Accessing the risk of overfishing faced by mullet fisheries and its ongoing economics in Pakistan

1416-1424In this study, catch statistics of mullets are first time evaluated to know their exploitation status and ongoing economic implications. Catch and effort (CE) figures of mullets acquired from Sindh, Pakistan was statistically evaluated by employing surplus production models (SPMs), non-equilibrium versions, through two famous fishery related software, viz., catch and effort data analysis (CEDA) and a stock production model incorporating covariates (ASPIC). In total three SPMs, i.e., Fox, Schaefer and Pella-Tomlinson were used to investigate CE statistics, 1995 to 2012. Obtained results reveal that catch per unit effort (CPUE) has considerably dropped from 0.206 (1995) to 0.055 (2012). CEDA estimates of maximum sustainable yield (MSY) remained conservative as they were calculated between 5100 to 6500 t against ASPIC for which estimates of this parameter remained between 5800 and 7600 t. Considering the results, it can be concluded that mullet fishery is experiencing overexploitation (OE). This OE is an indicator of economic losses by increasing costs and decreasing profits. Thus, mullet resource conservation is necessary for its long-term economic utilization. Therefore, it is suggested that the target reference point (TRP) with respect to harvest should be between 5100 to 5500 t. However, this study is a preliminary study, hence; further in-depth studies are suggested before making and implementing any management plan for mullet fishery in Sindh, Pakistan

Application of Gordon-Schaefer Model to evaluate bioeconomic and management aspects of Scomberomorus sinensis fishery in Shandong, China

1250-1257Commercial marine fishery resources of China are generally considered to be overexploited. This condition may lead to the extinction of fishery resources and overcapitalization of the fishing fleets. Therefore, this study simultaneously evaluates the stock status and economic efficiency of a very important commercial marine fishery resource, i.e., Scomberomorus sinensis of Shandong, China by using a data for a period between 2003 and 2016. It employs a famous fishery surplus production model, viz., Gordon-Schaefer Model (GS-model) to compute various harvest levels and their corresponding effort levels. These levels or reference points (RPs) were estimated for three exploitation states, i.e., maximum sustainable yield (MSY), maximum economic yield (MEY), and open access yield (OAE). At MSY the harvest, effort, and revenue were calculated as HMSY = 185357 metric tons (MT), EMSY = 35624 and 1.80 billion RMB. On the other hand, the same parameters computed at MEY remained HMEY = 137177 MT, EMEY = 17462 and 5.01 billion RMB, in that order. Harvest and corresponding effort levels at OAE were computed as HOAY = 185285 MT and 34924, respectively. It is also found that despite controlling the effort levels, CPUE is showing a decreasing trend in the past few years which may be an outcome of overexploitation. Moreover, the revenue generated at MEY is about three times greater than the revenue generated at MSY. This increased revenue can be achieved by further lowering the effort levels. Thus, there is a dire need to make and implement such policies which can conserve S. sinensis fishery resource and increase the revenue at the same time. Therefore, further comprehensive studies are needed in this regard as this study is just a preliminary work

Priority decision of risk management for Chinese fisheries by using an analytic hierarchy process (AHP) approach

410-418This study aims to (1) identify risk types faced by the Chinese fisheries; and (2) give priority ranks to the risks and their sub-types for better management. For this purpose, data was collected from fishery researchers/experts working in Shandong, Fujian, Liaoning, and Guangdong provinces of China through questionnaire based survey. In total, 33 questionnaires were obtained among which only 25 questionnaires, consistency ratio (CR) value below than 0.1, were employed in this study. Data was statistically analyzed by using the Analytical Hierarchy Process (AHP). Obtained results indicate that Chinese fisheries is facing five diverse risk types, viz., natural risk, ecological risk, market risk, technical risk, and management risk. The calculated rank and importance of these risks types are management risk (1 and 0.509), ecological risk (2 and 0.220), technical risk (3 and 0.131), natural risk (4 and 0.076), and market risk (5 and 0.063). On the other hand, overfishing is the biggest risk sub-type faced by Chinese fisheries followed by lack of knowledge and hazardous inorganics. Overall, 18 risk sub-types are identified in this study. The estimated rank and importance of top 3 risk sub-types are overfishing (1 and 0.239), lack of knowledge (2 and 0.169), and hazardous inorganics (3 and 0.130)

Mechanistic Basis for Regioselection and Regiodivergence in Nickel-Catalyzed Reductive Couplings

The control of regiochemistry is a considerable challenge in the development of a wide array of catalytic processes. Simple π-components such as alkenes, alkynes, 1,3-dienes, and allenes are among the many classes of substrates that present complexities in regioselective catalysis. Considering an internal alkyne as a representative example, when steric and electronic differences between the two substituents are minimal, differentiating among the two termini of the alkyne presents a great challenge. In cases where the differences between the alkyne substituents are substantial, overcoming those biases to access the regioisomer opposite that favored by substrate biases often presents an even greater challenge. [Image: see text] Nickel-catalyzed reductive couplings of unsymmetrical π-components make up a group of reactions where control of regiochemistry presents a challenging but important objective. In the course of our studies of aldehyde-alkyne reductive couplings, complementary solutions to challenges in regiocontrol have been developed. Through careful selection of the ligand and reductant, as well as the more subtle reaction variables such as temperature and concentration, effective protocols have been established that allow highly selective access to either regiosiomer of the the allylic alcohol products using a wide range of unsymmetrical alkynes. Computational studies and an evaluation of reaction kinetics have provided an understanding of the origin of the regioselectivity control. Throughout the various procedures described, the development of ligand-substrate interactions play a key role, and the overall kinetic descriptions were found to differ between protocols. Rational alteration of the rate-determining step plays a key role in the regiochemistry reversal strategy, and in one instance, the two possible regioisomeric outcomes in a single reaction were found to operate by different kinetic descriptions. With this mechanistic information in hand, the empirical factors that influence regiochemistry can be readily understood, and more importantly, the insights suggest simple and predictable experimental variables to achieving a desired reaction outcome. These studies thus present a detailed picture of the influences that control regioselectivity in a specific catalytic reaction, but they also delineate strategies for regiocontrol that may extend to numerous classes of reactions. The work provides an illustration of how insights into the kinetics and mechanism of a catalytic process can rationalize subtle empirical findings and suggest simple and rational modifications in procedure to access a desirable reaction outcome. Furthermore, these studies present an illustration of how important challenges in organic synthesis can be met by novel reactivity afforded by base metal catalysis. The use of nickel catalysis in this instance not only provides an inexpensive and sustainable method for catalysis, but also enables unique reactivity patterns not accessible to other metals