Numerical simulations using a population model of three cladoceran species, Daphnia magna, D-galeata and Bosmina longirostris, in a single-species and a competition environment

Models were simulated for single species and two species together, to study population levels, food assimilation and usage for reproduction, average b rood sizes, and effect of two levels of food on the time of first reproduct ion. In the simulation of a single-species population, both species had hig her numbers in abundant environmental food conditions, whereas the smaller species had relatively better numbers than the larger species when food was less abundant. In the simulated two-species competition, the larger specie s dominated when food was abundant, whereas the smaller B. longirostris out numbered the larger Daphnia species when food availability was low. The bio mass conversion based on the length-weight relationship gave different resu lts: even under low-food conditions the larger species, although few in num ber, had a clear dominance over their smaller Bosmina counterparts in terms of biomass. At both food levels, the proportion of young adults (adolescen ts) and adults to juveniles was considerably higher in B. longirostris than in the Daphnia species.