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

We collected fishes from June of 1986 to February of 1987 at three sampling station; one in the Palo Seco estuary and the other two at Damas estuary (Damas and San Bosco), Central Pacific, Costa Rica. Water temperature didn’t show significant differences between the Damas and San Bosco stations, but did show differences between Damas-Palo Seco and San Bosco-Palo Seco. The salinity changed significantly between the three stations and pH was very similar at all sities. We collected samples from 25 families, 39 genera and 54 species. Eighteen species are from all three sampling sites while seven came exclusively from Palo Seco; five from Damas and six from San Bosco. Out of all species collected, 7,41% are shared between Palo Seco and Damas; 3,70% between Palo Seco and San Bosco and 22,22% between Damas and San Bosco. Similarity analysis indicates that Damas and San Bosco stations share 41,40% of the species; while Palo Seco only showed 9,9% of common species with the group Damas-San Bosco. Most species are marine and they use these estuaries for breeding (42,59%) and feeding (40,74%). Freshwater specie, estuarines and occasional visitors are not well represented. The most diversity was found San Bosco and we found statistically significant differences in the H’ values among all three stations. The most similarities were found between Damas and San Bosco stations, suggesting that these areas are under a stronger influence from continental waters facilitating a better distribution of species. We concluded that the ichthyofauna from the studied estuaries is transitory at the sampling sites and that it is also heterogeneously distributed.

Since the need of having good population estimates to lower administrative areas in the post census periods, it has been proposed the possibility if using auxiliary variables as simple alternative to produce indirect estimates. These variables have been called “Symptomatic indicators” of population change. This article researches about them using information got from the last population and housing census of 2000. It is analyzed the contingence of the produced estimates to cantonal level according to the census value. On the other hand it is discussed the coherence of these results with the ones got in a previous study that was done to census of 1984. The results showed that the combination of the indicators: electoral census, births, primary school registration, can bring right estimates even though there is a strong international immigration. There were used four methods that showed to be a good alternative to get these population estimates.

Se analiza el efecto perturbador que una característica puede provocar en la relación entre dos o más variables. Se utilizó la información correspondiente a un cuestionario que se aplicó a una muestra de educadores de enseñanza primaria en 1998. Por medio de ejemplos concretos se observa como la relación entre dos variables que aparentan una dependencia estadística importante, desaparece cuando se controla su efecto con una tercera variable. Esto se debe a que las variables utilizadas para explicar un determinado fenómeno, en general, se encuentran muy correlacionados entre sí, y es precisamente esa correlación la que algunas veces provoca un efecto espurio sobre la relación original. Los análisis se efectúan por medio de tablas de contingencia y contrastes Chi-Cuadrado para independencia estadística. Estas herramientas mostraron su utilidad para determinar algunos de los efectos confusores entre las variables.

Simulation Monte Carlo is an effective technique used to analyze the critical path in a project, this simulation will be used to estimate the probability of finishing the project on time. Monte Carlo is necessary due to the hight uncertainty showed in the estimations of time operations from the differents activities in the project. For facility the calculations, @Crystal Ball software is a popular spreadsheet add-in used for simulations and risk analysis.

Se realizó un estudio para evaluar el efecto de tres dietas sobre el crecimiento de alevines de Ictalurus balsanus en condiciones de laboratorio. La talla inicial de los peces fue 39.68 ± 2.0 mm de longitud total y 411.47 ± 17.00 mg de peso corporal, colocados en grupos de 10 peces por acuario de 80L. Los bagres fueron alimentados con tres dietas diferentes: I(31,13% proteína, 2,70% grasa, 56,53% carbohidratos), II(39,12%, 3,0%, 35,0%), III(53,57%, 19,37%, 4,17%). Los resultados indican que el incremento en el peso y en la longitud total de I. balsanus fueron mayores (P<0.05) con la dieta III(Daphnia sp., 53,57% proteína), respecto a la dieta I(31,13% proteína) y la dieta II(39,12% proteína). Los mayores incrementos 32.10 mg/día y 0.30 mm/día están relacionados directamente con la mayor concentración de proteína del alimento. La tasa de crecimiento específico para el peso y la longitud fueron 12,33% y 8,92% mayor(P<0.05) con la dieta III. La sobrevivencia no difirió (P>0.05) entre los peces nutridos con los distintos alimentos. Por lo que se concluye que las características propias del alimento vivo y, en particular, la alta concentración proteica de Daphnia sp. Generaron mayor incremento en la tasa de crecimiento especifico de I. balsanus.

Germination and in vitro culture of three species of figs: Ficus obtusifolia Kunt, F. jimenezii Standl and F. morazaniana Burger were studied Semi-ripen seeds of these species were distributed in four types of substrates (culture medium, sand, soil and newspaper) under three different conditions (in vitro, ambient and greenhouse). In vitro germination and micropropagation was only possible in F. jimenezii due to the fact that seeds of the other species presented high bacterial contamination. This was also the best method for the production of this species. The newspaper substrate showed high germination percentages in the three test species and this facilitated the transference of plantlets to other substrates for their growth under in vitro conditions. F. obtusifolia and F. jimenezii showed the lowest germination percentages in the sand substrate 60% y 10% respectively. The germination of F. obtusifolia and F. morazaniana was possible in pots under greenhouse conditions but the plantlets growth was lower with respect to other methods evaluated. For those plantlets germinated under ambient conditions the best growth was obtained in closed flasks with pit substrate placed in a growth chamber with a photoperiod of 16 hrs light and a light intensity of 30 μE m-2s-1. Plants developed well in the greenhouse where they were fertilized and grew for a period of 12 months.