1. In the Amazon, migratory catfishes of the genus Brachyplatystoma are apex predators that are important for fisheries and conservation. The life cycle of Brachyplatystoma platynemum Boulenger, 1898 is poorly known, although it has been hypothesized to be very similar to that of Brachyplatystoma rousseauxii Castelnau, 1855, which uses the entire length of the Amazon basin to complete its life cycle (from the Andes to the estuary). This study provides the first data on the migratory patterns of B. platynemum at the individual level using otolith microchemistry.2. In total, 94 individuals were sampled close to major breeding areas in the Amazon basin (78 fish from the middle and upper Madeira River and 14 fish from the upper Amazon), and their lifetime movements were assessed by measuring variations in 87 Sr/ 86 Sr along transverse sections of their otoliths (ear stones), using laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS).3. The migrations of B. platynemum are not as extensive as those of B. rousseauxii, and do not involve natal homing. Furthermore, the estuary is not a nursery area, at least for fish hatched in the Madeira. Nevertheless, B. platynemum migrates several
-In Amazonian fisheries, the silver arowana, Osteoglossum bicirrhosum (Cuvier 1829) is heavily exploited for human consumption as an adult, and for the aquarium trade as a small juvenile (yolk sac juvenile mainly). The periodicity of annuli formation on otoliths and growth variability of the silver arowana were studied in different river river-basins of the Peruvian Amazon between 2006 and 2009. Transverse stained sections of 606 individual otoliths were analysed from four different river-basins, the Amazonas, Ucayali, Napo and Putumayo, of which 554 could be interpreted. These belonged to 274 females ranging from 15 to 91 cm (standard length) and 280 males ranging from 30 to 91 cm. In addition, yolk sac juveniles of known age were collected to improve growth modelling. Monthly proportions of stained otolith edges validated the formation of a single annulus per year in two different river-basins with lagged hydrological cycles: the Amazonas-Ucayali and the Putumayo. Stained growth mark counts resulted in a longevity estimate of at least 16 years for the silver arowana in the Peruvian Amazon. This fish grew quickly during the first two years, and asymptotic growth was reached after four to five years, except in the Putumayo where it was reached slightly earlier. Results showed no significant growth dimorphism between sexes within basins, but indicated significant growth differences among river basins. Silver arowanas measured, on average, between 38 and 40 cm at the end of their first year. Length-at-age differences among river basins increased with age to reach over 14 cm (and >3 kg) after 7 years between the faster and slower growing populations (Amazonas and Putumayo, respectively). The growth differences observed emphasize the need for further investigation on the population structure of this species as, although these differences might merely be phenotypic responses to contrasted environmental conditions, they could alternatively reflect the existence of several populations with distinct genetic and life history characteristics. The consequences of such differences would be very important for the management and conservation of this fragile and extensively exploited species.
The present study objective was to determine some of the main life history characteristics of the chiochio, Psectrogaster rutiloides, a heavily fished, yet poorly studied species of the Peruvian Amazon. Over an annual cycle between 2006 and 2007 a monthly sampling of P. rutiloides on the Iquitos market provided a total of 2973 individuals. The species reproduces during the rainy season, during the first part of the flooding period. First sexual maturity is reached at about 2 years of age and 95 mm standard length (SL) for both males and females. Batch fecundity was related to fish size and varied from 59 800 to 149 100 oocytes, with oocytes diameters of 1.34 AE 0.11 mm, valid for females of 141 and 152 mm SL and of 102.9 and 149.6 g body mass, respectively. Females grew faster than males in every age class, a difference gradually increasing from 7% at age one to 10% at age nine, which corresponded to the oldest individuals sampled. Estimated mortality parameters and exploitation rates suggested over-exploitation of the species in the Loreto region.
Summary The aim of this study was to assess the variability of reproductive characteristics of the silver Arowana, Osteoglossum bicirrhosum, in four sub‐basins of the Peruvian Amazon: the Amazonas, Ucayali, Napo and Putumayo rivers. An illustrated, detailed gonadal maturation scale is proposed for a clearer determination of the reproductive status of male and female Arowana. The breeding season occurred during the dry season and early rising waters in the Amazonas and Ucayali, whereas it was restricted to the dry season in the Napo and Putumayo. A same female can reproduce more than once during the breeding season. Age at maturity was reached during the second year, at sizes varying between 43–45 cm for males and 46–50 cm SL for females. Important variations in fecundity were observed between fish of the four sub‐basins, whereas mean oocytes diameter and mass did not vary significantly, suggesting differences in reproductive investment. Together with previously reported variations of growth patterns in the same sub‐basins, these results suggest the existence of distinct populations in the Peruvian Amazon, with important consequences for management and conservation, but also for future aquaculture development programs.
RESUMENSe presenta el análisis de la información de los desembarque de pescado fresco, en los principales puertos de la ciudad de Iquitos, durante el período comprendido entre los años 2008 y 2012. Desembarque que está compuesto por el 79% de pescado fresco desembarcado utilizando un sistema de cajones isotérmicos que son transportados en las embarcaciones de carga y pasajeros. Las embarcaciones de la flota pesquera comercial representan sólo el 21% de los desembarques totales al estado fresco. Ucayali fue la cuenca más importante de pesca en este periodo con un promedio de 63,3% de los desembarques, seguido de Amazonas con 31,5 %. Las embarcaciones formales categorizadas entre 6 a 8 toneladas son las que mayor representatividad tienen en la flota pesquera comercial.PALABRAS CLAVE: Desembarque, flota pesquera, cajones isotérmicos, río Ucayali. FRESH FISH LANDING IN THE IQUITOS CITY, LORETO REGION -PERUVIAN AMAZON ABSTRACTThis study presents the analysis of the information of the in the main ports of the city of fresh fish landing Iquitos, in the years from 2008 to 2012. Landing is composed by 79% of fresh fish using a system of isothermal boxes that are transported in the cargo and passenger vessels. The commercial fishing fleets provide only 21% of total landings at fresh state. The Ucayali basin was the most important fishing area during the study period, with an average of 63.3% of the landings, followed by the Amazon basin with 31.5%. The formal vessels categorized from 6 to 8 tons are the most representative in the commercial fishing fleet.
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