Entering the Culvert: Leap or Swim


Fish will swim up rather than leap at very low falls, as observed by several researchers (Collin and Ellis 1961, Mayama 1987, Orsborn and Aaserude 1986, Stuart 1962).

FishXing allows you to evaluate passage conditions at the culvert outlet based on one of two methods, depending on which one is selected in the Outlet Criteria:

1. Maximum Leap Speed

2. Maximum Outlet Drop

When the Outlet Criteria is set to Max Leap Speed, FishXing will first determine whether the fish can swim into the culvert or if it must leap. FishXing assumes the fish is able to swim into the culvert outlet rather than leap when any of the following conditions are satisfied:

 1.       Tailwater Elevation > Outlet Bottom Elevation,  

 2.        Fish Length > Outlet Drop,


3.       Fish Length > Hypotenuse formed by the plunge height and distance.

NOTE: This calculation is only used when the Outlet Criteria is set to Max Leap Speed in the FishXing Input Window.  Fish that are unable to leap should have a Max Leap Speed set to zero.

See also: Leaping Calculations, Measures of Fish Length