A Tagging Study of the Freshwater Elasmobranchs of Central America
1973
Thorson, Thomas B.
From 1966 to 1972, 1634 adult and 1203 juvenile bull sharks (Carcharhinus leucas) and 345 sawfish (Pristis perotteti) were tagged in the Lake Nicaragua-Rio San Juan system. Recoveries by 1 January, 1973 have included 225 adults (13.8%), 206 juveniles (17.1%) and 153 sawfish (44.3%). Six adults have traversed the full length of the Rio San Juan upstream and twenty downstream, demonstrating that the species moves freely between Lake Nicaragua and the Caribbean Sea in both directions, and that the sharks and sawfish in the lake are not landlocked. The juvenile recoveries have in general been shorter term and have shown shorter movements, although one moved the full length of the river, downstream. Sawfish have been shown to move freely within the river and the lake. That they move between the lake and the sea has been clearly established by three individuals tagged in the lake and recovered at the river mouth.
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