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Carmelo J. León Juan M. Hernández Eucario Gasca‐Leyva 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3-4):147-170
Abstract This paper studies cost minimization decisions by utilizing a simple bioeconomic model for gilthead seabream (Sparus aurata). This model is based on a biological growth model which accounts for the effects of temperature and ration size. Although the implicit production function derived from the growth model is shown to be quasiconcave, it is not homothetic nor quasilinear. Further, technology shows increasing returns with respect to ration size and harvesting time. Optimization decisions are analyzed in two different contexts, a restricted biological setting and an expanded economic problem. It is shown that the optimal ration size increases for the latter context, reaching values commonly accepted in current industrial practice. Even though the elasticity of substitution to the shadow input prices is positive at the optimal ration size, the latter is rather robust to changes in input prices. However, optimal costs show larger sensitivity to the labor price than to the feeding and managerial costs. 相似文献
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Eucario Gasca-Leyva Carmelo J. León Juan M. Hernández 《Journal of the World Aquaculture Society》2003,34(1):29-39
For decades, research and development efforts have focused on fish cultivation in floating cages. Despite this focus, and the considerable private and public sector resources invested in these systems, there is a scarcity of economic data derived from the great number of variables present in these systems. A reliable way of generating economic studies is through systems modeling that relates biological, environmental, technical, and economic variables. This study presents results from a computer simulation of seabream production in floating cages under two scenarios: one representing conditions in the Mediterranean Sea, and the other in the Atlantic Ocean. A company operating in the Atlantic (Canary Islands, Spain) provided the majority of data, though some of them were provided by the University of Las Palmas, also in the Canary Islands. Given the assumptions in the simulation case study, the production cost for 1 kg of seabream in floating cages in the described systems is US$2.64 in the Mediterranean and US$2.90 in the Atlantic, and the internal rates of return were 27% and 59%, respectively. The results of model sensitivity analysis for both scenarios show that this cultivation system is more sensitive in the Mediterranean than in the Atlantic. This means that changes in system variables convey lower effects on the production and economic results in the Atlantic scenario than in the Mediterranean. In both scenarios, the feed ration size was one of the variables that improved feed conversion rates. It also improved costs and profitability in greater proportions than the other variables. The reduction of the feed ration below the levels recommended in feed tables lowered the feed conversion rate but increased the number of days in the seabream cultivation cycle, leading to higher production costs and lower internal rates of return. The analysis also showed that greater benefits and profitability could be obtained by raising production capacity through increases in the final stocking density of the system. 相似文献
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Roger Domínguez-May Juan M. Hernández Eucario Gasca-Leyva Gaspar R. Poot-López 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):278-301
Size heterogeneity is a common phenomenon in aquaculture systems and influences final production and economic yield. Among other factors, this variability is determined by ration. These variables directly affect potential returns and therefore influence the recommendations made for optimum aquaculture system management. As part of the search for more profitable culture strategies, a bioeconomic model was developed to analyze the effect of size heterogeneity and ration on optimum harvest time and size, thus creating a new methodological tool. Size dispersion was included using a continuous, size-structured population model incorporating the effect of ration on growth. Theoretical results were applied in a case study of tilapia culture in Yucatan State, Mexico, in which optimum ration levels and harvest times clearly differed between size heterogeneity and homogeneity models. Case study results indicated the use of different recommended ration and harvest management strategies depending on real and/or potential target market. 相似文献
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Gaspar Román Poot‐López Eucario Gasca‐Leyva 《Journal of the World Aquaculture Society》2009,40(3):351-362
The main challenge for tilapia culture in rural areas of Mexico is low producer income and difficulty in acquiring inputs (fingerlings and balanced feed). In response, some rural producers feed tilapia with locally available vegetal inputs such as chaya, Cnidoscolus chayamansa. This plant is a bush endemic to the Yucatan Peninsula, Mexico, that is traditionally used for human and animal nutrition. In these rural culture systems, chaya is provided ad libitum as fresh leaves. Its use to date is empirical, and therefore, little is known about optimum substitution levels. A bioeconomic model was developed using experimental data. The von Bertalanffy model was parameterized using chaya/balanced feed combinations that produced growth not statistically different than a diet with sole use of balanced feed. This model included biological, economic, and management components. The results indicate that balanced feed can be substituted by chaya leaves at up to 50% and that this substitution level provides the lowest production costs during the warm season. Maintenance of this production level requires 2.23 units of chaya per unit of balanced feed, with the restriction that only 50% of the ration can be substituted by chaya leaves. 相似文献
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