Influence of the river flow on the structure of fish assemblage along the longitudinal gradient from river to reservoir

Abstract

ABSTRACT. Changes in fish assemblage structure along a longitudinal gradient of the Paraíba do Sul River and Funil reservoir were studied to detect distribution patterns and the seasonal influence of the inflowing river. Fish were caught by gill nets in three zones (riverine, transition and lentic) during two seasons (dry and wet). A total of 3,721 individuals were captured, comprising five orders, 14 families, 27 genera and 33 species. Five species were non-native and amounted to 17.7% of the total number of individuals. The 10 most abundant species were used to assess spatial-temporal pat- (Eigenmann, 1908) and the benthics Hoplosternum littorale (Hancock, 1828) and Hypostomus auroguttatus Kner, 1854 had higher abundance in the wet season, with the two first species occurring mainly in the riverine zone, and latter two species in the transition zone. The highest diversity for both seasons was recorded in the transition zone, which is an ecotone that allows the co-existence of both riverine and lentic species. A major shift in assemblage structure occurred along the longitudinal gradient due to changes in discharge of the inflowing river, with increased fish abundance in the riverine zone caused by increased habitat availability in wet season, and the reverse of this situation in the dry season.

Evidence for Serial Discontinuity in the Fish Community of a Heavily Impounded River

“…Attesting to the importance of the transition zone as a persistent speciose ecotone, Santos et al . () found greater species richness and diversity in the transition zone of a Brazilian Neotropical reservoir across both wet and dry seasons relative to that in riverine and lacustrine zones. Typically, the lacustrine and transition zones contribute most to the changes in fish assemblage composition and structure seen in impounded rivers (Oliveira et al , ; Santos et al ., ), and their effect becomes more pronounced in reservoirs further upstream as lacustrine zones comprise a progressively larger fraction of an impounded reach.…”

Intra-Annual Variation in River-Reservoir Interface Fish Assemblages: Implications for Fish Conservation and Management in Regulated Rivers

“…Thus, RRI fish assemblages should be included in integrated management efforts aimed at conserving native riverine fish assemblages and maintaining sport fisheries in river–reservoir ecosystems. Similar research of transitional habitats between rivers and reservoirs in Brazil has also reported highly diverse fish assemblages representing both riverine and lentic species (Carvalho et al ., ; Oliveira et al ., ; Santos et al ., ; Terra et al ., ), suggesting that these findings may be applicable to other regulated rivers.…”

“…Although artificial, RRIs incorporate many features of adjacent river and reservoir habitats and may function similar to ecotones of natural systems, which support highly diverse assemblages (Odum, ). Recent studies generally support this idea, finding high fish species richness in transitional habitats between reservoirs and their upstream tributaries (Carvalho et al ., ; Oliveira et al ., ; Kaemingk et al ., ; Santos et al ., ; Terra et al ., ; Yang et al ., ). Transitional habitats associated with RRIs can also support high zooplankton species richness (Nogueria et al ., 2008) and be important for phytoplankton production (Scott et al ., ).…”

Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

“…In addition to the high abundance of piscivores, the most frequently captured species in this reservoir (Geophagus proximus) was usually found in the lacustrine zone. Santos et al (2010) found that a Geophagus species was also among the most abundant species in Funil Reservoir, southeastern Brazil. It exhibited restricted distribution to lacustrine sites, to which Geophagus species are well adapted.…”