11 resultados para habitat factors
em Aquatic Commons
Resumo:
This report was developed to help establish National Ocean Service priorities and chart new directions for research and development of models for estuarine, coastal and ocean ecosystems based on user-driven requirements and supportive of sound coastal management, stewardship, and an ecosystem approach to management. (PDF contains 63 pages)
Resumo:
The plant Crassula helmsii (Kirk) Cochayne, was likely to become widely distributed and to dominate many damp and wet areas of nature reserves, recreational waters and agricultural drainage of Britain. The aim of this report was to study Australian Swamp Stonecrop in its natural habitat where it is in balance with its environment. This contrasts with its rapid and widespread distribution in the U.K. where its growth interferes with the use of fisheries and amenity lakes but also reduces the value of nature reserves and sites of special scientific interest by suppressing native flora. It was proposed to observe its growth at a variety of sites over its natural distribution and to include some environmental factors, e.g. water-level, water-chemistry (nutrients, acidity and alkalinity), frost-tolerance, salinity, with the help of portable sensors, locally-available services or data. 8 weeks of travel in Australia allowed time to study the plant in its natural habitat including the coastal areas of the southern half of the continent i.e . Western Australia, South Australia, New South Wales, Victoria, Tasmania and southern Queensland. The overall objective was to determine the environmental range by visits to selected sites of Crassula helmsii over its geographic range.
Resumo:
A description of the foraging habitat of a cetacean species is critical for conservation and effective management. We used a fine-scale microhabitat approach to examine patterns in bottlenose dolphin (Tursiops truncatus) foraging distribution in relation to dissolved oxygen, turbidity, salinity, water depth, water temperature, and distance from shore measurements in a highly turbid estuary on the northern Gulf of Mexico. In general, environmental variation in the Barataria Basin marine environment comprises three primary axes of variability (i.e., factors: temperature and dissolved oxygen, salinity and turbidity, and distance and depth) that represent seasonal, spatial-seasonal, and spatial scales, respectively. Foraging sites were differentiated from nonforaging sites by significant differences among group size, temperature, turbidity, and season. Habitat selection analysis on individual variables indicated that foraging was more frequently observed in waters 4–6 m deep, 200–500 m from shore, and at salinity values of around 20 psu. This fine-scale and multivariate approach represents a useful method of exploring the complexity, gradation, and detail of the relationships between environmental variables and the foraging distribution patterns of bottlenose dolphin.
Resumo:
To determine if shoreface sand ridges provide unique habitats for fish on the inner continental shelf, two cross-shelf trawl surveys (23 km in length) were conducted in southern New Jersey (July and September 1991−95 with a beam trawl and July and September 1997−06 with an otter trawl) to assess whether species abundance, richness, and assemblages differed on and away from the ridge. The dominant species collected with both gears were from the families Paralichthyidae, Triglidae, Gobiidae, Serranidae, Engraulidae, Stromateidae, and Sciaenidae. Overall abundance (n=41,451 individuals) and species richness (n=61 species) were distributed bimodally across the nearshore to offshore transect, and the highest values were found on either side of the sand ridge regardless of gear type. Canonical correspondence analysis revealed three species assemblages: inshore (<5 meters depth), near-ridge (9−14 meters depth), and offshore (>14 meters depth), and variation in species composition between gear types. Environmental factors that corresponded with the assemblage changes included depth, temperature, distance from the top of the ridge, and habitat complexity. The most abundant near-ridge assemblages were distinct and included economically important species. Sand ridges of the inner continental shelf appear to be important habitat for a number of fish species and therefore may not be a suitable area for sand and gravel mining.
Resumo:
A review of available information describing habitat associations for belugas, Delphinapterus leucas, in Cook Inlet was undertaken to complement population assessment surveys from 1993-2000. Available data for physical, biological, and anthropogenic factors in Cook Inlet are summarized followed by a provisional description of seasonal habitat associations. To summarize habitat preferences, the beluga summer distribution pattern was used to partition Cook Inlet into three regions. In general, belugas congregate in shallow, relatively warm, low-salinity water near major river outflows in upper Cook Inlet during summer (defined as their primary habitat), where prey availability is comparatively high and predator occurrence relatively low. In winter, belugas are seen in the central inlet, but sightings are fewer in number, and whales more dispersed compared to summer. Belugas are associated with a range of ice conditions in winter, from ice-free to 60% ice-covered water. Natural catastrophic events, such as fires, earthquakes, and volcanic eruptions, have had no reported effect on beluga habitat, although such events likely affect water quality and, potentially, prey availability. Similarly, although sewage effluent and discharges from industrial and military activities along Cook Inlet negatively affect water quality, analyses of organochlorines and heavy metal burdens indicate that Cook Inlet belugas are not assimilating contaminant loads greater than any other Alaska beluga stocks. Offshore oil and gas activities and vessel traffic are high in the central inlet compared with other Alaska waters, although belugas in Cook Inlet seem habituated to these anthropogenic factors. Anthropogenic factors that have the highest potential negative impacts on belugas include subsistence hunts (not discussed in this report), noise from transportation and offshore oil and gas extraction (ship transits and aircraft overflights), and water quality degradation (from urban runoff and sewage treatment facilities). Although significant impacts from anthropogenic factors other than hunting are not yet apparent, assessment of potential impacts from human activities, especially those that may effect prey availability, are needed.
Resumo:
This is the River habitat survey and geomorphological evaluation of the Glaze Brook Catchment report produced by the Environmental Research and Consultancy of the University of Liverpool in 2002. The major aims of the project were to provide baseline information on river habitats in the Glaze catchment using standard River Habitat Survey (RHS) methods (sampling 25% of the catchment length) and, through the geomorphological audit, to assess the distribution and intensity of geomorphological processes, notably sediment transfer, sources and sinks. This information was then used to develop informed management recommendations. The Glaze catchment is a heavily modified watercourse of generally poor habitat quality. The most important factors contributing to the low quality of the sites are poor bank and channel features; low diversity/absence of channel vegetation; paucity of bankside trees and, to a lesser extent, a lack of channel substrate diversity. The high degree of modification relates principally to extensively resectioned banks and channels plus extensive culverting in the urban parts of the catchment.
Resumo:
This is the Brown trout habitat assessment on the River Bela catchment produced by the Environment Agency North West in 1997. The Environment Agency (EA) and its predecessor the National Rivers Authority undertook strategic fish stock assessments in 1992 and 1995 on the River Bela catchment. These surveys found low numbers of brown trout {Salmo trutta) at some sites. Following this, habitat evaluation assessments were undertaken on the eleven poorest sites Factors probably responsible for declining trout populations on the three main tributaries of the Bela catchment include: Overgrazing by farm stock; Lack of suitable cover for parr; the absence of suitable spawning areas; existing potential of certain areas within the catchment not being utilised, due to poor dispersal. Habitat Improvement Schemes (H.I.S) are discussed and prioritised.
Resumo:
The Ecological Society of America and NOAA's Offices of Habitat Conservation and Protected Resources sponsored a workshop to develop a national marine and estuarine ecosystem classification system. Among the 22 people involved were scientists who had developed various regional classification systems and managers from NOAA and other federal agencies who might ultimately use this system for conservation and management. The objectives were to: (1) review existing global and regional classification systems; (2) develop the framework of a national classification system; and (3) propose a plan to expand the framework into a comprehensive classification system. Although there has been progress in the development of marine classifications in recent years, these have been either regionally focused (e.g., Pacific islands) or restricted to specific habitats (e.g., wetlands; deep seafloor). Participants in the workshop looked for commonalties across existing classification systems and tried to link these using broad scale factors important to ecosystem structure and function.