Movement and longitudinal distribution of a migratory fish ( Salminus brasiliensis) in a small reservoir in southern Brazil

Abstract

We investigated whether the movement and distribution of the migratory fish, Salminus brasiliensis, were affected by a small reservoir. We also examined how movement and distribution were related to water temperature, flow, and rainfall. In December 2011 and January 2012, 24 individuals were captured downstream from the dam, tagged with radio transmitters and released in the reservoir (5.46 km² total area). After being released in the reservoir, 18 of the 24 tagged fish travelled upstream, taking an average of 16.6 days to leave the reservoir, with daily movements varying from < 5 km/day to > 24 km/day. However, only seven tagged specimens (29.16%) returned to the lower reservoir section, while the rest remained in the intermediate and upper reservoir sections. Longitudinal distributions and movements were positively related to both upstream flow into the reservoir and water temperature. We found evidence that S. brasiliensis can recognize the longitudinal gradient and is able to continue its upstream migration. On the other hand, the reservoir negatively affected downstream movements, possibly because disorientation prevented movement to the lower reservoir section. Based on these results, we suggest that the impact of small reservoirs on migratory fish species should be objectively addressed in environmental impact assessments and management programs.

Dazed and confused: Behavioural constraints impose major challenges to fish passage in the neotropics

“…Large dams act like ecological barriers to downstream dispersal of eggs and larvae (Pelicice, Pompeu & Agostinho, 2015), but the results of the present study indicate that they may also serve as a barrier to upstream movements of adult fish. Previous reports have shown that neotropical migratory fish species released in reservoirs pass rapidly through the impounded area, reaching upper lotic reaches (Antonio et al, 2007;Makrakis et al, 2007;Silva, 2012;Fries et al, 2019). However, the reservoirs in these studies have smaller impounded areas and shorter water residence times than the Três Marias reservoir.…”

“…The second approach for evaluating fish passage effectiveness consists of tracking fish movements both upstream and downstream of the dam (Antonio et al, 2007;Silva, 2012;Fries et al, 2019;Hahn et al, 2019a;Hahn et al, 2019b). In this case, translocated individuals are identifiable by some type of tag and tracked along the river.…”