A Synthesis of the Ecology and Conservation of Pseudoplatystoma Catfishes in the Neotropics

Abstract

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.

Population structure and reproductive indicators of the surubim Pseudoplatystoma punctifer (Siluriformes, Pimelodidae) in the São Miguel River, Amazon basin, Brazil

“…Our findings showed that females exhibit a higher sex ratio, length, and weight compared to P. punctifer males. The dominance or size structure of individuals in one sex over the other may be related to differential individual growth rates and early gonad maturation (Pereira et al, 2023;Suzuki et al, 2013). However, females invest significantly more effort in reproductive development compared to males (Barneche et al, 2018;Freitas & Montag, 2019).…”

“…Hydroelectric dams can cause deleterious consequences for fish populations, including the surubim, as they prevent reproductive migrations, and reduce individual biomass and spawning potential, reflecting negatively on the recruitment of natural stocks and fisheries productivity (Andrade et al, 2019;Pereira et al, 2023).…”

Flood Pulse Effects on the Growth of Pseudoplatystoma fasciatum in the Amazon Basin

“…One species for which no studies have investigated the effects of interannual variability in flood pulses on growth is Pseudoplatystoma fasciatum. This catfish species transports nutrients and connects habitats through migration [31,32]. 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 [33]. P. fasciatum is distributed in four countries of the Amazon basin, including the Amazon mainstem and the Madeira, Solimões, and Tapajós tributary rivers [31]. Understanding how interannual variability in flood pulses affects its growth is key to managing and conserving it.…”

“…The eggs and larvae of P. fasciatum drift downstream with the current during the high-water season (typically referred to as the peak-flow period) when adults and juveniles migrate laterally to the floodplains to prey on other fish and grow faster. During the falling-water season (typically referred to as the descending limb), P. fasciatum migrates back to the mainstream river and stays there for the low-water season, where it predates less and grows more slowly [31]. In line with this migratory ecology, growth studies showed that the vertebrae of P. fasciatum deposit one growth ring per year [32,34], with slower growth (opaque ring formation) occurring during the low-water season and faster growth (the hyaline ring) in the rising-water season.…”