Author:
Downing John A.,Downing William L.
Abstract
We studied aggregation in 76 populations of freshwater mussels from relatively homogeneous surroundings in a wide range of habitats. Chi-square tests for spatial aggregation found only 53% of mussel populations significantly (p < 0.05) aggregated. The variance of replicate mussel samples (s2) varied with the mean number collected (m) as 1.49m1.17, but conformed to the general variance relation found for other aquatic taxa (m1.5) at m > 1. The number of replicate samples ([Formula: see text]) required to estimate mussel abundance with a given level of precision (D = SE/m) is approximately m−0.5D−2. Sampling mussels with large quadrats requires between 5 and 25 samples for 20% precision. Sampling designs to determine significant impacts (α = (β = 0.05) require 7–50 samples of each population to detect doubling or halving of the population density, or three to nine to detect order-of-magnitude changes. Large sampling units are recommended to ensure acceptable sampling precision and accurate chi-square analyses of spatial aggregation and to permit ecologists to detect significant impacts on freshwater mussel populations.
Publisher
Canadian Science Publishing
Subject
Aquatic Science,Ecology, Evolution, Behavior and Systematics
Cited by
70 articles.
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