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171.
Edward P. Glenn Christopher Lee Richard Felger Scott Zengel 《Conservation biology》1996,10(4):1175-1186
The lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. No river water is officially appropriated to support delta wetlands, yet large marsh areas of conservation interest still exist below the agricultural fields in Mexico. These are supported by flood water, agricultural drainage water, municipal sewage effluent, and seawater in the intertidal zone. From 1973 to 1993 the area of freshwater and brackish marsh varied widely, from 5800 to 63,000 ha. A new opportunity exists to restore wetlands in the delta now that the upstream water impoundments on the Colorado River are filled and flood flows are once again being directed to the delta. But flood control structures now channel most of the flood water directly to the sea, and most of the effluent waters are deposited in evaporation basins rather than used to support wetlands. If the Yuma Desalting Plant in the United States becomes operational and if the Rio Hardy wetlands continue to be drained, the area of brackish wetlands could decrease to less than 2000 ha in the near future. Preserving the remaining wetlands will require a binational water management plan. The plan should maximize the benefits to wetlands of flood and irrigation return flows that enter the delta, and it should minimize flood risks. 相似文献
172.
The regulation of pollen foraging by honey bees: how foragers assess the colony's need for pollen 总被引:2,自引:0,他引:2
Scott Camazine 《Behavioral ecology and sociobiology》1993,32(4):265-272
Summary The honey bee colony presents a challenging paradox. Like an organism, it functions as a coherent unit, carefully regulating its internal milieu. But the colony consists of thousands of loosely assembled individuals each functioning rather autonomously. How, then, does the colony acquire the necessary information to organize its work force? And how do individuals acquire information about specific colony needs, and thus know what tasks need be performed? I address these questions through experiments that analyze how honey bees acquire information about the colony's need for pollen and how they regulate its collection. The results demonstrate features of the colony's system for regulating pollen foraging: (1) Pollen foragers quickly acquire new information about the colony's need for pollen. (2) When colony pollen stores are supplemented, many pollen foragers respond by switching to nectar foraging or by remaining in the hive and ceasing to forage at all. (3) Pollen foragers do not need direct contact with pollen to sense the colony's change of state, nor do they use the odor of pollen as a cue to assess the colony's need for pollen. (4) Pollen foragers appear to obtain their information about colony pollen need indirectly from other bees in the hive. (5) The information takes the form of an inhibitory cue. The proposed mechanism for the regulation of pollen foraging involves a hierarchical system of information acquisition and a negative feedback loop. By taking advantage of the vast processing capacity of large numbers of individuals working in parallel, such a system of information acquisition and dissemination may be ideally suited to promote efficient regulation of labor within the colony. Although each individual relies on only limited, local information, the colony as a whole achieves a finely-tuned response to the changing conditions it experiences. 相似文献
173.
Glenn T. Crossin Scott G. Hinch Steven J. Cooke David W. Welch Sonia D. Batten David A. Patterson Glen Van Der Kraak J. Mark Shrimpton Anthony P. Farrell 《Marine Biology》2007,152(4):905-918
Adult sockeye salmon (Oncorhynchus nerka, N = 179) from six Fraser River populations (British Columbia) were intercepted in continental shelf waters ∼215 km from the
Fraser River mouth, gastrically implanted with acoustic transmitters, non-lethally biopsied for blood biochemistry, gill Na+,K+-ATPase activity and somatic energy density and then released. Migration behaviour and travel times to the river mouth and
into the river were monitored by underwater telemetry receivers positioned at the river mouth and in the river. Post-release
survival of salmon was excellent, with 84% (N = 150) of fish reaching the furthest receiving station ∼85 km upriver. Fish from Late-summer run populations (Adams and Weaver
Creek) averaged a migration rate of ∼20 km day−1 through the marine area and held at the river mouth and adjacent areas for 7–9 days before entering the river. Summer-run
populations (Birkenhead, Chilko, Horsefly and Stellako) had a migration rate ∼33 km day−1 and held for only 1–3 days. Once in river, similar patterns were observed: Late-run populations migrated at ∼28 km day−1 and Summer-run populations at ∼40 km day−1. From point of release to the river mouth, males migrated faster than females, but once in river migration rates did not
differ between sexes. Among all females, a correlation was discovered between levels of circulating testosterone and river
entry timing. This correlation was not observed among males. Plasma K+, Cl−, glucose, lactate and osmolality were also correlated with entry timing in both sexes. 相似文献
174.
Jeffrey Conner Scott Camazine Daniel Aneshansley Thomas Eisner 《Behavioral ecology and sociobiology》1985,16(2):115-118
Summary The tenebrionid beetle Bolitotherus cornutus everts a pair of quinone-producing defensive glands in response to mammalian breath. Experiments with a controlled airstream indicate that the beetle recognizes breath on the basis of temperature, humidity, and airflow dynamics. Under attack by mice the beetle everts the glands immediately upon being mouthed and may secure its release as a result. Against ants the beetle is protected by its tough exoskeleton and usually refrains from everting the glands. Other arthropods also show defensive responses when breathed upon.Paper No. 77 of the series Defense Mechanisms of Arthropods 相似文献
175.
176.
Long-term environmental monitoring places a set of demands on a sampling strategy not present in a survey designed for a single time period. The inevitability that a sample will become out of date must be a dominant consideration in planning a long-term monitoring programme. The sampling strategy must be able to accommodate periodic frame update and sample restructuring in order to address changes in the composition of the universe and changes in the perception of issues leading to new questions and concerns. The sampling strategy must be capable of adapting to such changes while maintaining its identification as a probability sample and its capacity to detect trends that span the update occasions. These issues are examined with respect to sub-population estimation, post-stratification via conditioning, and sample enlargement and reduction. Design features that involve complex sample structure create potentially serious difficulties, whereas an equal probability design permits greater adaptability and flexibility. Structure should be employed sparingly and in awareness of its undesirable effects. 相似文献
177.
Gregory W Whitledge Charles F Rabeni Gust Annis Scott P Sowa 《Ecological applications》2006,16(4):1461-1473
Moderation of stream temperatures by riparian shading and groundwater are known to promote growth and survival of salmonid fishes, but effects of riparian shade and groundwater on to be growth of warmwater stream fishes are poorly understood or assumed to be negligible. We used stream temperature models to relate shading from riparian vegetation and groundwater inflow to summer water temperatures in Missouri Ozark streams and evaluated effects of summer water temperatures on smallmouth bass, Micropterus dolomieu, growth using a bioenergetics model. Bioenergetics model simulations revealed that adult smallmouth bass in non-spring-fed streams have lower growth potential during summer than fish in spring-fed streams, are subject to mass loss when stream temperatures exceed 27 degrees C, and will likely exhibit greater interannual variation in growth during summer if all growth-influencing factors, other than temperature, are identical between the two stream types. Temperature models indicated that increased riparian shading will expand the longitudinal extent of thermal habitat capable of supporting adult smallmouth bass growth in spring-fed stream reaches when mean daily air temperatures exceed 27 degrees C. Optimum growth temperature (22 degrees C) will be present only in spring-fed streams under these conditions. Potential for increasing shade through riparian restoration is greatest for streams <5 m wide and along north-south reaches of larger streams. However, temperature models also indicated that restoring riparian shading to maximum levels throughout a watershed would increase the total stream mileage capable of supporting positive growth of adult smallmouth bass by only 1-6% when air temperatures are at or near average summer maxima; increases in suitable thermal habitat would be greatest in watersheds with higher spring densities. Riparian management for maintenance or restoration of the thermal habitat of adult smallmouth bass during summer should be focused in areas strongly influenced by groundwater. Restoring riparian shading along spring-fed warmwater streams will likely benefit adult smallmouth bass growth and may ultimately influence population sizes. 相似文献
178.
Laela S. Sayigh Peter L. Tyack Randall S. Wells Michael D. Scott A. Blair Irvine 《Behavioral ecology and sociobiology》1995,36(3):171-177
Signature whistles of 42 free-ranging bottle-nose dophin calves were compared to those of their mothers. Humans judged their similarity by inspection of spectrograms. There was a sex difference in the tendency of calves to produce whistles similar to or different from those of their mothers; most female calves produced whistles that were different from those of their mothers, whereas male calves were more likely to produce whistles that were similar to those of their mothers. Because matrilineally related females associate together and use signature whistles to establish and/or maintain contact with their calves, there may be a selective pressure for females to produce whistles that are distinct from those of their mothers. There may be fewer constraints governing whistle development in males, with the result that some males produce whistles similar to those of their mothers and others do not. 相似文献
179.
/ Tidal marshes have been actively restored in Connecticut for nearly 20 years, but evaluations of these projects are typically based solely on observations of vegetation change. A formerly impounded valley marsh at the Barn Island Wildlife Management Area is a notable exception; previous research at this site has also included assessments of primary productivity, macroinvertebrates, and use by fishes. To determine the effects of marsh restoration on higher trophic levels, we monitored bird use at five sites within the Barn Island complex, including both restoration and reference marshes. Use by summer bird populations within fixed plots was monitored over two years at all sites. Our principal focus was Impoundment One, a previously impounded valley marsh reopened to full tidal exchange in 1982. This restoration site supported a greater abundance of wetland birds than our other sites, indicating that it is at least equivalent to reference marshes within the same system for this ecological function. Moreover, the species richness of birds and their frequency of occurrence at Impoundment One was greater than at 11 other estuarine marshes in southeastern Connecticut surveyed in a related investigation. A second marsh, under restoration for approximately ten years, appears to be developing in a similar fashion. These results complement previous studies on vegetation, macroinvertebrates, and fish use in this system to show that, over time, the reintroduction of tidal flooding can effectively restore important ecological functions to previously impounded tidal marshes.KEY WORDS: Estuarine; Tidal marsh; Wetland birds; Restoration 相似文献
180.
Richard H. Shertzer David W. Hall Scott A. Steffy Rodney A. Kime 《Journal of the American Water Resources Association》1998,34(1):13-26
ABSTRACT: Spatial and temporal variability in rainfall concentrations of nutrients, major ions, and herbicides was monitored at 7 locations in or near the Conodoguinet Creek watershed in south-central Pennsylvania from 1991.1993. Results were used to (1) compare precipitation quality in forested, agricultural and urban areas, and (2) assess the practicality of using volunteer citizen monitoring in such a study. As indicated in previous studies, sulfate and nitrogen concentrations in precipitation were linked to sample pH. Concentrations of major ions in precipitation appeared to relate more to regional influences rather than local influences. However, concentrations of herbicides in precipitation may have been influenced by both regional and local use which caused compounds like atrazine, deethylatrazine, propazine, simazine, metolachior, alachlor, ametryn, and prometon to be present in detectable concentrations in rainfall. Seasonality was evident in nitrogen, sulfate, pH, and herbicide data and was suggested in calcium, iron, manganese, magnesium, orthophosphate, and chloride data. Agricultural weed control activities were probably responsible for the seasonal pattern in pesticide data which peaked in May and June. Tropical storm Danielle may have caused the apparent seasonal patterns for the other nine parameters. This storm did not follow the typical west to east movement pattern and consequently produced rainfall of relative high quality. A variety of quality assurance checks indicated that trained volunteer citizen monitors were successful participants in this intensive and extensive scientific study, collecting good quality samples in a timely manner. Without this kind of volunteer help, it is extremely difficult to complete studies that require sampling in response to natural events such as rainfall. 相似文献