Fish Community Structure and Function along Two Habitat Gradients in a Headwater Stream

Abstract

The stream continuum concept suggests that the physical structure of the stream channel coupled with the hydrological cycle and energy inputs results in a consistent pattern of community structure and function along a stream. I evaluated this concept in a headwater fish community along two physical gradients: upstream to downstream and riffle to pool.Habitat diversity and volume increased from upstream to downstream, and from riffle to pool. Temporal variation in habitat diversity was greater upstream. Upstream, and in riffles, habitat volume tended to vary more with time. Fluctuations in rainfall regime caused annual variation in habitat, especially in volume. Benthic insect density was highest from autumn (October-November) through spring (May-June). Following emergence of adults in late spring, invertebrate densities were low in summer in areas with riparian vegetation, but were not lower where riparian vegetation was absent and stable substrates were present. Along a gradient of substrates from silt-sand to gravel-rock, insect production increased, as indicated by adults and pupae in the drift. Peak resource availability for insectivore-piscivore fishes occurred in late summer and autumn, due to increased abundance of young-of-the-year fish.Pool and raceway-pool habitat guilds and insectivore and insectivore-piscivore trophic guilds contained the largest number of species. Increases in species richness were primarily associated with the addition of deeper habitats. Species richness of the pool insectivore-piscivore guild was especially variable over time. Biomass in shallow areas consisted predominantly of generalized insectivores. In deep, stable habitats, generalized insectivores were replaced as the predominant trophic group by insectivore-piscivores and large benthic insectivores. Immigration of fish occurred in spring and autumn, the periods of highest resource availability. Immigration between midriver and headwater regions primarily involved older age classes (III+), and was associated with changes in flow regime, habitat structure, and seasonal dynamics of the resource base of particular trophic groups. Flow regime and habitat volume appeared to be important factors limiting immigration in autumn, especially in pool species.Habitat diversity (depth, current, and substrate; DCS) was significantly correlated with fish species diversity (FSD). However, considerable variation occurred in the relationship between the two variables, including: (I) FSD decreased in winter in shallow, less diverse habitats due to emigration, and increased in spring due to recolonization; (2) FSD increased in spring and autumn when resource availability increased; (3) FSD was least predictable from DCS in autumn, when flow regimes were low and large numbers of fish recruits were present; and (4) DCS did not predict FSD as accurately in temporally variable upstream areas where large numbers of small fish dominated the community, especially in areas with human disturbance.Young age groups (O-Il) were primarily found in shallow, ...

Fish assemblage structure in a first order stream, southeastern Brazil: longitudinal distribution, seasonality, and microhabitat diversity

“…The interpretation for this apparent disparity is that, despite the continuous recruitment of juveniles throughout the year, a well documented life-history strategy for headwater stream fishes (Schlosser 1982, Garutti 1989, the reproduction must be increased and the mortality rate should be smaller during the wet season probably due to a higher availability of critical resources (food and shelter probably). The pattern of higher food availability and shelter during the wet season is cited both for temperate (Schlosser 1982) and tropical streams (Angermeier & Karr 1983, Lowe-McConnell 1987. Thus, in the studied stream reproduction throughout the year with the hypothesized higher reproduction and juveniles survival rates during the wet season should play an important factor in the maintenance of the fish community.…”

Influência da urbanização sobre as assembléias de peixes em três córregos de Maringá, Paraná

“…Para as assembléias de peixes, variações na composição, estrutura e distribuição das espécies têm sido associadas com mudanças na morfologia do canal (SCHLOSSER 1982), profundidade, tipo de substrato e corrente (GORMAN & KARR 1978, ANGERMEIER & KARR 1984, com a estruturação da vegetação marginal (JONES III et al 1999, BARRELA et al 2001) e aspectos químicos da água, como concentrações de nutrientes, oxigênio dissolvido (HUGHES 1987, SILVA 1995, HONNEN et al 2001, substâncias cloradas (OSBORNE et al 1981) e metais pesados (TURNPENNY & WILLIAMS 1981).…”

Fish diversity and assemblage structure in Ken River of Panna landscape, central India

“…The influence of habitat structure and complexity on fish assemblage structure has been tested mostly in North American streams (Gorman & Karr 1978;Schlosser 1982Schlosser , 1985Capone & Kushlan 1991) and Australian streams (Bishop & Forber 1991;Pusey et al 1993). In India, few studies have been initiated to document the fish diversity and assemblage structure along the environmental gradients (Johnson 1999;Arunachalam 2000;Bhat 2003;2004;Sreekantha et al 2007;Shahnawaz et al 2010).…”