Sturgeon numbers swimming shallow

A majority of fish at the Nechako White Sturgeon Conservation Centre in Vanderhoof have died.

Cory Williamson

Over three quarters of the fish at the Nechako White Sturgeon Conservation Centre have died over the past month.

The new sturgeon recovery facility in Vanderhoof found difficulty dealing with the recent heat wave and water-temperature fluctuation, which created high levels of stress in the fish, said Cory Williamson, facility manager and chair of the Nechako White Sturgeon Recovery Initiative.

“It’s a complicated piping system and understanding how it operates was challenging. The river temperatures have been high and a bacterial outbreak happened at the same time,” said Mr. Williamson. “But the biggest factor here is learning how to use the technology. It’s all new to us, learning to grow fish in these tanks.”

The goal for the Fresh Water and Fisheries Society project was to release 12,000 sturgeon back into the Nechako river this spring. The hatchery started with 100,000 eggs, expecting to loose over half by their first feeding; it is normal to have a high loss during this stage because the juvenile (young) fish are extremely picky eaters. It is also normal to loose a few more throughout the process but by mid July numbers were lower than anticipated (around ten thousand) and have now dwindled to two thousand over the past month.

“Unfortunately the other stressors occurred during the critical feeding stage that caused even more of a loss. If this happened two weeks later, or if the fish were two weeks older, we wouldn’t have had this problem,” said Mr. Williamson. “It’s bad timing.”

Water temperatures were seen as high as 20 degrees during the initial feeding stage, which created stress on the fish and a viable temperature for bacteria to grow. Since the type of bacteria the fish naturally carry becomes more active once fish are stressed, an infection broke out killing most of the smaller fish with less developed immune systems, said Mr. Williamson.

“[However] the expected survival rate is actually higher now because with less fish in the facility, there is more room for the remaining fish to grow,” said Mr. Williamson, who anticipates the release of 1,000-1,500 strong fish by spring.

Prepared for some challenges, Don Peterson, president of the Fresh Water and Fisheries Society, is confident the project will have better success next year. “It’s a learning experience for the staff and the society in general. We expected to have some challenges and hoped to overcome them quickly enough without impact on the fish, but unfortunately the situation arose we couldn’t mitigate it quickly enough. It’s a brand new facility with brand new hatchery technology, which gives advantages but is definitely a learning curve. We are confident we will get better in upcoming years with the focus now on getting as many of the last few thousand fish to yearling size as possible.”