Barriers to Fish Movement

Fish in most bodies of water are often capable of swimming anywhere that the body of water reaches. In some instances, however, barriers can arise that prevent the fish from passing through a certain area. These barriers can work to contain the fish. However, the barriers can also prove harmful by preventing fish from their natural movements.

  1. Physical Barriers

    • Physical barriers to fish movement are impediments in the water that cause a blockage which the fish cannot pass. Physical barriers can range from natural barriers, such as beaver dams, to human blockages, like flood gates. The fish can regain their natural movements if the physical barriers are removed.

    Hydraulic Barriers

    • While a physical barrier is easy to spot, a hydraulic barrier to fish movement can prove more difficult to identify. In a hydraulic barrier, the fish are dissuaded from passing through the area due to the movement of the waters in that area. Hydraulic blockages include areas of high water flow, which the fish are unable to swim against, and areas of increased turbulence, which disturb the fish and prevent them from passing through.

    Chemical Barriers

    • Chemical barriers can be equally difficult to identify, as some chemical barriers can appear to be like the waters the fish are freely swimming through. A chemical barrier is a change in the chemical make-up of the waters in an area, such as man-made pollution or discharge from the ground beneath the water. The injection of the new substances makes the water lethal or damaging to the fish.

    Behavioral Barriers

    • A behavioral barrier can affect one species of fish in a body of water while not obstructing the movement of other fish in the body of water. A stretch of a river that moves underground through dark areas may prove impassable for some fish, who will see it as a barrier. Others comfortable in dark areas can continue through to other areas in the river.