Publication Abstract

Aphanomyces astaci, the crayfish plague pathogen, may be a common cause of crayfish mass mortalities in the Czech Republic

E. Kozubikova, A. Petrusek, Z, Duris and B. Oidtmann

On three occasions crayfish plague (Aphanomyces astaci) has been identified as the cause of mass mortalities of native crayfish in the Czech Republic in 2005 and 2006. The true number of plague outbreaks is likely to be higher since crayfish mortalities often go unnoticed and only the result, the disappearance of a native crayfish population, is noted. Crayfish plague may have a significant negative impact on the successful restoration of indigenous crayfish populations in Central Europe.  Indigenous species of freshwater crayfish (the noble crayfish Astacus astacus and the stone crayfish Austropotamobius torrentium) have become rare and as a result have been classified as threatened by extinction in the Czech Republic during most of the second half of the 20th century (Holzer, 2000). The main reasons considered were water pollution from industrial and agricultural sources and loss of suitable habitats due to watercourse regulations. The improvement of water quality in the last decades should have been followed also by increase of crayfish populations. However, localised mass mortalities of indigenous crayfish still occur nowadays. Correct diagnosis of the cause of crayfish mass mortalities is very important for effective management of native crayfish protection. Although mass mortalities may be (and certainly often are) caused by chemical of physical factors, such as release of pollutants, oxygen deficits or high turbidity, biological factors, i.e. parasites and diseases, may be of critical importance (see reviews in Edgerton et al., 2004 or Souty-Grosset et al., 2006). An involvement of pathogens is to be suspected especially in cases where sensitive aquatic organisms such as fish or other crustaceans are not negatively affected, not all crayfish show clinical signs at the same time, and the mortality spreads also upstream from originally affected regions.

Reference

E. Kozubikova, A. Petrusek, Z, Duris and B. Oidtmann (2007) Aphanomyces astaci, the crayfish plague pathogen, may be a common cause of crayfish mass mortalities in the Czech Republic. Bulletin of the European Association of Fish Pathologists, 27(2):  79-82