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Maximum Sustainable Yield (maximum + sustainable_yield)
Selected AbstractsThe relationship between fishing methods, fisheries management and the estimation of maximum sustainable yieldFISH AND FISHERIES, Issue 4 2002Mark N Maunder Abstract The allocation of effort among fishing gears is as important as controlling effort with respect to both sustainable yield and ecosystem management. Differences in age-specific vulnerability to the fishing method can modify the maximum sustainable yield (MSY) that is obtainable from a fish stock. Different gears or methods are more or less selective for the species targeted, and MSY is rarely, if ever, attainable simultaneously for all species. The different fishing methods capture different types of nontarget species. Some methods will often be more profitable than others, and different user groups will prefer different methods. In many fisheries, it is unlikely that fishing can be limited to a single gear or method, so compromises among them will be required. Global MSY is discussed as a possible reference point for fisheries management. The yellowfin tuna fishery in the eastern Pacific Ocean (EPO) shows all the above characteristics and is used to illustrate effort allocation among fishing methods. [source] Does infectious disease influence the efficacy of marine protected areas?JOURNAL OF APPLIED ECOLOGY, Issue 4 2005A theoretical framework Summary 1Marine protected areas are increasingly being recommended as an essential component of the management of exploited marine species, but virtually no attention has been given to the influence of parasites. This may be substantial, as a primary effect of marine reserves is to increase the density of an exploited population within the reserve relative to outside the reserve, which may facilitate parasite transmission. 2We used a simple deterministic model of microparasitic infection in a fishery with a reserve to investigate equilibrium yield and parasite prevalence inside and outside the reserve as a function of three control variables: the proportion of habitat inside the reserve, fishing mortality and the rate of interchange between the stock and the reserve. 3While our model is generic, we parameterized it with values that may be appropriate to the interaction between abalone and Rickettsia. 4The presence of a pathogen does not necessarily decrease yield when a reserve is present, particularly if the rate of movement of adult hosts between stock and reserve is low. 5Synthesis and applications. Pathogens have important implications for the design of marine reserves. Our modelling identifies two key considerations. First, ,fishing out' a pathogen by reducing the host population density to a level below the threshold for disease maintenance is a potential management strategy that is made more difficult by establishing a reserve. Secondly, the effect of a highly transmissible pathogen without a reserve is to cause a rapid decline in equilibrium yield for efforts beyond those that produce maximum sustainable yield, making the fishery prone to collapse. Introducing a reserve decreases yield in this case, but makes the fishery much more resistant to collapse. [source] Population structure, growth, mortality and estimated stock size of the introduced tench, Tinca tinca (L.), population in Lake Bey,ehir, TurkeyJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2009. Bal Summary Population structure, growth, length,weight relationship, mortality and stock size of tench, Tinca tinca (L.), was studied in Lake Bey,ehir, Turkey in 2005. Totals of 3360 tench (1865 males; 1795 females) were captured with gill- and trammel-nets of various mesh sizes. Male to female ratio was 1.04 : 1. The study covered length year classes. Fork lengths and total weights ranged from 9 to 37 cm and 13 to 815 g. For all individuals, the von Bertalanffy growth equation and length,weight relationship were Lt = 54.2[1,exp(,0.1350(t + 1.0281)] and W = 0.0151 L2.9993, respectively. Growth performance index and mean condition factor of the tench population were 2.598 and 1.513, respectively. Mortality rates were Z = 1.97 year,1, M = 0.29 year,1 and F = 1.68 year,1 for total, natural, and fishing mortality, respectively. The exploitation rate was E = 0.85, and the percentage of surviving fish was 13.9%. Tench stock was assessed as about 6,7 million individuals and 1450,1500 tonnes in biomass. It was determined that maximum sustainable yield could be obtained with an 80% level of the current fishing effort. [source] Deferred Harvests: The Transition from Hunting to Animal HusbandryAMERICAN ANTHROPOLOGIST, Issue 2 2001Michael S. Alvard We define animal husbandry as prey conservation. Conservation is rare among extant hunters and only likely to occur when prey are highly valued, private goods. The long-term discounted deferred returns from husbandry must also be greater than the short-term returns from hunting. We compare the returns from hunting and husbanding strategies as a function of prey body size. Returns from husbanding are estimated using a maximum sustainable yield (MSY) model. Following Charnov (1993), allometric analyses show that the MSY is nearly independent of prey body size. The opportunity costs of husbanding are measured as prey standing biomass times the discount rate. Since standing biomass scales positively with body size, the opportunity costs of husbanding are greater for larger animals. An evolutionary discount rate is estimated following Rogers (1994) to be between 2.4% and 6%. Using these values, the prey body size for which hunting and meat-only husbanding provide the same return is approximately 40kg. Animals greater than 40kg are predicted to be hunted, [animal husbandry, evolutionary ecology, allometry, hunting, Neolithic transition] [source] Maximizing profits and conserving stocks in the Australian Northern Prawn FisheryAUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 3 2010Tom Kompas The Australian Northern Prawn Fishery (NPF) is one of the few that has adopted a dynamic version of a ,maximum economic yield' (MEY) target, and, on this basis, the fishery is undergoing a process of substantial stock rebuilding. This study details the bioeconomic model used to provide scientific management advice for the NPF, in terms of the amount of allowable total gear length in the fishery, for both the MEY target and the path to MEY. It combines the stock assessment process for two species of tiger prawns with a specification for discounted economic profits, where the harvest function in the profit equation is stock-dependent. Results for the NPF show a substantial ,stock effect', indicating the importance of conserving fish stocks for profitability. MEY thus occurs at a stock size that is larger than that at maximum sustainable yield, leading to a ,win-win' situation for both the industry (added profitability) and the environment (larger fish stocks and lower impact on the ecosystem). Sensitivity results emphasize this effect by showing that the MEY target is much more sensitive to changes in the price of prawns and the cost of fuel, and far less so to the rate of discount. [source] Carrying Capacity and Potential Production of Ungulates for Human Use in a Mexican Tropical Dry ForestBIOTROPICA, Issue 4 2007Salvador Mandujano ABSTRACT Data are provided on the carrying capacity and potential production for sustainable human use of white-tailed deer (Odocoileus virginianus) and collared peccary (Pecari tajacu) in a protected tropical dry forest at Chamela on the Pacific coast of Mexico. In this paper, the carrying capacity was defined as the equilibrium density plus the number of animals removed by predators. The equilibrium point was estimated from the density dependent relationship between the finite population growth rate and the current density according to a logistic model. Annual density was estimated using the line transect method. Carrying capacity estimates were 16.5 to 17.2 deer/km2 and 9.3,9.5 peccaries/km2, representing a combined biomass of 841,874 kg/km2. A potential production for human use of 2.1 deer/km2 and 4.4 peccaries/km2 was estimated employing the model of Robinson and Redford (1991). The data suggest that, in the protected tropical dry forest of Chamela, the density and biomass of wild ungulates can maintain a similar or greater density and biomass than other Neotropical forests. To obtain an accurate estimation of the maximum sustainable yield (MSY), it is necessary to consider predation. From a management point of view, it is important to consider that carrying capacity varies as a function of the rainfall pattern. RESUMEN Se presentan datos acerca de la capacidad de carga y la producción potencial del venado cola blanca (Odocoileus virginianus) y pecarí de collar (Pecari tajacu) para aprovechamiento humano en un bosque tropical seco de Chamela en la costa Pacífica de México. En este trabajo se definió capacidad de carga como la densidad en el punto de equilibrio del crecimiento poblacional más el número de animales removidos por los depredadores. La densidad en equilibrio se estimó a partir de la relación de denso-dependencia entre la tasa finita de crecimiento poblacional y la densidad anual de acuerdo al modelo logístico. La densidad anual se estimó empleando el método de transecto de línea. La capacidad de carga se estimó en 16.5 a 17.2 venados/km2 y 9.3 a 9.5 pecaries/km2, y una biomasa combinada de 841 a 874 kg/km2. Empleando el modelo de Robinson y Redford (1991) se estimó una producción potencial para aprovechamiento humano de 2.1 venados/km2 y 4.4 pecaries/km2. Los datos indican que en bosque tropical seco protegido de Chamela la densidad y biomasa de los ungulados silvestres puede ser similar o mayor en comparación con otros bosques neotropicales. Para obtener una estimación precisa de la cosecha máxima sostenible es importante considerar el efecto de la depredación. Desde una perspectiva de manejo, se debe incorporar la variación en la capacidad de carga en función del patrón de lluvias. [source] | |||||||||||||