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251.
Non-compliance and the quota price in an ITQ fishery 总被引:4,自引:0,他引:4
This paper examines the effects of non-compliance on quota demands and the equilibrium quota price in an ITQ fishery. I show that whereas lower quota prices are implied unambiguously by expected penalties which are a function of the absolute violation size, the expectation of penalties based upon relative violations of quota demands can, under certain conditions, produce higher quota prices than in a compliant quota market. If there are both compliant and non-compliant firms in the fishery, the result would then be a shift in quota demand from compliant to non-compliant firms, rather than the reverse. The findings are generally applicable to quota markets in other industries, including pollution permit markets. 相似文献
252.
Determining the evolutionary basis of variation in reproductive skew (degree of sharing of reproduction among coexisting individuals) is an important task both because skew varies widely across social taxa and because testing models of skew evolution permits tests of kin selection theory. Using parentage analyses based on microsatellite markers, we measured skew among female eggs (n=32.3 eggs per colony, range=20–68) in 17 polygynous colonies from a UK field population of the ant Leptothorax acervorum. We used skew among eggs as our principal measure of skew because of the high degree of queen turnover in the study population. Queens within colonies did not make significantly unequal contributions to queen and worker adult or pupal offspring, indicating that skew among female eggs reflected skew among daughter queens. On average, both skew among female eggs (measured by the B index) and queen–queen relatedness proved to be low (means±SE=0.06±0.02 and 0.28±0.08, respectively). However, contrary to current skew models, there was no significant association of skew with either relatedness or worker number (used as a measure of productivity). In L. acervorum, predictions of the concession model of skew may hold between but not within populations because queens are unable to assess their relatedness to other queens within colonies. Additional phenomena that may help maintain low skew in the study population include indiscriminate infanticide in the form of egg cannibalism and split sex ratios that penalize reproductive monopoly by single queens within polygynous colonies. 相似文献
253.
Janette Wenrick Boughman 《Behavioral ecology and sociobiology》2006,60(6):766-777
Many studies assume that selection molds social traits and have investigated the manner in which this occurs, yet very few studies have measured the strength of selection on social traits in natural populations. In this paper, I report results of phenotypic selection analyses on two social traits – the size of social groups and the frequency of group foraging – in Phyllostomus hastatus, the greater spear-nosed bat. I found significant positive directional selection on individual group foraging frequency, but no directional selection on individuals in different-sized social groups. These results have implications for the structure of social groups, cooperative behavior among group mates, and maternal investment strategies. I argue that combining studies of natural selection on wild populations with experiments to identify the agents and mechanisms of selection can do much to increase our understanding of social evolution. 相似文献
254.
In 1994, the sinking of the ‘Apollo Sea’ off the West coast of South Africa led to the deposition of ca. 2 500 tons of heavy
fuel oil over 150 km of coastline. The impact of the spill on rocky shore invertebrates, rock-pool fish fauna and rock lobsters
was assessed by conducting surveys shortly after the spill, and again two months later. Where possible, results of these surveys
were compared with existing data from before the sinking of the Apollo Sea. Among the fish fauna of rock-pools, changes in
total density of fishes were largely due to changes in the abundance ofClinus superciliosus and were within the range of natural variation for the species and the community as a whole. Community structure of the rock-pool
fish fauna also remained unaffected.
At three of four impacted rocky shore sites no changes could be detected in overall benthic community structure, although
the winkleNodilittorina africana was affected. At the fourth site, a boulder beach, statistical analysis showed distinct differences in community structure
between heavily and lightly contaminated areas, as well as between all areas compared with previously existing data. There
were also significant changes in the lightly oiled areas between the first and second surveys after the spill.
Oil-fouled lobster were found at one of three sites investigated. Ca. 7 % of the seabed in this particular area was polluted.
Antennae and forelegs of almost all lobsters in the vicinity of the oil were fouled. Examination of the gut-contents confirmed
that oil inhibits the ability of lobster to feed. Although there was no evidence that mortalities of lobster were caused by
the spill, growth rates may be reduced by the decreased feeding rate. Overall, the impact of the spill was strikingly less
than might have been predicted from the effects of other oil spills.
Nomenclature: Names of fish species follow Smith & Heemstra (1986). 相似文献
255.
Summary Using the linked gas chromatographical/electroantennogram (GC/EAG) technique it was revealed that the reindeer warble fly (H. tarandi) was specifically able to sense the same components from reindeer interdigital pheromone gland as the reindeer nose bot fly (C. trompe) another reindeer endoparasite. These two species belong to the same family (Oestridae), but different subfamilies, and the evolution towards an endoparasitic life cycle is thought to have been independent. The development of olfactory abilities to find reindeer from long distances is hypothesized to have taken place through convergent evolution or exists because of their common ancestry. 相似文献
256.
POLLUTION THREATS IN THE MEDITERRANEAN SEA: AN OVERVIEW 总被引:3,自引:0,他引:3
Roberto Danovaro 《Chemistry and Ecology》2003,19(1):15-32
This overview summarises the present knowledge on major sources of pollution, which are of concern for the Mediterranean Sea. Eutrophication, red tides, organic loads, hydrocarbon spills, heavy metal contamination and their biological effects are described on the light of the ecological characteristics of the Mediterranean. In particular special attention is paid to the "new pollution" processes; i.e. , the introduction of novel substances with biological activity that might have synergetic effects with "classical pollutants". Different compartments and marine ecosystems are considered and compared. The degree of anthropogenic impact and its apparent trends are discussed. Possible monitoring plans and remedial actions for a sustainable management of coastal zones subjected to increasing pollution are also suggested. 相似文献
257.
Natalia Yoshida Mariano Castro Cecile du Mortier Alicia Fernández Cirelli 《Environmental Chemistry Letters》2007,5(3):157-160
The increase of intensive bovine production systems in Argentina involves the use of therapeutic agents and growth promoters
that reach the environment through animal excreta. The growth promoter most widely used in Argentina is monensin, an ionophore
polyether antibiotic produced by Streptomyces cinnamoniensis. Here, the behavior of monensin in different solid environmental matrices is analyzed, and preliminary results that suggest
a strong dependence of monensin retention with the organic matter content of the matrix are discussed. 相似文献
258.
姚寿福 《长江流域资源与环境》1998,7(3):198-204
长江上游沿江产业带是一个资源富集,开发潜力巨大的区域,既是长江产业带的重要组成部分,也是西南地区经济发展的重心地带。区域经济的快速发展有赖于区域产业结构的有序演进。本文在分析长江上游沿江产业带产业结构演进背景-产业基础,经济基础,资源基础和宏观环境的基础上,根据国外产业结构演进手一般经验,对本区产业结构演进的历史进程和目前所处阶段进行了分析和判定。 相似文献
259.
260.
广州李坑垃圾填埋场水环境污染调查 总被引:7,自引:1,他引:7
通过现场采样与历史资料统计,分析了广州市李坑垃圾填埋场垃圾渗滤液的水质特征,及其对地睛水和地表水的影响强度及范围,结果表明,该场对环境产生影响的主要污染物是以NH3-N、CODCr为代表的高浓度有机物、垃圾渗滤液对地下水的影响强度不大,对作为农业灌溉用水的地表水影响不超过2000m,对10km上的饮用水源不造成影响 相似文献