Warm Water Bacteria Responsible for Killing Hundreds of Sockeye Salmon in Osoyoos Lake
by Keith Lacey, Osoyoos Time, August 29, 2012
The combination of massive amounts of sockeye salmon travelling thousands of miles, the warm water that makes Osoyoos Lake the warmest lake in the country and a lack of oxygen all played a significant role in hundreds of fish dying and washing up on the shores of Osoyoos Lake early last week.
Robert Rogers, a fish and wildlife expert with the Washington Department of Fish and Wildlife, made the trip from Omak to Osoyoos last Wednesday after numerous reports were forwarded about dozens of dead fish washing up near Haynes Point Provincial Park.
Rogers said the fish died from Columnaris disease, a very common cold and warm-water fish pathogen that affect fish stocks worldwide.
“Some species are more susceptible than others. Unfortunately, sockeye salmon are very susceptible to this particular pathogen,” said Rogers. “It’s not uncommon when you get very warm water like we have here (Osoyoos Lake) and the gathering of an enormous amount of fish in one area.”
Not only does Columnaris bacteria breed and grow in warm water, but it also leads to the elimination of dissolved oxygen at lower depths as the salmon try and swim deeper to access colder water, he said.
“We had a large number of perch dying and washing up on shore of Osoyoos Lake a couple of years ago and it was from exactly the same thing,” said Rogers. “When you have the combination of a tremendous amount of fish accessing the same area and warm water, this bacteria tends to breed quickly and some of the fish simply aren’t going to make it.”
Rogers said estimates that 300,000 sockeye salmon entered Osoyoos Lake since the end of July are accurate.
With this amount of fish coming into a lake with the warmest temperatures in the country, there is going to be natural selection and a small percentage of fish are going to die, he said.
There is no threat whatsoever to human health relating to these dead fish, he said.
“It’s not in any way, shape or form a risk to human health, except for the fact it can become quite odiferous with any significant amount of fish dying,” he said.
After studying fish and fish habitat for more than three decades, Rogers said a small number of salmon are going to die during the annual run into Osoyoos Lake, but this year’s numbers might be higher than usual because it has been so hot throughout the months of July and August.
Osoyoos Mayor Stu Wells said he received about a half-dozen phone calls from worried citizens last Monday and Tuesday after dozens of dead sockeye salmon were reported dead and washing up along different shores in town, with the vast majority of dead salmon being spotted near the shores of Haynes Point Provincial Park.
When people realize that more than 300,000 salmon made their way into Osoyoos Lake over the past several weeks, most understand a small percentage are going to be killed, he said.
“Not all of the fish are going to make it to the spawning beds,” he said. “The reality is salmon don’t do well in warm water as they came from the cold waters of the Pacific Ocean and travel up the Columbia River near Portland, Oregon and they have a very long and difficult trip before they make it here to Osoyoos Lake.
“As everyone knows, we have a very warm lake and salmon just don’t do well in warm water. When the water temperature is over 21 degrees, a lot of them are being stressed and some of them die. It’s just the way it is.”
Because there are so many salmon and they travel so far over an extended period of time, it’s actually encouraging to know more than 99 per cent of the fish survive, said Wells.
“The CBC had a report about the dead fish and it was heartening to know there wasn’t a single comment looking to blame anyone,” he said. “The good news is the annual salmon run is back in record numbers and most of the fish are surviving and doing quite well when you consider everything.”
Bryan Holgate, a member of the Osoyoos Lake Water Quality Society, which is made up of a group of 15 volunteers who head out once a week to test water quality on the lake, said his group volunteered to pick up some of the dead fish that washed ashore.
The group went out on Sunday and helped collect more than 120 fish weighing almost 500 pounds, said Holgate.
“We had so many fish, we didn’t know what to do with them,” he said. “We could have kept going all day.”
A Town of Osoyoos half-ton truck was used to haul the dead fish to the local landfill Monday morning.
Richard Varty, park manager at Haynes Point Provincial Park, estimated he and parks staff picked up over 800 dead fish between Aug. 21-25.
“We picked up 400 fish the first day on Tuesday and between 150 and 200 per day on Wednesday and Thursday, but we only had about 40 on Friday because it looks like the salmon run is almost done,” he said.
“We had a lot of complaints from the campers about the smell and as park manager, I took it upon myself to try and clean up as many fish as we possibly could.
“We spent a good four or five hours a day for those three days cleaning up the mess. The good news is it looks like the worst is over, at least for this year.”
