Migração de peixes no rio Jequitinhonha: padrões migratórios e habitats críticos para o recrutamento

• Autor(a) principal: Fernanda de Oliveira Silva
• Data de Publicação: 2020
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/53656
• topic: Migração; peixes; rio Jequitinhonha; Ecologia; Peixes; Migração animal; Jequitinhonha, Rio

Migration, spawning and recruitment dynamics of Neotropical migratory fishes are widely studied in river-floodplain systems, where the flood pulse and wetlands play a central role. In semi-arid systems, where the flow regime is less predictable and water-bodies intermittent, migratory fishes may employ different migratory behavior and recruitment strategies, although studies on these systems are scarce. Additionally, impacts of habitat fragmentation and species introduction can be intensified in semiarid river systems, making them a study priority. In this thesis, we investigated factors affecting the recruitment dynamics and migratory behavior of curimbas (Prochilodus hartii) in a semi-arid river basin (Jequitinhonha River, Brazil) subjected to river regulation and hybridization with non-native species. We sectioned the thesis into two independent studies, presented in two chapters. In the first chapter, we investigated the relationship between flood and recruitment. We sampled eggs, larvae and young of the year (YOY) over 2 years and sub-adult over seven years, at several sites distributed upstream and downstream of a hydroelectric dam, UHE Irapé, about 300 km of the Jequitinhonha River. We found higher densities of eggs and larvae at sites with no influence of river regulation, affected mainly by weekly and daily variations in water level. The probability of YOY detection increased by 40% when a lateral stream was present, and the probability of YOY occupancy was affected by the length of the lotic stretch. Sub-adult abundance was not correlated with any predictor related to the flooding regime.These results show that curimbas from a semi-arid river and without a floodplain had different relationships with the flood regime when compared to curimbas from lowland rivers. In the second chapter, we investigated the migratory behavior of P. hartii under impacts of habitat modification and hybridization using telemetry techniques (radio and acoustic) and genetic analysis. We studied four groups based in the release site. We monitored fish in the UHE Irapé tailrace (RL1) and 80 km below the dam, near to the main tributary, Araçuaí River (RL2), downstream to the dam. In the upstream reach, we monitored fish from the reservoir (RL3) and fish passed to the reservoir (RL4), simulating a fish passage system. The longest distances migrated were detected in RL2 goup, and the main free-flowing tributary proved to be an important migratory route. Fish under dam influence tended to move over shorter distances, both in the reservoir and immediately below the dam. Almost all fish released in the reservoir were unable to migrate to upstream lotic stretches, especially those passed from downstream sites. We detected a high proportion of hybridization in the lower reach of the river, and native and hybrids fish showed very similar migratory behavior. Considering all results together, we conclude that there are two segregated populations upstream and downstream the dam. However, both populations are been severely impacted by human interventions. The habitat modification and fragmentation imperiled migratory behavior and recruitment in a long river reach, particularly upstream the dam. Besides that, genetic introgression, especially downstream reaches, threatens the permanence of P. hartii in Jequitinhonha River Basin. This indicates that conservation measures, such as the preservation of lotic stretches, are urgent to protect the remaining populations upstream and downstream of the dam.