4.1 - Species' average body mass and numerical abundance in a community food web: Statistical Questions in Estimating the Relationship

Abstract

This chapter examines some of the statistical foundations of estimating the quantitative relationship between average body mass and abundance. The empirical example analyzed here is the pelagic food web of Tuesday Lake, Michigan. Tuesday Lake is a mildly acidic lake in Michigan, with a surface area of 0.9 ha. The fish populations were not exploited and the drainage basin was not developed. In 1985, the three planktivorous fish species were removed and replaced by a single piscivorous fish species. In 1984, the 56 biological species consisted of 31 phytoplankton species, 22 zooplankton species, and 3 fish species. In 1986, the 57 species consisted of 35 phytoplankton species, 21 zooplankton species, and one fish species. The important conclusion that the biomass of biological species in Tuesday Lake increased with the average individual body mass of biological species was not evident. However, in these cases the confidence intervals of the slopes were statistically unjustified. If unjustified models were to be used, an important conclusion about the upward trend of biomass with increasing average individual body mass of biological species in the Tuesday Lake pelagic food web would be lost.