Reproductive pattern and population dynamics of Anchovia surinamensis in a seasonal floodplain lake of the Amazon basin*

The Surinam anchovy (Anchovia surinamensis) is a small fish of commercial and ecological interest in the Amazon basin. To understand the reproductive and population dynamics of this species, in 2019 and 2020, experimental fisheries were carried out during periods of flood and low water in the Cujubim Lake in Porto Velho (Rondônia, Brazil). This study aimed to analyze the seasonal pattern (flood and low water) for the reproductive period and the population dynamics of the Surinam anchovy in this region, which resulted in the collection of 870 individuals. The specimens showed mean lengths (Ls) of 6.85 ± 0.51 cm to 9.01 ± 2.56 cm and mean weight (Wt) of 5.8 ± 3.37 g to 6.6 ± 2.72 g between low and flood water periods, respectively. The growth parameters for this species (Wt = 0.0226*Ls2,6635; Natural mortality, M = 1.66 year-1; Growth rate, k = 0.70 year-1; Asymptotic length, L∞ = 16.53 cm; Theoretical maximum weight, W∞ = 42.83 g) and the quantity of individuals in mature stages during periods of flood and low water were also evaluated. The mean values of Gonadosomatic index - GSI (5.41 and 4.96 between females and males) and animal welfare index, Kn (1.009 and 1.010 between low and flood water periods) did not show significant differences. All the population growth information presented, added to the values of physicochemical parameters of the water (which were suitable for tropical fish) indicates that the Surinam anchovy population is governed by hydrological seasonality and is well adapted to the floodplain lake where it colonizes and reproduces.