The competition between Bosniina coregoni and B. longirostris was st,udied by culturing of mixed and isolated populations in lake water. While interaction was detectable between the two species, they were capable of coexist,ing for a t least 124 days. The pattern of predominance was found t o depend on init,ial frequencies. The ratio of B. coregoni to B. longirostris in tlie pelagic zone of a mesot.rophic lake could be explained on the basis of competition between either species. Birth, death, and population growth rates proved to be delayed functions of stock density, as was borne out, by cross-correlation analysis of experimental population dynamics. Time lag estimates for all t,hree rat,es vaiiecl for diffnrent phases of population oscillation. For accurate assessment of time lags, tlie phases of monotonoua changes in density should have been separated from one another. The time lag estimated for t,he rate of populat,ion growth in mixed cultures was significantly higher for the superior competitor ( B . coregoni). This estimate may well be predicted as an arithmetic mean value cf time lag estimates for birth and death rates. The duration of population growth (or decline) was correlated to the time lag of the deat,h rate, whereas the amplitude was not correlated to any time lag a t all.
Contents