Population dynamics of Macrobrachium rosenbergii (De Man, 1879) from the Narmada Estuary, west coast of India

In the current study, population characteristics of Macrobrachium rosenbergii (De Man, 1879) were assessed from the Narmada Estuary during January to December 2019. The length-weight relationships were established as W = 0.0085 L3.085. The length groups150-159 and 170-179 mm accounted for most of the commercial M. rosenbergii catch. Different growth parameters were estimated as L∞ = 288.75 mm, K = 0.46 yr-1 and t0 = -0.71 y. Annual mortality coefficients for mortality (Z, M and F) were estimated at 1.43, 0.57 and 0.86, respectively. The exploitation rate (E) reached 0.60, marginally surpassing the optimal value of 0.50. The recruitment pattern of M. rosenbergii showed that the species follows two recruitment patterns, one from January to February and the major recruitment from May to August. The maximum sustainable yield (MSY) was estimated at 267.05 t, if the recommended length at first capture (Lc = 137.91 mm TL) is maintained throughout the capture periods. The relative yield per recruit (Y/R) analysis indicated that the present exploitation rate (0.72) already exceeded the maximum fishing pressure (Emax = 0.68), indicating that the stock is already in the decline stage at the present level of fishing pressure.