Littoral invertebrate abundance in bluegill spawning colonies and undisturbed areas of a small pond

Abstract

Bluegill (Lepomis macrochirus) spawning activity creates benthic disturbances in the littoral zone of ponds and lakes. We assessed invertebrate densities and biomass in bluegill spawning colonies and nearby undisturbed areas before and after the onset of nest construction in a small pond. Juvenile fish abundance and prespawning sediment particle size distributions were also quantified. These data were used to evaluate whether bluegill spawning activity affects the abundance of benthic invertebrates. Densities and biomass of most macroinvertebrate taxa were similar before and just after nest construction. Insects tended to be more abundant in undisturbed areas 6 weeks after nest construction, while oligochaetes were more abundant in spawning areas. Total macroinvertebrate densities and biomass did not differ significantly on any sampling date. Micro-invertebrates (principally cladocerans and copepods) were much more abundant in undisturbed areas before spawning. Copepods and ostracods were more abundant in spawning areas after nest construction. Juvenile fish abundances were similar before spawning, but were significantly greater in undisturbed areas after spawning began. Macrophyte inhibition, reduced invertebrate colonization, differential predation pressure from juvenile fish, and other potential effects of spawning activity may account for some of these patterns.