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The penaeid prawns Fenneropenaeus indicus and Metapenaeus monoceros support shallow-water prawn fisheries in the south-west Indian Ocean. They are sympatric and have similar life histories, including developmental stages that depend on estuarine and marine habitats and a short dispersal duration. Nevertheless, M. monoceros juveniles display a more generalist habitat preference in estuaries and recruit to offshore habitats during a different season than F. indicus. We hypothesised that these differences would affect dispersal patterns, leading to dissimilar geographic genetic structure between the two taxa. Given their short dispersal phase, we also hypothesised that the Mozambique Channel would form a barrier to dispersal between the southeastern African mainland and Madagascar sites. Population differentiation was assessed based on analysis of mitochondrial DNA control-region sequences. Both species displayed high haplotype and low nucleotide diversity. Pairwise ?ST statistics supported the existence of admixed populations along the African mainland sites for both species, with geographic distance isolating populations at the extremes of the sampled range (Kenya and east coast of South Africa). The Madagascar population differed significantly from African mainland populations. The concordant patterns in population differentiation suggest that F. indicus and M. monoceros can be considered as single African stocks, or fisheries management units. 相似文献
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T. K. Hincks W. P. Aspinall P. J. Baxter A. Searl R. S. J. Sparks G. Woo 《Bulletin of Volcanology》2006,68(3):266-284
Frequent ash fallout from long-lived eruptions (with active phases greater than 5 years) may lead to local populations experiencing
unacceptably high cumulative exposures to respirable particulate matter. Ash from Montserrat has been shown to contain significant
levels of cristobalite and other reactive agents that are associated with an increased risk of developing pneumoconiosis (including
silicosis) and other long-term health problems. There are a number of difficulties associated with estimating risks in populations
due to uncertain and wide ranging individual exposures, change in behaviour with time and the natural variation in individual
response. Present estimates of risk in workers and other population groups are simplifications based on a limited number of
exposure measurements taken on Montserrat (1996–1999), and exposure−response curves from epidemiological studies of coal workers
exposed to siliceous dust. In this paper we present a method for calculating the long-term cumulative exposure to cristobalite
from volcanic ash by Monte Carlo simulation. Code has been written to generate synthetic time series for volcanic activity,
rainfall, ash deposition and erosion to give daily ash deposit values and cristobalite fraction at a range of locations. The
daily mean personal exposure for PM10 and cristobalite is obtained by sampling from a probability distribution, with distribution parameters dependent on occupation,
ground deposit depth and daily weather conditions. Output from multiple runs is processed to calculate the exceedance probability
for cumulative exposure over a range of occupation types, locations and exposure periods. Results are interpreted in terms
of current occupational standards, and epidemiological exposure−response functions for silicosis are applied to quantify the
long-term health risk. Assuming continuing volcanic activity, median risk of silicosis (profusion 1/0 or higher) for an average
adult after 20 years continuous exposure is estimated to be approximately 0.5% in northern Montserrat to 1.6% in Cork Hill.
The occupational group with the highest exposure to ash are gardeners, with a corresponding 2% to 4% risk of silicosis. In
situations where opportunities for in-depth exposure studies are limited, computer simulations provide a good indication of
risk based on current expert knowledge. By running the code for a range of input scenarios, the cost-benefit of mitigation
measures (such as a programme of active ash clearance) can be estimated. Results also may be used to identify situations where
full exposure studies or fieldwork would be beneficial.
Editorial responsibility: J Stix 相似文献
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A. Neri W.P. Aspinall R. Cioni A. Bertagnini P.J. Baxter G. Zuccaro D. Andronico S. Barsotti P.D. Cole T. Esposti Ongaro T.K. Hincks G. Macedonio P. Papale M. Rosi R. Santacroce G. Woo 《Journal of Volcanology and Geothermal Research》2008
Probabilistic characterizations of possible future eruptive scenarios at Vesuvius volcano are elaborated and organized within a risk-based framework. In the EXPLORIS project, a wide variety of topics relating to this basic problem have been pursued: updates of historical data, reinterpretation of previous geological field data and the collection of new fieldwork results, the development of novel numerical modelling codes and of risk assessment techniques have all been completed. To achieve coherence, many diverse strands of evidence had to be unified within a formalised structure, and linked together by expert knowledge. For this purpose, a Vesuvius ‘Event Tree’ (ET) was created to summarise in a numerical-graphical form, at different levels of detail, all the relative likelihoods relating to the genesis and style of eruption, development and nature of volcanic hazards, and the probabilities of occurrence of different volcanic risks in the next eruption crisis. The Event Tree formulation provides a logical pathway connecting generic probabilistic hazard assessment to quantitative risk evaluation. In order to achieve a complete parameterization for this all-inclusive approach, exhaustive hazard and risk models were needed, quantified with comprehensive uncertainty distributions for all factors involved, rather than simple ‘best-estimate’ or nominal values. Thus, a structured expert elicitation procedure was implemented to complement more traditional data analysis and interpretative approaches. The structure of the Vesuvius Event Tree is presented, and some of the data analysis findings and elicitation outcomes that have provided initial indicative probability distributions to be associated with each of its branches are summarized. The Event Tree extends from initiating volcanic eruption events and hazards right through to human impact and infrastructure consequences, with the complete tree and its parameterisation forming a quantitative synoptic framework for comprehensive hazard evaluation and mapping of risk impacts. The organization of the Event Tree allows easy updating, as and when new information becomes available. 相似文献
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