Reproductive biology of Copella arnoldi (Characiformes: Lebiasinidae), a terrestrial-spawning fish from the Amazon

Abstract We assessed the reproductive biology of the splash tetra, Copella arnoldi, an ornamental species with an extraordinary reproductive strategy. We collected 171 individuals from a river in the eastern Amazon between August 2016 and June 2017. The sex ratio remained relatively stable during the study period. Gonadosomatic indices for both female and male indicated heightened reproductive activity during the rainy season. On average, each mature female produced 47 oocytes ranging from 200 to 800 μm in diameter, releasing a batch of oocytes during each reproductive period. Length-mass ratios suggested similar growth proportions for both sexes. The L50 was estimated at 18.09 mm for females and 18.52 mm for males. The condition factor exhibited minimal variation throughout the year. The spawning period seemed to correlate with increased precipitation rates, as evidenced by two reproductive peaks, one in December (early rainy season) and another in April (peak rainy season). Spawning in C. arnoldi appeared synchronized with the rainy season, likely due to the reduced risk of egg dehydration and the enhanced survival potential for juveniles.