Macroinvertebrates - Great Lake

​​Application for Scientific Permit - Available for Public Comment

Public comment on the following application for a Scientific Research (Fauna) Permit is open until 21 May 2024.

Applicant: Hydro Tasmania

Species/Taxon:  Target species: Onchotelson brevicaudatus, Onchotelson spatulatus, Uramphisopus pearsoni, Mesacanthotelson setosus, Mesacanthotelson tasmaniae, Tasniphargus tyleri, Triplectides elongatus, Costora iena, Asmicridea grisea
Also includes non-target macroinvertebrate species – identified to a higher taxonomic level

Location: yingina / Great lake
The location of activities is below the high water line at yingina / Great Lake. This land is vested to Hydro Tasmania

Title of research: yingina / Great Lake macroinvertebrate monitoring

Aim of project: There has been a substantial decrease in water level at yingina / Great Lake over the summer/autumn period of 2023/24 as a result of sustained low inflows and a number of generation outages. yingina / Great Lake is forecast to enter low lake levels in the coming weeks unless there is significant rainfall. 
The objective of the project is to monitor the distribution and abundance of freshwater macroinvertebrates within yingina / Great Lake during low lake level conditions.

Justification: 
- Implementation of internal low lake level monitoring procedure.
- Long-term monitoring designed to improve understanding of macroinvertebrate habitat, distribution and lake level management implications.
- Monitor any impact and recovery of macroinvertebrates from low lake levels

Maximum likely numbers of individuals involved: Unable to estimate – effort indicated instead.
Effort:
- 18 transects at near shore sites (from 6m depth to shore) with 1m2 quadrats applied at each interval. Benthos sampled and collected via airlift
- Van-veen grab samples (30 cm2) at 9 bays (3 samples taken at each site)

Activities undertaken and methods:
Transect Sampling: Sampling is to be undertaken using an airlift pump system along transects at near shore sites. The following procedure will be followed: 
1. The outer transect depth is located and marked with a lead weight and rope to shore marked at 1m depth intervals with a maximum transect depth of 6m. 
2. Divers enter the water and place a 1m2 quadrat on the lake bed at each interval along the transect. 
3. A description of habitat is to be recorded with date/time, substrate and a GPS waypoint. 
4. Benthos from quadrat area is to be dislodged by hand and drawn up the airlift. In rocky habitats, rocks are to be dislodged by lifting and scraping the surface and underside of rocks. 
5. Sampling is to be prioritised to the dominant habitat of the transect at each site. In instances where there are two distinct habitats, 0.5m2 of each habitat should be collected. 
6. Samples drawn to the surface are then collected in a nylon sample bag (0.8mm mesh).
7. Samples are to be labelled, securely tied and stored in an eski containing lake water and ice bricks. 
8. Once stored, divers are to move onto the next depth along the transect (i.e. 5m depth followed by 4m depth and so on until ~0.5m depth sampling is completed).
9. Upon returning to the boat ramp all sample bags are to be transferred to barrels containing a 10% (v/v) formalin buffered with borax. 
​Note: It is expected that the number of samples taken will vary as a result of lake level height at the time of sampling. 

Grab Sampling: Nine deeper basin sites are to be sampled with a Van-Veen grab sampler (approx. 30cm2 surface area). Each site should have three samples collected and combined into a tote box, washed into a nylon bag and stored in a chilled eski (same method as transect sampling). After all sites are sampled, nylon bags are to be transferred to barrels containing a 10% (v/v) formalin buffered with borax.

Fate of animals: Euthanised and preserved in formalin buffered with borax.

Likely impact on species involved (including any by-catch): Broader impacts to target species unknown but expected to be minimal.





Contact

Scientific Research Permits

Environment Division
GPO Box 44,
Hobart, TAS, 7000.