Back in the old days of coal mining, and even up to today, ventilation has always been a vital part of the equation.

Back in the old days of coal mining, and even up to today, ventilation has always been a vital part of the equation.

Ancient attempts to explore caves or create new mine shafts rarely had workable methods to introduce fresh air or expel harmful vapors from the chamber depths. Early coal miners, not wanting to succumb to dangerous gases, particularly following a fire or explosion, came up with an ingenious solution. They discovered that the canary, with its increased metabolism, rapid respiration rate and small size, made a very good indicator of air quality down deep underground. Mice were also used as similar biological harbingers of danger, but they were not as demonstrative as the little birds in the face of peril. When dangerous levels of carbon monoxide or methane were present, canaries would sway or fall from their perch — a sure sign to get out of the mine or employ the artificial respirators on hand.

These feathered carbon monoxide indicators must have been effective and must have protected the miners that used them since we still mention them today. The common expression "canary in a coal mine" is still utilized as an idiom for anything, especially an organism, whose demise or distress provides an early warning of danger. And the scientific description for such peril-announcing creature is an animal sentinel. These are animals that show some measurable response to the hazard in question, which can include its death or sickness (like the canary), or in the environment as a whole when they are no longer found in an area.

Here at the hatchery we are working with a humble sort of animal sentinel — endangered mussels. They don't seem like much, and they aren't very showy or seemingly useful to people, but they are a type of aquatic canary for our environment. Increasingly, mussels and clams and other filter-feeding sessile organisms are disappearing from our streams and lakes. Like the dangerous gases in the coal mines, these dying mussels are an indicator that things are not as they should be in our aquatic systems. We would be wise to heed their message!

Fortunately, people like Dr. Christopher Barnhart of Missouri State University are studying what makes these mollusks tick, and doing everything possible to restore them in environs where they have been depleted. We are working with him to raise mussels and their host fish, the freshwater drum, and trying to learn with him and his team how to best care for our water resources in Missouri as well as across the nation. So while we're not about to evacuate from our "coal mine" situation, even the humblest creature can teach us a great deal about our world and help us change for the better.

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Bruce Hallman is the environmental education specialist for the Neosho National Fish Hatchery.