Abstract Fecundity is an integral component of the calculation of Atlantic salmon, Salmo salar L., egg depositions in rivers. Fecundity determinations can be time consuming and prohibitively expensive in terms of application on a broad scale. Consequently, where river specific and annual data are not available, default means are used in calculations in Newfoundland and Labrador. It is important therefore to know the extent of variability among rivers, years and seasons and the potential error involved in using default values. Annual fecundity data were available for one river in Labrador and nine rivers in Newfoundland. Fecundity was determined from ovaries collected in the recreational fishery in the summer for all 10 rivers. For three of these rivers, fecundity determined from summer sampling was compared with that obtained from sampling at time of spawning in autumn. There was significant variability in fecundity with length as a covariate among rivers, years and seasons. Mean number of eggs per female decreased between 8.3% and 29.0% from summer to autumn while mean number of eggs per cm decreased from 5.0% to 28.5%. Depending on the measure of relative fecundity used (no. of eggs kg−1 or no. of eggs cm−1), results of simulations showed that estimates of egg deposition incorporating defaults can deviate from those obtained by applying year-specific and river-specific values by 50–75%, without adjusting for the seasonal reduction in fecundity, and by 30–50% with an adjustment. A sensitivity analysis revealed that of three parameters used in the calculation of egg deposition (size, percent female and fecundity), fecundity was the most influential. 相似文献
Habitat change, mainly through the actions of humans, poses a threat to great white (Pelecanus onocrotalus) and pink-backed (P. rufescens) pelicans in northeastern KwaZulu-Natal, the southernmost distributions of these species on Africa’s eastern seaboard. This study assessed the relative importance and state of the potential pelican habitat in the northeastern KwaZulu-Natal region, focusing particularly on Lake St Lucia and the Phongolo River floodplain. Great white pelicans breed on islands in Lake St Lucia. Should these islands be lost through falling water levels or their becoming joined to mainland by deposits of silt, or by flooding, no suitable habitat for their breeding will remain in the region. By contrast, the pink-backed pelican nests in trees, and there appears to be plentiful alternative habitat. Lake St Lucia and, to a lesser extent, the Phongolo River floodplain, are important foraging areas for both pelican species. The hydrology of both these systems has been affected by human activities. 相似文献
Zoonotic pathogens cause an estimated 70% of emerging and re‐emerging infectious diseases in humans, affecting various aspects of human development on a global scale. The significance of bats as a source of emerging infectious diseases is being progressively appreciated. This study was undertaken post‐Ebola virus disease in West Africa and assessed the public health implications of human–bat interactions by exploring the reasons for contact between humans and bats, as well as reported actions taken upon experiencing bat bites or scratches. The paper highlights the nuances of human–bat interactions, stressing zoonotic disease risk awareness as well as the sources of information. The study used questionnaires to solicit information from 788 respondents in five communities with significant bat populations. We show that bat consumption was one of the main reasons for human–bat interactions. More men across the various communities ate bat meat. Only a small number of respondents (4.4%) reported being bitten by a bat, and 6.1% had been scratched by a bat. More than 21% had come into direct contact with bat blood. An even lower number went to the hospital after been bitten or scratched by bats. There was little knowledge on post‐exposure management. The most common places human–bat interactions occurred were at home and on farms. Seventy‐three per cent of the respondents believed that bats carried diseases, with Ebola virus disease being the most mentioned. Respondents indicated that the way they interacted with bats had not changed, even though they believed bats carried diseases and 46% stated that they had not changed the way they interacted with bats over the last two years. Apart from providing information on avoiding bites and scratches, a more holistic framework is needed to reduce human–bat interactions. The paper recommends a comprehensive and coordinated approach to optimizing an effective response to a potential bat‐borne zoonotic disease spillover. 相似文献
The threat posed by invasive alien species to global crop production and biodiversity is recognized as one of the major drivers of global change today. Here we report on a successful implementation and operational use of new technology to support risk- and crisis management in the case of fighting an invasive plant disease. The open geospatial standards Web Feature Service Transaction (WFS-T) was implemented in software for GPS-enabled mobile phones communicating with a GeoServer backend in order to track down and eradicate disease outbreaks and susceptible host plants. This new technology offering georeferenced events online from field provides new possibilities for real time action in risk and crisis management. 相似文献
This paper reviews the knowledge on effects of climate change on agricultural productivity in Europe and the consequences for policy and research. Warming is expected to lead to a northward expansion of suitable cropping areas and a reduction of the growing period of determinate crops (e.g. cereals), but an increase for indeterminate crops (e.g. root crops). Increasing atmospheric CO2 concentrations will directly enhance plant productivity and also increase resource use efficiencies.
In northern areas climate change may produce positive effects on agriculture through introduction of new crop species and varieties, higher crop production and expansion of suitable areas for crop cultivation. Disadvantages may be an increase in the need for plant protection, the risk of nutrient leaching and the turnover of soil organic matter. In southern areas the disadvantages will predominate. The possible increase in water shortage and extreme weather events may cause lower harvestable yields, higher yield variability and a reduction in suitable areas for traditional crops. These effects may reinforce the current trends of intensification of agriculture in northern and western Europe and extensification in the Mediterranean and southeastern parts of Europe.
Policy will have to support the adaptation of European agriculture to climate change by encouraging the flexibility of land use, crop production, farming systems etc. In doing so, it is necessary to consider the multifunctional role of agriculture, and to strike a variable balance between economic, environmental and social functions in different European regions. Policy will also need to be concerned with agricultural strategies to mitigate climate change through a reduction in emissions of methane and nitrous oxide, an increase in carbon sequestration in agricultural soils and the growing of energy crops to substitute fossil energy use. The policies to support adaptation and mitigation to climate change will need to be linked closely to the development of agri-environmental schemes in the European Union Common Agricultural Policy.
Research will have further to deal with the effect on secondary factors of agricultural production, on the quality of crop and animal production, of changes in frequency of isolated and extreme weather events on agricultural production, and the interaction with the surrounding natural ecosystems. There is also a need to study combined effects of adaptation and mitigation strategies, and include assessments of the consequences on current efforts in agricultural policy to develop a sustainable agriculture that also preserves environmental and social values in the rural society. 相似文献
Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi-gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best-known capture site of the species in Canada, to parameterise multi-gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long-term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made. 相似文献
Negative human–black bear interactions in New York's Adirondack Park campgrounds pose risk management challenges. Communication is one tool available to modify human behavior and reduce associated risks, but knowledge of constructs influencing risk perception among key stakeholder groups is needed to design effective risk communication approaches. We interviewed managers (n = 14) and users (n = 40) at 7 Adirondack Park campgrounds to characterize risk perceptions between groups. We identified eight constructs influencing risk perceived by users and/or managers with three constructs congruent between groups, and five constructs divergent. We discuss how congruencies and shared understanding across groups, and explicit recognition by risk communicators of differences between groups, may offer opportunities to maximize successes of risk communication efforts in campgrounds. 相似文献
Wash-off of plant protection products from crops is represented in current European Union (EU) surface water models and future EU soil models by a coefficient that estimates its contribution to soil loadings following rainfall. Replacing the default coefficient with experimental data requires a harmonized protocol and this research forms part of the development of such a protocol. Following a successful test of the proposed protocol on a single crop across eight laboratories, a range of crops were tested in a single laboratory to assess the impact of crop type on the results. 相似文献