Khadim Hussain Memon

Evaluation of the fishery status for King Soldier Bream Argyrops spinifer in Pakistan using the software CEDA and ASPIC

Catch and effort data were analyzed to estimate the maximum sustainable yield (MSY) of King Soldier Bream, Argyrops spinifer (Forsskål, 1775, Family: Sparidae), and to evaluate the present status of the fish stocks exploited in Pakistani waters. The catch and effort data for the 25-years period 1985–2009 were analyzed using two computer software packages, CEDA (catch and effort data analysis) and ASPIC (a surplus production model incorporating covariates). The maximum catch of 3 458 t was observed in 1988 and the minimum catch of 1 324 t in 2005, while the average annual catch of A. spinifer over the 25 years was 2 500 t. The surplus production models of Fox, Schaefer, and Pella Tomlinson under three error assumptions of normal, log-normal and gamma are in the CEDA package and the two surplus models of Fox and logistic are in the ASPIC package. In CEDA, the MSY was estimated by applying the initial proportion (IP) of 0.8, because the starting catch was approximately 80% of the maximum catch. Except for gamma, because gamma showed maximization failures, the estimated results of MSY using CEDA with the Fox surplus production model and two error assumptions, were 1 692.08 t (R2=0.572) and 1 694.09 t (R2=0.606), respectively, and from the Schaefer and the Pella Tomlinson models with two error assumptions were 2 390.95 t (R2=0.563), and 2 380.06 t (R2=0.605), respectively. The MSY estimated by the Fox model was conservatively compared to the Schaefer and Pella Tomlinson models. The MSY values from Schaefer and Pella Tomlinson models were the same. The computed values of MSY using the ASPIC computer software program with the two surplus production models of Fox and logistic were 1 498 t (R2=0.917), and 2 488 t (R2=0.897) respectively. The estimated values of MSY using CEDA were about 1 700–2 400 t and the values from ASPIC were 1 500–2 500 t. The estimates output by the CEDA and the ASPIC packages indicate that the stock is overfished, and needs some effective management to reduce the fishing effort of the species in Pakistani waters.

Population dynamics of Japanese threadfin bream Nemipterus japonicus from Pakistani waters

Japanese threadfin bream Nemipterus japonicus (Bloch, 1791) is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009 and May–June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7 530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b=2.778, a=0.032 and R2=0.973. The estimated von Bertalanffy growth function parameters were L∞=30.45 cm, K=0.270 year−1. Based on length-converted catch curve analysis the total mortality (Z) during this study was estimated at 0.960 year−1. The natural mortality coefficient (M) was 0.74 year−1 using Pauly’s equation (the annual average sea surface temperature was 27°C), therefore, the fishing mortality coefficients (F) were 0.22 year−1. The yield per recruit analysis indicated that when tc was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When tc was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax, which indicated that the fishery is about in a safe condition. When using Gulland (1971) biological reference point, Fopt was equals to M (0.74). The current fishing mortality rate of 0.22 was smaller than the target biological reference point.

Maximum sustainable yield of Greater lizardfish Saurida tumbil fishery in Pakistan using the CEDA and ASPIC packages

The catch and effort data analysis (CEDA) and ASPIC (a stock assessment production model incorporating covariates) computer software packages were used to estimate the maximum sustainable yield (MSY) from the catch and effort data of Greater lizardfish Saurida tumbil fishery of Pakistan from 1986 to 2009. In CEDA three surplus production models of Fox, Schaefer and Pella-Tomlinson were used. Here initial proportion (IP) of 0.5 was used because the starting catch was roughly 50% of the maximum catch. With IP = 0.5, the estimated MSY from Fox model were 20.59 mt and 38.16 mt for normal and log-normal error assumptions, while the MSY from Schaefer and Pella-Tomlinson were 60.40, 60.40 and 60.40 mt, for normal, log-normal and gamma error assumptions respectively. The MSY values from Schaefer and Pella-Tomlinson models of three error assumptions were the same. The R2 values from those three models were above 0.6. When IP = 0.5, the MSY values estimated from ASPIC from Fox were 132 mt, and from logistic model were 69.4 mt, with R2 value above 0.8. Therefore we suggest the MSY of S. tumbil fishery from Pakistan to be 60–70 mt, which is higher than the latest catch, thus we would recommend that the fishing efforts for this fishery may be kept at the current level.

Asymptotic behavior of an n-species stochastic Gilpin–Ayala cooperative model

An n-species stochastic Gilpin–Ayala cooperative model was investigated in this study. The Lyapunov function and the M-matrix method were applied to study the stability of the solutions. Sufficient conditions for the existence of a global positive solution of the Gilpin–Ayala cooperative model were established. Certain asymptotically stable results of a global positive solution of the cooperative model and its domain of attraction were estimated. That main objective of this study is to provide corrections for errors in some theorems given in the work of Lian et al. (2007). The errors of Theorems 2, 3, 5, and 6 from the published work appeared in the parameters θi and pii.

Application of a continuous time delay-difference model for the population dynamics of winter-spring cohort of neon flying squid (Ommastrephes bartramii, Lesueur 1821) in the North-west Pacific Ocean

A continuous time delay-difference model (CD-DM) was applied to the Chinese neon flying squid ( Ommastrephes bartramii ) jigging fisheries data (2001–2004) in the north-west Pacific Ocean. The continuous time delay-difference model (CD-DM) was modified from the discrete-time delay-difference model (D-DM), in which recruitment, growth and mortality rates are treated as varying continuously over time. Some commercially important stocks, such as shrimp and O. bartrami with recruitment, growth and mortality rates all varying continuously over time, may be better analysed by a continuous delay-difference model. We estimated the growth and recruitment of O. bartramii on the basis of the CD-DM, and biological reference points (BRPs) and accuracy of estimates are discussed in this study. We obtained population sizes of 183.9–201.8 million squid during early September 2004. The status of the stock was not in a sustainable state at this time with the available data, which suggests that measures should be taken for the sustainable utilization of this stock. The ability to calculate reference points without need of a full age-structured data makes CD-DM an attractive option for data-poor fisheries. We provided an alternative method for assessing O. bartramii stock and bridged the gap between simple surplus production models and complex fully age-structured models.

A continuous time delay-difference type model (CTDDM) applied to stock assessment of the southern Atlantic albacore Thunnus alalunga

A continuous time delay-diff erence model (CTDDM) has been established that considers continuous time delays of biological processes. The southern Atlantic albacore (Thunnus alalunga) stock is the one of the commercially important tuna population in the marine world. The age structured production model (ASPM) and the surplus production model (SPM) have already been used to assess the albacore stock. However, the ASPM requires detailed biological information and the SPM lacks the biological realism. In this study, we focus on applying a CTDDM to the southern Atlantic albacore (T. alalunga) species, which provides an alternative method to assess this fishery. It is the first time that CTDDM has been provided for assessing the Atlantic albacore (T. alalunga) fishery. CTDDM obtained the 80% confidence interval of MSY (maximum sustainable yield) of (21 510 t, 23 118t). The catch in 2011 (24 100 t) is higher than the MSY values and the relative fishing mortality ratio (F2011/FMSY) is higher than 1.0. The results of CTDDM were analyzed to verify the proposed methodology and provide reference information for the sustainable management of the southern Atlantic albacore stock. The CTDDM treats the recruitment, the growth, and the mortality rates as all varying continuously over time and fills gaps between ASPM and SPM in this stock assessment.