By Claire Eamer
March might seem an odd time of year to be thinking about fish, but not for the students and biologists involved in the McIntyre Creek fish hatchery. They’re already gearing up to feed thousands of hungry baby salmon within a few weeks.
The hatchery, which looks like a modest collection of sheds, freestanding roofs, and wooden walkways, is barely noticeable in the bottom of the small valley cut by McIntyre Creek between downtown Whitehorse and suburban Porter Creek.
It has been in operation for more than 20 years, providing up to 100,000 fry a year to bolster the Yukon River salmon population.
Trix Tanner of Fisheries and Oceans Canada was there at the beginning and served as education co-ordinator until 2010. She says the key to the McIntyre Creek hatchery is the water, which comes from groundwater sources, not surface meltwater. That means the temperature doesn’t change much with the seasons.
“The one really cool thing about this creek is that it’s about four to five degrees all year.”
That’s just the right temperature to keep the eggs developing steadily, and not too fast. By the time the eggs hatch and the tiny fish reach the fry stage, when they need to be fed, it’s mid-March to early April and warm enough for the fish to survive in the hatchery’s outdoor troughs.
At the Whitehorse Rapids hatchery, a much larger facility, the water is usually a degree or two warmer, the fish develop faster, and they need to be fed as early as February or March. The small McIntyre Creek hatchery couldn’t maintain fry that early in the season, Tanner says. “The outdoor facility wouldn’t work well if the water were warmer.”
Another advantage of groundwater, she adds, is that it’s fish-free and, therefore, doesn’t carry fish diseases or parasites that might harm the developing eggs and fry.
“Unless you’re going to treat the water, you pretty much need groundwater for an incubation project,” she says.
When the hatchery was first established, inmates from the Whitehorse Correctional Centre did much of the work. Then, in 2002, Yukon College’s Northern Research Institute took over responsibility for operating it, with Fisheries and Oceans Canada providing technical expertise. Today, the day-to-day operations are managed by students in the college’s Renewable Resources Management program.
The hatchery now has links throughout the education system. Not all the eggs that pass through the McIntyre Creek hatchery stay there. Many of them go to school – literally. In 2009-10, the hatchery provided salmon eggs to nine classrooms in Whitehorse-area schools and to classes in five other Yukon communities. Caring for the salmon eggs and rearing the fry teaches the kids about more than just the fish, says Tanner.
“When you’re looking after them, you have to understand the habitat requirements.”
High school students and crews from the Yukon Youth Conservation Corps help during pre-release tagging in June. All hatchery-reared fish that are released into the Yukon River system have to be tagged to distinguish them from wild stock, Tanner explains.
The marking process involves two steps. A coded-wire tag is injected into the snout of each little fish. The tag is just a tiny scrap of thin stainless steel wire carrying a code that tells researchers how old the fish is and where it came from. Once injected, the tag is invisible, so the fish’s adipose fin, a very small fin near the tail, is clipped off to indicate that this is a tagged fish.
The coded-wire tags aren’t perfect, Tanner says. Because the hatchery fish are so small when they’re released, they are fitted with half-size tags, and these may shift and drop out as the fish grow. At the McIntyre Creek hatchery, the managers are experimenting with a different kind of tagging—otolith thermal marking.
The otolith is a small, white structure found in the head of a fish. It’s part of the fish’s sensory system related to balance. However, the important point about otoliths, for fish-tagging, is that they have growth rings much like the rings in trees that record how quickly or slowly the tree grew. Otolith rings record the environmental conditions the fish experienced, including changes in water temperature – and they start forming even before the fish hatches.
At McIntyre Creek hatchery, some of the fish were exposed to cycles of warm water – three cycles for one group of fish and four for another group – to create a distinctive pattern in their otoliths. Years later, when those fish are caught or found after spawning, the marker should still be visible in the otoliths.
Tanner says the procedure has advantages. It’s cheaper to apply than coded-wire tags and requires less handling of the fish. However, interpreting the otolith markers is more expensive since it involves skilled lab work. And, when adipose clips are used as an external marker, the coded-wire tags still have to be used. Thermal marking might, nevertheless, be useful as a back-up to wire tags, she says.
“The big advantage is, you can’t lose this mark.”
Once the fish are tagged, the Northern Research Institute releases them into the Yukon River system. Many go into Tatchun Creek, where their eggs came from. For the past couple of years, a smaller number of fry, from eggs harvested at the Whitehorse Rapids fish ladder, have been released into Fox Creek as part of a joint program with the Ta’an Kwach’an Council to restore the creek’s salmon run. A year later the survivors will head downriver to the sea.
For more information about the McIntyre Creek Fish Hatchery, contact the Northern Research Institute at (867) 668-8772.
This column is co-ordinated by the Northern Research Institute at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at www.taiga.net/yourYukon.