Fish math program helps students estimate fish populations

GLASGOW – One of Montana Fish, Wildlife & Parks’ most popular educational programs across the state is Fish Math. Who says math can’t be fun?

Fish Math is often part of a school’s involvement in the FWP Hooked on Fishing aquatic education program or as an activity at Montana Wild and other events. About a decade ago, at the request of public educators across the state, FWP’s education specialist Ryan Schmaltz and former aquatic education coordinator Dave Hagengruber created this fun activity. It blends science and math to give students the real-life experience of biologists estimating fish populations, while at the same time meeting important Montana education standards.

Basically, Fish Math is a simulation of the mark-recapture method that is often used to estimate fish or wildlife populations. In fisheries, this is done through capturing a small sample of fish, marking or tagging them, and then recapturing fish to compare the marked to unmarked fish in a ratio to estimate the population.

FWP staff across the state use this method to perform yearly estimates for trout or other species in certain stretches of rivers or in small ponds. One study tagging and recapturing paddlefish on the upper Missouri has been going on for almost 50 years.

During the Fish Math activity, instructors start with a brief presentation of how and why FWP fisheries staff estimate fish populations. Students are then divided as “fisheries staff” into several crews. Each crew is tasked with completing an estimate of populations for a mile of river.

Crews are given a jar of fish, usually lima beans, that represent their mile of river. Students first take a guess at the number of beans in the jar, and usually this is not very accurate. Then the work and fun begin.

Students scoop and count a small sample of beans, mark them using markers, mix them back into the population and then scoop another handful. Using math, the mark-recapture equation gives them a population estimate. Instructors then add all the crews’ estimates together to get the population estimate on the whole stretch of river.

Lastly, students do a complete census by counting all the beans in the jar. Instructors explain that getting a census for a wild population is almost impossible, but in this case, it allows the class to see how accurate the mark-recapture estimates were. Often, crews will get within 5 to 10 percent accuracy of the actual population of hundreds of beans.

Recently, this popular activity was added to the world-renowned Project WILD curriculum guide so teachers across the world can incorporate it into their classrooms, making fish mathletes all over the globe.