Researchers come to grips with a fishy problem
ACTUALLY holding the ancient and endangered western trout minnow was difficult during the species’ first artificial breeding by UWA fish researchers earlier this year.
“Working as a fish biologist, this work was at the micro scale as usually we deal with breed stock trout at 5kg6kg, but these trout minnows were 5g6g,” Department of Fisheries principal research scientist Craig Lawrence said.
Dr Lawrence and his Shenton Park team used IVF techniques on the tiny trout minnow, which rarely grow to 20cm.
In 2006, 2000 to 5000 of the wild fish were estimated to live in three Great Southern rivers.
“They are very distantly related to the northern hemisphere’s trouts, but they are a Gondwana super-continentera relic,” Dr Lawrence said.
Other minnows and its relatives are in New Zealand and South America, both of which have species from the super-continent after it split from other ancient landmasses about 180 million years ago.
The trout minnow is WA’s only criti- cally endangered fish but its true plight was only discovered when no native fish were found in waterways near Perth in 2010.
Like northern hemisphere brown and rainbow trouts, the minnow swims upstream to find gravel beds – known as redds – to lay eggs, so dams that block breeding and a 20 per cent drop in South West rainfall in 30 years are thought to threaten the native fish.
Dr Lawrence said he initially consid- ered the trout minnow a remnant population, isolated by time and geography, and global warming would inevitably cause its extinction in 50 years.
However, the fish, maturing at two years, survives in water up to 28C and understanding that ability could have implications for aquaculture species facing global warming.
Saving the trout minnow using hatchery research started five years ago after the university’s team theorised spawning needed correct water temperatures, water flows and right air pressure.
They collected mature wild fish, their eggs and sperm and used IVF techniques for fertilisation before about 2000 fingerlings spawned at the Shenton Park hatchery during nights throughout April.
“These precious fish will now be used to develop a captive breeding program to save the species from extinction, by establishing an ‘ ark’, or repository population at the UWA laboratory, and in the longer term restocking water bodies,” Dr Lawrence said.
Kent Anderson is UWA’s new Deputy Vice-Chancellor for Community and Engagement.
Dr Craig Lawrence has bred tiny and endangered trout minnows for the first time at UWA.