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Author Topic: Predator training for stocked fish  (Read 3276 times)

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Predator training for stocked fish
« on: October 21, 2010, 12:24:41 AM »
Predator training for stocked fish
Trained silver perch in tank (far left) after 72 hours of training, position themselves as far away from the predator (far right) as is possible.

Fish stocking is one tool that can be used in conservation programs to help restore threatened fish stocks. Unfortunately hatchery-reared fish can have some behavioural deficits related to domestication that can hinder their survival in the wild.

Pre-release training of hatchery-reared and grow-out facility-reared fish is one strategy available to improve post-release survival. Tank-based training exposed fingerlings of Murray cod, silver perch and Freshwater catfish en masse to predatory fish and alarm signals from conspecifics’ skin extract.

Tank-based and wild release validation experiments confirmed that this training significantly changed the predator response behaviour of all three species, leading to improved survival.

Full title
Improving post-release survival of hatchery reared threatened fish
Status Complete
Dates Start date: July 2007
End date: June 2010
Project leader Dr Michael Hutchison, +61 7 3400 2037
Aims The aim of this project was to improve survival of stocked threatened species of fish by reducing hatchery domestication effects on fish before release.
Benefits Improving survival has applications to conservation stocking programs, and also improves the cost effectiveness of fish stocking for recreational fishing.
Micro-tagged fingerlings of Murray cod and silver perch were trained en masse to recognise predatory fish.  This was achieved by exposing 2500 fingerlings at a time to predatory fish in a large screened tank. The screen was permeable to fingerlings but not the predatory fish. Skin extract from the fingerling species was also released onto the predator side of the tank three times per day to enhance training. Skin extract contains chemical signals (alarm pheromones) that warn fish of danger.

Tank-based validation trials with silver perch, Murray cod and eel-tailed catfish showed that a significant change in behaviour could be achieved in three days of training for Murray cod and silver perch, and two days of training for eel-tailed catfish.

Untrained control fingerlings of Murray cod and silver perch were also micro-tagged. Trained and untrained fingerlings were released into the wild at several different sites. Within a site, control fish and trained fish were released up to 2 km apart to minimise behavioural interactions between the two groups. An index of predator abundance was recorded at each release site.

Post-stocking boat electrofishing surveys were used to recapture tagged fingerlings. The ratio of trained to untrained fingerlings recaptured was used to give an indication of the effectiveness of training on post-release survival.
On average, pre-release training of Murray cod fingerlings resulted in a doubling of survival. In sites with high predator densities, trained Murray cod fingerling survival was up to four times higher than untrained controls.

Murray cod are territorial fish so they did not disperse very far from release points in the first 24 hours after stocking. Therefore, the trained and untrained cod did not interact in the wild in the first few days after stocking.

In contrast, silver perch dispersed rapidly from release points. Silver perch are a social schooling species and can communicate with grunts. Silver perch were found in mixed schools of trained and untrained fish within 24 hours of stocking. It is thought that untrained fish learned predator avoidance behaviours from the response of trained fish in the school.  Therefore, no significant difference was found in survival between trained and untrained silver perch. In tank-based laboratory tests, trained silver perch had significantly different behaviours to untrained silver perch in the presence of predators. These tests confirmed that the training was effective.
Project staff
Michael Hutchison, Keith Chilcott, Danielle Stewart, Adam Butcher, Andrew Norris, Philip Smith, Mark McLennan, Angela Henderson
Murray-Darling Basin Authority $150KPA with matching in-kind from DEEDI
Collaborating agencies
Murray-Darling Basin Authority provided native fish strategy funding
Research locations Bribie Island Research Centre (Department of Employment, Economic Development and Innovation), Storm King Dam (Stanthorpe), Caliguel Lagoon, Condamine River and Cotswold Dam (Condamine)
Contact details
 Dr Michael Hutchison
+61 7 3400 2037

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