Selected biological parameters and the abundance of the spawning population of roach Rutilus rutilus [L.] from Lakes Gardno and Łebsko

The abundance of the spawning population of roach females from the coastal lakes Gardno (2 468 ha) and Łebsko (7 140 ha) located in the Słowiński National Park was estimated for the 1987-1992 period. Following bream, roach is the second most common cyprinid species in regulated fisheries catches. The size of the spawning population was estimated using Virtual Population Analysis and long-term fisheries statistics. Female roach dominated the exploited population at 62.4% in Lake Gardno and 64.3% in Lake Łebsko. During the analyzed period, more roach females were caught in Lake Gardno, which is more than twice as small as Lake Łebsko. Of the generations analyzed (1985, 1986, 1987, 1988, 1989 and 1990), more abundant years occurred in Lake Gardno. The most abundant generation in the two lakes was that of 1985, and following it, each subsequent generation was “weaker” than the preceding had been.