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Ruiz-Velazco J.M.J.,Autonomous University of Nayarit | Gomez-Munoz V.M.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Reviews in Aquaculture | Year: 2013

A bio-economic model was used to analyse the risks of intensive production of shrimp and to propose alternative schemes of risk management by controlling aeration, pond size, stocking density and duration of cultivation. The model was calibrated from databases of farm operations in the State of Nayarit, Mexico. Improving management allowed us to project an increase in the annual net revenue from $3900 to $26 600 ha-1 and to improve the benefit-cost ratio from 1.14 to 1.55. Managing an early start of aeration, small-sized ponds, high stocking densities and long cultivation periods maximized economic outcomes. Operating a small farm (consisting of a single 2.5 ha pond) involves more risk than operating a large one (50 ha, consisting of 20 ponds of 2.5 ha each). Improving management also resulted in diminished risk, as indicated by increased values of return per unit risk from 0.14 to 0.21 or from 0.42 to 0.51 (depending on farm size). From sensitivity analysis, we concluded that small ponds are recommended for intensive production of Litopenaeus vannamei and that white spot disease is a major risk factor that can be partly controlled by managing dissolved oxygen levels and aeration. © 2013 Wiley Publishing Asia Pty Ltd.

Bakun A.,University of Miami | Babcock E.A.,University of Miami | Salvadeo C.J.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Reviews in Fish Biology and Fisheries | Year: 2010

The Gulf of California system presents major challenges to the still developing frameworks for ecosystem-based management (EBM). It is very much an open system and is intermittently subject to important influxes of migratory visitors, including large pelagic predatory fishes and small pelagic forage fishes. These migrants include the more tropical species from the coastal ecosystems to the south and perhaps subtropical sardines and anchovies from the California Current upwelling system. In addition to the multi-annual ENSO-scale and what may seem to be rather erratic episodes of major population incursions, the Gulf presents nonstationary, transient aspects on a variety of longer time scales. Moreover, the removal of top predators by commercial and sport fisheries has introduced trends that must be affecting the entire ecosystem, and certainly the forage fishes that are their major prey base. In addition to size limits, fishing seasons, area closures and license limitations, the fishery is managed by an ad hoc adaptive management system, in which the fishing season can be shortened or additional areas closed to fishing if pre-season exploratory fishing surveys indicate a shortage of small pelagic fishes on the fishing grounds. Whether this system is likely to be sustainable in the long term is difficult to determine, given the potential for rapid changes in the system because of environmental changes and/or feedbacks within the food web. Thus it appears that innovative management frameworks, among other things utilizing the comparative method, may be required in order to determine defensible tradeoffs between precaution and resource utilization. © Springer Science+Business Media B.V. 2009.

Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Ecological Modelling | Year: 2014

The supply-demand curve is used to analyse the exchange of energy in food webs and measure its resilience. The slope of a supply-demand curve is an estimator of the redundancy of internal flows, which represents the energy in the reserve of the ecosystem, a concept defined as resilience. We found that resilience can vary according to the stress level to which the ecosystem is subjected. As an example, the pattern of variation of resilience due to the historical effect of climate change (almost six decades of a sustained perturbation of temperature increase) in the southern Gulf of Mexico indicates a significant decreasing trend of the resilience, which also represents a loss of vulnerability, suggesting that this measure of resilience could be of interest for the management of living resources. In a global sense, we also found a relationship suggesting that resilience tends to increase with latitude. © 2013 Elsevier B.V.

Lopez-Rocha J.A.,National Autonomous University of Mexico | Solana-Sansores R.,Autonomous University of Baja California | Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Fisheries Science | Year: 2014

A predator-prey model was applied to the red grouper Epinephelus morio fishery from Yucatan, Mexico, with the aim of understanding the spatial behaviour of a mid-sized fishing fleet. The heterogeneity of the environment was considered, and different habitat quality levels were determined to address environmental differences. The behaviour of the fleet was also evaluated based on a simulation of restricted fishing areas (RFA). The model was applied utilising 5 years of information on catch and fishing effort (1973-1977). Four levels of habitat quality were defined (low, medium, high and exceptional). The total costs and revenue for a fishing expedition in the areas of exceptional habitat quality were higher due to their location farthest from the base port. The fleet was most efficient during the winter at locations in the eastern continental shelf, with the number of these areas clearly decreasing in the autumn. The model simulation of the RFA showed a total revenue reduction of 7-27% in scenarios of RFA for adult protection. When the RFA was implemented for the protection of juvenile fish, the total revenue was not reduced, indicating that this type of RFA might be a feasible management strategy for a sustainable fishery. © 2014 The Japanese Society of Fisheries Science.

Lopez-Rocha J.A.,National Autonomous University of Mexico | Felix-Pico E.F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Hernandez-Rivas M.E.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Hidrobiologica | Year: 2012

Mangrove ecosystems are critical habitats for many species, and their productivity is important because of their contribution of organic detritus and secondary production. The objective of this study was to identify suitable indicators of secondary productivity of mangrove systems, in order to establish a baseline for measuring changes in the mangrove system due to natural or anthropogenic potential disturbances. The bivalve mollusks chosen as indicators of secondary productivity were the mangrove cockle Anadara tuberculosa and the mangrove oyster Crassostrea palmula. Samples were collected in three estuaries from August 2007 to July 2009. Abundance and secondary production were estimated from biomass increase, calculated from individual growth rates determined using length frequency distributions analysis. The average abundance was 1.27 and 510 ind · m-2 of mangrove cockle and mangrove oyster respectively. It was estimated a growth rate of 4.91 mm · month -1 (3.67 g · month-1) for mangrove cockle and 3.80 mm · month-1 (0.18 g · month-1) for the mangrove oyster. The mean secondary production of mangrove cockle was 4.51 g · m-2 · month-1 and was higher during spring, while for the mangrove oyster it was 97.9 g · m-2 · month-1, and the maximum production was recorded during summer. The results show that these indicators of benthos quality are suitable for measuring changes of the mangrove system in the Ensenada of La Paz, B. C. S., Mexico.

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