Life‐history characteristics of the large Amazonian migratory catfish Brachyplatystoma rousseauxii in the Iquitos region, Peru

Abstract

The main life-history traits of the dorado Brachyplatystoma rousseauxii, a large Amazonian catfish undertaking the largest migration known for a freshwater fish species (from the nursery area in the estuary of the Amazon to the breeding zones in the head waters of the western Amazon basin close to the Andes), were determined from a 5 year sampling of >15,000 specimens in the Peruvian Amazon. The breeding season occurred during the falling and low-water periods, which is hypothesized to be an adaptation to maximize the chances of young stages to reach the estuary. The size at first sexual maturity was slightly larger for females than males, c. 91 and 83 cm standard length (L(S)), respectively. Both males and females reproduce for the first time at >3 years old. The fecundity per spawning event ranged from 481,734 to 1,045,284 oocytes for females weighing 25 and 34 kg, respectively. Seasonal variations of body condition were similar among sexes, but differed between immature specimens that had a higher condition during the low-water period and lower condition during rising waters, and mature individuals that showed the opposite pattern. The growth characteristics were estimated by L(S) frequency analysis. For females, the best fitting models gave a mean birth date in August, during the height of the breeding cycle, with the following von Bertalanffy growth function parameters: L(Sinfinity) = 153.3, K = 0.29 and t(0) =- 0.37 years. For males, the best fitting model gave a mean birth date in July, also during the height of the breeding period, with L(Sinfinity) = 142, K = 0.30 and t(0) =- 0.36 years. At a given age, females were systematically larger than males and the size difference increased with age. The largest females sampled (148 cm L(S)) was 11 years old and the largest male (134 cm L(S)) was 9 years old. The mortality estimates were higher for males total (Z) = 1.34, natural (M) = 0.52 and fishing (F) = 0.82 than for females (Z = 0.98, M = 0.50, F = 0.48). The life-history patterns of B. rousseauxii are discussed in light of the available knowledge about this species and the understanding of its complex life cycle.

DNA Metabarcoding of Amazonian Ichthyoplankton Swarms

“…The results showed that the breeding activity of the Pimelodidae family was spread out over the eight months of the study. However, the results also suggested that more species reproduce during the falling and rising water periods, which is consistent with the results of earlier studies on adults [14,17] and on larvae [25,46]. Together with the work of García-Dávila et al .…”

“…Until now, the life cycle of only one species, B . rousseauxii [14] had been studied in the Peruvian Amazon. Although more samples will improve our understanding of this dynamics, this first study provides very interesting insights into both diversity dynamics and the reproductive activity of some species at specific periods.…”

“…The adults reproduce in the piedmont of Andean rivers in Bolivia, Colombia, Ecuador and Peru. The larvae then drift downstream to their nursery area in the Amazon estuary where they grow before migrating upriver to join the breeding adults in the headwaters [14–18]. This long-distance migratory life cycle is threatened by human activities, particularly overfishing and the construction of hydroelectric dams, which could drastically limit larval recruitment, hence the renewal of fisheries resources.…”

Periodic life history strategy ofPsectrogaster rutiloides, Kner 1858, in the Iquitos region, Peruvian Amazon

“…which gave an estimated birth date corresponding to the breeding peak) and that best described the distributions (i.e. which went through the largest number of large modes and yielded the largest Score = ‘goodness‐of‐fit’ parameter of the ELEFAN routine) was selected (García‐Vásquez et al., ). This process also permitted diminishing the ELEFAN method tendency to underestimate K and overestimate L∞ (Moreau et al., ).…”

“…Total mortality ( Z ) was estimated by the method of the length‐converted catch curves (LCC) (Pauly, ). Natural mortality ( M ) was evaluated using Pauly's equation, as implemented in the Fisat package, for a mean annual temperature of 27°C (García‐Vásquez et al., ).…”