Fishery, population dynamics and stock assessment of flat needlefish Ablennes hians (Valenciennes, 1846) from the south-eastern Arabian Sea off Kerala coast, India

Abstract

The age, growth, mortality parameters and stock status of Ablennes hians(Valenciennes, 1846) were assessed by using length frequency, catch, and effort datacollected from the commercial catches along the coast of Kerala (south-eastern ArabianSea) during 2015-2017. The growth parameters, L∞, K and t0 were estimated at 133.9 cm TL,0.72 yr-1 and -0.0026 yr, respectively. The instantaneous natural mortality (M), total mortality(Z), fishing mortality (F) and current exploitation rate (Ecur) were estimated as 0.95 yr-1,2.78 yr-1, 1.83 yr-1 and 0.66, respectively. Length at capture (Lc50) was estimated at 77.58cm TL, which is greater than Lm50. Beverton and Holt yield per recruit analysis, indicated thatmaximum Y/R could be obtained at an exploitation rate (Emax) of 0.75, suggesting scope foran increase in exploitation. In this analysis, spawning stock biomass (SSB) was not takeninto consideration, which is essential for maintaining recruitment in the future. In the presentstudy, E0.1 (0.61) and Ecur (0.66) were nearly equal, indicating that the fishery is running atan economic reference point i.e., maximum economic yield (MEY). Thompson and Bellprediction model showed that at the current level of exploitation, the SSB was reduced by20.49% and hence, there is no scope for further increase in fishing efforts to maintain the SSBat a relatively safe and sustainable level. The analysis revealed the maximum sustainableyield (MSY) of this species as 90.26 t, which can be obtained by increasing the present levelof fishing effort by 1.3 times but would result in the depletion of the SSB to a critically lowlevel of 15.65%. Therefore, a precautionary safe level of exploitation (E0.1), estimated at 0.61for the species, is recommended. Keywords:Belonidae, Fishery management, Population dynamics,Spawning stock biomass, Stock status