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121.
Using a mixed set of ethnographic methods including interviews and a structured survey, we evaluate local perceptions about the sustainability of salmon fisheries among fishers of the Cook Inlet region of Alaska. A majority of residents report participating in these fisheries, but we find significant disagreement about their sustainability. Household income and the types of fishing practiced both influence people's responses, and many implicated specific user groups for overharvesting and/or for receiving unfair catch allocations. Drawing on the theoretical areas of information theory and political ecology, we argue that these findings reveal a complex interplay among the practical, social, and political aspects of how local resource users, or “local experts,” develop and communicate their assessments of ecological conditions in a context of conflict. We conclude with notes on future research as it relates to the successful design of local-management and co-management solutions, especially in settings where resources are contested by stakeholders. 相似文献
122.
Jonathan R. Lee Emrys Phillips Stephen J. Booth James Rose Hannah M. Jordan Steven M. Pawley Martin Warren Russell S. Lawley 《Proceedings of the Geologists' Association. Geologists' Association》2013
Recent investigations from modern environments demonstrate that many terminal moraines do not simply record a single glacial maximum, but instead reveal a complex oscillatory pattern of ice-marginal behaviour including polyphase retreat. Within this study, we examine the geomorphology, geology and internal structure of a terminal moraine complex – the ‘Cromer Ridge’ in north Norfolk to reconstruct patterns of ice-marginal behaviour. Previously, this landform was interpreted as the limit of a southern extension of the British Ice Sheet during a Middle Pleistocene glaciation. Evidence presented here reveals a more complicated pattern of ice-marginal behaviour with the ‘Cromer Ridge’ reinterpreted as a ‘complex’ comprising several ridge elements. We propose that the maximum ice extent lay further to the south, with the size and morphology of the largest ridge element (the ‘Cromer Ridge’ as previously defined) a facet of thrust-stacking at an ice-marginal still-stand. We recognise multiple oscillations of the ice-front recorded against a twelve-stage model for the decay of the southern margins of a fast-flowing lobe of North Sea ice. Changes in ice-marginal dynamics are identified by the superimposition and lateral and vertical evolution of glacitectonic styles. Differences between these various states, and switches between ‘shallow’ and ‘deep’ thin-skinned glacitectonics, are strongly influenced by sub-marginal and proglacial water availability. Examination of the evidence for the morphostratigraphic proposals for the glacitectonic assemblage, within the context of the above interpretation, suggests that many of the ‘glacigenic landforms’ are erosional and a MIS 12 age of formation is favoured although several anomalies remain to be explained. 相似文献
123.
Yiannis Tsapras † Keith Horne Richard Carson Javier Méndez Alvarez Dan Batcheldor Alister W. Graham Philip A. James Johan Knapen Hannah Quaintrell Ignacio Gonzalez Serrano Peter Sorensen Nick Wooder 《Monthly notices of the Royal Astronomical Society》2002,337(1):41-48
We present observations of eight Galactic bulge microlensing events taken with the 1.0-m Jacobus Kapteyn Telescope (JKT) on La Palma during 2000 June and July. The JKT observing schedule was optimized using a prioritizing algorithm to automatically update the target list. For most of these events we have sampled the light curves at times where no information was available from the OGLE alert team. We assume a point-source point-lens (PSPL) model and perform a maximum likelihood fit to both our data and the OGLE data to constrain the event parameters of the fit. We then refit the data assuming a binary lens and proceed to calculate the probability of detecting planets with mass ratio q = 10−3 . We have seen no clear signatures of planetary deviations on any of the eight events and we quantify constraints on the presence of planetary companions to the lensing stars. For two well-observed events, 2000BUL31 and 2000BUL33, our detection probabilities peak at ∼30 and ∼20 per cent respectively for q = 10−3 and a ∼ R E for a Δχ2 threshold value of 60. 相似文献
124.
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126.
Hannah Parris 《Ocean & Coastal Management》2010,53(1):10-26
The Convention of the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean is a remarkable achievement in international fisheries cooperative management and significant, albeit slow and uneven, progress has been made by its Commission in promoting the conservation of vulnerable tuna stocks and managing fishing capacity. This paper evaluates current progress and suggests that further progress will be difficult to achieve unless attention is given to addressing the inherent risks in fisheries management and in the underlying incentives facing WCPFC members. Both issues could be addressed over the longer term by drawing on the strengths of existing management strategies that are actively debated within the WCPFC. 相似文献
127.
Despite the significant influence of temperature upon alpine stream benthic communities, thermal regimes of the water column and hyporheic zone of these mountain streams have received limited attention. This paper reports upon a detailed spatio‐temporal study of water column and streambed temperatures undertaken within the Taillon–Gabiétous catchment, French Pyrénées, that aims: (1) to characterize the nature and dynamics of alpine stream water column and streambed thermal patterns; (2) to investigate stream thermal variability under a range of hydroclimatological conditions; and (3) to consider the implications of (1) and (2) for alpine stream benthic communities. The catchment contains four highly dynamic hydrological sources and pathways: (1) two cirque glaciers (Taillon and Gabiétous); (2) seasonal snowpacks; (3) a karst groundwater system; and (4) hillslope aquifers. Water column temperatures were monitored continuously at four sites located along the Taillon glacial stream and at three groundwater springs (two karstic and one hillslope) over the 2002 summer melt season. An eighth site (Tourettes) was established on a predominantly groundwater‐fed stream with limited meltwater input. Bed temperatures (0·05, 0·20 and 0·40 m depth) and river discharge were measured at three sites: (1) the Taillon stream; (2) the Tourettes stream; and (3) below the confluence of (1) and (2). Air temperatures, incoming short‐wave radiation and precipitation were recorded to characterize atmospheric conditions. Glacial stream water column temperatures increased downstream, although groundwater tributaries punctuated longitudinal patterns. Karstic groundwater streams were cooler and more thermally stable than the glacial stream (except at the glacier snout). Hillslope groundwater stream temperatures were most variable and, on average, the warmest of all sites. Streambed temperatures in the glacial stream were coldest and most variable whilst the warmest and least variable streambed temperatures were recorded in an adjacent groundwater tributary. Temperature variability was strongly related to: (1) dynamic water source and pathway contributions; (2) proximity to source; and (3) prevailing hydroclimatological conditions. The high thermal heterogeneity within this catchment may sustain relatively diverse benthic communities, including some endemic Pyrénéan macroinvertebrate taxa. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
128.
Kyoko Ohashi Jinyu Sheng Keith R. Thompson Charles G. Hannah Harold Ritchie 《Ocean Dynamics》2009,59(6):809-825
A three-dimensional shelf circulation model is used to examine the effect of seasonal changes in water-column stratification
on the tidal circulation over the Scotian Shelf and Gulf of St. Lawrence. The model is driven by tidal forcing specified at
the model’s lateral open boundaries in terms of tidal sea surface elevations and depth-averaged currents for five major tidal
constituents (M2, N2, S2, K1, and O1). Three numerical experiments are conducted to determine the influence of baroclinic pressure gradients and changes in vertical
mixing, both associated with stratification, on the seasonal variation of tidal circulation over the study region. The model
is initialized with climatological hydrographic fields and integrated for 16 months in each experiment. Model results from
the last 12 months are analyzed to determine the dominant semidiurnal and diurnal tidal components, M2 and K1. Model results suggest that the seasonal variation in the water-column stratification affects the M2 tidal circulation most strongly over the shelf break and over the deep waters off the Scotian Shelf (through the development
of baroclinic pressure gradients) and along Northumberland Strait in the Gulf of St. Lawrence (through changes in vertical
mixing and bottom stress). For the K1 constituent, the baroclinic pressure gradient and vertical mixing have opposing effects on the tidal circulation over several
areas of the study region, while near the bottom, vertical mixing appears to play only a small role in the tidal circulation. 相似文献
129.
Hannah R. Griscom Scott N. Miller Thomas Gyedu-Ababio Ramesh Sivanpillai 《GeoJournal》2010,75(2):163-173
Considerable land cover changes have occurred in the Luvuvhu catchment in northeastern South Africa in the past two decades.
These changes are associated with human population growth and may be contributing to observed reductions in winter river baseflows
and increased episodes of river drying within Kruger National Park. Six-class land cover maps of the catchment were created
from 1978 (MSS) and 2005 (TM) Landsat imagery using an iterative technique. Results indicate a 1,000 km2 (12%) increase in Bare Ground between 1978 and 2005, with a concomitant decrease in shrubland and indigenous forest cover.
Overall classification accuracy in the 2005 image was 80%. Classification was most accurate for Water and Pine classes (100
and 92%) and least accurate for Indigenous Forest (46%), primarily due to misclassification as Shrubland. These maps are suitable
for land cover change and landscape modeling analyses, and can serve as baseline data for further research. 相似文献
130.
Kate Buckman Vivien Taylor Hannah Broadley Daniel Hocking Prentiss Balcom Rob Mason Keith Nislow Celia Chen 《Estuaries and Coasts》2017,40(5):1358-1370
Spatial variation in mercury (Hg) and methylmercury (MeHg) bioaccumulation in urban coastal watersheds reflects complex interactions between Hg sources, land use, and environmental gradients. We examined MeHg concentrations in fauna from the Delaware River estuary, and related these measurements to environmental parameters and human impacts on the waterway. The sampling sites followed a north to south gradient of increasing salinity, decreasing urban influence, and increasing marsh cover. Although mean total Hg in surface sediments (top 4 cm) peaked in the urban estuarine turbidity maximum and generally decreased downstream, surface sediment MeHg concentrations showed no spatial patterns consistent with the examined environmental gradients, indicating urban influence on Hg loading to the sediment but not subsequent methylation. Surface water particulate MeHg concentration showed a positive correlation with marsh cover whereas dissolved MeHg concentrations were slightly elevated in the estuarine turbidity maximum region. Spatial patterns of MeHg bioaccumulation in resident fauna varied across taxa. Small fish showed increased MeHg concentrations in the more urban/industrial sites upstream, with concentrations generally decreasing farther downstream. Invertebrates either showed no clear spatial patterns in MeHg concentrations (blue crabs, fiddler crabs) or increasing concentrations further downstream (grass shrimp). Best-supported linear mixed models relating tissue concentration to environmental variables reflected these complex patterns, with species specific model results dominated by random site effects with a combination of particulate MeHg and landscape variables influencing bioaccumulation in some species. The data strengthen accumulating evidence that bioaccumulation in estuaries can be decoupled from sediment MeHg concentration, and that drivers of MeHg production and fate may vary within a small region. 相似文献