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

Stock dynamics of flat needlefish

Abstract

The age, growth, mortality parameters and stock status of Ablennes hians
(Valenciennes, 1846) were assessed by using length frequency, catch, and effort data
collected from the commercial catches along the coast of Kerala (south-eastern Arabian
Sea) 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 77.58
cm TL, which is greater than Lm50. Beverton and Holt yield per recruit analysis, indicated that
maximum Y/R could be obtained at an exploitation rate (Emax) of 0.75, suggesting scope for
an increase in exploitation. In this analysis, spawning stock biomass (SSB) was not taken
into consideration, which is essential for maintaining recruitment in the future. In the present
study, E0.1 (0.61) and Ecur (0.66) were nearly equal, indicating that the fishery is running at
an economic reference point i.e., maximum economic yield (MEY). Thompson and Bell
prediction model showed that at the current level of exploitation, the SSB was reduced by
20.49% and hence, there is no scope for further increase in fishing efforts to maintain the SSB
at a relatively safe and sustainable level. The analysis revealed the maximum sustainable
yield (MSY) of this species as 90.26 t, which can be obtained by increasing the present level
of fishing effort by 1.3 times but would result in the depletion of the SSB to a critically low
level of 15.65%. Therefore, a precautionary safe level of exploitation (E0.1), estimated at 0.61
for the species, is recommended.

Keywords:
Belonidae, Fishery management, Population dynamics,
Spawning stock biomass, Stock status