Freshwater species and habitats are among the most threatened in the world. One way in which this growing conservation concern can be addressed is the creation of freshwater protected areas. Here, we present three strategies for freshwater protected-area design and management: whole-catchment management, natural-flow maintenance, and exclusion of non-native species. These strategies are based on the three primary threats to fresh waters: land-use disturbances, altered hydrologies, and introduction of non-native species. Each strategy draws from research in limnology and river and wetland ecology. Ideally, freshwater protected areas should be located in intact catchments, should have natural hydrological regimes, and should contain no nonnative species. Because optimal conservation conditions are often difficult to attain, we also suggest alternative management strategies, including multiple-use modules, use of the river continuum concept, vegetated buffer strips, partial water discharges, and eradication of exotic species. Under some circumstances it may be possible to focus freshwater conservation efforts on two key zones: adjacent terrestrial areas and headwaters. Áreas Protegidas de Agua Dulce: Estrategias para la ConservaciónResumen: Las especies y hábitats de agua dulce se encuentran entre los más amenazados del mundo. Una forma en la que esta creciente preocupación por la conservación puede ser abordada es la creación de áreas protegidas de agua dulce. Aquí presentamos el diseño de tres áreas protegidas de agua dulce y las estrategias de manejo: manejo global de la cuenca de captación, mantenimiento del flujo natural y exclusión de las especies no nativas. Estas estrategias están basadas en las tres amenazas principales que tienen las aguas dulces: perturbaciones por uso del suelo, hidrologías alteradas e introducciones de especies no nativas. Cada estrategia está planteada como resultado de la investigación en limnología y ecología de ríos y pantanos. Idealmente, las aguas protegidas de agua dulce deberán ser ubicadas en cuencas de captación intactos, que tengan regímenes hidrológicos naturales y que no contengan especies no nativas. Puesto que las condiciones óptimas de conservación son frecuentemente difíciles de alcanzar, también sugerimos estrategias alternativas de manejo que incluyen módulos de uso múltiple, uso del concepto de río continuo, bandas de amortiguamiento con vegetación, descargas parciales de agua y erradicación de especies exóticas. Bajo ciertas circunstancias, puede ser posible enfocar los esfuerzos de conservación de aguas dulces en dos zonas clave: áreas adyacentes terrestres y nacientes.

Two trials were conducted at the Mexican National Institute of Agricultural Research (INIA) experimental station, Yaqui Valley, Sonora, Mexico, to determine the genetic yield potential of bread wheat (Triticum aestivum L.) cultivars released in northwest Mexico over the period from 1950 to 1982, with emphasis on progress since 1970. Nonlimiting levels of fertility and moisture, a preventative pest and disease program, and netting to prevent lodging were used. Grain yield, yield components, and rates of phytomass production and grain filling were determined. Yield data on selected genotypes grown in 4 yrs of the International Spring Wheat Yield Nursery (ISWYN) at the same station were also examined. The grain yield potential of cultivars, successively released since 1950, has risen at an estimated (from a regression slope) average of 59 kg/ha/yr of release, or about 1.1%/yr. Although yield potential may have plateaued in the early 1970s, cultivars released since 1979, i.e., modern genotypes (e.g., ‘Ciano 79’, ‘Genaro 81’, ‘Glennson 81’, and ‘Seri 82’) have improved yield potential at an estimated rate similar to that prior to 1970. Improvements in grain yield were associated with increases in grain number per unit area (r = 0.74, P < 0.01), which has risen by about 34% in modern genotypes compared to pre‐1970 cultivars, and grain number per spike (r = 0.51, P<0.05). The 1000‐grain weight, was reduced slightly in the modern high grain number cultivars (r = −0.76, P<0.01). Harvest indices for modern genotypes were lower than those of the landmark cultivar ‘Yecora 70’, but the modern genotypes had, on average, 16% greater phytomass than pre‐1970 cultivars. However, only 43% of the variation in grain yield was attributable to phytomass. The improvements in yield potential are mainly the result of empirical selection for grain yield. Indications were that rates of grain filling and phytomass production in modern genotypes were similar to those in Yecora 70. The higher grain yield and phytomass in modern genotypes compared to Yecora 70 was probably due to the formation and survival of a larger grain sink (more grains/m2) and greater C assimilation during a longer preanthesis phase.

Abstract-The application of autonomous robots to efficiently locate small wildlife species has the potential to provide significant ecological insights not previously possible using traditional landbased survey techniques, and a basis for improved conservation policy and management. We present an approach for autonomously localizing radio-tagged wildlife using a small aerial robot. We present a novel two-point phased array antenna system that yields unambiguous bearing measurements and an associated uncertainty measure. Our estimation and informationbased planning algorithms incorporate this bearing uncertainty to choose observation points that improve confidence in the location estimate. These algorithms run online in real time and we report experimental results that show successful autonomous localization of stationary radio tags and live radio-tagged birds.

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