Biotelemetry, ichthyoplankton and genetic data can provide detailed information about the migratory dynamics and reproductive cycle of freshwater fishes. However, few studies have combined these techniques in Neotropical systems. The objective of this study was to examine the migratory and reproductive dynamics of Prochilodus costatus in the São Francisco River watershed, south‐east Brazil, by comparing the ecological importance of two rivers to the species, an undammed segment of the São Francisco River and a dammed segment of one of its main tributaries, the Pará River. In total, 215 fish were radio‐tagged over three years (2014–16). Eggs and larvae were sampled at seven locations and analysed by PCR to identify Prochilodus spp. ichthyoplankton. Most radio‐tagged individuals (97%) used the undammed segment of the São Francisco River as spawning migration route, even those captured and released in the Pará River. Fish migrated to spawn from late September to late November with the arrival of the rains and returned to feeding sites from December to May after spawning. The highest densities of fish eggs and larvae were recorded in the upper reaches of the São Francisco River during months of peak river discharge. Returning fish showed high fidelity to sites occupied before spawning migration. Fish spent roughly 71% of the year at feeding sites, 25% at spawning sites and 4% moving between them. This study provides novel information about the migratory dynamics of Neotropical fishes and underscores the key role of undammed river segments for the conservation of Neotropical migratory fish species.
AIM: This work aimed to describe a first record of Misgurnus anguilicaudatus, Cantor 1842 in São Paulo state, as well as your potential impacts on native populations. METHODS: The specimen was caught by eletro-fishing device, in Itaguapeva river, Ribeira do Iguape river basin, Ibiuna (SP), Brazil. Later, it was fixed in 10% formalin and taken to laboratory for species identification, morphometric data evaluation, diet analysis and stage of gondal maturity. RESULTS: The individual was an adult female, without parasites and with gonads in maturity stage B, which indicates vascularized ovaries and presence of oocytes in vitellogenesis process. The dietary analysis showed that 95.3% of the stomach was occupied by insect larvae. CONCLUSIONS: The diet analysis may suggest food overlap and consequent competition for food with native species of the genera Trichomycterus e Characidium, which consume essentially the same items. Still, the great morphological similarity with native species, especially Siluriformes, could generate competition for shelters. Additionally, the stage of gonadal maturity and a recorded ability of the species on establish invasive populations in different environments raise concerns about the possibility of Misgurnus anguillicaudatus reproduction on the studied site.
Alterations in stream environments can alter fish food availability, but there is little research data related to the impacts of urbanization on fish diets in tropical streams. Thus, we sought to compare the diet of ten fish species in urbanized and nonurbanized streams reaches. Fish stomach contents were obtained for four urban and five non-urban stream reaches from two medium-sized cities. We verified the similarity of diet composition from urbanized/non-urbanized streams. In-stream features mainly related to the substrate highlighted a perturbation gradient: gravel, pebbles and cobbles were associated to the wider urban reaches while silt were representative in the narrow pools from non-urban streams. Fishes changed their diet in response to urban and non-urban treatments. Omnivorous fishes consumed more detritus and Chironomidae and less terrestrial adult insects in urban reaches, while invertivorous fish consumed more terrestrial adult insects and Trichoptera larvae in the non-urbanized stream reaches. Although the management of the physical structure of streams in Brazil has been basically focused on riparian reforestation, our results suggest that a restoration plan for urban streams cannot be limited to reforestation of its surroundings, but also need to consider the physical structure of the channel, especially the substrate, which contributes to promote in-stream variability.
Details of migration dynamics of Neotropical fishes are poorly understood. This study aimed to examine upstream (spawning) and downstream (post-spawning) migration speeds, of curimatá-pioa (Prochilodus costatus) in the São Francisco River basin, southeast Brazil. Most upstream movements were recorded in October and November, in two well-defined migration windows, and downstream movements were frequent from December to March. Fish migrated upstream at an average migration speed of 34.4 km day-1 and no significant differences were detected in their speed between sexes and migration window they selected to migrate. No relationship was detected between upstream migration speed and biometric measures of tagged individuals. Upstream migrations speeds were significantly higher for fish that swam longer prior to reach telemetry stations in the same season, indicating that swimming performance may take some time to achieve its peak in upstream migration. Fish migrated downstream at an average migration speed of 97.7 km day-1, what is close to passive swimming in São Francisco River, and no significant differences in speed were detected between sexes or capture sites. The migration speeds measured here are the highest ever recorded for the genus Prochilodus and are among the highest reported for Neotropical migratory fish.
AIM: Life-history strategies in fish include essential parameters related to offspring survivorship, fecundity and time of reproduction, which represent adaptive traits that enable a species to deal with spatial and temporal variability of abiotic conditions. This study aimed to compare reproductive traits associated to life-history theory for three Hyphessobrycon species from two lentic environments (four natural oxbow lakes and a man-made reservoir) of Mogi Guaçu River, upper Paraná River basin. METHODS: Specimens were collected with four minnow traps between August 2005 and July 2006 to cover dry and wet seasons (three samples in each season, and three samples in each environment). RESULTS: Reproductive strategy of H. bifasciatus and H. eques, which predominated in the oxbow lakes, differed from H. anisitsi in the reservoir. Hyphessobrycon bifasciatus and H. eques were single spawners with lower fecundity and size at sexual maturity, but invested more in number of eggs per body gram, while H. anisitsi was a multiple spawner species with higher fecundity, larger size at sexual maturity and body size. CONCLUSIONS: In seasonal environments, single spawners are synchronized with the floods to maximize juvenile survivorship, while reservoirs harbors multiple spawners’ fish due to the reduced fluctuation between high and low floods resulting from dam operation. Therefore, the seasonal condition in the oxbow lakes due to the flood pulse favored single spawners’ tactic, as showed by H. bifasciatus and H. eques. In contrast, the multiple spawning of H. anisitsi seems to be related to the more stable environmental condition throughout the year provided by the dam. Life-histories reported herein to Hyphessobrycon species must be common to other characid fishes inhabiting similar environments.
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