摘要：R.D. Campbell (2006) in his paper argues on the inconsistency of data and statistics as wellas disagrees on the blaming of European beaver Castor fi ber in the decline fifi of freshwaterpearl mussel Margaritifera margaritifera. We thank Campbell for his comments on beavers.In addition, we must apologise on a mistake in the article (Rudzīte 2005). In the chapter“Results”, labels A and B were in reverse places in Fig. 1.Campbell (2006) does not use any information on the beaver population in Latvia. Hisarguments are partly based on the literature on the behaviour of Canadian beaver Castorcanadensis. However, Canadian beaver has never been found in Latvia (Balodis 1990).Why do we argue that beaver is a threat for freshwater pearl mussel in Latvia? Th efreshwater pearl mussel is a highly threatened bivalve. A 85 to 100 % decline in knownpopulations in Central and Southern Europe has been estimated, which may be due toa number of factors, including increasing siltation and eutrophication of rivers, and alsothe recent declines in migratory salmonids upon which the larvae depend (Skinner etal. 2003). Most pearl mussel populations have lacked successful reproduction for 30 to50 years. Formerly dense and connected populations have oft en become fragmented.However, a potential for recovery is off ered by the longevity of this species, i.e. a lifespan ofmore than 100 years, together with the high reproductive potential of adult pearl musselseven in polluted rivers and in extreme old age (Geist 2005).
