Death by Degrees
UBC Fish Researcher Uses Treadmill to Test Optimum Temperatures for Salmon
By Lorraine Chan
Just how hot is too hot for fish?
To find out, UBC researcher Erika Eliason is using a “fish treadmill” to put salmon through their paces. At a research lab in Cultus Lake, Eliason has fish swim through a white tunnel that measures 15’ long, 8’ high and about 9” wide. She tests different stocks using variables of water speed and temperature, from 15º to 22ºC.
Her study probes possible links between climate change and the increasing number of fish deaths in the Fraser River, which in some years have been as high as 70 per cent for some stocks.
“This is the first study of its kind to look at the optimum temperatures for the swimming and cardiovascular performance of Pacific sockeye salmon,” says Eliason, a PhD candidate in the Dept. of Zoology.
Eliason monitors how hard fish hearts are working using a flow cuff around the heart. She tests the oxygen levels in the blood using catheters. She also records oxygen levels in the water to measure metabolism, all within variables of temperature and speed.
“This way, I’m hoping to look at the mechanism of the collapse in addition to characterizing the thresholds and optimums for swimming and cardiovascular performance.”
Eliason’s preliminary results show that swimming and cardiovascular performance is hindered above 18ºC. At 20º–22ºC, the fish are visibly flagging.
“We think that the fish’s heart is no longer able to cope with the high temperature and oxygen becomes limited. The high temperature makes it harder for the heart to get oxygen to the muscles.”
Her research encompasses salmon physiology, ecology, evolution and conservation and is carried out jointly with the Dept. of Fisheries and Oceans (DFO), the Pacific Salmon Forum and UBC colleagues working with Tony Farrell, a professor in the Dept. of Zoology and Faculty of Land and Food Systems.
The Fraser River is a critical watershed that supports more than 100 distinct sockeye species. Records show that since the 1950s, temperatures in the lower Fraser River are steadily climbing. For example, the mean temperature at Hells Gate on August 6 has increased from 17ºC in the 1950s to 18.2ºC in the 2000s.
“While that may seem like a minor change, it can make a big different to salmon,” says Eliason, explaining that unlike mammals, fish cannot regulate their body temperature.
“If the water is 15ºC, the fish is 15ºC. If the water is 20ºC, the fish is 20ºC.”
During the past five years, the mean temperatures in some areas of the Fraser River have exceeded 19ºC.
“In 2004, an especially hot year, the in-river mortality was more than 70 per cent for some stocks.”
Eliason says under normal circumstances, about 20-30 per cent of adult salmon will die before making it back to their spawning grounds “due to disease, fishing, seals, insufficient energy stores and just plain exhaustion.”
And given that some species migrate as far as 1,000 km upstream, higher temperatures could be a factor in their decreased resistance to disease and their ability to make it through difficult conditions upstream.
Eliason says DFO telemetry shows that a percentage of adult fish are entering the mouth of the Fraser River, but they don’t make it to the spawning ground. Each time, spikes in the Fraser River’s temperatures coincide with missing fish.
“A whole bunch of fish aren’t showing up at DFO monitoring check points after Mission.”
The B.C. coast has about 300 Pacific salmon stocks, whose life spans about four years. On average, they spend three years in the ocean. Once they successfully reproduce, their hatchlings remain in the river or nearby lakes, which act as a nursery during their first year of life.
Eliason’s preliminary findings support previous research that suggests that salmon perform best in temperatures that are closest to the average found in their natal spawning ground.
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Topic: Death by Degrees (Read 4255 times)