Fluctuations in year-class strength and growth of the vendace (Coregonus albula (L.)) in the small, mesohumic, oligotrophic Suomunjärvi, a lake in eastern Finland

Year-class variation and growth of the vendace (Coregonus albula (L.)), the most important commercial freshwater fish species in Finland, was assessed in Suomunjarvi from 1974-2001 seine and gill net catches. We estimated the relative abundances and growth of the individual year-classes. The year-classes 1980, 1985, 1990, and 2000 were strong. There were often oscillations of year-class strengths, although the period of oscillation was not regular. Strong year-classes dominated catches for almost as long as they were present in the lake. The strongest year-class was about 300 times greater in size than the weakest. The growth of the year-classes varied considerably; the difference in growth rate between the strongest and weakest year class was about 2.5-fold. Comparison of the growth of a year-class with its strength showed a marked negative correlation (p < 0.001). The size of the whole stock (CPUE data) also had a negative effect on yearly growth (p < 0.005).