Life histories and abundance of crustacean zooplankton in the outlet of Lake Superior, 1971-72

Abstract

In sampling throughout a year, at about 3-wk intervals, of the crustacean zooplankton discharged from Lake Superior through the St. Marys River, 30 species were collected, including three not previously recorded for the lake: the copepod Cyclops strenuus , and the cladocerans Alona costata and Alonella acutirostris . Five copepods, Cyclops bicuspidatus thomasi , Diaptomus ashlandi , D . sicilis , Limnocalanus macrurus , and Senecella calanoides were present in the plankton throughout the year while three other copepods, Diaptomus minutus , Epischura lacustris , and Mesocyclops edax , along with all cladocerans, were present only during summer and fall. Five species of copepods, Diaptomus sicilis , D . minutus , Limnocalanus macrurus , Senecella calanoides , and Epischura lacustris produced a single generation annually; three other copepods and all cladocerans produced two or more generations. All species breed 1–3 mo later in Lake Superior than in lakes Michigan and Erie.