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Browsing by Author "Duponchelle, Fabrice"

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    Ecology, Growth, and Migration of Pseudoplatystoma fasciatum in the Amazon Basin
    Alves Pereira, Luciana (Virginia Tech, 2024-05-22)
    Freshwater fishes include diverse lineages collectively summing to over 18,000 species, representing ~51% of all fishes and ~25% of all vertebrates. About one-third of all freshwater species occur in the Neotropics, with an estimated 4,475 species within 71 families. Catfishes of the Order Siluriformes include 39 families with 498 accepted genera and 4,123 species. More specifically, members of the Family Pimelodidae, the long-whiskered catfishes, and the genus Pseudoplatystoma are distributed from South America to southernmost Mexico. The family Pimelodidae includes 30 genera and 116 described species. Fishes of the genus Pseudoplatystoma support important commercial and artisanal fisheries, and some species have become important to regional aquaculture. Most species of the genus are under pressure by dam construction and overfishing. Pseudoplatystoma fasciatum is a catfish species that transports nutrients and connects habitats through migration. It is also a source of food security and income for riverine people in the Amazon basin. This species is heavily fished and may be threatened by the growing construction of hydropower dams. One ecological aspect lacking in the literature is how the growth of Pseudoplatystoma species is affected by interannual variations in the flood pulse. Another crucial aspect of fish ecology is migration. In this dissertation, I review the ecology and conservation of the genus Pseudoplatystoma. Then, I evaluated how inter-annual hydrological variations within the Amazon basin influence the growth of the catfish P. fasciatum. Finally, I used otolith microchemistry to understand the migration ecology of P. fasciatum in the Amazon Basin. I found an inverse relationship between increment width in fish hard parts and hydrological indices. I also found that growth of P. fasciatum was no different in years with intense and mild floods across age-classes 1-5, although different for age-class 6. However, the growth of P. fasciatum was faster in years of mild droughts for all age-classes. I found that thirty-four percent of all fish analyzed migrated between rivers with different Sr signatures, and 66% did not. Also, eighty percent of all fish migrated between rivers with the same type of water (i.e., white-water and black-water rivers), while only 10% migrated between different water types. The mean migration distance migrated was 126 km, with most specimens migrating between 72 and 237 km. I also found that no fish of age one or age six or older migrated. My results on the migratory ecology of P. fasciatum allow me to put forward two main implications for the sustainable management of its fisheries and species conservation. The growth of P. fasciatum can be affected by construction and operation of hydropower dams, climate change, and fisheries. With continued research and collaboration among research groups, understanding the biology and ecology of this genus would fill these knowledge gaps and contribute to fisheries management and conservation of the eight species of the genus Pseudoplatystoma. These actions would contribute to regional ecological and economic sustainability.
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    Flood Pulse Effects on the Growth of Pseudoplatystoma fasciatum in the Amazon Basin
    Pereira, Luciana Alves; Castello, Leandro; Hallerman, Eric; Rodrigues, Edson Rubens Ferreira; Doria, Carolina Rodrigues da Costa; Duponchelle, Fabrice (MDPI, 2024-06-12)
    Fish growth is a fundamental biological process driven by a multitude of intrinsic (within-individual) and extrinsic (environmental) factors that underpin individual fitness and population dynamics. Interannual variability in river hydrology regarding the intensity and duration of floods and droughts can induce interannual variations in the biotic and abiotic variables that regulate fish growth. However, the understanding of how interannual variability in river hydrology affects fish growth remains limited for most species and ecosystems. We evaluated how inter-annual hydrological variations within the Amazon River basin influence the growth of the catfish Pseudoplaystoma fasciatum. Our research questions were as follows: Do floods lead to the faster growth of P. fasciatum and droughts lead to the slower growth? And do floods and droughts affect all age classes in the same manner? We sampled 364 specimens of P. fasciatum from five sites in the Amazon basin, estimated their growth rates, and related the growth rates to indices of the intensity of floods and droughts. We fitted linear mixed-effects models to test the relationship between growth increments and hydrological indices (with F and D quantifying the intensities of floods and droughts, respectively), age as fixed effects, and basins and Fish ID as random effects. We found an inverse relationship between the increment width in the fish hard parts and hydrological indices. That is, intense floods and droughts negatively affected the growth rates. We also found that the growth of P. fasciatum was no different in years with intense and mild floods across age classes 1–5, although was different for age class 6. However, the growth of P. fasciatum was faster in years of mild droughts for all age classes. Our results showing that the growth of P. fasciatum was slower in years of intense droughts are supported by those of previous studies in the Amazon basin and elsewhere. However, our results showing for the first time that the growth of P. fasciatum is slower in years of intense flooding is the opposite of patterns found in other studies. These results thus suggest that the growth of P. fasciatum is maximized within an optimum range of hydrological conditions, where neither floods nor droughts are intense.
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    Migratory Ecology of Pseudoplatystoma fasciatum in the Amazon Basin Revealed by Otolith Microchemistry
    Pereira, Luciana A.; Castello, Leandro; Hallerman, Eric M.; Orth, Donald J.; Duponchelle, Fabrice (MDPI, 2024-06-29)
    Fish migrate for varied reasons, including to avoid predators and to access feeding, spawning, and nursery habitats, behaviors that enhance their survival and reproductive rates. However, the migratory ecology of many important fishes, especially those in river–floodplain ecosystems, remains poorly understood. One fish of the Amazon Basin whose migratory behavior is poorly understood is the catfish Pseudoplatystoma fasciatum. Here, we used otolith elemental microchemistry to characterize the migration ecology of P. fasciatum in the Amazon Basin. The main research questions of this study were: (1) does P. fasciatum move between waters with different Sr isotopic signatures (87Sr/86Sr) and chemical compositions? (2) What distance do they migrate? (3) Is the migration of P. fasciatum related to age? And (4) does P. fasciatum migrate mainly upstream, downstream, or in both directions? We assessed whether P. fasciatum migrates between waters with different 87Sr/86Sr values, comparing the Sr isotopic signature of otolith transects of each individual with the range of Sr isotopic signatures within the respective rivers. We found that 34% of the 71 fish analyzed migrated between rivers with different Sr isotopic signatures and 66% did not. The mean migration distance migrated was 126 km, with most specimens migrating between 72 and 237 km. Apparently, no fish of age one or age six or older migrated. All fish that migrated were between two and five years of age, with 20% of the specimens that migrated being two years old, 40% three years old, 30% four years old, and 20% five years old. Sixty-six percent of all individuals that migrated between rivers with different Sr signatures did so bidirectionally, while 33% moved unidirectionally. According to our definition of homing behavior in which fish migrated back to the same river where they were born, 41% of all fish that migrated displayed apparent homing behavior. Our findings provide insights into the migratory ecology of P. fasciatum, corroborating and refining knowledge reported in the literature. Our results on the migratory ecology of P. fasciatum have implications for sustainable fisheries conservation and management: conserving P. fasciatum requires habitat maintenance and suitable fishing practices in spawning and nursery habitats, and managers must consider large geographic areas for effective fishery management and conservation.
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    A Synthesis of the Ecology and Conservation of Pseudoplatystoma Catfishes in the Neotropics
    Pereira, Luciana A.; Castello, Leandro; Orth, Donald J.; Duponchelle, Fabrice; Hallerman, Eric M. (MDPI, 2023-06-07)
    Species of the genus Pseudoplatystoma, the long-whiskered catfishes, are important in commercial and recreational fisheries in South America, and some species have become key to regional aquaculture. Some species of the genus are under pressure due to overfishing and the negative impacts of dams. Six questions are asked in this review: (i) What species are in the genus, and where are they distributed? (ii) What are the life histories and ecologies of Pseudoplatystoma species? (iii) What are the patterns of somatic growth for these species? (iv) What is known about the biomass, production, and population dynamics of Pseudoplatystoma? (v) What is the geographic distribution of genetic variation within Pseudoplatystoma species? (vi) What are the threats to the conservation of these species? The taxonomy of the genus currently includes eight species, respectively, distributed over the Orinoco, Amazon, Paraná, and São Francisco basins. Pseudoplatystoma catfishes typically exhibit longitudinal migrations for reproduction and lateral migration for feeding, but these patterns may vary among populations. The size of the first maturation of these catfishes varies between 57 cm to 82 cm in total length. Five of the eight species spawn during the rising water season. Pseudoplatystoma species can grow to about 130 cm in total length and 100 Kg in weight and live until 30 years of age, depending upon the species. Biomass production and population dynamics of these catfishes have not yet been fully described. Their life-history characteristics indicate that they are periodic strategists with associated population recruitment dynamics. Population genetic patterning varies among Pseudoplatystoma species, with some degree of homing behavior and genetic differentiation among populations, indicating the need for management by applying the Management Unit and perhaps Evolutionary Significant Unit concepts. The main threats to the persistence of these catfishes are overfishing and alterations in and obstruction of river flow due to the construction of hydropower dams. After synthesizing existing information on species of the genus Pseudoplatystoma, we offer suggestions for future research to fill critical gaps in the knowledge of this group.