Population dynamics of Prochilodus nigricans (Characiformes: Prochilodontidae) in the Putumayo River

Age validation and contrasted growth performances of Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) in two river systems of the Western Amazon

Abstract The doncella Pseudoplatystoma punctifer is an economically and ecologically important catfish in the Amazon basin. However, little is known about its age, growth and population dynamics parameters. This study aims to validate the formation of growth marks in vertebrae of individuals collected from two rivers systems of the Peruvian Amazon (Amazon-Marañón-Ucayali and Putumayo) and compare growth parameters using the von Bertalanffy growth function between sexes and systems. A total of 372 individuals from the Amazon-Marañón-Ucayali (AMU) system and 93 from the Putumayo River were analyzed. The formation of one growth ring per year was validated and the individual ages ranged from zero to nine years old. Females grew significantly larger than males in both systems. Both females and males grew significantly better in the AMU system than in the Putumayo River. Maximum observed length and size at maturity in the AMU system were lower than those reported in previous studies in the area, and together with an important proportion of juveniles in the catches, suggest that the species is heavily exploited. Further studies on the reproductive biology and population dynamics of the doncella are needed in order to implement management measures more in line with the current situation.

Life history trait variations and population dynamics of Calophysus macropterus (Siluriformes: Pimelodidae) in two river systems of the Colombian and Peruvian Amazon

ABSTRACT The catfish Calophysus macropterus is heavily exploited in the Amazon basin, yet its life history characteristics are poorly documented, hampering proper fisheries management. In order to fill this gap, monthly sampling in the upper Putumayo River and in the Amazonas, lower Marañón and Ucayali (AMU) rivers were carried out over several years (2013-2015 in the AMU, 2013-2017 in the Putumayo) to provide detailed information about its reproduction, growth and mortality patterns (using length frequency data). Reproduction, which occurs during the dry and early flooding season, was only observed in the upper Putumayo River and not in the sampled portion of the AMU system, suggesting that the species reproduces closer to the Andes than other pimelodid catfishes. Size at first sexual maturity did not differ significantly among sex or among river systems, ranging from 25-28 cm SL. In both river systems, females had a faster growth than males and both genders also tended to have a better growth in the AMU than in the upper Putumayo. Mortality and exploitation estimate all indicated overexploitation of the species in both river systems. The implications of these results for fisheries management and conservation are discussed.

Hidden diversity in Prochilodus nigricans: A new genetic lineage within the Tapajós River basin

Highly spread through the Amazon River basin, Prochilodus nigricans have had its taxonomic validity recently questioned, when genetic differences between Western and Eastern Amazon populations from the Brazilian shield were detected. This area has been seeing as a region of high ichthyofaunal diversity and endemism, in which the hybrid origin of the Tapajós River basin has been raised. In this paper, we report a new molecular lineage within P. nigricans of Tapajós River, highlighting this region still hides taxonomically significant diversity. Haplotype networks were reconstructed using the mitochondrial COI and ATP6/8 markers, which were also used to calculate genetic distances among clusters. We additionally conducted a delimiting species approach by employing a Generalized Mixed Yule-Coalescent model (GMYC) with COI sequences produced here, and previous ones published for individuals sampled across the Amazon River basin. In addition to the genetic differentiation within P. nigricans, our findings favor the hypothesis of hybrid origin of the Tapajós River basin and reaffirm the importance of studies aiming to investigate hidden diversity to address taxonomic and biogeographic issues, that certainly benefit better biodiversity conservation actions.