Aamir Mahmood Memon

Probiotics and prebiotics associated with aquaculture: A review

There is a rapidly growing literature, indicating success of probiotics and prebiotics in immunomodulation, namely the stimulation of innate, cellular and humoral immune response. Probiotics are considered to be living microorganisms administered orally and lead to health benefits. These Probiotics are microorganisms in sufficient amount to alter the microflora (by implantation or colonization) in specific hosts compartment exerting beneficial health effects at this host. Nevertheless, Prebiotics are indigestible fiber which enhances beneficial commensally gut bacteria resulting in improved health of the host. The beneficial effects of prebiotics are due to by-products derived from the fermentation of intestinal commensal bacteria. Among the many health benefits attributed to probiotics and prebiotics, the modulation of the immune system is one of the most anticipated benefits and their ability to stimulate systemic and local immunity, deserves attention. They directly enhance the innate immune response, including the activation of phagocytosis, activation of neutrophils, activation of the alternative complement system, an increase in lysozyme activity, and so on. Prebiotics acting as immunosaccharides directly impact on the innate immune system of fish and shellfish. Therefore, both probiotics and prebiotics influence the immunomodulatory activity boosting up the health benefits in aquatic animals.

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.

MSY Estimates of Cephalopod Fishery and Its Bioeconomic Implications in Pakistani Marine Waters

In this study maximum sustainable yield of cephalopod fishery resource, 1999-2009, was estimated by employing surplus production models through CEDA and ASPIC computer packages. Obtained results show that this fishery resource is overexploited. CEDA software computed MSY in a range between 4,600-4,900 t (tons). On the other hand, ASPIC range for MSY estimation remained between 4,800-5,200 t for this fishery resource. It is vivid that MSY range computed by both the computer packages overlap each other. CEDA showed conservation in MSY estimation as compared to ASPIC. Moreover, ASPIC results showed higher R 2 values. Considering the MSY estimates, it is recommended that target reference point of MSY for cephalopod fishery resource in Pakistani marine waters should be around 4,900-5,000 t. Harvest of this fishery resource beyond 5,200 t should be considered as limiting reference point. Thus, concrete steps are directly needed to conserve this fishery resource for future.

Fishery stock assessment of Kiddi shrimp ( Parapenaeopsis stylifera ) in the Northern Arabian Sea Coast of Pakistan by using surplus production models

Pakistani marine waters are under an open access regime. Due to poor management and policy implications, blind fishing is continued which may result in ecological as well as economic losses. Thus, it is of utmost importance to estimate fishery resources before harvesting. In this study, catch and effort data, 1996–2009, of Kiddi shrimp Parapenaeopsis stylifera fishery from Pakistani marine waters was analyzed by using specialized fishery software in order to know fishery stock status of this commercially important shrimp. Maximum, minimum and average capture production of P. stylifera was observed as 15 912 metric tons (mt) (1997), 9 438 mt (2009) and 11 667 mt/a. Two stock assessment tools viz. CEDA (catch and effort data analysis) and ASPIC (a stock production model incorporating covariates) were used to compute MSY (maximum sustainable yield) of this organism. In CEDA, three surplus production models, Fox, Schaefer and Pella-Tomlinson, along with three error assumptions, log, log normal and gamma, were used. For initial proportion (IP) 0.8, the Fox model computed MSY as 6 858 mt (CV=0.204, R2 =0.709) and 7 384 mt (CV=0.149, R2 =0.72) for log and log normal error assumption respectively. Here, gamma error produced minimization failure. Estimated MSY by using Schaefer and Pella-Tomlinson models remained the same for log, log normal and gamma error assumptions i.e. 7 083 mt, 8 209 mt and 7 242 mt correspondingly. The Schafer results showed highest goodness of fit R2 (0.712) values. ASPIC computed MSY, CV, R2, FMSY and BMSY parameters for the Fox model as 7 219 mt, 0.142, 0.872, 0.111 and 65 280, while for the Logistic model the computed values remained 7 720 mt, 0.148, 0.868, 0.107 and 72 110 correspondingly. Results obtained have shown that P. stylifera has been overexploited. Immediate steps are needed to conserve this fishery resource for the future and research on other species of commercial importance is urgently needed.

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.