Distributional patterns of sunfishes on the New Jersey coastal plain

Synopsis

Sunfishes of the genera Lepomis and Enneacanthus are characteristic inhabitants of quiet waters on the New Jersey coastal plain. In southern New Jersey, E. chaetodon and E. obesus are now almost totally restricted to the Pine Barrens region of the Outer Coastal Plain. In contrast, E. gloriosus is widely distributed. Lepomis gibbosus and L. macrochirus are also widespread, but have established few populations in the more acidic waters of the Pine Barrens. Factor analysis was used to determine underlying patterns of distribution among these 5 species, using 6 habitat variables, measured over 54 collection sites in New Jersey. Two general factors account for 41% of the distributional variation. Habitat variables most strongly associated with factor 1 suggest an underlying trophic gradient (dystrophy to eutrophy) with its associated species. Factor 2 suggests an underlying current-bottom gradient. The basis for the scarcity of Lepomis spp. from acidic waters was explored by examining the tolerance of recently hatched embryos to reduced pH. No increase in mortality was observed at pH 4.25 for L. gibbosus eleutheroembryos and pH 4.5 for L. macrochirus eleutheroembryos. The two species appear to be poorly suited to dystrophic habitats; young Lepomis are primarily planktivores, a dietary niche that is conspicuously reduced in dystrophic waters. Fish of the genus Enneacanthus glean invertebrates on substrate or vegetation, a behavior well suited for dystrophic habitats where most primary and secondary production is associated with aquatic macrophytes and substrate.