Warm Water Rainbows
Optimising water temperature
to improve early growth
Sub-optimal growth in icy waters
Despite the Australia’s hot reputation, winter water temperatures at Gaden Trout Hatchery, in the NSW Snowy Mountains, can drop below 5 °C – restricting hatching and development in Rainbow trout.
Why winter cold matters
Warming to boost early growth
DPIRD staff trialled artificially warming the water used for trout production, which comes cold out of the Thredbo River
Turning up the heat
Coded-wire tags tell the story
The groups of trout raised in different water temperatures were tagged with coded-wire tags before release.
Later, fish were recaptured in the Gaden fish trap or reported by anglers and citizen scientists, allowing comparison between warm-water and normal stocking groups.
Tracking every fish
Warmed fish grew faster
A head start
Trout reared in warmer water were about 30% bigger at release, compared to those raised in colder river water.
More fish back, more fish caught
Better odds on return
Trout reared in warm-water were reported in higher numbers in the Gaden fish trap compared to other groups and also appeared more in angler catches, showing stronger post-release survival.
Nature catches up
Level playing field
After a year in the wild, warm-water and river raised rainbow trout were similar in size. Suggesting nature evens things out.
Science guiding better timing
Smart stocking
Warming water lets hatcheries stock earlier, before heatwaves or low flows hit. Therefore, building resilience and better fishing for all.
This hatchery and field-based research provides critical information to guide management of trout fisheries in NSW, including balancing ecological productivity with the needs of anglers.
Check out the scientific paper for more information...
Data for decision making