White sturgeon population shows signs of recovery
An attempt to boost the declining population of endangered white sturgeon in the Columbia River is beginning to show signs of success, a biologist says.
James Crossman, a specialist who works for BC Hydro, said there has been an increase in sightings of the fish near the city of Trail. Mr. Crossman has been involved in a program that has reared and released about 100,000 young sturgeon over the last decade. Of those, an estimated 25 per cent have survived.
But Mr. Crossman said there still is cause for concern.
“Currently, only 0.5 per cent of the juvenile sturgeon we collect in our monitoring programs in the Upper Columbia River resulted from natural breeding,” he said. “If these prehistoric fish are to survive long-term, we need to understand why younger age classes are not surviving to adulthood.”
The sturgeon is North America’s largest freshwater fish. It can grow up to six metres in length, weigh up to 800 kilograms and can live more than 100 years.
BC Hydro is just one of 25 partners from government, first nations, industry, and environmental groups that formed the Upper Columbia White Sturgeon Recovery Initiative in 2001. The group has attempted to stimulate the spiralling sturgeon population with the introduction of juveniles from hatcheries.
The face of the river has changed dramatically over the last 30 years with the creation of dams, Mr. Crossman said. A number of predatory species have been introduced, like northern pike and smallmouth bass, which eat the smaller fish.
Paradoxically, more stringent regulatory frameworks resulting in clearer rivers has also improved visibility for these predatory species to catch their prey.
“The river is also a lot clearer than it used to be with the regulation of rivers that has settled out a lot of the sediment,” Mr. Crossman said. “That makes it easier for predators to pick off younger fish.”
He said that while numbers of younger sturgeon are undoubtedly increasing, it’s important to recognize that these numbers are being artificially controlled through their release program.
Equally worrying, said Gerry Nellestijn, a co-ordinator for the Salmo Watershed Streamkeepers Society, is that the adult population – sturgeon over 35 years old – has flatlined at 1,000, the same figure from a decade ago.
“We know that they’re producing eggs and sperm but we’re certainly not finding a great deal of larvae,” Mr. Nellestijn said.
But it seems that this issue is not isolated only to the Upper Columbia River. A 2010 press release issued by the Fraser River Sturgeon Conservation Society identified an unexplained decrease in juvenile numbers.
Mr. Crossman said the Upper Columbia White Sturgeon Recovery Initiative is currently investigating what happens to the hatched larvae when they move downstream.
“This is ultimately a long-term investment,” Mr. Crossman said. “For example we may not have a female reproducing until later than 20 years old – so we’re looking at another 10 years or more until the fish we’ve put in start to reproduce.”