An Analysis of the Variability of Fish Populations Taken by Otter Trawl in Biscayne Bay, Florida

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Abstract
Three bottom habitats in Biscayne Bay were sampled by 120 trawl samples taken during both day and night from April to Aug. 1963. Daylight samples contained 1391 fishes representing 41 species. Night samples contained 1440 fishes and 49 species. The number of species per sample followed a Poisson distribution, the number of individuals per sample followed a negative binominal distribution, and the number of individuals per species followed Fisher''s logarithmic series. The following generalizations apply to both number of species and number of individuals. More fishes were taken in the Thalassia area than in the Thalassia-sand area, which in turn had more than the mud-sand area. More were taken at night than during the day. Tidal direction had no significant effect. Analysis of data on the sample variance for paired 2-minute samples showed that 7-8 replicates are needed to detect a difference of 5 species and 10 samples are needed to detect a 10% change in the number of individuals with 95% confidence.