Abstract
Fish community composition was assessed among six macrophyte habitats, including hydrilla, Hydrilla verticillata (L.F.) Royle, common native species (bulrush, Scirpus spp., muskgrass, Chara spp., eelgrass, Vallisneria americana Michx. and Illinois pondweed, Potamogeton illinoensis Morong) and no‐plants, to assess potential impacts of recent hydrilla colonisation on the littoral fish community at Lake Izabal, Guatemala. Fish biomass was significantly different among habitats, with hydrilla supporting the highest fish biomass. Fish density did not differ significantly among habitats. Total fish species richness was similar (12‐15 species) among habitats, but community composition changed with macrophyte presence. Biomass of mojarra, Cichlasoma maculicauda Regan, which supported the most important subsistence fishery at the lake, was significantly different among habitats and had the greatest biomass in the hydrilla habitat. Although hydrilla may adversely affect native plants, lake access and other uses, it provided useful fish habitat and likely was not detrimental to the Lake Izabal fish community composition.