South Baja California Research Articles

Assessment of Coastal Locations Safety Using a Fuzzy Analytical Hierarchy Process-Based Model

Worldwide tourist beaches have been an ideal destination for people searching for a recreational place to visit; however, several conditions could generate risks for these visitors. At present, the main efforts to assess these risks and prevent people from danger are essentially focused on monitoring tidal height in the zone, ignoring other risk sources. Therefore, this work generates an overall evaluation that considers the tidal height, bathymetry, temperature, solar radiation, and wind speed, establishing a relationship between parameters and safe beach conditions using a fuzzy logic approach. In addition, this paper presents the design and implementation of a computational model, based on a fuzzy analytical hierarchy process (FAHP), to evaluate coastal and climatological parameters involved in tourist safety, which can be continuously monitored. Tourist beaches in South Baja California, México, with diverse environmental and coastal conditions, were assessed with the proposed model, providing several safety scenarios that contrast the results between sites and demonstrate the capacity of the model to evaluate them. The evaluation, obtained as a result of the computational model, presents information about the safety conditions in the assessed zone, considering the possible risks for all the parameters analyzed, which could be presented to beach visitors to prevent dangerous situations and avoid accidents.

Crecimiento y mortalidad de la madreperla <i>Pinctada mazatlanica</i> en poblaciones naturales del litoral oriental de Baja California Sur, México

The Mexican Pacific mother-of-pearl Pinctada mazatlanica was placed in forbidden fisheries status for the Mexican Federal Government and considered in extinction danger since 1939. This decree was modified in 1994 to allow the capture of spat for research or marine culture. We estimated the growth and mortality of mother-of-pearl from the eastern littoral of South Baja California wild stock in the periods 1992-93 and 1997-99. We used 38 sample stations at 2 bays and 6 insular complexes. The maximum length was 187.22 mm (179.83-195.81 mm, P > 0.95). Seasonal von Bertalanffy growth (ELEFAN I routine) values are: L(infinity) = 193.31 mm, k = 0.54 year(-1), t(0) = -0.1805 year, C = 0.49 and WP = 0.75. The growth performance index was Phi' = 4.305. The total mortality was calculated from a length-converted catch curve Z = 2.03 año(-1). Length-weight relationship W(i) = 0.0005418 * L(i)(2.7301). The growth parameters were similar to those for Pinctada margaritifera var. cumingi (open ocean wild stocks). The wild stock oysters differ from culture individuals at experimental repopulation conditions in Paz Bay. The total mortality is similar to that for Pinctada radiata in the Red Sea.

Epibiotic traits of the invasive red seaweed Acanthophora spicifera in La Paz Bay, South Baja California (Eastern Pacific)

AbstractThe aim of this study was to analyze the interaction of a non‐native macroalga (Acanthophora spicifera) with native macroalgae (Sargassum spp.) and sponge assemblages in a subtropical embayment of the Mexican Pacific. The intensity of A. spicifera epiphytism on the native seaweed Sargassum varied significantly over time and was inversely related to the Sargassum density and size. The higher intensity (up to 28 individuals per host plant) occurred when Sargassum was smaller and was lower in density (senescence period). The lower intensity was recorded during the growth period of Sargassum and the subsequent increase in intensity was attributed to a high fragmentation period of A. spicifera, which was evidenced by a decrease in its average size and biomass and by the presence of larger free‐floating accumulations on the subtidal zone. The facultative interaction between A. spicifera and Sargassum appears to be neutral, as no negative or positive effects were found for epiphytic or basibiont seaweeds. However, this invasive seaweed characteristically monopolizes almost all types of hard substrate, and its effects on other algae and benthic organisms should be investigated. Moreover, A. spicifera was often epizoic on epilithic sponges. This invasive seaweed was found anchored on the sponge tissue by rhizome‐like structures. In addition, free‐floating fronds of A. spicifera were frequently found carrying small pieces of the basibiont sponge in its basis (60% of them with eggs and embryos), which suggests a novel facilitation mechanism for some sponge species, as the A. spicifera epizoism could favor fragmentation, dispersal and recruitment of these invertebrates. This study shows that A. spicifera is not only a species that adapts rapidly to the new conditions of the receiving environment but, due to its epibiotic traits, it can directly interact with and influence the life histories of some native species.

Caracterización molecular y biológica del virus de la Rabia que circula en zorrillos de México enfocado a la variante del gen de la fosfoproteína (P)

The objective of this work was to characterize molecularly rabies viruses from Mexican skunks, by comparison of a portion of the viral P gene sequence with corresponding regions from other skunk-adapted rabies virus variants and with other genotype 1 rabies viruses that circulate in the Americas. Furthermore, incubation period and histopathologic lesions after virus inoculation by the intra-cerebral route in mice was characterized. According to the results of phylogenetic studies the Mexican skunk strains (Antigenic Variant (AV) 8 and AV10) are evolutionarily quite distinct. The AV10 isolate from South Baja California is quite closely related to the viruses that circulate in Californian skunks, while the AV8 isolate from San Luis Potosi was most closely related to the South central skunk strain that circulates in southern states such as Texas. These variations were reflected in some biological properties of both strains in mice.

Responses of Crops to Soil Salinization in South Baja California, Mexico

ABSTRACT Soil salinization has become a serious problem all over the world. In this study, the influence of salinity of irrigation water and soil on plant nutrition and physiological disorders were investigated. The study was conducted in three agricultural fields in South Baja California, Mexico where saline stress of crops by soil salinization has become a serious problem under the arid climate. There was a significant correlation (P < 0.05) between sodium (Na) concentration and electrical conductivity (EC) of the water. The soil pH was extremely high in all areas, and the Na concentration was higher than that of other elements. In spite of the salinized water and soil, vegetables did not show symptoms of nutritional disorders. Unlike the vegetables, fruit leaves showed symptoms of nutritional disorders. There was not a correlation between the concentration ratio (CR) of elements of the leaves, which showed symptoms to healthy leaves in a same tree, and the visible symptoms of the nutritional disorder.

Distribución de aves acuáticas en las lagunas de oxidación de la ciudad de La Paz, Baja California Sur, México

Taxonomic composition, spatial and temporal distribution of aquatic birds in oxidation lagoons (LO) of La Paz city in south Baja California, Mexico, were determined during 24 censuses realized in two-week intervals (April/98-March/99). There are five lagoons of5 Ha each and 17 ha of terrains constantly flooded that serve as feeding areas for cattle and birds. One hundred twenty three species were observed, 75 of which were aquatic birds. A total of 46 041 observations were made (average 1 918 birds/census). Richness and abundance of aquatic birds were influenced mainly by migration of anatids and sandpipers. The first group had the greatest abundance due to its affinity towards fresh water bodies. The terrains were the favorite sites of dabbling ducks (Anas) and sandpipers. In contrast, two of the most abundant species (Oxyura jamaicensis, 12.5% of all species, and Fulica americana, 8.8 %) restricted their presence to the oxidation lagoons. LO presented a bird structure of its own and atypical, according to the dryness of the region.

Spatfall of pearl oyster, Pteria sterna (Gould), on experimental collectors at Bahía de La Paz, South Baja California, Mexico

Spatfall of pearl oyster, Pteria sterna (Gould), was analysed at two sites, stations Gaviota and Merito, at Bahía de La Paz, South Baja California, Mexico, during an annual cycle in 1991-1992. and from surface to 15 m depth. Sampling was carried out monthly using experimental collectors which remained immersed for 60-65 days. Four different substrates were tested for spat settlement preference: a native bush called ‘chivato’, dry palm leaves, and red and yellow plastic onion bags: temporal variations, and horizontal and vertical spatfall distribution patterns were evaluated between and within stations. Spat settlement showed significant differences depending on the structure and texture of the substrate type. Chivato bush was in general the best spat collector, but was difficult to handle for large-scale operations; plastic onion bags were more suitable and spat yield was adequate; palm leaves were poor spat collectors. There was no evidence for colour preference of spat settlement between red and yellow onion bags. Pteria sterna spat were present throughout almost all of the study period. Main spatfall was detected in winter-spring, coinciding with low temperatures; most spat then occurred from surface to 4-5 m depth. Few spat were present in summer and most then occurred below 7-9 m depth. The distribution patterns of spat within substrate replicates were apparently influenced by the abundance of spatfall. Aggregated spatial patterns were evident in shallow water during months of maximum spatfall but not when spat was less abundant. These events did not occur in the same substrate type, and differences were also detected between stations. Trends were related to oceanographic conditions prevailing at each site. Two patterns of spatfall abundance and vertical distribution were evident, one for winter-spring, and the other for summer. Samples at station Gaviota were grouped by spatfall abundance and spat vertical distribution patterns, while the latter defined better the grouping of samples at station Merito. Geographical variations of spatfall characteristics for Pteria sterna itself, and in comparison with Pinctada mazatlanka (Hanley) in the Gulf of California, are discussed.

History of Pearling in La Paz Bay, South Baja California

History of Pearling in La Paz Bay, South Baja California

The Lichen Genus Trichoramalina

The Lichen Genus Trichoramalina

Influence of X-Rays on Limb Regeneration in Urodele Amphibians

Influence of X-Rays on Limb Regeneration in Urodele Amphibians