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Do the Dew for a bleeding fish? An Ottawa biologist investigates the healing power of pop

Updated: June 25, 2019

A �Ӱ�ԭ�� University biologist is putting to test the belief of an Ottawa River muskie guide who says that pouring Diet Coke on a bleeding fish can save its life.

Prof. Steven Cooke has launched the first scientific study of what has, in recent years, become a controversial tenet of fish first aid.

Advocates of the practice contend that the carbon dioxide in soda causes blood vessels in the gills to constrict and halt bleeding; critics call it dangerous pop science.

Cooke decided to launch a research project to determine if it’s the real thing.

“It has had legs for long enough that it’s time to figure out whether there’s something worthwhile there — or whether it’s just nonsense,” said Cooke, an expert in fish ecology and conservation physiology.

His research team is now testing various kinds of soda pop — Mountain Dew, Diet Coke and carbonated lake water — on the injured gills of northern pike pulled from the Rideau Waterway.

The research is being funded in part by Muskies Canada and by John Anderson, the crusading owner of , a guiding company.

Anderson has launched a Facebook site, , to spread the water-borne doctrine that soda pop can save the life of a bleeding fish.

“I felt people had to learn about this,” said Anderson, 58, who has been guiding on the Ottawa River for almost 20 years. “I make a living with fishing so giving back to the fishing world is important to me.”

John Anderson is a leading Ottawa River muskie guide who has launched a website called Save One Million Fish, based on his belief that pouring a can of pop on a bleeding fish can save its life. Tony Caldwell / Postmedia

Four years ago, while on a fishing trip with writer and outdoorsman Gord Pyzer, Anderson was introduced to the “magic” of soda pop. Pyzer, a longtime senior manager in the Ministry of Natural Resources and Forestry, told Anderson he uses spring water, supersaturated with CO2, to cauterize hook wounds in a fish’s mouth, throat or gills.

Anderson started using the technique in his guiding business. In the first season, he said, it saved five injured fish. He has since used it successfully 16 times — — and has even recaptured one of the fish that he had previously treated.

It was proof, he said, that fish could survive the application of soda to their gills.

Critics contend that soda pop is not a magic elixir, and that its acid content may do more harm than good.

Outdoor writer , pleading with anglers to stop dousing fish with Mountain Dew. “Not only is this soda theory wrong,” he wrote, “but it’s potentially bad for fish. The weak acid from pop would throw off the chemistry of the fish.”

Biology professor Solomon David, a fish expert at Louisiana’s Nicholls State University, , saying he has a “difficult time believing this works, and isn’t actually harmful to the fish.”

Cooke said there’s no science on the topic, just anecdotal evidence, which is why he decided to launch a formal research project earlier this year. He wants to understand if the technique works, and if it does, what biological mechanism might explain it.

The experiment is now underway on the Rideau Waterway where Cooke’s team of researchers is fishing for pike. (They’re easier to catch than muskie.)

Each fish is assessed to understand if the hook has damaged its gills. Injured fish are treated with Mountain Dew, Diet Coke, carbonated lake water, or plain lake water, and held in a fish tank for 30 minutes to observe what happens to their bleeding.

Fish landed without injury have a one-centimetre piece of their gills snipped with end-cutting pliers, and the injury is treated with soda or lake water. Again, the fish is held and observed, and the findings recorded.

The colour of the fish’s gills is assessed before and after treatment since the more blood a fish loses, the lighter its gill colour. The colour scoring system gives researchers a simple way to determine the merits of a treatment.

Cooke said 150 pike have already gone through the process, and another 150 will go through testing once the water has warmed. Researchers want to understand the effect of cold soda applied to warmer fish.

A Canada Research Chair in environmental science and biology, Cooke said he expects to publish results in late August.

John Anderson is confident the research will support his years of experience on the river. A former restaurateur and office manager, Anderson is now among Canada’s most celebrated muskie guides.

“I already know you can save fish with this,” he said. “I know it sounds like a terrible thing to do — to pour pop on a fish — but I’m confident from what I’ve seen that it does work.”