Impoundments affect fish reproduction regardless of reproductive strategy

Abstract

Major changes to local river habitats, after impoundment, are expected to restrict the reproductive activity of fishes with migratory strategies, although the changes are not expected to have relevant effects on fishes with other strategies. The reproductive activity of fishes with different reproductive strategies was evaluated along a longitudinal gradient before, and after, the formation of a reservoir on the Tocantins River (Tocantins State, Brazil). Samples were collected at six sites distributed along 80‐km stretch of the reservoir (R1 to R6 in the upstream–downstream direction) before and after the impoundment. The highest mean values of the reproductive activity index (RAI), considering all species in the river phase, were recorded for the intermediate segments (R4). The reproductive activity was classified as intense at the two sites located further upstream (R2 and R1). The highest mean RAI value after impoundment was observed for the site further upstream (R1). The reproductive activity was classified as intense, however, at every site, except for R6. Regardless of the reproductive strategy, mean RAI values were higher in this phase at site R1, particularly for long‐distance migratory species (LDM). The most lacustrine area (R6) was only relevant for the group of species with parental care. For non‐long‐distance migratory species, without parental care, the reproductive activity was intense at every site, except for R6. Overall, after the impoundment, the fish species tended to seek more lotic environments to spawn, including the riverine zone of the reservoir and side tributaries, regardless of the reproductive strategy. The results of this study provide evidence that impoundments affect the reproduction of the fish, independent of the reproductive strategy, although the intensity of the effect is different for each group.

Damming and seasonality as modulators of fish community structure in a small tributary

“…For instance, oxygenated waters enable the viability of eggs and running waters carry the early larval stages to marginal lagoons, which are used as nursery areas (Baumgartner et al, ). The preservation of predamming conditions in lotic area contributes to maintaining viable populations of migratory species, as observed in several other studies (Agostinho et al, ; Angulo‐Valencia et al, ; Araújo et al, ) and reinforces the importance of the preservation of dam‐free stretches of small rivers and tributaries.…”

“…On the other hand, larger‐bodied fish species with complex life history requirements often has population decline in this environment (Agostinho et al, ; Araújo et al, ). However, in environments subject to damming, upper regions can be utilised as reproductive areas for rheophilic species, contributing to the maintenance of their populations (Angulo‐Valencia, Agostinho, Suzuki, Luz‐Agostinho, & Agostinho, ).…”

“…We expected that spatial variation would be more pronounced than temporal variation because damming and the lack of downstream riparian vegetation likely decreases seasonal variability of fluvial habitats (Lima et al, ). Therefore, we expected that the fish community would show evidence of: (a) greater richness in the transitional areas (ecotones) between river and lake (Willis & Magnuson, ), (b) more pronounced differences in species composition and structure in sampling sites geographically more distant (Legendre, Borcard, & Peres‐Neto, ) and (c) higher proportion of migratory fish species in the lotic compartment (Angulo‐Valencia et al, ).…”

Fish trophic guild responses to damming: Variations in abundance and biomass

“…From the Corumbá Reservoir, samples were collected at seven sampling sites: three from the lacustrine zone, one from the transitional zone, and three from the upstream zone (Dias, Bailly, Antônio, Suzuki, & Agostinho, ). From the São Salvador Reservoir, samples were collected at six sampling sites: two from the lacustrine zone, three from the transitional zone, and one from the upstream zone (Angulo‐Valencia, Agostinho, Suzuki, Luz‐Agostinho, & Agostinho, ). The number of months sampled and periodicity in each period varied across the reservoirs (Table ).…”

Mosaic environments shape the distribution of Neotropical freshwater ichthyoplankton

“…Watersheds worldwide exhibit an association between dam presence and variation in ichthyofaunal population structure (Agostinho, Pelicice, & Gomes, ; Angulo‐Valencia, Agostinho, Suzuki, Luz‐Agostinho, & Agostinho, ; Lima et al, ; Schork & Zaniboni‐Filho, ; Winemiller et al, ). Dam construction in response to increasing electricity demands has large‐scale impact on river systems (Suzuki, Dunham, Silva, Alves, & Pompeu, ), modifying water flow and existing environments (Agostinho, Gomes, Santos, Ortega, & Pelicice, ; Pelicice, Pompeu, & Agostinho, ; Reynalte‐Tataje, Nakatani, Fernandes, Agostinho, & Bialetzki, ).…”