Time filter

Source Type

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.

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.

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.

Salcedo-Bojorquez S.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Journal of Fisheries and Aquatic Science | Year: 2011

This contribution is aimed to the identification of reproductive patterns of billfishes, which is in turn a key issue supporting management and conservation policies. Information reported in the literature on features of reproductive processes of billfishes was examined with a Principal Components Analysis (PCA) to identify groups of species with similar reproductive strategies. PCA was applied based in a correlation matrix and the significances (p<0.05) of the factors and loadings of the variables were used as criteria for the identification of reproductive patterns. In general, four groups were found. The first group consists of Tetrapturus albidus and T. audax, which are characterised by rapid growth, an early age at first maturity with respect to maximum age (T/Tmax) and high values of reproductive variables (e.g., Spawning Duration (Sd), Spawning Frequency (Sf), Annual Fecundity (AF) and Relative Fecundity (RF). A second group consists of T. belone, T. georgii and T. pfluegeri, which present rapid growth, high Tm/Tmax ratios and Batch Fecundity (BF) values and low Sd values. Another group consists of the genera Makaira and Xiphias, which present low Lm/Lmax ratios and high values for AF, RF, Sf and BF. The last group consists of species of the genus Istiophorus, which present the lowest AF values and the highest RF and BF values. In billfishes, the reproductive pattern is strongly influenced by the growth process and the age at which a species reaches sexual maturity relative to its maximum age. The observed differences in reproductive variables result from adaptive mechanisms that allow species greater reproductive success in the epipelagic environment. © 2011 Academic Journals Inc.

del Monte-Luna P.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Villalobos H.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Continental Shelf Research | Year: 2015

The seasonal and interannual variability of sea surface temperature (SST) in the southwestern Gulf of Mexico (SGM) is related to changes in atmospheric forcing, subsurface water inputs, advection and surface currents. However, little is known about temperature variability in the gulf on decadal and multidecadal timescales. Temperature time series (1900-2010) were analysed in 36 2°×2° geographic quadrants that covered the SGM. A cluster analysis was applied to the data for the seasonal cycle and for the annual anomalies in each quadrant to describe SST variability, with a special focus on low frequencies (i.e. >10 years). Temperature anomalies were correlated with the identified cyclic components of the Atlantic Multidecadal Oscillation (AMO), and temperature variability in coastal quadrants of the gulf was described using multivariate analysis and harmonic analysys. There is a latitudinal separation of quadrants regading the seasonal cycle and a longitudinal separation in the total variability that is related to the Loop Current. The highest SST correlations were those related to a ~60-year cycle of the AMO and were found on the Yucatan shelf. The ~60-year variability is present in the entire gulf, but signals with periods shorter than ten years are more evident in the northern part. Extrapolation of the dominant sea surface temperature cycles in coastal areas of the gulf, shows that there will be a cooling event in the next 20 years. © 2015 .

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.

Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Hidrobiologica | Year: 2011

"Top-down" and "bottom-up" control processes in exploited ecosystems have been characterised using their impacts on the mean trophic level of catches, changes in biomass, and certain ecosystem attributes. Most scientific contributions have been based on case studies of particular ecosystems. So, the aim of this study is to identify and understand ecosystem processes governing their response to fishing in a more global sense. Simulations were developed using different ecosystems models using the Ecopath with Ecosim suite of programs. Two cases were examined by selecting target species to be exploited during simulations experiments. A high trophic level group (sharks) and a low trophic level group (shrimp) were chosen to represent potential "top-down" and "bottom-up" control situations, respectively. For both cases, a gradient of exploitation was simulated, and ecosystem attributes were estimated. Harvest rates (HR) varied along a gradient of HR = 0.4 to HR = 0.7 for sharks and HR = 0.3 to HR = 0.8 for shrimp. For each simulation, only the target group was modified. Principal Components Analysis was applied, and outputs were obtained using ecosystems as variables and attributes as factors, and vice versa. For sharks, outputs indicate that under a low HR, group attributes govern the response to exploitation. However, when a high HR was applied (higher than the maximum sustainable yield), ecosystem attributes emerged as relevant instead of stock attributes. For sharks, representing "top-down" control, a graphical arrangement of the first two components clearly shows a gradual pattern of response reflecting the transition from stock-level to ecosystem-level processes as HR increases. For shrimp, representing "bottom-up" control, no clear patterns emerged; in this case, the same relevant stock and ecosystem attributes appear across all HRs applied. These results are explained in terms of stock life histories, trophic level, and transfer efficiencies through the food web, suggesting that ecosystem processes behind overfishing are related to the trophic level, and then, fisheries management practice must recognise such particularities.

Sanchez-Cardenas R.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn
Journal of Fisheries and Aquatic Science | Year: 2012

This study contributes to the existing knowledge of temporal reproduction patterns in tropical fish species which is potentially relevant to regional fisheries management. The latitudinal variation in Spawning Season Length (SSL) and its relationship with spawning season temperature (SPST) was explored, as well as the latitudinal variation in Spawning Aggregation Duration (SAD), through Spearman's rank coefficient. Additionally, the lunar synchrony of spawning and the time of day at which spawning occurs were described. We found variable trends for SSL with respect to latitude in the tropics; most patterns did not satisfactorily explain the variation in SSL. The minimum SPST consistently tended to be lower for longer spawning seasons, both within each species and for the entire dataset. We observed SSLs of one to six months across the entire range of latitudes (-30° to 35°) but most spawning seasons longer than six months were observed at latitudes lower than -4° or higher than 10°, where lower water temperatures can be found. The latitudinal tendencies of SAD were variable and poorly supported, but the data on Epinephelus striatus hinted that SSL may vary spatially. Furthermore, the studied species most likely follow lunar and semilunar spawning cycles which are likely to be related to specific daily spawning patterns. © 2012 Academic Journals Inc.

Diaz-Uribe J.G.,Instituto Nacional Of Pesca | Diaz-Uribe J.G.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Del Ipn | Lercari-Bernier D.,UNDECIMAR | And 4 more authors.
Ecological Modelling | Year: 2012

Understanding of the intricate interactions of endemic species with anthropogenic impacts of diverse economic interests on ecosystems is of paramount importance to the implementation of effective conservation programs. A trophic mass-balance model was used to analyze the structural properties of the North and Central Gulf of California (NC-GulfCal) ecosystem, the most important fishing area in Mexico and where conservation efforts for protecting the endangered endemic porpoise known as vaquita (. Phocoena sinus) have been carried out for the last two decades. Results allowed to discuss the role of fisheries in the ecosystem and its implications for conservation of the endangered endemic porpoise. The trophic model was constructed with 166 functional groups and 3 regional fishing fleets. Abundance and catch from the early 1980s were used for balancing the model. Maturity indices of ascendency and production to respiration ratio indicate this ecosystem had a relatively high resilience and a high potential for development; this is in accordance with the highly variable environment found in the NC-GulfCal ecosystem. Mixed trophic impacts analysis confirms that pelagic and plankton groups have the most generalized impacts in this ecosystem. The model also shows that fisheries in the NC-GulfCal ecosystem, by the early 80s, were already operating in multiple habitats and landing a great variety of species. However, the highest exploitation pressure was focused on a few species. Although vaquita, since then, has also been under a high incidental mortality by gillnet fisheries, results suggest that predation should also be considered as a key factor on vaquita population dynamics and regulations focused exclusively on fisheries probably are not enough to achieve a successful vaquita recovery program. © 2012 Elsevier B.V.

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.

Loading Centro Interdisciplinario Of Ciencias Marinas Del Ipn collaborators
Loading Centro Interdisciplinario Of Ciencias Marinas Del Ipn collaborators