Estimating relative abundance of seagrass fishes: a quantitative comparison of three methods

Abstract

Precise descriptions of ecological patterns are fundamental to generating hypotheses about both the patterns and the mechanisms generating them. Fishes in seagrass meadows are difficult to sample because dense vegetation and turbid water make it necessary to rely on traps, nets or enclosure devices. We compared the relative abundance of species and community structure in a North Carolina estuary caught by otter trawls, throw traps and minnow traps and determined how habitat structure affected estimates of abundance from the different sampling methods. We collected more fishes with otter trawls than with throw traps or minnow traps, and our estimates of species richness were highest with trawls. The rank order of pinfish, Lagodon rhomboides, abundance and species richness were concordant among all three sampling methods, but varied for pigfish, Orthopristis chrysoptera. Our results suggest that minnow traps and throw traps were not affected by variability in seagrass biomass. Our results also indicate that selection of a particular sampling method may have important consequences for conclusions drawn from studies using different methodologies.