No abstract

The benthic and limnetic distributions, and size-frequency, of the overwintered larval populations of three Chnoborus species, C. puncti~ennis (Say), C. albutus Johnson, and C. fhicans (Mcigcn) in Frains Lake, Michigan, were investigated on three dates in May and June 1965. The three species made up 91, 3, and 6% of the Chaoborus fauna. Little overlap in total length was found between species. C. fhicuns tended to be concentratecl in decpcr benthic zones during the day than C. punctipennis. C. ulbutus, but not the other two species, underwent an adlittoral benthic migration. limnetic zone at night, but none reached the surface. All three species migrated into the Most limnetic C. punctipennis larvae were found higher in the water column than C. fhicuns larvae. The larvae of C. ulbutus were stunted, showed late growth, ancl may have been unable to avoid competition with larvae of the closely related C. punctipennis. Differcnccs in distribution ancl morphology between C. flavicuns and C. gunctigennis, although slight, help to cxplnin the apparent lack of competitive exclusion in this genus.

ABSTRACT. Long-term trends in the abundance of unionids in the western basin of Lake Erie were examined from data collected at 17 stations in 1961, 1972, and 1982

No abstract