Animal Science and Zoology, Aquatic Science, Ecology, Evolution, Behavior and Systematics, Agricultural and Biological Sciences
72
Scopus Publications
Scopus Publications
Spatial and temporal variation of fish eggs and larvae in a cascade of small hydropower plants in south-eastern Brazil Eduardo Meneguzzi Brambilla, Andréa Bialetzki, Fabio Porto-Foresti, Marcos Gomes Nogueira Marine and Freshwater Research, 2025 Context Studies focusing on ichthyoplankton distribution are important tools for the establishment of conservation actions, including the management of fish stocks. Aim To investigate the distribution of ichthyoplankton in a reservoir cascade of three small hydropower plants in the Sapucaí-Mirim River, south-eastern Brazil. Methods Six sampling sites were distributed in the river stretch under the direct influence of the most upstream and downstream dams. Samples were collected fortnightly between November and February (spring–summer) in 2015–2016 and 2016–2017. Key results In total, 5004 eggs (unidentified) and 3189 larvae belonging to 4 orders and 15 families were sampled. Temporally, higher densities of eggs and larvae occurred during periods of increased rainfall and associated changes in environmental variables. Spatially, higher densities of eggs were observed in the most upstream reservoir, in the lotic (2015–2016) and transition (2016–2017) zones. For larvae, abundance was higher in the transition zones. Conclusions The study demonstrated that the small hydropower plants reservoir cascade is not an impediment to fish spawning and the drift of eggs and larvae, including important migratory fish species from the river basin. Implications This stretch of Sapucaí-Mirim River is a critical area for fish recruitment and efforts to preserve it are necessary.
External Morphology of Leporinus oliveirai (Characiformes: Anostomidae) During Early Life Stages Ian Solon Bortoloci Ito, Mariana Pascoal Boaretto, Marcos Venturieri, Andréa Bialetzki, José Luís Olivan Birindelli Journal of Morphology, 2025 Leporinus oliveirai is a recently described species from Serra do Cachimbo, Pará State, Brazil, notable for its small size and vibrant coloration. This species has been successfully reproduced in captivity and is commercially traded internationally. Herein, we describe the early development of Leporinus oliveirai , documenting its external morphology with photographs and illustrations. The ontogeny of L. oliveirai is compared with that of other anostomids for which ontogenetic data are available, and developmental patterns are described for the family. In Anostomidae, the critical processes associated with the transition to exogenous feeding occur within the first 5 days post‐hatching. Fin formation occurred in two distinct phases: the anal, dorsal, caudal, and adipose fins developed first, followed by the pelvic and pectoral fins. The sequence of fin ossification in anostomids is generally consistent with patterns described for other Characiformes. Additionally, a marked increase in growth rate and indications of allometric growth were observed following notochord flexion.
Feeding ontogeny: A new approach to predator–prey interactions Rafael Rogério Rosa, Sybelle Bellay, Andréa Bialetzki Ecology of Freshwater Fish, 2025 Diets of fish larvae may vary within populations and among species and are affected by larval prey availability and foraging capacity. We aimed to describe the diet of fish larvae based on empirical field observations, emphasizing the interaction and organization of the predator–prey network using Auchenipterus osteomystax as a species model. The network showed few interactions (low connectance and modularity) but a nested structure (some items that had fewer records tended to occur together with the most frequent ones), low complementary specialization (the proportions of ingested items tended to be equivalent) and a pattern of segregation (some items tended not to be consumed together) in the use of resources among individuals. Robustness was low when the removal of prey with a higher consumption frequency occurred. The correlation between morphological variables and network attributes was significant and positive for abundance and strength, while the correlation with nested rank was negative. The availability of suitable dietary resources is likely to be the key factor for success and survival in the early stages of development. With changes in morphology during larval development, A. osteomystax showed a generalist position in the network as its predation capacity increased. A new approach to trophic ecology studies of fish larvae incorporating network analysis may help explain the individual characteristics of larvae and assess the pattern of interactions in the population.
Ichthyoplankton dynamics in the Brazilian Pantanal: Contribution of an important tributary and maintenance of connectivity Mateus Babichi Veiga de Souza, Karina Keyla Tondato‐Carvalho, Andréa Bialetzki Ecology of Freshwater Fish, 2025 In order to investigate the reproductive dynamics of the ichthyofauna in the Brazilian Pantanal, this study examines the spatial and temporal distribution of ichthyoplankton, taxonomic composition, and its correlation with environmental factors within one of the most important sub‐basins, the Taquari River. Egg and larvae collections were conducted at 11 sampling points between October and March of 2017/2018 and 2018/2019. Significant differences were observed between collection points, months, and years, with higher ichthyoplankton densities in the Coxim and Taquari rivers, particularly between November and January. Twenty‐eight genera and/or species of fish were identified, including 10 long‐distance migratory species. Egg density showed a negative correlation with water temperature and rainfall. For larvae, water transparency and rainfall were both significant, negatively influencing larval abundance. However, different species tend to occur in environments with distinct abiotic qualities. Yolk‐sac, preflexion, and flexion larval development stages were distributed throughout the sub‐basin, especially near the Pantanal. Considering the data and analyses presented in this study, the importance of connectivity between these environments, specifically between the plateau and Pantanal, is evident, highlighting the significance of the entire sub‐basin for fish reproductive processes. Therefore, research focusing on the ecological processes influencing the distribution of ichthyoplankton offers valuable insights for ecosystem conservation and aids in effective environmental management.
Extreme climatic events affecting freshwater fish reproduction in the Neotropics E. M. Brambilla, M. R. Suiberto, A. Bialetzki, F. Porto-Foresti, M. G. Nogueira Brazilian Journal of Biology, 2025 This study aimed to evaluate the effect of extreme climatic events on fish reproduction by comparing the density of eggs and larvae in two consecutive, but contrasting, reproductive cycles: one atypically dry and the other with intensive rains caused by a strong El Niño event. Samples were collected fortnightly between December and February of 2014-2015 (drought cycle) and 2015-2016 (wet cycle) at six sampling sites along the Sapucaí-Mirim River, southeastern Brazil. The wet cycle presented a higher density of eggs and larvae (around 10 times more) than the drought cycle (p<0.05), with a higher proportion of families with migratory species. Principal Component Analysis explained 74.2% of environmental data variability, and all the environmental variables showed statistical differences between the two reproductive cycles, except for pH and oxidation-reduction potential. Extreme climatic events clearly affect the reproduction of freshwater fish, with a negative effect during drought periods and the opposite during wet periods. A drought period can result in the loss of a reproductive cycle, especially for flooding dependent species. Nevertheless, this reproductive failure can be compensated for by a prolonged period of intensive rain and flooding. Management actions are proposed to safeguard species in the Sapucaí-Mirin River.
Ichthyoplankton in a regulated river: community structure and distribution patterns in a run-of-river dam cascade system in the Neotropics Douglas Ticiani, Andrea Bialetzki, Jislaine Cristina da Silva, Mateus Babichi Veiga de Souza, Rosilene Luciana Delariva Neotropical Ichthyology, 2025 Run-of-river (ROR) hydroelectric systems drastically reduce discharge in the reduced flow stretch (RFS). We evaluated the influence of RFS formation and environmental variables on the species composition and spatio-temporal distribution of fish eggs and larvae in a ROR system. Samples were collected fortnightly (Oct 2016 to Jan 2017) at the Rio das Antas Energy Complex. A total of 5,681 eggs and 2,124 larvae were collected. The study confirmed ichthyoplankton structure is shaped by strong spatio-temporal variations; species composition and egg and larval densities differed significantly among sites and months, primarily influenced by flow, temperature, dissolved oxygen, and transparency. However, the expected longitudinal progression of larval stages from upstream spawning grounds was absent, indicating the natural drift process is disrupted by the dam cascade. This disruption is confirmed by distinct ichthyoplankton densities and compositions between the upstream (S1) and downstream (S4) sections of the Complex. Furthermore, no reproductive evidence was found for migratory species historically present in the basin, corroborating our initial predictions. These findings demonstrate that cascaded ROR systems modify natural drift dynamics and species distribution, challenging their sustainable image and highlighting the importance of preserving free-flowing river stretches to maintain ichthyofauna reproductive processes.
Impacts of small-scale engineering projects on Neotropical freshwater fishes Franco Teixeira de Mello, Carla Simone Pavanelli, José Luis Olivan Birindelli, Ana Cristina Petry, Andréa Bialetzki, et al. Neotropical Ichthyology, 2025 Neotropical freshwater ecosystems harbor some of the world’s most diverse fish communities, playing a fundamental role in ecosystem functionality and providing essential and free services to human societies. However, this exceptional biodiversity faces escalating threats from multiple and widespread anthropogenic pressures, particularly small-scale engineering activities such as channelization, damming, road crossings, water extraction, and mining, which remain insufficiently assessed despite their cumulative and synergistic impacts. This Special Issue, Impacts of Small-Scale Engineering Projects on Neotropical Freshwater Fish Diversity compiles eleven studies to assess how small-scale interventions affect fish diversity and ecosystem processes. Collectively, these studies consistently demonstrate ecological trends including habitat simplification, loss of sensitive species, predominance of tolerant or generalist taxa, and disturbances on reproductive and trophic dynamics. Hydrological alterations and reduced habitat heterogeneity are key drivers of biotic homogenization and simplification of functional diversity. Overall, these publications emphasize that both local and regional disturbances synergistically compromise the structural and functional integrity of fish assemblages. Maintaining ecological connectivity and functional diversity is essential for maintaining integrity and resilience of Neotropical freshwater ecosystems, and findings underscore the urgent need to integrate small-scale impacts into basin management and conservation, recognizing their cumulative and often underestimated influence on biodiversity and ecosystem functioning.
NEOTROPICAL FRESHWATER FISHES: A dataset of occurrence and abundance of freshwater fishes in the Neotropics Lívia Helena Tonella, Renata Ruaro, Vanessa Salete Daga, Diego Azevedo Zoccal Garcia, Oscar Barroso Vitorino, et al. Ecology, 2023 The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.
Morphological development of Hypophthalmus fimbriatus and H. marginatus post-yolk-sac larvae (Siluriformes: Pimelodidae) Zootaxa, 2008
Early development of Hoplias aff. malabaricus (Bloch, 1794) (Osteichthyes, Erythrinidae) in the upper Paraná river floodplain, Brazil Acta Scientiarum Biological Sciences, 2008
Morphology of digestive tract and diet of Bryconamericus aff. iheringii larvae (Boulenger, 1887) (Osteichthyes, Characidae) Acta Scientiarum Biological Sciences, 2006
Initial development and temporal distribution of larvae and juveniles of Bryconamericus stramineus Eigenmann, 1908 (Osteichthyes, Characidae) in the floodplain of Upper Paraná River Acta Scientiarum Biological Sciences, 2003
