Environmental Biology of Fishes

, Volume 7, Issue 4, pp 341-347

First online:

The bull shark (Carcharhinus leucas) and largetooth sash (Pristis perotteti) in Lake Bayano, a tropical man-made impoundment in Panama

  • Rafael Vásquez MontoyaAffiliated withCentro de Ciencias del Mar y Limnologia, Universidad de Panamá, Ciudad Universitaria
  • , Thomas B. ThorsonAffiliated withSchool of Life Sciences, University of Nebraska-Lincoln


The Río Bayano in eastern Panama is one of many tropical rivers in which bull sharks (Carcharhinus leucas) and largetooth sawfish (Pristis perotteti) have been known to occur. Since both species can osmoregulate in fresh water throughout life, theoretically, both could survive in landlocked situations for many years.P. perotteti reproduces in fresh water, butC. leucas ordinarily does not, so only the former would appear to have the potential for establishing a breeding stock in such a landlocked freshwater body.

The damming of the Rio Bayano and the creation of a large impoundment in 1976 provides a test of the ability of members of both species trapped there to survive and to establish breeding stocks. In 1980 and 1981 three mature femaleC. leucas were found dead in Lake Bayano and three sub-adult femaleP. perotteti were taken by trammel net. These events confirm the ability of both to survive in fresh water for long periods, but the establishment of breeding stocks appears doubtful and the question may not be answered for many years.


Elasmobranchii Euryhalinity Freshwater adaptation Dam lake Osmoregulation Central America