Fisheries biologists collect information on fish. They track what number fish area unit believed to be in an exceedingly specific body of water at any given time, what number of them area unit breeding and at what times, and whether or not fish stocks are compact by environmental factors. They additionally study migrations and alternative fish activity. Some fisheries biologists target only one species of fish or on one stream or lake. Fisheries biologists additionally collect samples of the fish they're learning and take them back to a science laboratory for analysis.