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

In this study we present new data of biogenic opal (BO), organic carbon (OC), and calcium carbonate (CaCO3) in a highresolution record from the western coast of Baja California Sur, Mexico. The variability of marine biological productivity in this area is dominated by El Niño and La Niña events on different time scales. The BO and OC contents showed a decrease between AD 1100 and 1400. From AD 1400 to the present, BO and OC showed a significant increase, indicating permanent upwelling conditions. The CaCO3 content showed an inverse correlation with OC, which suggests that the exported OC fluxes are a significant factor controlling CaCO3 dissolution in the sediment. The increase in BO and OC was synchronic with a decline in the number of El Niño events (6 ± 4 every 100 years) over the last 600 years of the millennium. 

In a comparative study using the hybrid tilapia Oreochromis mossambicus × Oreochromis aureus grown in seawater and freshwater, no significant differences in growth performance (weight gain) and biological indices (e.g., feed conversion efficiency and survival) was observed after 90 days of experimentation. A common feed was formulated to contain 40% crude protein and 8.5% crude fat. Fish meal and poultry by-product meal (50:50) were used as a source of protein in the formulation. The study was conducted using recirculation systems and organisms already adapted to seawater and freshwater with an initial weight of 25.0 ± 0.06 g and 24.70 ± 0.32 g, respectively (four replicates per treatment); at the end of the experiment their final weight was 161.80 ± 12.78 g and 167.60 ± 7.29 g, respectively. The thermal growth coefficient was 0.91 and 0.89 (seawater vs freshwater), and there were no significant differences; however, the apparent digestibility of dry matter as well as per nutrient (protein, lipid, and carbohydrate) was significantly higher for the organisms in the seawater treatment. The digestibility could be associated with greater enzymatic activity in the presence of higher ionic strength. The respirometric study indicated that the O:N ratios were similar for organisms reared in seawater and freshwater, with values of 21 and 18, respectively. This indicates that this strain of tilapia uses a mixture of proteins and lipids as energy substrates. We conclude that this strain of tilapia has the potential to adapt and thrive in a marine environment and that its production practices could be expanded.

Six silvofishery systems were constructed to estimate the potential use of mangrove seedlings for nutrient removal. Two systems did not contain seedlings (i.e., control treatment), while the remaining systems were divided into separate treatments using two mangrove species (Laguncularia racemosa and Rhizophora mangle). Each system consisted of two water tanks linked by two hoses. The first tank contained 150 poeciliid fishes, while the second contained a biological filter of gravel and sand on the bottom, as well as a hydroponic arrangement of 34 seedlings. Water exchange between both tanks was performed over a 24-h period, every ten days for seven months, and the concentration of nutrients (NH4+, NO2–, NO3–, and PO4–3) was measured every 8 h. Laguncularia racemosa showed a higher growth rate compared to R. mangle, but there were no differences regarding the growth of fishes among the six systems. Final dissolved inorganic nitrogen removal was 42% in the control treatment and 90% in both treatments using mangroves. Dissolved inorganic phosphorus removal was 45% in the control treatment, 44% in the L. racemosa treatment, and 35% in the R. mangle treatment. Our results indicate that both mangrove species are capable of removing a considerable amount of nitrogen, but phosphorus removal was unsatisfactory.

Due to their sensitivity to climate forcing that may alter their abundance and distribution, small pelagic fish are important ecological indicators of the state of the California Current System. They are schooling, planktivorous fish that provide forage for higher trophic levels. We describe the life cycle histories and patterns of distribution of sardine, anchovy, and mackerel species occupying the waters along the west coast of the Baja California Peninsula (Mexico). The links between the physical and biological forcing and the structure and condition of their habitats, their patterns of movement, productivity, and stock structure (where information is available) are described in relation to the fisheries. We have used the catches as a proxy for the history of the different stocks, while recognizing that fisheries-derived information is biased by the operational scale and only covers areas where fish are available. We have relied mainly on studies of sardines to evaluate the validity of the principal paradigms in fisheries oceanography. We describe how the environment can structure a population by relating an example given by the spatiotemporal variability of the northern and southern stocks of Pacific sardine (Sardinops sagax) and Pacific mackerel (Scomber japonicus) from 2000 to 2014. During this period, the northern stocks showed a marked tendency to contract southwards, as far south as Magdalena Bay, in response to the regional cooling that began in the previous decade. It appears that the combined effects of fishing and climate change may sufficiently alter habitat characteristics so that both the distribution and productivity of a population are shifted. 

The California sea lion (CSL) and the northern elephant seal (NES) are the two most abundant pinniped species inhabiting the San Benito Archipelago (Baja California, Mexico). This study reports the results of the first survey to gather abundance information from continuous breeding seasons (2012–2015) and over the course of a single year (2014). Relative to the previous year, the abundance of CSLs declined in July 2014; however, based on historical censuses, the colony at the archipelago was catalogued as “stable”. Intra-annually, the CSL abundance was regulated by pups and adult females, which reached their peak during the breeding season (July). Moreover, we hypothesize that subadult males from the west coast of Baja California enter the Gulf of California. The NES fluctuations were most affected by the breeding season (February), when the number of pups and adult females peaked, and by the important presence of juveniles in May and September. The NES colony at the archipelago was catalogued as “in decline”, based on previous countings. This high-resolution survey complements past and future studies in the region, and adds another dimension to our understanding of these species, which is largely based on information from their main rookeries in California.

The common dolphinfish (Coryphaena hippurus) is an important resource for the sport-fishing industry in Mexico. It is captured incidentally by the eastern Pacific purse-seine tuna fishery and in coastal areas by artisanal fisheries. Although it is considered a highly migratory species, only few studies of its movements are available. In this study, the behavior of the common dolphinfish was analyzed by means of acoustic telemetry at three locations within La Paz Bay (southern Gulf of California) from summer to autumn 2013. Acoustic transmitters were attached to six individuals and they were tracked for periods of up to 48 h. Every hour, vertical profiles of temperature and bathymetry were made. To determine the effect of biotic (sex) and abiotic (water temperature and depth, thermocline depth, hour, and bathymetry) variables on the horizontal and vertical movements of tagged organisms, generalized additive mixed models were applied. The results showed a tendency of horizontal movements to the southwestern zone of the bay; two individuals crossed from the eastern to the western side. The average speed was 0.51 m s–1. The vertical movements showed that the individuals spent 80% of the time above 34 m depth, of which around 45% was spent in the upper 10 m of the water column. During daylight hours they swam in shallow waters (upper 10 m) and at night they performed deeper dives (73 m maximum depth). Biotic and abiotic variables influenced both types of movements; however, bathymetry and temperature largely explained fish movements.

The paper presents an overview of studies that link various measures of religious orientation with prosocial and anti-social attitudes and behaviors, including, on one hand, various scales of religiosity, and on the other, prosocial and antisocial attitudes and behaviors (for example, charity and altruism, prejudice and discrimination). The conclusion includes several implications as well as directions for future studies in this area.

The aim of the research was to examine and describe convergent and divergent aspects from the representational field of political leadership, based on a sample of 461 university students of Psychology and Arts Faculties from National Tucuman University, Argentine. A questioning test (MEC) was used, while percentage, principal component, hierarchical clusters, t student´s test and variance analysis ANOVA were performed for its examination. Results show a representational nuclear matrix, integrated by categories such as: Representation, Ideology, Leadership, Guide, Political Ideals, Commitment, Control and Society, while revealing the existence of two opposite dimensions: Positive Political Features/ Aspects versus Negative Political Features/Aspects, and two main clusters coincident with the latter dimensions. Differences are also observed when introducing variables such as age, charges in college’s student associations and political characters of varied nature, revealing the coexistence of share references and differential positioning among university students´ representations.