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Evaluation of crayfish stocking success in Finland
Erkamo E, Ruokonen T, Alapassi T, Ruokolainen J, Järvenpää T, Tulonen J and Kirjavainen J 
Published Online: 12/31/2010
Abstract
The last two decades of the 20th century saw more crayfish stockings than any other 20 year period in Finland. During the 1990s alone, 1.5 million noble crayfish (Astacus astacus) were restocked and 1.6 million signal crayfish (Pacifastacus leniusculus) were stocked into Finnish lakes and rivers. The Finnish Game and Fisheries Research Institute (FGFRI) and its partners monitored the success of the stockings by test trappings during the years 1974 – 2005. The FGFRI collected and analysed follow-up information on 174 noble crayfish and 98 signal crayfish stockings in this survey. In about half of the cases, it could not be concluded whether the stocking was successful. In the cases where the success of stocking could be evaluated, about a third of noble crayfish stockings proved successful, a third failed completely and the rest produced weak and very slow growing populations. About 80% of the signal crayfish stockings were successful and the rest either failed completely or produced sparse, unproductive populations. In the most successful stockings, it took on average 5 years for signal crayfish and 8 years for noble crayfish to reach a CPUE > 1, a threshold for a commercially exploitable population. Better stocking outcomes for signal crayfish were supposedly a consequence of beneficial species specific characteristics and more favorable stocking sites. At least 30 stocked noble crayfish populations suffered mass mortality during the monitoring period, and in 25 cases, the only obvious explanation was crayfish plague (Aphanomyces astaci) infection.
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Erkamo E, Ruokonen T, Alapassi T, Ruokolainen J, Järvenpää T, Tulonen J and Kirjavainen J. (2010). Evaluation of crayfish stocking success in Finland. Freshwater Crayfish 17(1):77-83. doi: 10.5869/fc.2010.v17.77
Author Information
Esa Erkamo,* Evo Game and Fisheries Research Station, Finnish Game and Fisheries Research Institute, Fin-16970 Evo, Hämeenlinna, Southern Finland, Finland16970. E-mail: esa.erkamo@rktl.fi
Timo Ruokonen, Department of Biological and Environmental Science, University of Jyväskylä, Survontie 9, Fin-40014 PL 35 Jyväskylä, Jyväskylä, Western Finland, Finland40014. E-mail: timo.ruokonen@jyu.fi
Tarja Alapassi, Fisheries department, Finnish Game and Fisheries Research Institute, Viikinkaari 4, PL 2, Fin-00790 Helsinki, Helsinki, Southern Finland, FinlandFin-00790. E-mail: tarja.alapassi@rktl.fi
Janne Ruokolainen, Fisheries Advisory Centre Häme, Pro Agria Häme, Mariankatu 8A, Fin-15110 Lahti, Finland, Lahti, Southern Finland, FinlandFin-15110. E-mail: janne.ruokolainen@proagria.fi
Teuvo Järvenpää, Fisheries Department, Finnish Game and Fisheries Research Institute, Viikinkaari 4, PL 2, Fin-00790 Helsinki, Helsinki, Southern Finland, FinlandFin-00790. E-mail: teuvo.jarvenpaa@rktl.fi
Jouni Tulonen, Evo Game and Fisheries research station, Finnish Game and Fisheries Research Institute, Fin-16970 Evo, Finland, Hämeenlinna, Southern Finland, FinlandFin-16970. E-mail: jouni.tulonen@rktl.fi
Jorma Kirjavainen, Fishery sector, Employment and Economic Development Centre for Häme, Raatihuoneenkatu 11, Fin-13100 Hämeenlinna, Finland, Hämeenlinna, Southern Finland, FinlandFin-13100. E-mail: jorma.kirjavainen@te-keskus.fi
Corresponding Author indicated by an *.
Publication History
Manuscript Submitted: 8/19/2009
Manuscript Accepted: 10/31/2009
Published Online: 12/31/2010
Published in Print: 12/31/2010
Funding Information
No specific funding statement is available for this article.