The reproductive season of tilapia was studied by monthly samplings at Emiliano Zapata dam, Morelos State, Mexico. From February 1999 through 2000 a sample 50 fish taken from the commercial catch (castnet, 6.5 cm mesh size). observed sex ratio 1:1.29 (females:males) (χ²=10.26; p<0.05). reached maturity 151.3 mm (females) and 152.0 (males) total length. Rainy (August) dry (February) seasons were determined as breeding period. Fecundity variation better correlated with length (r=0.7473;...

The reproductive cycle and diet of a population the viviparous lizard Sceloporus torquatus from Pedregal de San Angel, Distrito Federal, Mexico, were studied. Ovarian activity began in June, by October, one to five preovulatory follicles per ovary present Ovulation took place November December, parturition occurred late April or early May. Relative litter egg masses higher at end development than beginning. Testes increased size June through September, when they reached their maximum volume...

Variable bandwidth kernel density estimators increase the window width at low densities and decrease it where data concentrate. This represents an improvement over fixed estimators. In this article, we explore use of one implementation a variable estimator in conjunction with several rules procedures for selection applied to real datasets. The considered examples permit us state that when working tens or few hundreds observations, least-squares cross-validation rarely produces useful...

Age and growth of Nile tilapia (Oreochromis niloticus) were determined using 1 039 specimens collected in a tropical shallow lake Mexico, from January to December 1993. Standard length females ranged 9.0 16.5 cm males 8.9 14.8 cm. The standard length?weight relationships for all individuals was BW=0.1207 SL2.469. age data, derived opercular bone readings, used estimate the parameters von Bertalanffy equation: L8=17.88 cm, K=0.3409, to=-1.543, W8=149.21 g. oldest male female 2.5 years old....

SUMMARY Prorocentrum micans Ehrenberg , gracile Schütt and sigmoides Böhm are planktonic dinoflagellates present along the Mexican Pacific coast. These three species can be treated as a complex because of similar shape size. The taxonomy group has been based on cell form size, presence or absence apical spines ornamentation main valves. A morphometric study samples from 11 locations coast laboratory cultures is presented. mucron (small tooth) in antapical region P. morphotypes was recorded...

Fish assemblages change significantly with physical and chemical characteristics of water; however, their response to the variability geomorphic habitats has been rarely evaluated in lagoon-estuarine one these systems Mexican Pacific. Spatio-temporal variation fish assemblage structure was assessed for three habitats: lagoon, estuarine, channel inlet. The hypothesis that sheltered areas support comparatively higher richness abundance species, more small-sized specimens than most exposed...

The growth, mortality and migration pattern of the population Litopenaeus vannamei Boone 1931 in Carretas-Pereyra coastal lagoon system, Mexico, were studied. shrimp spatial distribution abundance analyzed relation to salinity, water temperature, substrate. A total 2 669 shrimps was collected at 22 sites sampled monthly from March 2004 August 2005. Juvenile L. present system throughout year, reaching densities 0.001 0.302 ind/m2. estimated daily growth rate 0.06 0.27 mm carapace length (CL)....

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The dolphinfish Coryphaena hippurus, is one of the main species caught by artisanal fisheries in Tehuantepec Gulf, Mexico.Age was estimated counting growth rings scales 266 fish.Dolphinfish size ranged from 20 to 140 cm Fork Length (Lf).The length-weight relationship showed negative allometry females and positive males.The between Lf scale radius for combined data both sexes as: = 37.829 R + 3.8209 (r 2 0.8276).The value Average Percent Error (1.3%) considered acceptable.An annual...

The ectothermic nature of reptiles makes them especially sensitive to global warming. Although climate change and its implications are a frequent topic detailed studies, most these studies carried out without making distinction between populations. Here we present the first study an Aspidoscelis species that evaluates effects warming on distribution using ecological niche modeling. aims our were (1) understand whether predicted warmer climatic conditions affect geographic potential different...

Abstract Ambient temperature is a primary factor affecting the physiology and activity of reptiles. Thermoregulation involves series mechanisms to maintain an organism’s body within narrow range. The study thermal ecology lizards relevant for understanding their distribution, life history, requirements. Moreover, determining how species are able attain physiologically active temperatures in challenging environments necessary assessing risk extinction due climate change, especially threatened...

Assessment of an artisanal shrimp fishery Litopenaeus vannamei in a lagoon-estuarine system based on the concept maximum sustainable yieldEvaluación de una pesquería artesanal del camarón

This paper, introduces the use of kernel density estimators (EDK's) as a modern tool for examining length-frequency distribution Litopenaeus vannamei in its estuarine stage. The data were obtained monthly at 22 sampling sites Carretas-Pereyra lagoon-estuarine system, from March 2004 to August 2005, covering both seasons year: dry and rainy. Shrimp caught with 4 m diameter cast net 10 mm mesh size. size each sample was analyzed by means EDK's, using Gaussian weight function bootstrap...

Antecedentes: Los estudios sobre los patrones de floración, sincronía floral y éxito reproductivo en cactáceas son incipientes muchas especies se desconoce prácticamente su biología reproductiva como ocurre con la cactácea globosa Neolloydia conoidea . Preguntas: ¿Cómo es el patrón floración a nivel poblacional? floral? ¿Existe relación entre reproductivo? Especie: Britton &amp; Rose (Cactaceae) Sitio estudio fechas: Municipio Tolimán Querétaro, México. Dos años observaciones (N = 146...

The Chilean round ray (Urotrygon chilensis, Günther, 1872) is commonly caught as bycatch in the Mexican Pacific, but changes its reproductive ecology a consequence of fishery effects have never been investigated. In this work, species was determined Southern Gulf California (SGC). Total length (TL) ranged from 11.4 to 51.6 cm, and females were larger than males. Size at maturity (TL50) estimated 27.5 cm for 25.3 seasonal variation mature individuals, presence pregnant females, mean oocyte...

In order to answer this question, we compare intragonadal contents of testosterone (T) in males two neighboring populations Peromyscus melanotis J. A. Allen and Chapman, 1897, that differin their population density its seasonal fluctuations, even though they inhabit quite similar habitat conditions. Although an affirmative question would corroborate the idea androgen has a density-dependent effect, since it been proposed T increases at low densities vice versa, our results did not confirm...