Optimal Rotation Time for the Polyculture of Tilapia Nilótica and White Shrimp in Freshwater

It was obtained the optimal rotation time for the polyculture of tilapia nilótica and white shrimp in freshwater, with a bioeconómic model. Data for modelling were extracted from an experiment conducted in CINVESTAV-IPN, unit Mérida, during the summer of 2008. The stocking densities studied were 32.2 tilapia/m3 and 33.7 and 50 shrimp/m2. For simulation were considered the technical and economic characteristics of tilapia culture in Yucatán Mexico. Randomness was included in the two most influential variables of the system, in order to obtain more attached to reality results. The optimal rotation time strategy was longer than the commonly used by the tilapia farmers

ECONOMIC VALUE OF CARIBBEAN FLAMINGO (PHOENICOPTERUS RUBER) AT CELESTUN BIOSPHERE RESERVE, YUCATAN, MEXICO: A BIRDWATCHING TOURISM APPROACH

Abstract · Bird watching activities are increasing worldwide, allowing for a closer citizen-nature experience. These activities are considered to promote biodiversity conservation values. We assessed the economic value of the Caribbean Flamingos (Phoenicopterus ruber) at the Celestun Biosphere Reserve, Yucatan, Mexico. Celestun has become an important destination for birdwatching-based tourism because of the presence of flamingo flocks in its coastal lagoon. Flamingos at Celestun attract approximately 50,000 national and international visitors yearly. The human population of Celestun is approximately 6,800 inhabitants; their livelihoods mainly depend on fishing, and more recently on bird watching tourism. In order to assess the economic value of flamingo-watching at Celestun, we interviewed 427 visitor groups after they took a flamingo-watching motorboat tour. We conducted the interviews during three of the highest tourism seasons within a year period (2012–2013). The interview questions were directed towards the visitors’ place of origin, their main reasons for visiting Celestun, and how much money they spent traveling, using a direct questionnaire with a total of 37 items. We applied the Travel Cost Method in order to estimate the economic value for flamingo-watching at Celestun. For approximately 80% of the interviewed visitors, flamingos were the main reason to visit Celestun. We obtained a total of US$16,542,004 as the “Flamingo value” placed by visitors.Resumen · Valor recreativo de la observación de Flamencos del Caribe (Phoenicopterus ruber) en Celestún, Yucatán, México Las actividades de observación de aves han aumentado a nivel mundial, permitiendo una experiencia más cercana entre ciudadanos y naturaleza. Se considera que estas actividades promueven los valores de la conservación de la biodiversidad. Estimamos el valor económico del Flamenco del Caribe (Phoenicopterus ruber) en la Reserva de la Biosfera de Celestún, Yucatán, México. Celestún se ha convertido en un importante destino para el turismo basado en la observación de aves, debido a la presencia de parvadas de flamencos en la laguna costera. Los flamencos de Celestún atraen aproximadamente 50,000 visitantes nacionales e internacionales al año. La población en Celestún es de aproximadamente 6,800 habitantes, que viven principalmente de la pesca y más recientemente del turismo de observación de aves. Para estimar el valor económico de la observación de flamencos en Celestún, entrevistamos a 427 grupos de visitantes después de que tomaron el recorrido para observación de flamencos en lanchas de motor. Cubrimos tres temporadas altas de turismo en un periodo anual (2012–2013). Preguntamos acerca del lugar de origen de los visitantes, principal razón para visitar Celestún y cuál fue la cantidad de dinero gastada en su viaje, utilizando un cuestionario directo con un total de 37 ítems. Aplicamos el Método de Costo de Viaje para estimar el valor económico para la actividad de observación de flamencos en Celestún. Para cerca del 80$ 16,542,004.00 como el “valor del flamenco” en función de la tasa de visitación

Partial substitution of balanced feed by Chaya leaves in Nile tilapia production: a bioeconomic analysis

Tilapia culture in Yucatan State, Mexico, is largely semi-intensive. The producers are mostly poor farmers who receive government subsidies for purchase of fingerlings and balanced feed. Feeding practices are often inadequate (satiety rations), moreover, producers frequently suffer financial and resource shortfalls. During feed shortages producers are known to use empirical application of chaya (Cnidoscolus chayamansa) leaves, used traditionally in human and animal nutrition. A study was done of growth in juvenile tilapia using diets containing balanced feed with chaya (25 and 50% of substitution), complete, half-complete and satiety rations of balanced feed, during the warm season. The results were used to develop a bioeconomic model and implemented in MS Excel program, with a one-day time step. In order to minimize the cost of tilapia feeding, and maximize the benefits by using a limited amount of balanced feed per cycle. In addition the analysis was completed using the Marginal Rate of Technical Substitution (MRTS). According to results from MRTS, it is necessary to add 2.51-3.91 units of chaya for each reduced unit of balanced feed, to maintain the same level of production. In a resource limited situation, substitution of 50% of balanced feed for raw chaya leaves generates a harvest size greater than complete and satiety rations of 24.8 and 28.8% respectively. When considering sale prices that are consistent with size at harvest and costs, treatments with chaya considerably maximized profits

Bioeconomic analysis of ration size in intensive tilapia culture

Balanced feed represents approximately 60 % of production costs in fish culture and ration size has significant effects on this parameter. Ration size varies according to culture strategies and producer knowledge. It can also have environmental implications since feed can be a pollutant. A bioeconomic model was developed for an intensive system with recirculation considering different ration sizes (100 % recommended levels, 80 %, 50 % and satiety). Assumptions for model parameterization were based on previous production experiments and market factors in Mexico. The 80 % ration resulted in the greatest reduction in water changes, energy and operating capital, and was profitable. The 50 % and satiety rations were not profitable, and the latter had the highest water change and operating capital requirements

Optimal Harvesting Time in Aquaculture Assuming Nonlinear Size-Heterogeneous Growth

This study explores the optimal harvesting time in a size-heterogeneous population dynamics. The model includes the effect of population density in both the mortality rate and individual growth. An application to specific conditions of shrimp culture in Mexico is presented. The optimal harvesting rule is numerically found for different economic and productive scenarios. Parallel results are also obtained under the hypothesis of homogeneous population growth, which has been traditionally considered in the economic literature. In general, the discounted net revenue of the firm is underestimated if the size-heterogeneity phenomenon is not taken into account, while the calculated harvesting time shortens the predictions based on the homogeneous growth hypothesis. These results reveal that optimal management rules are significantly mistaken if the size-heterogeneity phenomenon is not taken into account.Keywords: Aquaculture, Aquaculture Efficiency and Management, Fisheries Economic

Optimal Harvesting Time in Fish Farming with Heterogenous Population

The optimal harvesting time in a fish farm is analyzed in the paper. Fish population is assumed to be heterogeneous with respect to weight, so a distributed parameter dynamic model is considered. Theoretical and numerical results are obtained and compared with the ones concerning homogeneous fish cultures only. The results are applied to the tilapia farming in Mexico for which empirical and market data were obtained. The actual managerial practices turn out to be close to the optimal solution in the model where weight-heterogeneity of the culture is taken into account

Economic Analysis of Polyculture Tilapia and Australian Redclaw Crayfish

The present paper studied system viability of tilapia nilotica and Australian redclaw crayfish in polyculture, considering tialpia as main species. Three scenarios were analyzed: tilapia monoculture with 38.7 fish/m3 and tilapia and Australian redclaw polyculture, considering the same stocking density for fish in monoculture and 17.5 crustaceans/m2, of which one included a physical separation between species. Modelling and simulation was conducted with the PowerSim software. The results showed the polyculture without physical separation, generated sales revenue (3.261,30 dls) and net income (479,98 dls), a harvesting time and size of 197 days and 350.7 g for tilapia. Modeling data proved useful tools for decision-making allowing establish optimal harvest time for the monoculture and polyculture of the studied species

Análisis bioeconómico del cultivo de dorada en Canarias y en el Mediterráneo

[EN] Aquaculture is an expanding industry, which represents an altemative to the limited fishing resources. This paper develops a bioeconomic model for the production of gilthead seabream, a species with large market potential. The model is based on a biological growth submodel, where fish growth is related to fish weight, ration size, and temperature. Random factors are introduced through the functions for temperatura and market price. A dynamic system methodology is utilised for analysing the temporal evolution of the biological and economic relationships. Since plant localisation is determined by environmental factors, and therefore has an influence on firm retums, the model is utilised for evaluating the impact of two altemative scenarios: the Mediterranean and the Canary Islands. As a main conclusion, it is obtained that competitiveness in the Canaries depends on the production of 750g. extralarge size, which is not profitable in the Mediterranean sea due to large costs. The results also show increasing retums to scale, and the efficient plant capacity for the representative firm.[ES] La acuicultura es una industria en continua expansión, representando una alternativa a los limitados recursos pesqueros. En este trabajo se desarrolla un modelo bioeconómico para la producción de dorada, la cual es una de las especies con mayor potencial de mercado. El modelo incorpora un submodelo biológico de crecimiento, que relaciona el crecimiento del pez con su peso, la ración alimentaria, y la temperatura. Los factores aleatorios entran a formar parte del modelo a través de la temperatura y el precio de mercado. Se utiliza la metodología de la dinámica de sistemas para representar la evolución temporal de las relaciones biológicas y económicas. Dado que la localización de la empresa determina los factores ambientales y, por tanto, influye significativamente en los resultados, el modelo se utiliza para analizar el impacto de dos escenarios alternativos: el Mediterráneo y Canarias. Como principal conclusión, se obtiene que la competitividad en Canarias depende de la producción de la talla súper de 750 g, la cual no es viable en aguas del Mediterráneo debido a los altos costes incurridos. También se obtienen rendimientos de escala crecientes, así como el tamaño de planta eficiente para la empresa representativa.Gasca-Leyva, E.; León, C.; Hernández, JM.; Vergara, JM. (2001). Análisis bioeconómico del cultivo de dorada en Canarias y en el Mediterráneo. Economía Agraria y Recursos Naturales - Agricultural and Resource Economics. 1(1):55-76. doi:10.7201/earn.2001.01.03SWORD55761

The Economics of Kappaphycus Seaweed Cultivation in Developing Countries: A Comparative Analysis of Farming Systems

The farming of the red seaweed Kappaphycus alvarezii and related species as raw material for the hydrocolloid carrageenan rapidly spread from the Philippines in the late 1960s to Indonesia, Tanzania, and other tropical countries around the world. Although numerous studies have documented positive socioeconomic impacts for seaweed farming, factors such as diseases and distance to export markets have led to an uneven development of the industry. Using standard budgeting techniques, this study adapted production and market data from a FAO-led global review of seaweed farming to develop comparative enterprise budgets for eight farming systems in six countries (Indonesia, the Philippines, Tanzania, India, Solomon Islands, and Mexico). Although the basic technology package is the same across countries, the study revealed large differences in the economic performance of systems due to wide variations in farm prices and the scale of operations. Although seaweed farming is a suitable activity for small-scale producers, a minimum of 2,000m of cultures lines are still necessary to ensure adequate economic returns. Greater farming plots may be needed if farm prices are well below the average farm prices paid in Indonesia and the Philippines. Policy recommendations are made to improve the economic potential of underperforming systems

Bioeconomic Evaluation of Substitution of Balanced Feed with Chaya (Cnidoscolus Chayamansa) Leaves in Tilapia Production

In Mexico, the culture of tilapia has developed in rural areas, where the main problem is low producer income. The state of Yucatan also experiences this situation, and scarcity of money needed to purchase inputs results in complementary feeding with chaya (Cnidoscolus chayamansa), whose leaves are edible for humans and animals. In this situation, CINVESTAV conducted experiments to determine the optimal level of substitution of balanced feed with ray chaya leaves. The test with 25% and 50% reduced balanced feed complemented with chaya (ad libitum) did not show significant differences (P>0.05) in growth compared to fishes fed with a complete ration of balanced feed (100% feed table). A bioeconomic model was developed, including a submodel of growth according to observed results in each test. The model was developed in Excel, considering economic and management components. In addition, the analysis was completed using the Marginal Rate of Technical Substitution (MRTS) to evaluate cost minimization. According to the MRTS results, it is necessary to add 2.4 units of chaya for each reduced unit of balanced feed, in order to maintain the same level of production. Substituting 50% of the recommended ration (feed table) with chaya resulted in lower production costs, generating profit maximization