Name _______________________________________ Date _______________ Per ___ Fish Population Estimates What is a population? _________________________________________________________ Formula for estimating the size of a fish population: N = M · C R Formula for % error: N = estimated population size measured value – actual value actual value M = # of fish marked and released in first sample Example: 35 – 42 42 x 100 x 100 = 16.6 % error C = # of fish (total) in second sample R = # of marked fish in second sample * % error = measures the % inaccuracy of experimental results Repeat the experiment using different size samples to see what effect that has on your results. Using the formula above, determine the % error for each sample collection. M C R N % error Pop Size Prediction #1 Pop Size Prediction #2 Pop Size Prediction #3 Conclusions: Pretend that you are the fishery biologist in charge of estimating the population of fish in Craig, Montana. Your goal is to estimate as close as you can to the actual # of fish in the population. How will you do this…what kind of samples will you try and collect (hint: think size!) Why? What did you learn about how sample size affects the accuracy of your estimates?