18,798 research outputs found
First Record of the Mosquitoes \u3ci\u3eAedes Dupreei Psorophora Horrida,\u3c/i\u3e and \u3ci\u3ePsorophora Mathesoni\u3c/i\u3e (Diptera: Culicidae) in St. Joseph County, Indiana
(excerpt)
Adult females of Aedes (Ochlerotatus) dupreei (Coquillett), Psorophora (lanthinosoma) horrida (Dyar and Knab), and Psorophora (Janthinosoma) mathesoni (Belkin and Heinemann) were collected on 18 and 19 June 1981, in an oak woodlot in South Bend, Indiana
A video method for quantifying size distribution, density, and three-dimensional spatial structure of reef fish spawning aggregations
There is a clear need to develop fisheries independent methods to quantify individual sizes, density, and three dimensional characteristics of reef fish spawning aggregations for use in population assessments and to provide critical baseline data on reproductive life history of exploited populations. We designed, constructed, calibrated, and applied an underwater stereo-video system
to estimate individual sizes and three dimensional (3D) positions of Nassau grouper (Epinephelus striatus) at a spawning aggregation site located on a reef promontory on the western edge of Little Cayman Island, Cayman Islands, BWI, on 23 January 2003. The system consists of two free-running camcorders mounted on a meter-long bar and supported by a SCUBA diver. Paired video “stills” were
captured, and nose and tail of individual fish observed in the field of view of both cameras were digitized using image
analysis software. Conversion of these two dimensional screen coordinates to 3D coordinates was achieved through a matrix inversion algorithm and calibration data. Our estimate of mean total length (58.5 cm, n = 29) was in close agreement with estimated lengths from a hydroacoustic
survey and from direct measures of fish size using visual census techniques. We discovered a possible bias in length
measures using the video method, most likely arising from some fish orientations that were not perpendicular with respect to the optical axis of the camera system. We observed 40 individuals occupying a volume of 33.3 m3, resulting in a concentration of 1.2 individuals m–3 with a mean (SD) nearest neighbor distance of 70.0 (29.7) cm. We promote the use of roving diver stereo-videography as a method to assess the size distribution, density, and 3D spatial structure of fish spawning aggregations
Nassau grouper (Epinephelus striatus) spawning aggregations: hydroacoustic surveys and geostatistical analysis
With the near extinction of many spawning aggregations of large grouper and snapper throughout the Caribbean, Gulf of Mexico, and tropical Atlantic, we need to provide baselines
for their conservation. Thus, there is a critical need to develop techniques for rapidly assessing the remaining known
(and unknown) aggregations. To this end we used mobile hydroacoustic surveys to estimate the density, spatial extent, and total abundance of a Nassau grouper spawning aggregation at Little Cayman Island, Cayman Islands, BWI.
Hydroacoustic estimates of abundance, density, and spatial extent were similar on two sampling occasions. The location
and approximate spatial extent of the Nassau grouper spawning aggregation near the shelf-break was corroborated by diver visual observations. Hydroacoustic density estimates were, overall, three-times higher than the average density observed by divers; however, we note that in some instances diver-estimated densities in localized
areas were similar to hydroacoustic density estimates. The resolution of the hydroacoustic transects and geostatistical
interpolation may have resulted in over-estimates in fish abundance, but still provided reasonable estimates of total spatial extent of the aggregation. Limitations in bottom time for scuba and visibility resulted in poor coverage of the entire Nassau grouper aggregation and low estimates
of abundance when compared to hydroacoustic estimates. Although the majority of fish in the aggregation were
well off bottom, fish that were sometimes in close proximity to the seafloor were not detected by the hydroacoustic survey. We conclude that diver observations of
fish spawning aggregations are critical to interpretations of hydroacoustic surveys, and that hydroacoustic surveys provide a more accurate estimate of overall fish abundance and spatial extent than diver observations. Thus, hydroacoustics is an emerging technology that, when coupled
with diver observations, provides a comprehensive survey method for monitoring spawning aggregations of fish
The adequacy of Victoria's protected areas for conserving its forest-dependent fauna
Networks of protected areas are a key component of efforts to conserve biodiversity. However, there are concerns about an uncritical focus on the percentage area of reserves without an assessment of how well formal reserves are actually protecting biodiversity. We completed a spatial analysis of the formal reserve system in the Australian state of Victoria. We quantified how well the reserve system captured a crude surrogate for vegetation communities (viz: Ecological Vegetation Classes) as well as distribution models for an array of threatened forest-dependent species. We found evidence of a high degree of overlap between areas subject to intensive forestry (clearcutting) operations and the modelled distribution of a suite of forest dependent species. A key outcome of our study was that areas around sites subject to past logging as well as new areas proposed for logging under the Timber Release Plan in Victoria had significantly higher values for threatened forest dependent species (as determined by habitat distribution models) than areas that had not been logged. We found significant differences in the spatial characteristics of the dedicated reserve systems and informal protected area networks, with the latter featuring much of its area close to a tenure boundary where logging occurs. Our empirical analyses demonstrating the impacts of ongoing logging operations on areas with high environmental suitability for threatened species has important implications. In particular, the current reserve system is inadequate for a suite of forest-dependent taxa, including Critically Endangered Leadbeater’s Possum (Gymnobelideus leadbeateri) and the vulnerable Greater Glider (Petauroides volans). This suggests a high degree of conflict between areas of high value for conservation and areas targeted for wood production.Threatened Species Recovery Hub, National Environmental Science Progra
Where there is fire, there is smoke
In his In Depth News story “Scientists aim to smoke out wildfire impacts” (1 June, p. 948), W. Cornwall discusses wildfire-generated smoke and the associated large quantities of particulate matter. We agree that research on smoke demands more sustained scientific attention, particularly given its impacts on human communities [e.g., (1)]. However, not all fires are created equal in terms of their (natural or deliberate) origins, the amount of biomass they consume, and the amount of smoke they generate as a result.
High-intensity wildfires (those exceeding 200,000 kW/m2) in very high biomass forests may consume 9 to 14% of the biomass (burning green parts of living trees but often leaving dense wood) or 40 to 58 tons per hectare (2). This is substantially less than half of the 140 to 450 tons of biomass per hectare consumed when logging slash (i.e., dense waste wood) is burned after logging operations in these same kinds of forest (3, 4).
Moreover, such logging burns consume at least 10 times as much biomass as hazard reduction burns designed to reduce wildfire risk (5). The smoke generated from logging therefore represents a substantial form of industrial pollution, but it is not treated as such. Beyond improving efforts to quantify the chemical composition of smoke and its long-term impacts on human health, there is an urgent need to examine the problem in a more holistic manner. This demands far more careful consideration of the origins of smoke, the relative amounts of smoke originating from different kinds of fires, and the forest and land use policies that generate smoke (and might reduce it)
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