Ecology of the burrowing amphipod, Pontoporeia affinis, in Lake Michigan / by Wayne Paul Alley.

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constructing the frequency histograms. The chi square test for goodness of fit comparing the theoretical distributions with the observed
frequency histograms showed that small and total Pontoporeia followed
the normal distribution while large Pontoporeia conformed to the Poissono
Henson (1954) showed in a study of Cayuga Lake that Pontoporeia
larger than 6 mm in length were randomly distributed, those 4 to 5 mm
in length were distributed on the "borderline" between randomness and
contagiousness, and those smaller than 3 mm in length were contagiously
distributedo Green (1965), also in an investigation of Cayuga Lake,
found that adult Pontoporeia were randomly distirubted while the 1-2 mm
size group were strongly clumped.
The investigations of Henson and Green and the present study all
indicate that larger Pontoporeia are randomly distributed within the sediments. It was difficult to compare the distributional patterns of the
smaller amphipods from the three studies because Henson utilized two
small-size categories. Both Henson and Green used the variance-mean
relationship to determine if the size groups were rendomly distributed.
The smallest size group of the short-term investigation of the present
work was tested in the same manner and also found to be contagiously
distributed.
Long-Term Study Area
Sampling variability (heterogeneity of error) may be classified as
irregular and regular. Irregular error is characterized by certain