Epiphytic Macroinvertebrates as a Food Resource for Bluegills in Florida Lakes

Biomass of aquatic macrophytes, densities of benthic and epiphytic macroinvertebrates, and the food consumed by bluegills Lepomis macrochirus 75 mm in total length and longer were quantified and compared in different macrophyte communities in February, April, June, and August 1983 in two Florida lakes (referred to as community-date comparisons). Densities of benthic macroinvertebrates ranged from 88 to 1,933 individuals/m2. Densities of epiphytic macroinvertebrates ranged from 721 to 34,379 individuals above 1 m2 of bottom and were 30–99% of the total macro-invertebrates in and above the bottom. The composition of the bluegill diet was positively related (P ≤ 0.05) to the epiphytic macroinvertebrate assemblages in 13 of the 15 possible community-date comparisons but not related to the benthic macroinvertebrate assemblages in any community-date comparisons. The greater similarity of the bluegill diets to the epiphytic than to the benthic macroinvertebrate assemblages suggested that bluegills obtained most of their macroinvertebrate prey in the vegetation and little from the benthos. Linear selectivity indices indicated positive selection for chironomids, caddisflies, mayflies, odonates, hemipterans, and Palaemonetes spp. Except for Palaemonetes spp., these taxa generally were more abundant among the epiphytic than among the benthic assemblages. Because of the abundance of epiphytic macroinvertebrates and their consumption by bluegills, management for macrophytes can enhance the prey resource for adult bluegills.