First account of microplastics in pelagic sporting dolphinfish from the eastern Mexican coast of Baja California Sur.

This study is a baseline data on the presence of MPs from the gastro-intestinal tracts (GITs) in Coryphaena hippurus Linnaeus, from eastern Baja California Sur, México. 878 MPs items (in %) of fibers (29%), fragments (68%) and films (1.3%) were detected from 51 GITs of Coryphaena hippurus. Transparent, white, blue and black were the prevalent colours. Morphological features observed through SEM analysis, the presence of heavily weathered MPs is due to the mechanical, microbiological and chemical weathering process. PP (29%), Nylon (29%), PS (17%), PE (11%), PET (6%) and HDPE (8%) presence indicates their source from regional anthropogenic stress. Trophic level transition is enforced by polymer derivative, permitting the sinking behavior of MPs and increased ingestion probability. Fishes were classified as slim despite their higher feeding capabilities and ingested MPs indicates a relationship with environmental contaminants. Current study emphasizes the health risk linked to biological aspects of MPs ingestion.

Mercury concentrations in Baja California Sur fish: Dietary exposure assessment.

Total mercury concentrations ([THg]) in muscle were determined in commercial finfish and elasmobranchs from Baja California Sur (BCS), Mexico to evaluate dietary Hg exposure for BCS communities, including the relationship of trophic ecology, length and mass with [THg] that might drive future consumption advice (e.g., recommend limited consumption of large fish for some species). The [THg] ranged from 0.06 to 528.02 µg kg-1 ww in finfish and 17.68-848.26 µg kg-1 ww in elasmobranchs. Relative to the consumption threshold set for predatory fish in Mexico, all species had a concentration below 1000 µg kg-1 ww. As expected, 16 (4.02%) and 75 (18.84%) individual fish were above advisory thresholds of 500 and 200 µg kg-1 ww, respectively. The hazard quotients (HQs) in most species were significantly <1.0, only banded guitarfish showed a significant median HQ > 1.0. Thus, the relative level of risk of high Hg exposure is low for most species.

Age-Appropriate Wisdom? : Ethnobiological Knowledge Ontogeny in Pastoralist Mexican Choyeros.

We investigate whether age profiles of ethnobiological knowledge development are consistent with predictions derived from life history theory about the timing of productivity and reproduction. Life history models predict complementary knowledge profiles developing across the lifespan for women and men as they experience changes in embodied capital and the needs of dependent offspring. We evaluate these predictions using an ethnobiological knowledge assessment tool developed for an off-grid pastoralist population known as Choyeros, from Baja California Sur, Mexico. Our results indicate that while individuals acquire knowledge of most dangerous items and edible resources by early adulthood, knowledge of plants and animals relevant to the age and sex divided labor domains and ecologies (e.g., women's house gardens, men's herding activities in the wilderness) continues to develop into middle adulthood but to different degrees and at different rates for men and women. As the demands of offspring on parents accumulate with age, reproductive-aged adults continue to develop their knowledge to meet their children's needs. After controlling for vision, our analysis indicates that many post-reproductive adults show the greatest ethnobiological knowledge. These findings extend our understanding of the evolved human life history by illustrating how changes in embodied capital and the needs of dependent offspring predict the development of men's and women's ethnobiological knowledge across the lifespan.

Hidden in plain sight: Morphological and phylogenetic evidence for Bouteloua arizonica, a species distinct from Bouteloua aristidoides (Poaceae, Chloridoideae).

Two varieties of Bouteloua aristidoides have been recognized, the widespread var. aristidoides and the more narrowly distributed var. arizonica. The two varieties differ in inflorescence form even more than that seen between many other closely related species of Bouteloua. We therefore asked whether these taxa might be better regarded as distinct species. A total of 93 vouchers were studied by using morphometry (principal components analysis and statistical tests), leaf micromorphology, ancestral state reconstruction, and/or molecular (ITS, trnC-rpoB and trnT-L-F) phylogenetic analyses. Except from the ITS tree, all results supported elevation of B. aristidoides var. arizonica to the rank of species, thus the new combination Bouteloua arizonica (M.E. Jones) L.F. Cuellar & Columbus comb. nov. et stat. nov., is proposed. Chloroplast and combined chloroplast-nuclear molecular trees depicted var. arizonica as monophyletic (even in sympatric populations with var. aristidoides) and reveals phylogenetic structure within var. aristidoides for which the presence of new undescribed varieties of B. aristidoides (different from B. arizonica) is addressed. B. arizonica differs from B. aristidoides in having fewer branches per inflorescence, a bigger branch with more spikelets, and a shorter branch extension. Scanning electron microscopy revealed the presence of papillae on leaves of B. arizonica as a clear synapomorphy. Growing mature plants of B. arizonica from seeds in a greenhouse revealed a strong cleistogamous nature for this species for which gene flow in sympatric populations with B. aristidoides seems unlikely. A taxonomic treatment and distribution map for identification of B. arizonica is provided.

Bioaccumulation and trophic transfer of potentially toxic elements in the pelagic thresher shark Alopias pelagicus in Baja California Sur, Mexico.

Pelagic thresher shark (Alopias pelagicus) is a circumglobal species with high ecological and economic importance. Concentrations of mercury, selenium and cadmium in the muscle and liver tissues of A. pelagicus captured from Baja California Sur, Mexico were determined for assessing the potential human hazard. Results revealed that the average concentrations of Hg (0.76 mg kg-1) and Cd (0.18 mg kg-1) in muscle tissues were below the maximum permissible limits for human consumption. Se in the muscles were relatively low (mean: 0.30 mg kg-1 -1) resulting in a molar excess of Hg over Se. Average levels of hepatic Cd were extremely higher than the maximum limit for consumption. Organotropism of Hg was muscle > liver, whereas Se and Cd presented an order of liver > muscle. Biomagnification Factor (BMF) emphasized the trophic transfer of elements. Selenium Health Benefit value was negative (-3.76) posing potential health risks demanding regular monitoring for health risks.

Seasonal ecology of a migratory nectar-feeding bat at the edge of its range.

Migratory species that cross geopolitical boundaries pose challenges for conservation planning because threats may vary across a species' range and multi-country collaboration is required to implement conservation action plans. The lesser long-nosed bat (Leptonycteris yerbabuenae) is a migratory pollinator bat that was removed from the Endangered Species List in the United States in 2018 and from threatened status in Mexico in 2013. The seasonal ecology and conservation status of the species is well understood in the core part of its range on mainland Mexico and in the southwestern United States, but relatively little is known about the species on the Baja California peninsula in northwestern Mexico, a part of its range range separated by the Gulf of California. We studied the seasonal ecology of lesser long-nosed bats on the Baja peninsula at 8 focal roosts along a 450-km north-to-south transect to test hypotheses about migratory or residential status of the species on the Baja peninsula. We provide evidence of an extensive population of lesser long-nosed bats on the Baja peninsula that is primarily seasonally migratory and includes 2 mating roosts with males on the southern part of the peninsula. Seasonal ecology of lesser long-nosed bats was closely associated with the flowering and fruiting season of the cardón (Pachycereus pringlei), the dominant columnar cactus on the peninsula. However, we discovered that some female lesser long-nosed bats arrive and give birth at southern roosts in mid-February, about 2 months earlier than other migratory populations in more northern Sonoran Desert habitats. We documented the loss of nearly a third of the known maternity roosts during the study, demonstrating that action to protect key roosts remains a high priority. Migratory pollinators are particularly vulnerable to climate and land-use changes and we recommend continued monitoring and research to guide effective range-wide conservation of the species. Las especies migratorias o con rangos de distribución amplios que incluyen fronteras geopolíticas, representan desafíos particulares para la planificación de estrategias de conservación, ya que las amenazas así como las tendencias poblacionales pueden variar a lo largo de su rango geográfico y se requiere la colaboración de múltiples países para implementar planes de acción que permitan su conservación. El murciélago magueyero menor (Leptonycteris yerbabuenae) es un murciélago polinizador migratorio que recientemente fue sacado de la lista de especies en peligro en los Estados Unidos en 2018 y en México en 2013. La ecología estacional y el estatus de conservación de esta especie, ha sido bien estudiado en el centro de su rango de distribución en México continental, pero se sabe muy poco acerca de la especie en la Península de Baja California en el noreste de México, región que está separada del resto del rango por el golfo de California. Nosotros estudiamos la ecología estacional del murciélago magueyero menor, en ocho cuevas a lo largo de un transecto de 450 km norte-sur, en la Península de Baja California y pusimos a prueba la hipótesis del status migratorio o residente de sus poblaciones en esta región. Proporcionamos la primera evidencia de una extensa población de esta especie en la península, a cual es principalmente migratoria estacional e incluye dos cuevas de reproducción ubicadas al sur de esta región. La ecología estacional del murciélago magueyero menor estuvo fuertemente asociada con la estación de floración y fructificación del cardón (Pachycereus pringlei), el cactus columnar dominante en la península. Nosotros también descubrimos que algunas hembras llegan y dan a luz en las cuevas más sureñas, a mediados de febrero, cerca de dos meses antes que otras poblaciones migratorias, en el desierto de Sonora del norte. Durante el tiempo de este estudio, documentamos la destrucción de una de las cuevas de maternidad, lo que demuestra la necesidad de acciones de conservación para proteger estos refugios. Los polinizadores migratorios son particularmente vulnerables a cambios en el uso del suelo y al cambio climático y recomendamos continuar con el monitoreo y la investigación, con el fin de guiar su conservación a lo largo de todo el rango de distribución de la especie.

Description of Califorctenus (Cteninae, Ctenidae, Araneae), a new spider genus from Mexico.

Califorctenus gen. nov. (Araneae: Ctenidae) a new genus and a new species (Califorctenus cacachilensis sp. nov.) from the Baja California Peninsula in Mexico are described and illustrated. Califorctenus gen. nov. can be diagnosed by the morphology of the male palp, with embolus cylindrical and elongated, locking lobes of embolus positioned retrolaterally and the cup-shaped and elongated median apophysis.

Edad y crecimiento del pez Fundulus lima (Cyprinodontiformes: Fundulidae) en el río La Purísima, Baja California Sur, México

Introducción: El estudio de la edad y crecimiento en peces es un prerrequisto básico para generar información sobre la longevidad, tasas de crecimiento y estructura poblacional, entre otros atributos, todos ellos para la aplicación de políticas enfocadas en el manejo y conservación poblacional. Evaluamos estos atributos en la sardinilla peninsular en peligro de extinción (Fundulus lima) que habita los oasis de Baja California Sur, con la perspectiva de generar información base de este pez endémico. Objetivo: Determinar la edad, crecimiento somático y estructura de las poblaciones de F. lima en una de las cuencas hidrológicas más importantes de su ámbito de distribución. Métodos: De octubre 2002 a julio 2004 se muestreó F. lima en 4 sitios del río La Purísima por métodos de captura pasiva y activa. Los individuos fueron medidos y pesados en el campo, donde submuestras fueron seleccionadas para el análisis de la edad en escamas. Todos los individuos fueron liberados vivos a sus sitios originales de captura. Estimamos edad, relaciones longitud-peso y longitud-longitud, y estructura poblacional, basados en 802 individuos examinados por técnicas no invasivas. Resultados: El crecimiento somático de F. lima fue alométrico positivo (b > 3.0) en todas las poblaciones estudiadas, con valores de "b" variando de 3.126 (Ojo de Agua) a 3.420 (El Pilón). Tres clases de edad (0, 1 y 2 años) fueron reconocidas, de las cuales la edad 1 fue la más frecuente (49 %). El método polimodal basado en datos de frecuencia de tallas identificó tres clases de edad. Longitudes totales retrocalculadas en edades previas basadas en incrementos de crecimiento en escamas fue entre 38.61 y 68.81 mm para individuos de 1 y 2 años, respectivamente. Conclusiones: Tres clases de edad (0, 1 y 2 años) fueron determinadas para las poblaciones de F. lima en el río La Purísima, basadas en la interpretación de anillos de crecimiento anual en escamas y en la distribución modal de frecuencia de tallas observadas. Todas las poblaciones examinadas demostraron un crecimiento alométrico positivo (b > 3.0).

Introduction: The study of age and growth in fishes is a basic prerequiste to generate information on longevity, growth rates, population structure, among other attributes, all of them for the application of policies focused on the population management and conservation. We evaluated these attributes in the endangered Baja California killifish (Fundulus lima) that inhabits the oases of Baja California Sur, Mexico, with the perspective of generating base information for the conservation of this endemic fish. Objective: To determine the age, somatic growth and population structure of F. lima in one of the most important hydrological basins of its distribution range. Methods: From October 2002 to July 2004 we sampled for F. lima in 4 sites of La Purisima river by using passive and active collection methods. Individuals were measured and weighed in the field, where subsamples were selected for analysis of age based on scales. All of the individuals were released alive to its original sites of capture. We assessed the age, length-weight and length-length relationships and population structure on the basis of 802 individuals examined by non-invasive techniques. Results: The somatic growth of F. lima was of positive allometric type (b > 3.0) in all the populations studied, with values of "b" ranging from 3.126 (Ojo de Agua) to 3.420 (El Pilón). Three age class (0, 1 and 2 years old) were recognized, of which the age 1 year was the most frequent (49 %). The polimodal method based on length-frequency data also identified three age classes. Back-calculated total lengths at previous ages based in increments of growth in scales were 38.61 and 68.81 mm for individuals of 1 and 2 years, respectively. Conclusions: Three age classes (0, 1 and 2 years old) were determined for the populations of F. lima in La Purisima river, based on the interpretation of annual growth rings in scales and in the modal distribution of observed length frequencies. All the populations examined showed a positive allometric growth (b > 3.0).

Further observations on scorpion genera Hadrurus and Hoffmannihadrurus (Scorpiones, Caraboctonidae).

Multiple populations of Hadrurus pinteri from Baja California Sur, Mexico have been examined. It is demonstrated that the southern populations of this species have a larger number of accessory trichobothria (neobothriotaxy) than the northern populations, numbers exceeding the maximum currently recorded for the genus. Examination of carapace and chela coloration and its patterns show a close affinity between Hadrurus pinteri and the dark phase of Hadrurus concolorous. A new morphometric ratio of the carapace is defined that distinguishes Hadrurus from Hoffmannihadrurus, further supporting the monophyly of the latter genus.

Incremento de la temperatura ambiental y su posible asociación al suicidio en Baja California Sur (BCS) 1985-2008 / Environmental temperature increase and its possible association with suicide in the population of Baja California Sur (BCS) 1985-2008

Introduction During the last decade we have observed important climate changes, especially in environmental temperatures. There is considerable information linking the increase in hot weather and human health. For example, hot weather is associated with an increased risk of suicide in different countries around the world. Objective To evaluate the relationship between suicide rates and the environmental temperature in Baja California Sur, Mexico, from 1985 to 2008. Method Suicide mortality data for Baja California Sur (BCS) were obtained for the years 1985-2008 from the Instituto Nacional de Estadística, Geografía e Informática (INEGI). The selected codes were: E950-E959 (ICD-9) and X60-X84, Y87.0 (ICD-10) for BCS. The BCS weather data used was the maximum temperature from 1985 to 2008, obtained from the Extractor Rápido de Información Climatológica (ERIC III). Lineal and quadratic models were used to assess the annual rate changes of suicide and generalized lineal models (GLM) to assess the effect of the climatological variables to the suicide rate. The p≤0.05 was considered significant. Results In BCS, 582 suicide deaths were reported from 1985 to 2008. The 9% (53) of the total reported were women with a yearly average rate 1.6/100 000; 91% (529) were men with a yearly average rate 16.3/100 000. Lineal and quadratic models explained the tendency of the annual increment observed in the number of suicides in both seasons. The quadratic model better explained such increment during the warmer months (R²=0.64 p<0.01). The temperature was positively correlated with the rate of suicides in both seasons (p<0.01). Two predictive GLMs were created by season. Discussion These results suggest a potential link between an increase in environmental temperature and the rates of suicide during 24 years in BCS. This relationship is clear during the hot season; however, a positive trend was found during the cold season, perhaps due to the result of warmer winters.

Introducción Durante las últimas décadas se ha podido apreciar un cambio en las variables climáticas, en especial en la temperatura ambiental. Hay evidencias que asocian el aumento de la temperatura ambiental con el incremento en las tasas de mortalidad por suicidio. Objetivo Evaluar la relación entre la tasa de suicidio y la temperatura ambiental en Baja California Sur (BCS) durante los años 1985-2008. Método Los datos de suicidio fueron obtenidos de las bases de Mortalidad del INEGI de 1985-2008. Se tabularon los registros con códigos: E950-E959 CIE-9 y X60-X84, Y87.0 CIE-10 para BCS. En el análisis climático se usaron las temperaturas máximas de 1985 al 2008 para BCS del Extractor Rápido de Información Climatológica (ERIC III). Para evaluar la tendencia, se utilizaron modelos de regresión lineal y cuadráticos. Los modelos lineales generalizados (GLM) se utilizaron para evaluar el efecto de las variables ambientales sobre la tasa de suicidios, con una significancia de p≤0.05. Resultados Un total de 582 suicidios ocurrieron en BCS de 1985 a 2008. Las mujeres representaron el 9% (53), con tasa anual promedio de 1.6/100 000. Los hombres 91% (529), con tasa promedio anual de 16.3/100 000. La tendencia de incremento anual se explicó con modelos lineales simples y cuadráticos en ambas temporadas. En los meses cálidos el modelo cuadrático explicó mejor dicho incremento (R²=0.64 p<0.01). La temperatura se correlacionó positivamente con la tasa en ambas temporadas (p<0.01). Se generaron dos modelos GLM predictivos por temporada. Discusión En este trabajo se observó una posible relación entre el incremento de la temperatura ambiental y el número de suicidios registrados durante 24 años en BCS. Esta relación se encuentra bien definida en los meses cálidos, pero con una tendencia en aumento para los meses fríos.

Relación entre las capturas de Megapitaria squalida (Bivalvia: Veneridae) y la temperatura superficial del mar en la Bahía de la Paz, Baja California Sur, México

Megapitaria squalida (Bivalvia: Veneridae) fishery landings and temperature relationship in Bahía de la Paz, México. The clam Megapitaria squalida is a fishing resource with increasing importance in Northwestern Mexico. Nevertheless, this fishery has shown important variations that could be related to environmental factors. To assess this, monthly landings of M. squalida were analyzed during 2002-2005 for Bahía de La Paz, B.C.S., and were related with monthly time series of sea surface temperature, derived from MODIS-Aqua Sensor. The results showed a positive and significant relationship between sea surface temperature and clam landings. The likely impact of anomalous conditions of sea temperature on this resource is discussed. Rev. Biol. Trop. 59 (1): 151-157. Epub 2011 March 01.

La almeja chocolate Megapitaria squalida es un recurso pesquero con creciente importancia en el noroeste de México al registrarse un incremento en los volúmenes de captura. Sin embargo, esta pesquería ha observado variaciones importantes en las capturas que podrían estar relacionadas con factores ambientales. Se obtuvieron datos mensuales de producción de M. squalida durante 2002- 2005 y se estimaron series de tiempo de temperatura superficial del mar en la Bahía de La Paz B.C.S. a partir de imágenes mensuales derivadas del sensor MODIS-Aqua. Los resultados indican una relación positiva significativa entre la temperatura superficial del mar y los volúmenes de captura, razón por la cual nuestro trabajo tiene como objetivo estudiar las relaciones entre capturas de Megapitaria squalida (Bivalvia: Veneridae) y la temperatura superficial del mar en La Bahía de la Paz, Baja California Sur, México.

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (%N) and volume (%V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (%RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener’s resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat. Rev. Biol. Trop. 59 (4): 1669-1678. ...

Fundulus lima habita sistemas de aguas continentales, y se encuentra amenazado tras la introducción de cíclidos en el área de estudio. Para poder llevar a cabo programas de conservación, fue determinada la dieta de la sardinilla peninsular en peligro de extinción, en dos sistemas de oasis de Baja California Sur, México (cuencas de los rios San Ignacio y La Purísima), durante las épocas secas y de lluvias. Una gran proporción de arena fue encontrada en el contenido estomacal de este pez para ambas cuencas (39% y 47%, respectivamente). La composición de la dieta fue similar entre ambas cuencas (74%), como también dentro de sus respectivas clases de tallas; sin embargo, fue diferente entre sexos. Durante la época de secas, F. lima consumió principalmente diatomeas, larvas de dípteros y tricópteros, además de escamas de peces; mientras que en la época de lluvias tuvo preferencia por las larvas de dípteros, algas filamentosas y ostrácodos. Este pez exhibe una estrategia alimentaria de tipo oportunista durante la época de lluvias, la cual cambia a tipo especialista en la época de secas. Esta información será la base para futuras investigaciones relacionadas con la conservación de esta especie, en peligro de extinción, y su hábitat.

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

Growth and mortality of the mother-of-pearl Pinctada mazatlanica in natural populations of the east coast of Baja California Sur, Mexico. 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: = 193.31 mm, k = 0.54 year-1, t0 = -0.1805 year, C = 0.49 and WP = 0.75. The growth performance index was ’ = 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. Rev. Biol. Trop. 57 (1-2): 53-61. Epub 2009 June 30.

La madreperla Pinctada mazatlanica esta en veda desde 1939 y considerada en peligro de extinción, cambiando su categoría a protección especial en 1994. El presente estudio estima su crecimiento y mortalidad en bancos naturales en el periodo 1992-93 y 1997-99. Se registró el alto de la concha de ostras en poblaciones desde el paralelo 28º a 23º LN del litoral oriental de Baja California Sur, abarcando 38 estaciones, 2 bahías y 6 islas. La longitud máxima estimada fue 187.22mm (179.83-195.81mm, P > 0.95). Las frecuencias de longitud se ordenaron en un "año virtual". Los parámetros de crecimiento de von Bertalanffy estimados con el programa ELEFAN I fueron: o = 193.31mm, k=0.54año-1, t0= -0.1805 años, C=0.49 y WP=0.75; el índice de desempeño del crecimiento fue’=4.305. La mortalidad total fue de Z=2.03 año-1 por longitud convertida a curva de captura. La regresión peso total y la altura tuvo la expresión W(i)=0.0005418 * L(i)2.7301. Los parámetros de crecimiento fueron similares a los de Pinctada margaritifera de bancos de mar abierto y diferentes a aquellos de ostras perleras en repoblamiento en bahía de La Paz. La mortalidad mostró valores parecidos a los estimados para Pinctada radiata del Mar Rojo.

Crecimiento y mortalidad de la concha nácar Pteria sterna en bancos silvestres de Baja California Sur, México

Growht and mortality of the mollusk Pteria sterna in wild banks of Southern Baja California, Mexico. The Gulf of California nacre shell Pteria sterna is an important marine resource in Mexico, and the main species for "half" and round pearl production in the American continent. Wild spat can only be extracted legally for research or culture activities. This study calculates growth and mortality parameters for wild stocks in the eastern coast of Southern Baja California. Height’s data (353 dorso-ventral measurements) were taken from 1997 to 1999 at Santa Rosalía, Mulegé and Loreto Bay coast. The maximum length was estimated at 130.35 mm (124.22-136.48 mm, p>0.95). The length frequency data were set in a "virtual year". Seasonal von Bertalanffy growth parameters were calculated in the ELEFAN I routine, the values are: L∞ = 156.02 mm, k = 0.48 year-1, t0 = -0.216 years, C = 0.43, WP = 0.73. and t s = 0.5. The growth performance index was Φ’ = 4.068. The total mortality was calculated from length-converted catch curve Z = 3.34 year-1. The length-weight relationship was fixed for the equation W = 0.000756 * L(i)2.7075 (r²= 0.90, n = 233). The growth parameters values in experimental repopulation conditions are quite different, in contrast with the growth estimated in wild stocks oysters. The value of total mortality is similar to the estimations for Pinctada fucata populations from the Red Sea and P. radiata from the Mediterranean Sea. Rev. Biol. Trop. 57 (3): 659-670. Epub 2009 September 30.

La concha nácar Pteria sterna sustenta los perlicultivos en México, y es la base de producción de perlas en el continente Americano. Está bajo protección especial desde 1994, y solo puede capturarse semilla natural para cultivo e investigación. Determinamos su crecimiento y mortalidad en bancos silvestres, registrando la altura de ostras de Santa Rosalía, Mulegé y Bahía de Loreto (1997-99). La longitud máxima estimada fue 130.35 mm (124.22-136.48 mm, P>0.95). Las frecuencias de longitudes se ordenaron en un "año virtual" (Guanco 1991). Los parámetros de crecimiento de von Bertalanffy estimados con el programa ELEFAN I fueron: L∞= 156.02 mm, k=0.48año-1, t0=-0.216 años, C= 0.43 y WP = 0.73; el índice de desempeño de crecimiento fue Φ’ = 4.068. La mortalidad total fue de Z = 3.34 año -1por longitud convertida a curva de captura. La regresión del peso total y la altura tuvo la expresión W = 0.000756 * L(i)2.7075 (r²=0.90, n=233). Mostramos la diferencia entre los parámetros de crecimiento en condiciones de repoblamiento experimental y aquellos de individuos silvestres de P. sterna. El valor de mortalidad total es comparable a aquellos de Pinctada fucata en el mar Rojo o P. radiata en el mar Mediterráneo.

Composición taxonómica y relaciones zoogeográficas de los peces demersales de la costa occidental de Baja California Sur, México

Taxonomic composition and zoogeographic relations of demersal in the western coast of Baja California Sur, Mexico. The composition of demersal fish along the western coast of the State of Baja California Sur, México, including the limit of the northern distribution of the ichthyofauna of the eastern tropical Pacific, is presented. The survey was carried out on four oceanographic cruises between autumn 2004 and March 2006. Of 220 species in 132 genera and 73 families, 26.3% are species of wide distribution from San Diego County, USA to Panama and 21.7% are species restricted to the eastern tropical Pacific. Six species are new findings for the area or range expansions. The families with the most species are Paralichthyidae and Scorpaenidae, each with 16 species. The most frequent genus was Sebastes, with nine species. We present a table with common Spanish names, size range and status of each species inside the community. Rev. Biol. Trop. 56 (4): 1765-1783. Epub 2008 December 12.

Se presenta la composición sistemática de peces demersales de la costa occidental de Baja California Sur, límite de distribución norte de la ictiofauna del Pacífico Oriental Tropical. Se realizaron cuatro cruceros oceanográficos durante otoño de 2004 a marzo de 2006. Este listado incluye 220 especies, 132 géneros y 73 familias. El 26.3% corresponde a especies de amplia distribución desde la Provincia de San Diego a la Provincia Panámica y el 21.7% son especies restringidas a la región del Pacífico Oriental Tropical. Seis especies representan nuevos registros para la zona o ampliación de su ámbito de distribución. Las familias mejor representadas en número de especies fueron Paralichthyidae y Scorpaenidae, con 16 especies cada una. El género mejor representado fue Sebastes con 9 especies. Se presentan los nombres comunes, intervalo de tallas y el estatus de cada especie dentro de la comunidad.

Estructura de la comunidad y asociación de las aves acuáticas con la heterogeneidad espacial del complejo lagunar Bahía Magdalena-Almejas, Baja California Sur, México / Community structure and association of waterbirds with spatial heterogeneity in the Bahia Magdalena-Almejas wetland complex, Baja California Sur, Mexico

Community structure and association of waterbirds with spatial heterogeneity in the Bahia Magdalena-Almejas wetland complex, Baja California Sur, Mexico. To test the hypothesis that spatial heterogeneity determines waterbird diversity in a coastal wetland, we compared waterbird density, diversity, and species composition among various habitats and landscapes units in Bahia Magdalena-Almejas, Baja California Sur, Mexico. Based on diversity patterns and bird distribution, we assessed the effect of coastal development on the waterbird community structure. To gather information on habitat features and waterbird populations we conducted waterbird censuses in 329 habitat segments along the internal coastline of the study area, from February 2002 to February 2003. We performed non-parametric analyses to test the null hypothesis of no diference on waterbird density, and diversity among landscape units and seasons. The species composition was evaluated using ordination techniques. Waterbird density was higher in winter and autumn in the three lagoons of the study area, particularly in the insular coast, sandy beach and dunes; it was higher in the few segments of antropic sustrate. Diversity was significantly higher in mangrove habitat along the peninsular coast, and in mangrove-dunes association on the insular coast. Although modification of coastal natural habitat and boat transit disturbance had no influence on waterbird density or diversity, the highest richness of waterbirds occurred in well preserved areas. Species composition analysis showed differences between Santo Domingo Channel and Magdalena Bay. Pelagic and mangrove habitat had a species composition difference higher than those associations in other habitats. Such differences in species assemblages by habitat and landscape units suggest that communities are structured according to the range of available natural resources in structurally complex habitats, and that dominant piscivorous waterbird species...

Para probar la hipótesis que la heterogeneidad espacial determina la diversidad de aves acuáticas en un humedal costero, comparamos la densidad, diversidad y composición de especies de aves acuáticas entre habitats y otras unidades de paisaje del complejo Bahía Magdalena-Almejas, Baja California Sur, México. Se realizaron censos de aves acuáticas en 329 segmentos de habitat de la línea de costa interna del complejo lagunar, desde febrero 2002 hasta febrero 2003. La densidad de aves fue mayor en invierno y otoño en las tres lagunas del área de estudio; de las zonas, la densidad fue mayor en la costa insular; y de los habitats en playa arenosa y dunas pero en los pocos segmentos de sustrato antrópico la densidad fue alta. La diversidad fue significativamente mayor en otoño; en Canal Santo Domingo; en la costa peninsular; y de los habitats en manglar-dunas y manglar. La modificación del habitat natural costero y el disturbio por tránsito de embarcaciones no tuvieron influencia en la densidad o diversidad de aves acuáticas, pero la riqueza acumulada mayor ocurrió en las costas bien conservadas y sin disturbio. El análisis de la composición de especies mostró diferencias entre las asociaciones de Canal Santo Domingo y Bahía Magdalena. El ambiente pelágico y el manglar tuvieron diferencia mayor en la composición de especies con respecto a las asociaciones de los demás habitats, tales diferencias en elencos de especies por habitat sugieren que la comunidad de aves está estructurada de acuerdo a los recursos naturales disponibles de las lagunas, zonas y habitats, en relación con la complejidad estructural de las unidades de paisaje. Las condiciones ecológicas del complejo lagunar ocasionan que las aves acuáticas piscívoras sean el grupo dominante de esta comunidad.