staff members. Text reads: the BG trap (powered) sucks in nearby mosquitoes – emptied weekly]

[Image changes to show CSIRO staff members working in a laboratory. Text reads: in the lab we studied what we found and asked what species? How Many? What time of year? We found…]

[Image changes to show a line graph detailing the total number of Mosquitoes caught in the GAT trap over a period of time from December 2015 to September 2016. Text reads: over 30 different species of mosquito and a consistent number of Aedes aegypti.]

[New text appears: Aedes aegypti is an invasive species. Two animated mosquitoes appear on screen a smaller one labelled ‘Male’ and a larger one labelled ‘Female’]

[Image changes to two potted plants and a foot being added to the animation. Both mosquitoes land on the foot and the female draws blood, which is shown as a pool of red on the surface of the foot. Text reads: females bite and can transmit diseases like dengue and Zika]

[Image changes to show the male mosquito leaving the foot and flying off and landing on one of the potted plants. Text reads: males don’t bite they feed on nectar]

[Image changes back to show an aerial shot of Innisfail. Text reads: we now plan to study the behaviour of the male Aedes aegypti mosquito]

[CSIRO logo appears with text:]

Monitoring mosquitoes in Innisfail

2. What is the dye you are using?
Male mosquitoes are fed the red dye before they are released.

Male mosquitoes are fed the red dye before they are released.

The mosquitoes will be marked with small amounts of Rhodamine B, a biomarker that is regularly used in Australia by researchers and does not affect the fitness of the mosquito. The dye is not identifiable to the human eye but is visible under a powerful microscope in the laboratory.

3. Where and when do you plan to carry out this experiment?

We have identified an area in East Innisfail where we would like to carry out a small scale MRR study. While this area has been selected for its varying geographic layout the most important requirement for the study to proceed is support from local residents. Without this the study will not go ahead in the defined area.

In the coming weeks members of our field and engagement teams will be going door-to-door communicating with residents in the areas involved in the study, answering any questions and seeking support. This includes a signed consent form.

With community support we hope to carry out the small MRR study between mid-November and January. The study involves monitoring the number of mosquitoes in the areas for a week before releasing marked males over a three-week period, then monitoring the behaviour of the males through a network of traps for about seven days after the third release.

4. How many mosquitoes will you release and how often will you empty the traps?

We have calculated that we will need to release around 1000 male mosquitoes marked with the dye up to three times (weekly) over the study period.

Mosquito numbers for the second and third release may vary as we learn from the first release.

After the first release traps in the area will be emptied daily (including weekends) by CSIRO field officers for up to four weeks in total. Traps will then be removed.

Male mosquitoes marked with dye will be released across two residential blocks in Silkwood East (indicated by the dashed line).

5. Will residents experience more nuisance mosquitoes?

As we are only releasing male mosquitoes, residents should not experience any increased biting from mosquitoes. However, for a few days after each release residents may notice a greater number of mosquitoes around and even inside their home as the males we release will go looking for females that often rest inside houses.

6. How can Innisfail residents help?

We are asking all Innisfail residents to ask questions of our research team and we can be contacted on PH: 1800 40 30 83. CSIRO team members will be visiting homes in the Innisfail area to explain the MRR studies. We hope residents will have questions for us. We are also hoping residents will participate in the study by hosting a mosquito trap for the MRR.

7. How do the traps work?

CSIRO field officers check BG traps regularly.

We will be using the powered BG trap – Biogent’s sentinel trap. This attracts female mosquitoes looking for a place to rest and lay her eggs; males will also be caught in the trap as they go looking for the females. (We will reimburse power costs).

8. How will you know if you have the support of residents in the proposed MRR study area?

In the coming weeks the CSIRO team will go door-to-door in areas where it is hoping to conduct the MRR studies to talk to residents and ask for their support to carry out the release of marked male mosquitoes and possibly host a mosquito trap. A process of informed consent will be followed, where residents will be asked to sign a consent form indicating that they understand what they are being asked to participate in, and that they are supportive of this. We will also inform all residents in the surrounding area of the study.

We will inform the Innisfail community through local media and the CSIRO website, when we believe we have support for the study and the actual dates of the first releases.

We encourage all residents of Innisfail to contact us if they have any questions about the study on 1800 4030 83.

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