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Baja California Sur (baja + california_sur)
Selected AbstractsA constrained 2D gravity model of the Sebastián Vizcaíno Basin, Baja California Sur, MexicoGEOPHYSICAL PROSPECTING, Issue 6 2005J. García-Abdeslem ABSTRACT The subsurface geometry of the Sebastián Vizcaíno Basin is obtained from the 2D inversion of gravity data, constrained by a density-versus-depth relationship derived from an oil exploration deep hole. The basin accumulated a thick pile of marine sediments that evolved in the fore-arc region of the compressive margin prevalent along western North America during Mesozoic and Tertiary times. Our interpretation indicates that the sedimentary infill in the Sebastián Vizcaíno Basin reaches a maximum thickness of about 4 km at the centre of a relatively symmetric basin. At the location of the Suaro-1 hole, the depth to the basement derived from this work agrees with the drilled interface between calcareous and volcaniclastic members of the Alisitos Formation. A sensitivity analysis strongly suggests that the assumed density function leads to a nearly unique solution of the inverse problem. [source] Food habits of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) off the western coast of Baja California Sur, MexicoJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2010A. A. Cabrera-Chávez-Costa Summary The objective of this study was to establish the trophic niche of the silky shark and to determine the ecological role of this predator in the ecosystem close to Baja California. The trophic spectrum was analyzed from samples taken during summer and autumn (2000,2002) from the fishing camps of Punta Lobos and Punta Belcher on the western coast of Baja California Sur. A total of 263 stomach contents were analyzed (143 with food; 120 empty). The index of relative importance (IRI) showed that at Punta Lobos, silky sharks fed mainly on red crabs Pleuroncodes planipes (%IRI = 83%), whereas at Punta Belcher the main food item was the jumbo squid Dosidicus gigas (%IRI = 41%), followed by chub mackerel Scomber japonicus (%IRI = 33%). According to the Levin Index (Bi), the trophic niche breadth in silky sharks is low (Bi = <0.6), which means that silky sharks are specialist predators because they mainly consume three prey types: red crab, chub mackerel, and jumbo squid. The Shannon-Wiener Index indicated that all trophic categories at Punta Belcher (0.85,1.22) had lower diversity than at Punta Lobos (0.50,1.6), because the silky shark feeds more on tropical prey found close to Punta Lobos. The Morisita-Horn Index (C,) showed an overlap in the diet between the two areas analyzed and between sexes (C, = >0.6). The juveniles and adult females did not show any overlap. In the caloric analysis of the main prey, the jumbo squid (D. gigas) contributed the most calories to the silky shark diet (76%). [source] First reported records of the leopard cusk-eel Lepophidium pardale (Ophidioidei: Ophidiidae) off the west coast of Baja California Sur, MéxicoJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2008J. Rodríguez-Romero No abstract is available for this article. [source] Length,weight relationships of cryptic reef fishes from the southwestern Gulf of California, MèxicoJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2006E. F. Balart Summary Length,weight relationships of 33 cryptic reef fishes from the southwestern Gulf of California were estimated. The most common families were Gobiidae (seven species), Labrisomidae (four), Pomacentridae (three), and Tripterygiidae (three). These are the first length,weight parameters reported for 32 of these species. Specimens were sampled during a comparative ecological study of community structure of fish assemblages associated with coral heads, rocky walls, and artificial reefs in Bahía de La Paz, Baja California Sur. The b values varied between 2.63 and 3.61. New maximum length records for five of the species were established in the study. [source] GROWTH OF CULTURED ABALONE, HALIOTIS FULGENS, USING NATURAL ALGAL DIETSJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Pérez-Estrada, C. J.1,2, Serviere-Zaragoza, E.1, Mazariegos-Villareal, A.1, Reynoso-Granados, T.1 & Monsalvo-Spencer, P.1 1Centro de Investigaciones Biológicas del Noroeste (CIBNOR). P.O. Box 128, La Paz, Baja California Sur. 23000. México; 2Universidad Autónoma de Baja California Sur. Carretera al Sur km. 5.5 o 23080 o La Paz, B. C. S. Algal diets have been evaluated and used extensively for the aquaculture of abalone, especially in Japan. In other areas little is known about the nutritional value of the algae that the local abalone consume. In Mexico, regional hatcheries use Macrocystis pyrifera as a main source of natural food. Kelp availability, year round, has not generally been a problem for abalone aquaculturists. Most difficulties occur during severe storms, which may prevent access to kelp beds. El Niño also caused widespread destruction of M. pyrifera. In this study, growth rates of juvenile green abalone Haliotis fulgens, 31.7 " 1.5 mm shell length and 2.5 " 0.2 g body weight were evaluated during 136 days. Juveniles were fed with some of the algae used in regional hatcheries, Macrocystis pyrifera, Egregia menziesii, Eisenia arborea, Porphyra sp. and Ulva sp. Shell length growth rates varied between 2 mm day-1 for Ulva sp. and 18 mm day-1 for M. pyrifera. Body weight rates ranged from no growth for Ulva sp. to 14 mg day-1for E. menziesii. The percent of survival was between 46 and 75 %. Ulva sp. showed the lowest protein content followed by E. menziesii, E. arborea, M. pyrifera and Porphyra sp. [source] The effect of feral cats on the population viability of black-vented shearwaters (Puffinus opisthomelas) on Natividad Island, MexicoANIMAL CONSERVATION, Issue 3 2002Bradford S. Keitt Insular breeding seabirds are likely to be particularly vulnerable to introduced mammalian predators because they often lack behavioural, morphological and life-history defenses against predation. We studied the life-history of the black-vented shearwater (Puffinus opisthomelas) on Natividad Island, Baja California Sur, Mexico, to examine its vulnerability to introduced feral cats. Using an allometric equation, we estimated that feral cats consumed 328 g of food day -1 to satisfy their nutritional requirements. We used stable isotope analysis of cat scat to estimate that 90% of the cats' diet was composed of shearwaters. Using data from our focal species and from the closely related manx shearwater (Puffinus puffinus), we created a demographic model to evaluate the effects of cat population size on the annual growth rate (,) of the shearwater. The annual growth rate for black-vented shearwaters was estimated to be 1.006 in the absence of cat predation. With predation, we estimated that annual growth rate declined approximately 5% for every 20 cats in a population of 150,000 birds. Persistence times of bird colonies decreased both with an increase in the size of the feral cat population and with a decrease in the size of the initial bird population. [source] Growth and survival of the Calafia mother-of-pearl oyster Pinctada mazatlanica (Hanley 1856) under different sequences of nursery culture,late culture at Bahía de La Paz, Baja California Sur, MéxicoAQUACULTURE RESEARCH, Issue 12 2000Mario Monteforte The Calafia mother-of-pearl oyster, Pinctada mazatlanica (Hanley), and the Rainbow nacre shell, Pteria sterna (Gould), represent an important resource for México because of their potential in pearl production. The present work deals with the effect of different sequences of nursery culture-late culture on growth and survival of P. mazatlanica, from September 1993 to October 1994. The collected spat presented two main size groups: small (mean shell height of 7 mm), and large (13 mm). They were arranged into four experimental batches for each size group at a constant stocking density of 40,45 juvenile pearl oysters per Nestier cage. Three batches remained in nursery culture for 2, 4 and 6 months respectively, after which they were transferred to late culture in rail cages. A control group remained in nursery culture for 12 months. Growth was evaluated monthly and compared through anova and HSD Tukey tests. In addition to the shell height, width, depth (mm) and weight (g), data of shell volume (height × width × depth, in mm3) was also introduced to estimate and compare growth among the experimental groups. Mortality was estimated by counting the dead specimens every month and obtaining the percentage from a 100% initial survival at the start of the experiment. The juveniles showed different responses to the change from nursery culture to late culture; the level of each response varied significantly among the experimental groups at the end of the study. It seemed that a 6-month period for nursery culture was propitious for P. mazatlanica. [source] Clinoform nucleation and growth in coarse-grained deltas, Loreto basin, Baja California Sur, Mexico: a response to episodic accelerations in fault displacementBASIN RESEARCH, Issue 3 2005Estelle Mortimer We investigate the controls on the architecture of coarse-grained delta progradational units (PUs) in the Pliocene Loreto basin (Baja California Sur, Mexico), a half-graben located on the western margin of the Gulf of California. Dorsey et al. (1997b) argued that delta progradation and transgression cycles in the basin were driven by episodic fault-controlled subsidence along the basin-bounding Loreto fault. Here we test this hypothesis by a detailed analysis of the sedimentary architecture of 11 exceptionally well-exposed, vertically arranged fluvio-deltaic PUs, each of which shows lateral facies transition from proximal alluvial facies palaeo-seaward into distal pro-delta facies. Of these 11 PUs, seven exhibit a lateral transition from a shoal water to Gilbert-delta facies associations as they are traced palaeo-seaward. This transition is characterised by down-transport development of foresets, which grow in height up to 35 m. Foreset units thicken in a basinward direction, with initially an oblique topset,foreset geometry that becomes increasingly sigmoidal. Each delta is capped by a shell bed that records drowning of the delta top. This systematic transition in delta architecture records increasing water depth through time during individual episodes of progradation. A mechanism that explains this transition is an accelerating rate of fault-controlled subsidence during each PU. During episodes of low slip rate, shoal-water deltas prograde across the submerged topography of the underlying delta unit. As displacement rate accelerates, increasing bathymetry at the delta front leads to steepening of foresets and initiation of Gilbert deltas. Subsequent delta drowning results from sediment starvation at the shoreline at high slip rates because of sediment trapping upstream. The observed delta architecture suggests that the long-term (>100 kyr) history of slip on the Loreto fault was characterised by repetitive episodes of accelerating displacement accumulation. Such episodic fault behaviour is most likely to be because of variations in temporal and spatial strain partitioning between the Loreto fault and other faults in the Gulf of California. A physical explanation for the acceleration phenomenon involves evolving frictional properties on the episodically active Loreto fault. [source] | |||||||||||||||||||||||||