Fauna: |
Population densities are estimated from the survey data each year for each species of kangaroo. Densities are reported as an average density per species for each harvest sub-region, region and overall total cross South Australia. Densities are then used to estimate the harvest quota, which is calculated as a percentage of the population estimate (20% red kangaroo, 15 % grey kangaroos and 15% euros) for each harvest sub-region and region.
- Annual kangaroo aerial survey started in 1978
- Consists of flying transects west to east or east to west across the four commercial harvest regions of SA
- Fixed-wing plane is used for surveys with two (one on each side of plane) observers counting animals on either side of -the aircraft within 200 m belt transect (400 m in total separated by approx. 200 m underneath the plane). Plane travels at 100 knots (185 km/hr) and 250 ft (76 m) above ground.
- The smallest unit used is a 5km length (measured with a timer as 97 sec) with 7 sec break between each unit, therefore there is approx. 300 m between each unit not counted.
- Each unit = 2km2
- Each transect is made up of several to many units (uneven between transects).
- Transects are 28 km apart (15 nautical miles, see map attached).
- Surveys are conducted during July/August each year with morning and afternoon sessions (to avoid middle of day when kangaroos are more likely to be seeking shade under bushes).
- Two species of macropod are counted (red kangaroos and western grey kangaroo). Other animals are also noted (e.g. Camels, horses, eagles, goats, euros).
? Gawler sub-region lines flown annually since 1978.
? EP sub-region lines flown tri-annually since 1997.
? The method of survey is consistent, however the frequency of survey has varied between sub-regions due to differences in harvest rates.
DATA MANIPULATION.
- Waypoints are known for the beginning and end of transects, from these individual way points for the centre of each 5 km unit can be calculated.
- Left and right raw data is summed for each 5 km unit.
- A habitat correction factor is then applied to the data (5km unit) to correct for changes in visibility due to differences in vegetation structure (e.g. open vs dense vegetation). Habitat correction factors come from comparison of aerial survey with either vehicle counts, walked counts, helicopter counts or extrapolating from various survey heights using regression model (Caughely et al. 1976)
- A temperature correction factor is calculated from the air temperature recorded at beginning and end of each transect and applied to both species of kangaroos. Temp cf = 1/(1.474 - 0.0316*temp) if temp > 15 degrees C
- Coefficients of variation are calculated from the variation between transects. |