The state of populations of Lernaea cyprinacea L. (copepoda: lernaeidae) and crucian carp Carassius carassius L. in Dlinnoye Lake

The state of populations of the crucian carp Carassius carassius L. and the copepod parasite Lernaea cyprinacea L. was studied after 10 years of a sharp decrease in their abundance. Only one generation of Lernaea cyprinacea species was recorded each year. The alteration of the parasite generation occurred in the second half of July. Changes in the age structure of the copepod population did not affect the distribution pattern of its abundance in the host population, but the values of the K exponent changed in accordance with alterations of the parasite generations. By 2007 the sex ratio in the population became equal, males and females differed in their lengths and weights, and three dimensional groups were found in the catches. It is thought that males and females of the crucian carp have different roles in the maintenance of the L. cyprinacea abundance. The dominating fish sizes and the level of the host infection by copepods remained the same as in 1997-2003.