Biologists say humans, other animals not at risk
Large numbers of fish in Dexter’s Lake Van are dying again, with biologists determining the cause to be golden algae bloom, a situation that has led to die-offs several times in prior years.
Fermin Bejarano was raking up carp Friday morning from the shores of the lake. He is an employee with the town of Dexter, which owns and operates the fishing lake and campgrounds.
He said a backhoe filled two buckets full of dead fish to take from the area about a day ago.
“I started finding dead fish about a week and a half ago,” he said. “It started with just one or two, but then it was a lot more.”
He pointed to a long line of dead fish at the shores, but also dozens of fish affected by toxins that were flailing around at the edges of the water.
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Bejarano said he has worked for the town for about eight years and recalls a similar die-off in 2014.
This past week, about a thousand fish, mostly carp and catfish, have died, said Tristanna Bickford, communications director with the New Mexico Game and Fish Department, which stocks the lake with trout in the winter and catfish in the summer.
Game and Fish Department biologists became involved after the town of Dexter asked the help of biologists with the Southwestern Native Aquatic Resource and Recovery Center. That is a U.S. Fish and Wildlife Service facility adjacent to the lake off of Shoshoni Road, or State Highway 69. It is involved in research, conservation and rearing of fish.
Director Manuel Ulibarri said that he examined samples of water and fish, along with Game and Fish biologists. They determined that the invasive algae species has caused the problem this year, as it has several times since 2010.
“Usually when it’s really dry, as it is right now, the salinity in the lake tends to go up, which is desirable for this algae to bloom,” he said. “And when it blooms, it will at some point go into a toxic stage, which is toxic to the fish.”
According to a New Mexico State University publication, microscopic golden algae is a common organism that has been in North America since 1985, when it was first discovered in Texas in the Pecos River. It was reported in New Mexico in the 1980s. Extensive fish kills in various cities in New Mexico due to the algae began to occur in 2002.
The algae produce several toxins that can kill gill-breathing organisms, including plankton, crayfish and gilled amphibians, according to the NMSU document. The toxins make it difficult for the organisms to convert the water into oxygen and cause internal bleeding.
Ulibarri and Bickford said the toxins and algae are not known to affect anything except gill-breathing organisms. Anyone who caught fish two weeks or so ago can consume them, but people are not to eat dying or dead fish.
Ulibarri said the algae toxicity has subsided already. The fish already affected by toxins are expected to die during the next seven to 10 days.
He said the town is pumping fresh water into the lake to decrease salinity levels. Removing dead fish is also necessary. But Ulibarri said that the affected fish cannot be saved.
“Once the toxicity affects them, it is not reversible,” he said.
In years past, he said, some fish at Lake Van were able to avoid the areas in the lake with the algae bloom or survived by congregating next to the freshwater pump, but he said that might not have happened this year.
Although construction on four floating docks at Lake Van has been occurring for about a month, Ulibarri said he does not think the work contributed significantly to the algae bloom.
But Bickford said that water disturbances — which could be cold weather fronts, flooding, low water levels due to lack of rain or a combination of such factors — are considered the primary cause of golden algae blooms.
Ulibarri said he also was asked for his advice when a catfish die-off occurred at Lake Van around July. He said he determined that the fish kills were due to stress, as they had just been shipped to the lake from another state.
Ulibarri said the Aquatic Resource and Recovery Center, which has 76 ponds covering 35 surface acres, has not been affected by the golden algae.
“We have a fair amount of water running through ours,” he said, “and we do not get a shift in salinity.”
Bickford said restocking of the lake is expected to occur once tests indicate that toxins have diminished enough.
“For the near future, biologists will continue to monitor the water quality, so when that water is safe for fish, they will begin stocking the lake with rainbow trout as part of the winter stocking program.”
Senior Writer Lisa Dunlap can be reached at 575-622-7710, ext. 351, or at firstname.lastname@example.org.