Our Surveys: Counting Catch and Effort
Introduction to Sampling Surveys
MRIP collects information from recreational anglers about how often they’re going fishing and what they’re catching using a system of surveys. Just like polls that predict such things as Presidential elections within a few percentage points, NOAA Fisheries surveys can determine total catch by surveying a few thousand saltwater anglers.
Sampling is based on mathematical probability theory, which may sound complex, but the basic concept really isn’t. George Gallup, founder of the famous Gallup Poll, once described sampling with this simple analogy: he said sampling a population was like taste-testing soup; one spoonful can reflect the taste of the whole bowl, if the soup is well-stirred. In other words, a sample can accurately reflect a much larger population so long as the sample is representative of the whole.
When it comes to surveying saltwater anglers, NOAA Fisheries randomly selects sites in proportion to their expected fishing activity and sends personnel there to interview anglers about their catches. This broad representation is what “stirs the soup.” In addition to being representative, the sample size also has to be large enough to derive the most statistically accurate estimates.