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

In order to determine the seasonal distribution and the importance of each of the species of aquatic and semiaquatic birds in the Estero de San José del Cabo, B.C.S. (Mexico), monthly censuses were performed from September 1986 to September 1987. A total of 12,490 birds, belonging to 50 species, were recorded. The presence and abundance of birds, compared to those reported by other authors, are significantly reduced, probably due to the deterioration of this habitat. In this bird community, the American coot (Fulica americana) was, by far, the most abundant species (9,176 individuals). This lagoon is an important stop for migratory birds, mainly anatids.

Five samplings of benthic marine algae were carried out at Isla Asunción and Bahía Asunción, B.C.S., during 1988 and 1989. In total, 113 species of benthic marine algae were found. Three species of Cyanophyta, 78 species of Rhodophyta, 19 species of Phaeophyta and 13 species of Chlorophyta were determined. The floristic list includes data on the reproductive stage, tidal level, type of coast, substrate and epiphytism of the species found. Macrocystis pyrifera, Eisenia arborea and Corallina oficinalis var. chilensis are the principal components of the benthic vegetation of Asunción Island. The species composition found in Bahía Asunción is representative of the flora associated with Macrocytis pyrifera beds from the southern area of Baja California. The Rhodophyta are dominant in terms of diversity.

A total of 198 digestive tracts of ocean whitefish (Caulolatilus princeps, Jenyns, 1842) were examined from monthly catches, from February 1986 to January 1987. Using four indices (numeric, volumetric, frequency of occurrence and relative importance), the food components of the trophic spectrum were determined and categorized. This was made up of five major taxa: annelids, molluscs, crustaceans, echinoderms and fishes. The spectrum is dominated, most of the year, by the ostracod Conchoecia pacifìca, along with other secondary food items like hyperiid amphipods (Vibilia sp.), euphausiids (Nycthiphanes simplex), galatheids (Pleuroncodes planipes), pteropod molluscs (Hyaloselix striata, Clio piramidata), cephalopods (Loligo opalescens) and fishes, and with a range of incidental food items, like gammarids (Ampheliscidae), crab larvae (Callinectes sp.), isopods, penaeids, thalassinoideans, small gastropods, polychaetes and echinoderms. There are no significant differences in the spectra from males and females (Wilcoxon’s test, P = 0.05). The number of food components in the diet seems to increase with length. The most intensive feeding takes place between the end of the reproductive period and its start. In conclusion, the ocean whitefish is a passive predatory teleost, that feeds mainly during daylight hours upon organisms associated with the sea floor.

Fourier grain-shape analysis (FGSA) of detrital quartz grain was used to identify local sources for medium-grained (0.25 to 0.50 mm) sand in Creciente barrier island, which is located on the west coast of Baja California Sur, Mexico. A total of 52 samples from Creciente Island and vicinity were analyzed. The results of FGSA include mean values of harmonic amplitude values, which may be employed to characterize the shape composition for each sample. These values were used as for statistical procedures used to identify sand sources. Factor analysis (BMDP 4M), based on mean harmonic amplitude values for each sample, was used to identify sample groups, which, in turn, served to define the probable sources. Multivariate analysis of variance indicated how much of the shape information was explained by each factor or variable, and was also used to facilitate the sedimentologic interpretation of one factor (roughness). Levine’s F-test was used to determine whether or not the explained variance for each of the 23 shape variables (harmonics) is statistically significant. Levine’s F-test also was used to measure the difference between sample values resulting from analysis of variance. Discriminate function analysis was used to estimate the percentage of sand derived from each of the potential sources. The beach sand at Creciente Island has two primary sources. The first is the inner continental shelf, which contributed from approximately 50 to 57% of the sand in observed samples. The second source is the nearby rivers, which contributed from 43 to 50%.

The abundance and distribution of larvae and juveniles of the family Bregmacerotidae were studied at Campeche Bay (Mexico). The material was obtained from eight oceanographic cruises carried out between March 1981 and August 1988, covering the four seasons. Samples were taken with a bongo net in double-oblique tows. All larvae and juveniles were sorted from the samples and standard or notochordal length was obtained from each specimen, with a precision of 0.1 mm. A total of 6,122 larvae and juveniles were obtained of four species, which were, in order of abundance: Bregmaceros cantori (95.5%) B. atlanticus (4.2%), B. macclellandi (0.4%) and B. houdei (0.02%). The distribution and abundance of larvae in general and the size distribution in particular, let us characterize B. cantori as a neritic species, with its main spawning zone in areas between 20 and 100 m depth. Bregmaceros macclellandi, on the other hand, was characterized as oceanic, province in which it lives and spawns; the presence of some of its larvae over the continental shelf must be a consequence of local currents. Bregmaceros atlanticus had an intermediate situation between the two previous species, because the highest larval densities, particularly of those of smaller size, occurred in the outer shelf (areas ~100 m depth) and in the oceanic area adjacent to the continental slope.

In the present study, it is established that Macrocystis pyrifera collected in summer and winter, in Bahía Tortugas, B.C.S. (Mexico), presented variation in some components of nutritional interest for various animal species. The results showed significant difference (P < 0.01) in the content of ashes, crude protein, crude fiber and in vitro digestibility. Likewise, higher values were found, for summer, in most of the amino acids. It is concluded that the alga collected in summer is a potential resource, with a higher content of minerals and amino acids, with a good digestibility of the dry matter for ruminants and without the presene of antinutrient factors.

Bahía Magdalena, Baja California Sur (Mexico), is an interesting place where, because of its geographic location and environmental characteristics, a high biodiversity is found. In spite of marine resources of economic importance, few reports or papers dealing with the bay’s biodiversity have been published. To date a comprehensive check-list of the fishes of Bahía Magdalena has not been published. In the present work an integrated record of ichthyofauna is given; the list includes those species caught in a six-year survey, which are catalogued in the biological collection of the Centro Interdisciplinario de Ciencias Marinas (CICIMAR, IPN) at La Paz, Baja California Sur. The check-list includes 161 species belonging to 120 genera and 61 families, of which 20 correspond to the elasmobranchs and 141 to bony fishes.

The structure of the fish community of Raya Lagoon was analysed during 1990. Monthly catches were made in the mouth and inner part of the lagoon, using a 6 mm-mesh beach seine net, 31 m in length and 2.15 m in height. A total of 19,516 specimens, corresponding to 30 families, 50 genera and 62 species, were caught. The most numerous were Anchoa hepsetus, 36.60%, and Eucinostomus gula, 23.51%. Numerical diversity fluctuated between 1.74 and 3.51 bits/ind diversity in terms of weight, between 1.91 and 3.5 bits/ind, species richness, between 3.45 and 4.29; equitability, between 0.48 and 0.74; redundancy, between 0.28 and 0.67; dominance, between 42.25 and 80.61%. The dominant species were Eucinostomus gula, Diapterus rhombeus, Anchoa hepsetus, Archosargus rhomboidalis, Arius herzbergii and Xenomelaniris brasiliensis. Of the species found, 41.94% were occasional visitors, 30.65% were cyclical visitors and 27.42% were permanent residents. Likewise, 40.32% were first order consumer species; 40.32%, second order consumers; 19.36%, third order consumers. The low percentage of permanent residents indicates this area’s instability.

During critical seasons of environmental pollution, bacteriological samplings were made in Willard Bay and Los Angeles Bay, Baja California, in 1985-1987, and in Falsa Bay and Todos Santos Bay, B.C., in 1991-1993. The objective of this study was to determine the quality of the water for culturing bivalve molluscs. Bacteriological faecal indicators (total coliforms and faecal coliforms) were determined by MPN technique, according to standard methods. Except for summer 1985 in Willard Bay, when a significant amount of organic material was introduced by fishing boats, and winter 1992 in Falsa Bay and Todos Santos Bay, when there was an important input of bacteria due to rainfall, the bacteriological quality of the water was acceptable for culturing bivalve molluscs in the four locations, since the values were below the limit established by legislation.

Hydrographic data from two cruises, taken in February and August 1992, were used to describe the vertical thermohaline structure, the presence of water masses in the region of the mouth and central part of the Gulf of California, and meridional and zonal flows, respectively. The observations presented here show a marked thermal change between both seasons, with surface temperatures of about 19.00ºC in February and 32.00ºC in August. Thermal maxima (32.75ºC) and salinity minima (33.00) define a significant presence of Tropical water in the interior of the gulf in 1992, which suggests the occurrence of the El Niño phenomenon. This condition increased the intensity of the geostrophic flow and, in the central part of the gulf, velocities of 95 cm s–1 were recorded in February and of ll5 cm s–1 in August.