Alfredo Ortega-Rubio

Current status of rodents on islands in the Gulf of California

On islands in the Gulf of California, many species and subspecies of rodents are relict species, restricted to the islands, and now considered extinct or verging on extinction. From 1991 to 1999, each island was surveyed and an average of 15 work-nights were spent on each island, for a total of 15,000 trap-nights. A Fourier series was used to estimate population density. Five native taxa are now considered extinct (Chaetodipus baileyi fornicatus, Peromyscus guardia mejiae, P. g. harbinsoni, P. pembertoni, and Neotoma bunkeri). Two species are at risk of extinction (Dipodomys insularis and Neotoma albigula varia). The most probable cause for extinction is the introduction of nonnative species, specifically cats. We believe that the most vulnerable rodent populations of the islands in the Gulf of California to non-native species are Neotoma lepida latirostra on Danzante island and Neotoma lepida abbreviata on San Francisco island, both in the state of Baja California Sur.

The effect of environmental conditions on the growth and development of the oilseed halophyte Salicornia bigelovii Torr. in arid Baja California Sur, México

Due to its geographical situation, Baja California Sur is the most arid Mexican state, with the longest length of coast in the country. Hence, the study of halophytes for incorporation into rural agriculture is a priority for this region. In this research, the growth and development of a natural population of the oilseed halophyte Salicornia bigelovii Torr. as affected by environmental factors are analysed. Four transects were traced in the field, with sample sites of 1 mZ every 3m along each transect from which samples of soil and plants for laboratory analysis were taken, starting at the lowest seashore tide line. Edaphic and environmental factors as well as biomass, plant density, size, and dry matter were analysed through multivariate statistical methods. Three edaphic factors showed correlation with growth and development of individuals: growth was positively correlated with soil organic matter, and negatively correlated with the percentage of sand as a component of texture and with the balance of sodium (SAR parameter) in the soil saturated paste. Part of the results are unexpected because most of the previous work had dealt only with the salinity factor. The results will enable us to determine the next steps to promote the economic use of this species in the study region.

The Human Footprint in Mexico: Physical Geography and Historical Legacies

Using publicly available data on land use and transportation corridors we calculated the human footprint index for the whole of Mexico to identify large-scale spatial patterns in the anthropogenic transformation of the land surface. We developed a map of the human footprint for the whole country and identified the ecological regions that have most transformed by human action. Additionally, we analyzed the extent to which (a) physical geography, expressed spatially in the form of biomes and ecoregions, compared to (b) historical geography, expressed as the spatial distribution of past human settlements, have driven the patterns of human modification of the land. Overall Mexico still has 56% of its land surface with low impact from human activities, but these areas are not evenly distributed. The lowest values are on the arid north and northwest, and the tropical southeast, while the highest values run along the coast of the Gulf of Mexico and from there inland along an east-to-west corridor that follows the Mexican transversal volcanic ranges and the associated upland plateau. The distribution of low- and high footprint areas within ecoregions forms a complex mosaic: the generally well-conserved Mexican deserts have some highly transformed agro-industrial areas, while many well-conserved, low footprint areas still persist in the highly-transformed ecoregions of central Mexico. We conclude that the spatial spread of the human footprint in Mexico is both the result of the limitations imposed by physical geography to human development at the biome level, and, within different biomes, of a complex history of past civilizations and technologies, including the 20th Century demographic explosion but also the spatial pattern of ancient settlements that were occupied by the Spanish Colony.

A regional-scale sustainable development index: the case of Baja California Sur, Mexico

SUMMARY Sustainable development, as a multi-dimensional concept, is difficult to measure. Some efforts using indicators and indices have appeared in recent years, but most were developed on a national scale. Use of sustainability indicators has proven valuable for attaining better management of the environment by minimizing information gaps and maximizing community capabilities in terms of economic, social, environmental, and institutional sustainability dimensions. However, at least in the case of developing countries, the potential exists that national sustainability measures, based on national level indicators, may mask problems in sub-national zones with highly unsustainable conditions. This paper proposes a methodology to evaluate sustainable development at a local level, the use of which could be helpful in comparing different regions within a country or even among different countries. National sustainability indicators should result from a combination (whether additive or proportional) of regional sustainability indicators, as developed in this paper.

Managing a protected marine area for the conservation of critically endangered vaquita (Phocoena sinus Norris, 1958) in the Upper Gulf of California

We analysed fisheries trends in the northern region of the Gulf of California, within the Biosphere Reserve of the Upper Gulf of California and Colorado Delta River and the Vaquita Refuge Area, and suggest measures to protect the vaquita, Phocoena sinus. We compiled and analysed catch reports of artisanal fishermen in the three fishing communities of the Upper Gulf of California (San Felipe in the State of Baja California, and Golfo de Santa Clara and Puerto Peñasco in the State of Sonora) from 1995 to 2007. This information was categorised with respect to geographic information systems, and all fishing sites within two marine protected areas in the region were identified. In addition, from a survey based on direct interviews with artisanal fishermen in each of the three ports, we identified that 23% of fishermen will continue fishing despite on-going fishing buy-out programmes in the region. We suggest several specific courses of action to decrease the fishing impact on this critically endangered cetacean. However, given the critical situation of this critically endangered species, it is very uncertain whether enforcing a no-take zone within the biosphere reserve and the Vaquita Refuge Area, or even a wider fishing moratorium, will be enough to save this endangered species from extinction.

Ecological aspects of the land crab Gecarcinus planatus (Decapoda: gecarcinidae) in Socorro Island, Mexico

Abstract The results of a study are presented on the Socorro Island crab Gecarcinus planatus , a species inhabiting this oceanic island in a wide range of communities and altitudes. In February 1990, two transects in the forest community at Socorro Island were sampled and all crabs captured were recorded. Through mark-recapture methods the population density was estimated, and the individual home ranges were determined by means of Component Bivariate Model. The structure and phenology of the vegetation was recorded in the same two transects. It seems that crab density is related to cover of trees, particularl to Ficus cotinifolia, Guettarda insularis , and Bumelia socorrensis . In addition, the phenology of G. insularis also seems to be important to crab distribution. Home range of G. planatus is inversely associated to crab population density. Vegetation communities in Socorro Island are endangered by sheep overgrazing, so densities and home ranges of the crab in this forest may be affected in the future. To determine the real impact of exotic species on the structure and function of the communities present in Socorro Island (such as feral sheep) it will be necessary to study the relationships between vegetation and the different animal populations in the areas not strongly disturbed.

Ecology of Callinectes arcuatus and C. bellicosus (Decapoda, Portunidae) in a coastal lagoon of northwest Mexico

Some ecological aspects of the swimming crabs, Callinectes arcuatus and C. bellicosus are presented. Specimens were collected with a trawl net, both day and night, on a monthly basis from March 1998 to February 2000 in a coastal lagoon in northwest Mexico. A total of 1235 specimens were captured, C. bellicosus (n = 878) (abundance 0.5 to 60 ind. ha-1) was more abundant than C. arcuatus (n = 357) with an abundance from 0 to 38 ind. ha-1 during the study period. Both species were more abundant at night and usually were found in conjunction with macroalgae. Salinity (32 to 40‰) tended to favour the dominance of C. bellicosus over C. arcuatus (2.4 : 1) and the water temperature appeared to govern the breeding season (21 to 32°C). For both species, the breeding season runs from March until September (spring-summer), the recruitment of juveniles occurs during January and February (winter), and the lowest abundance of both species is found during October and November (fall). For both species, ovigerous females were observed in the mouth of the lagoon, and juveniles were found in the lagoons interior parts. The authors think that the observed ecological patterns of the species could be extrapolated to other coastal lagoons with a similar climate, oceanography, and geomorphology.

Analysis of management options for artisanal fishing of the Bigeye Croaker Micropogonias megalops (Gilbert, 1890) in the Upper Gulf of California

Bigeye Croaker (Micropogonias megalops Gilbert 1890) is captured in the Upper Gulf of California (UGC) by local community fishers from San Felipe in Baja California, El Golfo de Santa Clara and Puerto Peñasco in Sonora. The calculated sustainable fishery index (SFI) identifies four production periods, one of low capture before 1999 (∼1451.49 t year−1); a second of fleet expansion (∼2408 t year−1); a third showing a production decline related to overfishing (> 923.85 t year−1); and a fourth of recovery, with standardization of production of about 1057 t year−1 (2004). A GIS survey indicated that almost 84% of the Bigeye Croaker fishery in the UGC occurs within two marine protected areas, of which almost 74% takes place inside the Biosphere Reserve of the UGC, and almost 79% in the Vaquita Refuge Area. Bigeye Croaker captured in the marine protected areas generates a gross profit of around US

Food analysis and resource partitioning in a lizard guild of the Sonoran Desert, Mexico

501,000 year−1, with a return rate close to 73%. Fishing effort in the marine protected areas needs to undergo an interdisciplinary and complex evaluation due to the presence of endangered species in the region. This requires adequate management practices to enhance marine conservation without compromising fishermens individual interests. Some approaches to manage this fishery within the protected marine areas are discussed.

Environmental quantitative assessment of two alternative routes for a gas pipeline in Campeche, Mexico

Abstract The food niche relationships of a lizard community of an arid zone in the State ofSonora, NW Mexico, were studied during 1982, 1983 and 1984. The species with highly specialized diets showed little variation in food habits during those years, while the opposite occurred with more eclectic predators. The expected correlation between the size of the predator and the size of its prey can also be biased by food specialization. Food niche overlaps, based on analysis of the volume and the taxonomic status of the prey at a family level, were persistently low. The role that food niche partitioning could play in determining the organization of this lizard guild is discussed.