The plankton of Crystal Lake had been quantitatively sampled by the researchers in 1942 before Alosa was introduced. Resampling 10 years after Alosa had become abundant revealed plankton similar in composition to that common in the lakes with natural populations of Alosa pseudoharengus and unlike that characteristic of Crystal Lake before Alosa became abundant. The plankton of four lakes with natural populations of Alosa was sampled for comparison with that of Crystal Lake in 1964, and the plankton of four lakes, without Alosa, in the "alewife" region of southern Connecticut was sampled for comparison with the Crystal Lake plankton of 1942. The plankton of Crystal Lake in 1964, when Alosa aestivalis was abundant, was quite like that of the natural alewife lakes, and not at all like the plankton of Crystal Lake before Alosa was a significant element in the open-water community. Crystal Lake in 1942 resembled the lakes without alewives in that its plankton was dominated by Diaptomus and Daphnia. Thus this showed that the majority of the zooplankton are less than about 0.6 millimeter in length when Alosa is abundant, whereas the majority of specimens of the dominant species in the same lake before Alosa …show more content…
The size efficiency hypothesis is an attempt to explain the commonly observed inverse relationship between the abundances of small and of large bodied herbivorous zooplankton in freshwater lakes. The size efficiency hypothesis was originally stated as follows: Planktonic herbivores all compete for the fine particulate matter of the open waters. Larger zooplankters do so more efficiently and can also take larger particles. Therefore, when predation is of low intensity the small planktonic herbivores will be competitively eliminated by large form. This is considered a classic ecological paper because it lays the foundation for the optimal foraging