Key words: fish barriers, fish passage, migration, fishways, eels, Anguilla reinhardtii
Carla Hutchinson-Reade
Freshwater eels, like many other species, need to migrate to and from marine environments to complete their lifecycle. Throughout Australia large dams are restricting the migration success of native eels contributing to the overall decline of eel numbers. NQ Dry Tropics (the natural resource management body for north Queensland’s dry tropics) is conducting a project focused on removing fish barriers which will help to reverse this trend. An Eels on Wheels device is a simple yet effective method that can be employed in many locations that are impassable to eels. The device facilitates upstream migration of eels during the early stage of their lifecycle.
NQ Dry Tropics commissioned a study Eel passage over large dams of their catchment region in the dry tropics in Queensland, Australia. During the study no eels were recorded above the Burdekin Falls Dam while many were recorded below. This suggested a very real problem. The study identified the Ross River Dam as a major barrier to the Long-finned Eel (Anguilla reinhardtii), as several thousand elvers were observed attempting upstream migration by climbing dam wall abutments without success.
Elvers scale the blue netting up the sheer wall to get to the Astro Turf
To overcome this barrier an eel trap-and-transfer trial was established on 17 December 2010 prior to wet season rainfalls. (Local knowledge of previous migration history gave NQ Dry Tropics insight into migration events.) Since then around 3000 upstream migrants have been captured using a custom-designed trap we call Eels on Wheels and safely relocated within 48 hours. Trapping went on for 3 months.
Entry ramp lined with Astro Turf leads to a modified wheelie bin. The bin is filled with water and contains a live adult eel whose scent attracts elvers. The bin is then wheeled by project staff to the upstream side of the barrier.
The trap consists of a wheelie bin fitted with an Astro Turf-lined entry ramp which delivers a flow attraction fed from the upstream storage. The main drivers for trapping success and retention are in the level of attraction flow and trap accessibility. Once the elvers are in the wheelie bin they are transported and released by the project staff on the upstream side of the barrier. The Eels on Wheels device is a low cost and effective option to assist eels to overcome dam barriers. The same device can be replicated by natural resource managers around the country.
Contact: Paul Duncanson, NQ Dry Tropics (07) 4724 3544 or email paul.duncanson@nqdrytropics.com.au
EMR Project Summaries 