• Sculpin underwater

    Have you ever tried counting fish in an aquarium?

    It can be pretty hard to count all the fish in a crowded aquarium. So imagine how hard it is to count fish in the ocean! In the wild, fish live in a variety of habitats that range from the shallows near shore to the deep depths of the ocean. Fisheries scientists need to know how many fish are in a given area so they can determine the number of fish that can be harvested. This is used to ensure healthy fish populations for future generations.

    How many fish?

    Like you, scientists cannot count every fish in the ocean, so they use a variety of tools to estimate the size of a fish population. How they make these estimates depends on the species they are studying. Most commercial fisheries catch fish in deep offshore waters, so scientists must go to these locations to determine how many fish are present. In offshore waters, scientists use large ships with a big trawl net to catch a sample of fish which is then counted. Because the ocean is so vast, scientists must create a plan to count the fish. Sometimes they place an imaginary grid over the ocean area they want to study and then select sections on the grid to sample. They must select enough of these sections to get a representative sample size. Scientists then add up the weight of all the fish of the same species within the sample and extrapolate that weight to the entire area of the grid to arrive at an estimate of the number of fish. Play the Fish Fetch game to learn more about this process.