Spawning season, recruitment, and growth of the freshwater prawn Macrobrachium lamarrei (H. Milne-Edwards, 1837) in a perennial wetland, northeastern Bangladesh

Spawning season, recruitment, and growth of the freshwater prawn Macrobrachium lamarrei were studied in a perennial wetland, northeastern Bangladesh during October 2016 to September 2017. Spawning season was estimated based on the monthly variations of percent ovigerous females. Recruitment and growth were estimated using the time series of the length-frequency distributions. We compared the von Bertalanffy growth function (VBGF) and the Pauly and Gaschiitz growth function (PGGF) to identify any seasonal oscillation in growth rate. Ovigerous females occurred almost throughout the year, indicating a prolonged spawning season with two peaks between March-April (minor peak) and June-September (major peak). Both males and females with modal size similar to 8.0 mm carapace length first recruited in October, which synchronized with the major peak spawning season. There was seasonality in growth rate; hence, PGGF was adopted as the best-fitting model to describe the growth of both sexes. The estimated equations were L-t = 17.86 (1- exp [-2.432 (t/(12) - 0.072) - (1.766/27r) sin {27r (t/(12) - 0.982)}] for males and L-t = 23.18 (1- exp [-1.342 (t/(12) + 0.106) - (0.388/27r) sin {27r (t/(12) - 0.209)}] for females. Sexual dimorphism was found with larger size in females than males. Longevity was estimated to be - 14 months for both sexes. These findings can be useful to formulate management measures for this prawn.