Sharks & Other Fish
Fish are aquatic, swimming animals that were among the first vertebrates (animals with backbones) to evolve on Earth. Two broad groups of fish exist today: cartilaginous fish—the sharks, rays, and skates with cartilage skeletons instead of bones; and bony fish, which include most familiar fish species.
Scientists estimate that there could be as many as 40,000 species of both types, ranging in size from 1⁄2 inch long to whale sharks that may grow as long as 50 feet. Fish live in fresh and salt water or, in some cases, both depending on their life stage, and in nearly all marine habitats. Their highly diverse body forms and physiologies allow different species to live from the surface to sea floor, the poles to the equator, and coral reefs to hydrothermal vents.
Fish are critical to the ocean’s ecology, chemical cycles, and ocean food webs, providing food for larger fish, and other marine animals. Humans around the world also rely on fish for food and income. As a result, many wild stocks are now overfished and in danger of disappearing.
WHOI scientists and others are using tagging, genetic isotopic, and statistical techniques to study fish movements and migrations, as well as the connections between distinct populations, in order to better understand how to create protected areas to conserve many different species (not just fish) and a variety of marine ecosystems. Other WHOI scientists study the remarkable sensory systems of sharks, ancient animals that are wide-ranging predators, but whose numbers are declining worldwide due to fishing pressure.