Growth and mortality parameters of hairtail lepturacanthus savala from Pakistan waters

The length-frequency data of lepturacanthus savala (cuvier 1829) were collected by the four demersal trawl surveys in the pakistan waters in 2009-2010. a total of 4035 lengths and 1391 pairs of length-weight were measured. the length ranges from 5 to 127cm with an average length of 44.23±19.75cm while weight ranges from 1 to 1942g with an average weight of 110.81±229.57 g. the estimated values of length-weight relationship for l. savala were w=0.0001 l3.191 (r2=0.960) n=1391.the calculated von bertalanffy growth function parameters using elefan method in fisat computer package of l. savala were l133.35cm and k=0.130 year-1 and t0=-0.877. the estimated rate of total mortality z applying the length-converted catch curve analysis method for l. savala was z=0.49 year-1,natural mortality m were estimated as m=0.304 year-1 at an annual average sea surface temperature of 26c while the rates of fishing mortality f was calculated as f=0.185 year-1. hence,exploitation ratio (e=f/z) were calculated as 0.377 year-1. yield per recruit contour map reveals that when tc was assumed to be 1,fmax was estimated at 0.6 and f0.1 at 0.45. current age at first capture was about 1 year and fcurrent was 0.185,therefore,fcurrent was smaller than f0.1 and f max. when biological reference point fopt was equal to m (0.304),the current fishing mortality rate of 0.185 is smaller than the target biological reference point. the estimated values of growth performance index for the l. savala from pakistan waters were =3.364 year-1. the estimated value of msy was 26983t with the estimated biomass of 110135t. again the obtained results of maximum sustainable yield (msy) of 26983t for l. savala from pakistan waters were larger than the recent catch of 20375t; therefore,we may indicate that the l. savala fishery in pakistan waters may be in a sustainable state.