Skip to main content
Research article - Peer-reviewed, 2016

Signal Crayfish in Lake Saimaa Could be Maladapted to the Local Conditions Due to Aphanomyces astaci Infection: A Seven-Year Study

Jussila, Japo; Tiitinen, Vesa; Edsman, Lennart; Kokko, Harri; Fotedar, Ravi;


We conducted a seven-year survey (years 2009 to 2015) of the Lake Saimaa signal crayfish population. Lake Saimaa is the largest single waterbody in Finland, with a productive fishery and crayfishery. The signal crayfish were introduced to Lake Saimaa in mid-1990's and a commercial fishery was initiated in the mid-2000s. At first, there was a small proportion of noble crayfish among the catch, but after 2007, an acute crayfish plague epidemic eradicated them, and the signal crayfish stock started showing frequent gross symptoms of chronic crayfish plague infection (e.g., melanised lesions, eroded uropods and pleopods, lost appendages with melanised stumps). This stock now shows gross symptoms of the infection at a rate of 45% to 79% of the annual trap catch, in addition to showing signs of eroded swimmeret symdrome (ESS) at a rate of 2.8 to 15.4%. The CPUE has remained rather low, between one and three crayfish throughout the survey, while the proportion of the commercial grade catch has been between 35% and 68% of the total catch. The signal crayfish populations in Lake Saimaa are still rather fragmented, and production is low. It appears that the Lake Saimaa signal crayfish population has developed slowly and is producing less than expected.


commercial trapping, crayfish catch, crayfish plague, disease, ESS, Pacifastacus leniusculus

Published in

Freshwater Crayfish

2016, volume: 22, number: 1, pages: 53-60

Authors' information

Jussila, Japo
University of Eastern Finland
Tiitinen, Vesa
South Karelian Fisheries Advisory Center
Swedish University of Agricultural Sciences, Department of Aquatic Resources
Kokko, Harri
University of Eastern Finland
Fotedar, Ravi
Curtin University

UKÄ Subject classification

Other Veterinary Science
Fish and Aquacultural Science

Publication Identifiers


URI (permanent link to this page)