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LONG TERM STUDY OF COMPETITION BETWEEN TWO CO-OCCURRING CRAYFISH SPECIES, THE NATIVE ASTACUS ASTACUS L. AND THE INTRODUCED PACIFASTACUS LENIUSCULUS DANA, IN A FINNISH LAKE.

2001; EDP Sciences; Issue: 361 Linguagem: Inglês

10.1051/kmae

2777-3450

Kai Westman, Riitta Savolainen,

Marine and fisheries research

Since 1893, crayfish plague, Aphanomyces astaci Schikora, has devastated Finland's most productive populations of the native noble crayfish, Astacus astacus, causing great losses to once very valuable fisheries and exports. Efforts to halt the spread of the plague having failed, it was decided in the late 1960s to attempt to revive crayfish production and fisheries by introducing the plague-resistant North American signal crayfish, Pacifastacus leniusculus, into infected waters. So far P. leniusculus has been stocked in more than 300 waterbodies and is currently known to reproduce in roughly 100 of them. In some lakes both species live in sympatry. We have studied the interactions of co-existing A. astacus and P. leniusculus in the small lake of Slickolampi for 30 years. According to annual trap catches and population size estimates, A. astacus was clearly dominant up to the end of the 1980s, but in the 1990s P. leniusculus became dominant. In the last sampling, in August 1999, it accounted for > 98 % of total catches. In the course of three decades, then, P. leniusculus has almost completely replaced A. astacus.