title: Microhabitat use in a mediterranean riverine fish assemblage : Fishes of the lower Matarraña.
abstract: Over a 22 month period Barbus graellsii, Chondrostoma toxostoma, Cyprinus carpio, Esox lucius, Gobio gobio, and Leuciscus cephalus displayed non-random microhabitat use in the Rio Mattarraña, Spain and generally were overrepresented in deep microhabitats with low or undetectable flow velocities. Substrate composition did not strongly affect microhabitat use outside of its covariation with depth and velocity. Most seasonal differences in microhabitat use were attributable to seasonal changes in microhabitat availability, although all species selectively occupied deeper microhabitats during Spring 1984, 1985, and Early Summer 1984. Smaller specimens of B. graellsii, Ch. toxostoma, G. gobio, and L. cephalus all occurred closer to the substrate than larger specimens. Smaller specimens also tended to occupy shallower areas with greater amounts of erosional substrates (except for Ch. toxostoma). Assemblage members occupied statistically distinct microhabitats and could be classified as: 1) upper water column (L. cephalus), 2) mid-water column (Ch. toxostoma, C. carpio), 3) lower water column (B. graellsii), or 4) benthic (G. gobio, E. lucius). We hypothesize that the observed pattern of vertical segregation was produced by a combination of predator avoidance and differential evolutionary adaptation rather than by interspecific competition for space.
authors.affiliation: School of Forest Resources, University of Georgia, 30602, Athens, GA, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Grossman
authors.affiliation: Departamento de Biologia Animal (Vertebrados), Facultad de Biología, University de Barcelona, 08028, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: de Sostoa
authors.affiliation: School of Forest Resources, University of Georgia, 30602, Athens, GA, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Freeman
authors.affiliation: Museo Nacional de Ciencias Naturales, José Gutierrez Abascal 2, 28006, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Lobon-Cerviá
keywords: Cyprinidae; Microhabitat use; Predation; Spatial resource partitioning; Stream fishes