25,805 research outputs found
Gravel galore: Impacts of clear-cut logging on salmon and their habitats
Timber harvest may have both direct and indirect effects on salmon, and with
a few exceptions those effects result in lowered survival of salmon in their
stream habitats compared with unlogged forest (Hicks et al. 1991b). Some
impacts may be seen immediately or shortly after logging, whereas others can
take decades to be expressed. Central to analyzing these effects is the context
of the freshwater environment in which salmon are spawned and reared, and
the life histories of the salmon species. This chapter will examine the effects of
timber harvest on the freshwater habitat and life stages of salmon. It will also
investigate the hypothesis that the salmon species least affected by timber
harvest are those with the least reliance on stream habitats
Transportation and infrastructure, retail clustering, and local public finance: evidence from Wal-Mart's expansion
Transportation ; Retail trade ; Finance, Public
The Impact of Wal-Mart on Local Fiscal Health: Evidence from a Panel of Ohio Counties
This research analyzes selected fiscal impacts of Wal-Mart in Ohio from 1985 through 2003. Using a panel of counties, and accounting for spatial autocorrelation in an instrumental variable model I estimate impact of Wal-Mart and Super-Centers on selected revenues and transfer payments. On revenues I find that the presence of a Wal-Mart increases local commercial property tax assessments, resulting in collection increases of between 1.3 million. Wal-Mart also is associated with higher levels of local labor force participation. On expenditures I also find that the presence of a Wal-Mart dramatically increases the per capita EITC claims in a county (between 18 and 43 percent), while the dollar value of these claims experiences mixed impacts between Wal-Mart and a Supercenter. Similarly, the impact of Wal-Mart on Foodstamps expenditures is mixed, but small in any case. There are no in-county impacts of Wal-Mart on expenditures on Temporary Assistance to Needy Families and its predecessor Aid to Families with Dependent Children. However, Medicaid expenditures experience growth which may amount to roughly 16 additional cases per county attributable to a single Wal- Mart. The per worker costs of Medicaid estimated in this study is consistent with reported levels in a number of states, and study estimates by Dube and Jacobs [2004], Carlson [2005] and Hicks [2005a]. The magnitude and statistical certainty of these findings, accompanied by a review of previous research suggests that local fiscal intervention, either through incentives or the much touted “Wal-Mart Tax” is unwarranted.
What Do Quarterly Workforce Dynamics Tell Us About Wal-Mart? Evidence from New Stores in Pennsylvania
In this paper I seek to better inform debate regarding Wal-Mart’s local impact on wages, and employment dynamics by combining data on Wal-Mart stores with the recently release Quarterly Workforce Indicators provided by the US Census. Use a panel of Pennsylvania counties, who saw entrance of a Wal-Mart in 2002, I find a new store has no effect on existing employee wages in the retail sector. However, new retail sector hires experience a roughly 1,500 purchases of diapers annual since 1999 I have no financial relationship with Wal-Mart or any affiliate that I am aware of.Wal-Mart, Pennsylvania, Quarterly Workforce Indicators
Habitat requirements of black mudfish (Neochanna diversus) in the Waikato region, North Island, New Zealand.
Black mudfish (Neochanna diversus) were found at 39 of 80 sites in the Waikato region, New Zealand, ranging from large wetlands to small swampy streams. Of the sites with mudfish, 87% were dry at some time during summer. Sites with mudfish also generally had emergent and overhanging vegetation and tree roots, and showed low to moderate human impact. Black mudfish coexisted at some sites with juvenile eels or mosquitofish, but were absent from all sites with common bullies (Gobiomorphus cotidianus) or inanga (Galaxias maculatus). Sites with mudfish had almost exclusively semi-mineralised substrates or peat; only one site had mineralised substrate. Geometric mean catch rate for the 39 sites with mudfish was 0.70 fish per trap per night. Mean summer water depth was only 2.1 cm at sites with mudfish, compared to 22.6 cm at 41 sites without. Winter and maximum water depths were also less at sites with mudfish than at sites without mudfish. Mean turbidity was 11.5 nephelometric turbidity units (NTU) at sites with mudfish, but 21.3 NTU at sites without mudfish. Mudfish catch rates were negatively correlated with summer water depth, winter water depth, disturbance scale rating, and turbidity. A discriminant function model based on these variables successfully predicted 95% of the sites with mudfish. Habitat preference curves are also presented
Influence of open and closed river systems on the migrations of two northern New Zealand populations of banded kokopu (Galaxias fasciatus)
Otolith microchemical analysis by laser ablation inductively coupled mass spectrometry (ICP-MS) was used to investigate the migratory life histories of banded kokopu (Galaxias fasciatus) in two streams on the North Island of New Zealand. Known differences in marine and freshwater chemistry were used as a premise to document the migratory life strategies of banded kokopu between these environments. More specifically, temporal trends in high and low strontium/calcium ratios (Sr/Ca) identified in fish otoliths were used to determine evidence of migration between fresh and saltwater environments. Trace element analysis of fish captured above the Whau Valley Reservoir reflected non-migratory life histories and exhibited consistently low Sr/Ca ratios across the entire otolith. However, one fish from above the reservoir indicated unusually high Sr/Ca ratios in early adulthood. These high Sr levels were attributed to localised inputs from mineral-rich seepages associated with past mining practices in the region and low calcium availability within the Pukenui Stream. Otoliths from banded kokopu collected from Komiti Stream were shown to be migratory with a marine larval stage (high Sr/Ca ratio levels at the otolith nucleus), followed by a freshwater adult phase (low Sr/Ca ratio levels towards the edge) indicating their amphidromous origins. The study provides further evidence of non-diadromous recruitment for banded kokopu as a consequence of a large in-stream barrier and will add to the known distribution of landlocked species in New Zealand
The effect of a trapping procedure on the stress response of wild rainbow trout
Fish traps are a common research and management tool in which fish are subjected to procedures that elicit a stress response in other contexts. The effects of trapping on the stress response of sexually mature, wild rainbow trout Oncorhynchus mykiss were investigated during their upstream spawning migration by measuring concentrations of plasma cortisol, lactate, and glucose. Males had significantly lower basal plasma cortisol concentrations (6.1 ± 0.8 ng/mL [mean ± SE]) than females (21.4 ± 5.9 ng/mL). Similarly, the plasma cortisol response in males was significantly lower than that in females for all experiments. Fish working the barrier before entering the trap had increased concentrations of plasma cortisol. Confinement in the trap also induced a stress response. Plasma cortisol concentrations increased to 185.1 ± 40.9 ng/mL in males and 549.1 ± 60.1 ng/mL in females after confinement for 1 h. After processing, the magnitude of the stress response and the relative duration of recovery was less in fish that were confined longer in the trap. However, resting cortisol concentrations in females were not reached after 40 h of recovery in either group. Recovery to resting concentrations of plasma lactate occurred within 15 h after processing. In contrast, concentrations of plasma glucose remained significantly elevated at 40 h after processing. Postspawning fish had significantly lower plasma concentrations of cortisol, glucose, and lactate following application of an extreme stressor compared with prespawning fish. Based on the results of this study, we conclude that the trapping procedure induces a severe and prolonged stress response in wild rainbow trout
Macroinvertebrates and water quality: a teaching guide
Streams support a diverse community of plants and animals on or in the stream bed. These organisms comprise the benthos. Among the benthos are worms, molluscs, crustaceans, and larval insects. Insect larvae are usually the most numerous animals of the benthos. Collectively the animals of the benthos are known as benthic macroinvertebrates because of where they live, and their large size (often 10-35 mm)
Assessing movement of rainbow trout and common smelt between Lake Rotoiti and Lake Rotorua using otolith chemical signatures: A summary of work so far
This study used otolith microchemistry to investigate movement of common smelt and rainbow trout between Lake Rotorua and Lake Rotoiti. Rainbow trout were collected from Lake Rotoiti, Lake Rotorua and the Ohau Channel, and smelt were collected from several locations in Lake Rotoiti and Lake Rotorua
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