In this laboratory study we measured the independent effects of macrophyte growth form, plant density, and prey abundance on the foraging rate of the pumpkinseed sunfish (Lepomis gibbosus). We demonstrate that macrophyte growth forms are not all similar in their effects on fish foraging. Prey capture rates of pumpkinseeds foraging among Scirpus validus (cylindrical stems) were 53 and 365% times greater than for Potamogeton amplifolius (leafy stems) for cladoceran (Sida crystallina) and larval damselfly (Coenagrionidae) prey, respectively. Plant growth form influenced prey capture rates more than charges in natural plant density. Plant density effects ranged from none on damselfly capture rates to a 29% decline in cladoceran capture rate over a twofold increase in plant density. Our results indicate that in plant-structured habitats, variation in plant growth form can be an important determinant of fish foraging and habitat associations.

Dionne M, Folt CL, Canadian Journal of Fisheries and Aquatic Sciences 48 (1): 123-131 JAN 1991