He would season the pan fish with salt and pepper, bread it with cornmeal and flour, then fry it in butter. The flaky meat, for an independent Westerner like himself, gave lip-smacking satisfaction: the landscape he loved also brought him healthy protein.
Then the Smithfield man found out those scrumptious dinners might very well be making him sick, polluting his body with toxic mercury.
For about five years, Robertson had suffered from what he thought might be gout or old age. His feet hurt. His arms would get numb at night. His joints ached. His hands cramped. He felt tired all the time.
"I've never gotten old before," said the semi-retired educator, an active 59-year-old, "so I presumed this was what it was like."
But, while researching his symptoms, he formed a hunch. He caught five fish and sent them to a nationally recognized mercury-testing laboratory. He sent in a hair sample, too.
The tests showed that not only were methylmercury levels high in the fish, but there was way more mercury in him than the U.S. Food and Drug Administration considers safe.
"Toxic waste!" thought Robertson when he saw the results. "Holy cow!"
His story can't exactly be called a cautionary tale.
Even though both the fish and his hair had high levels of mercury, and although he would eat three, hearty servings of local fish a week, there might possibly be other reasons why Robertson's mercury levels were so high. It's impossible to say for sure without doing a scientific review.
But his case is certainly raising some eyebrows.
Lloyd Berentzen, director of the three-county Bear River Health Department, has heard about Robertson's case.
"No question," he said, "it raises some questions."
One is, what's the cause of contamination? He wonders because Berentzen's neighbor, "a heavy fish eater" who frequents the same places as Robertson, showed normal mercury levels.
Mercury builds up in the food chain. Generally speaking, the more fish people eat, the higher the levels of methyl mercury, the metal's toxic form.
Fish consumption advisories are in effect in seven locations in Utah, where officials suggest that eating too many can be harmful, especially to children and women of childbearing age. People also are urged not to eat any of three species of Great Salt Lake ducks - the common goldeneye, the cinnamon teal and the northern shoveller - because of high mercury.
Infants and children, in particular, can suffer from learning delays and impaired brain function that can result in difficulty thinking, talking and/or remembering. Adults with high levels of mercury often complain nausea, muscle weakness, memory loss and cardiovascular problems.
Utah's mercury problems shot to the forefront three years ago, after scientists reported they had found mercury levels in the Great Salt Lake that were higher than those found in any other lakes. Ever since, the state has been scrambling to understand the extent of the contamination and what that means to Utahns and their environment.
"Fish is a good source of protein," said Berentzen, "and we try to not discourage them from eating fish. But we try to tell them to do it in moderation."
"What we need is more information," he added. "It would be interesting to see a follow-up."
John Whitehead, who oversees the state's mercury program, spoke to Robertson about his test results and urged him to forward any results he learns of from fellow Cache Valley anglers.
The state, which has already tested about 1,100 fish from about 220 locations in the past three years, has plans to have another 450 tested by January. Some of them will come from flat water in Robertson's area, including Porcupine, Newton, Cutler and maybe Hyrum reservoirs.
But, like Berentzen, he cautions against raising a public alarm based on Robertson's experience.
"He's picking up mercury from somewhere," Whitehead said, "and where that is, I can't say You've got to be careful about saying it's the fish."
In addition, Robertson's very favorite fishing spot was the Glendale Reservoir, which is in the Cache Valley but over the Idaho state line and out of the reach of Utah's state and local officials.
Robertson went cold turkey on fish a couple of months ago. His symptoms? "They're all gone."
He's sad about having to give up fish. And he's sad that the beautiful landscape that provided so much good now has a bad side, too.
But Robertson says he refuses to despair and feels more determined now. He wants more people to be aware of his experience and the role locally caught fish played.
"We don't have this information out there," he said. "Why don't we have it out? Because the Legislature is more interested in building a darned highway or in gay marriage and that's not right."
He's not the only one who "can't drink the water, can't breathe the air and can't eat the fish" because of pollution, he said. And he hopes that he can inspire others disgusted with the status quo to transform their concern into action.
"The next question," he said, "is, now, what do we do about it?"