Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This article aims to present a new problem of planning of resources and activities related to soccer, which is a variant of the Project Scheduling Problem. Soccer projects are intended to meet the requirements and expectations of time, cost and quality of the processes of the Soccer-related activities. In this article, original and unique in the world to date, is presented the mathematical modelling based on the Project Scheduling Problem of soccer in order to make optimal use of the resources of time, money and human resources of enterprises that you take care to engage in Soccer. The CPLEX model was used to find the optimal use of resources of the Soccer Project Scheduling Problem.

The southwestern Gulf of California is an important source of ornamental marine species traded worldwide, wherein spider crabs Stenorhynchus debilis are popular items. However, little is known about species biology and ecology. This study involves young ovigerous females (28 in total) recollected at Bahía de La Paz, Mexico, into bivalve mariculture devices cleaned every 3-4 months. Total carapace length (TL) and carapace width (CW), weight without eggs (TW), and fecundity (F, number of eggs) were analyzed for multiple relationships. F varied into 162 and 2205 eggs (x̄ = 1171 ± 689 eggs), their diameter into 0.38 to 0.45 mm (x̄ = 0.396 ± 0.027 mm). Three persistent and interactive modes were detected: low/moderate/high F, small/medium/large size (TL and CW), and light/middle/heavy TW. Log-linearized allometric regressions were applied to determine the relative fecundity constants (RFC) by body complexion, finding high parallelism between TL and CW related to step-wise growth and size categorization upon the isosceles-shaped carapace. In contrast, TW denoted an increase in body complexion across intermolt phases. S. debilis likely completes three maturation/molt cycles within 3-4 months after the first crab instar. RFC values confirmed positive trends by body complexion where egg size and F are related to species size and shape, establishing the trade-off proportions in this study case.

This study analyzes the spatial and temporal variability of phytoplankton biomass and taxonomic composition in the surface waters of Todos Santos Bay, a semi-enclosed bay within the upwelling zone of the Baja California peninsula (México). Two methodological approaches (microscopy and chemotaxonomy [CHEMTAX]) were used to describe the variability of some genera and species (observed under the microscope) and the importance of those groups that cannot be observed microscopically. Phytoplankton biomarker pigments were measured with high-resolution liquid chromatography and used as input to run the CHEMTAX software to determine the contribution of the main phytoplankton groups to chlorophyll-a (Chl-a). The microscopic analyses showed that diatoms and dinoflagellates comprised 65 and 33% of the total cells, respectively. Dinoflagellates were most abundant in the inner bay and during cold months; the most frequent and abundant genera were Tripos, Protoperidinium, and Prorocentrum. Among diatoms, the most frequent genera were Cylindrotheca, Guinardia, Navicula, Pseudo-nitzschia, and Chaetoceros. CHEMTAX indicated that, together with diatoms, the flagellates prymnesiophytes and chlorophytes contributed a median of 80% to Chl-a, with chlorophytes as the most important group (29.9%). The high contribution of these flagellates suggests that they are represented by small-sized cells not visible by the light microscopy used. However, CHEMTAX largely underestimated the contribution of dinoflagellates (due to the presence of many mixotrophic species). Hence, our results emphasize the importance of using both techniques for a more detailed evaluation of the taxonomic composition of phytoplankton in this and other coastal regions.

Remote sensing (RS) and geographic information systems (GIS) have been used to guide the selection of suitable areas for aquaculture. This systematic review synthesizes the key suitability factors and constraints reported in the literature for establishing inland pond aquaculture. We searched for primary studies on Scopus and Web of Science according to preferred reporting items for systemic reviews and meta-analysis (PRISMA) guidelines. Between 1991 and 2020, 354 articles were published in 104 academic journals. The maximum annual number of publications occurred in 2020, with 22 publications, and there is an increasing trend in studies published over the past 30 years. From 12 selected studies, we identified 48 suitability factors, 11 related to soil suitability, 19 to socioeconomic and infrastructure suitability, and 18 to water quality and availability. The most frequently used suitability factors were road proximity, local market center distance, soil texture, soil slope, and water temperature. We listed 15 constraints that restrict or limit the selection of specific geographic locations for inland aquaculture. Urbanized areas, roads, and forests were the most frequently restricted areas. Geotechnologies provide powerful tools for spatial planning and management of aquaculture. Availability, quality, and access to spatial data are critical for the use of geotechnologies in the process of aquaculture site selection.

Backyard aquaculture is gaining importance as a source of food and economic input for rural families in Mexico. The profitability of this system needs to be determined. Bioeconomic tools allow for making profit projections of any production system. A bioeconomic model composed of biological, production, and economic sub-models was developed to evaluate a low-cost backyard aquaculture system (BAS) appropriate for rural communities, considering theoretical productive parameters at certain environmental conditions. The BAS consisted of a 2800 L water reservoir stocked with 168 masculinized 1 g fingerlings of tilapia (Oreochromis niloticus) at 60 ind m-3 density and aerated with two ventury-type submerged pumps of 0.046 hp at a rate of 1400 L h-1 each. Two culture cycles of 25 weeks each were analysed. The initial investment was USD 1200 (USD 775 equipment + USD 425 operation cost yr-1). Results from the model indicate the production of 303 fishes of 614 g, equivalent to 186 kg yr-1, considering 10% mortality. Selling at USD 3.62 kg-1, net profits varied from USD 184 to 16 at 0 and 25% self-consumption. The payback period was three and four years at 0 and 10% self-consumption but was longer than five years at 25%. A response surface plot of profitability indicators (cost-benefit, net present value, and internal rate of return) was constructed at different self-consumption percentages, sale prices, and temperatures. In conclusion, BAS is a viable self-sustainable alternative for tilapia production at a low scale in rural areas of Mexico and other Latin American countries.

Anthropogenic activities and the demand for trace elements have risen, causing an increase in their environmental levels, which could affect biota. High levels of trace elements in living beings have been associated with toxicity, metabolic disorders, oxidative stress, and cancer. Seabirds, such as gulls, have been used as bioindicators of environmental pollution caused by anthropogenic sources. Gulls are widely distributed worldwide, usually occupying high trophic levels, and living close to humans. Among gulls, Larus spp. are omnivorous, predominantly carnivorous, nest on the ground, and capture live food or steal it opportunistically. The present work summarizes the data of trace elements found in eggs, feathers, blood, and feces, among other internal tissues, of several gull species of the genus Larus around the world. Most of the reports are from the Northern Hemisphere (70%), particularly from Europe and North America. The elements Cd, Hg, Mn, Pb, and Se are the most studied (54%), among which Hg represents about 19%. On the other hand, there is no information for lesser-known trace elements such as Rb, Ti, new technology elements (e.g. Ge, Re, Ta), rare earth elements (e.g. Ce, La, Y), or elements of the platinum group (e.g. Os, Ir, Ru). Even though Larus spp. is a suitable bioindicator of chemical contamination in marine ecosystems, only 28 of the 53 species of the Larus genus have been used on trace elements pollution. Future research should address lesser-known elements which are increasingly used by new technologies.

Four treatments were established to evaluate the effect of delayed first exogenous feeding and subsequent feeding periods on the development of goldfish larvae. The fasting and feeding periods were arranged as follows: T1 (0DFA:30DF), T2 (4DFA:26DF), T3 (8DFA:22DF), and T4 (12DFA:18DF), where DFA are the days of fasting and DF are the days of feeding. The larvae were kept in community tanks for each repetition, with 75 larvae per tank (3.75 larvae L-1). There was no significant difference in total length or final weight between larvae submitted to 0, 4, and 8 days of feed deprivation. However, larvae submitted to 12 DFA had higher values of the same variables than the other treatments. No significant difference in larval survival was observed between T1, T2, and T3, but T4 negatively influenced survival. Under the conditions evaluated, the point of no return was 4 DFA. Dead larvae were partly eaten in the fasting treatments. The delayed first feeding should be avoided in large-scale productions since it significantly reduces survival during cultivation. This article results from research funded by the Pescarte Environmental Education Project (PEA/IBAMA).