摘要
Objective:To evaluate the stock of Alepes djedaba(A.djedaba)by describing the length composition,growth parameters,mortality rates of A.djedaba captured in Arabian Gulf off Saudi Arabia and adopting yield per recruit and biomass per recruit models.Methods:A random sample of 490 fish representing a moderate range of total lengths(16.5-32.4cm)and weights(60-410 g)were sampled in Arabian Gulf off Dammam,Saudi Arabia during the period from August 2008 to July 2009.LFD5 software was used for estimation of growth parameters.Total mortality was calculated using the length converted catch curve.Natural mortality was estimated using Pauly and David's formula.Fishing mortality was computed by subtracting natural mortality from total mortality.Per recruit analysis was made using Beverton and Holt model.Results:Length-frequency analysis revealed four peaks and the length range from 22 cm to 27 cm dominated the catch,constituting about 71%of the catch.Values of the von Bertalanffy growth parameters were computed using LFD5 software as follows:the asymptotic length(L_(∞))=41.71 cm,curvature parameter(K)=0.36 year^(-1),and hypothetic age at zero length(t_(0))=-0.76 year.The total mortality(Z)was estimated as 2.07 year^(-1),and natural mortality was 0.8 year^(-1).Fishing mortality F=1.27 year^(-1),which was higher than F_(0.1)(0.3 year^(-1)),F_(SB(50))(0.59 year^(-1))and FS_(B(40))(0.86 year^(-1)).Atthe current levels of fishing and natural mortality,the biomass per recruit is 34%of the virgin biomass.Conclusions:These may indicate an overexploitation state of the fisheries of A.djedaba in Arabian Gulf.
