Multivariate analysis was adopted to analyze 30 morphometrical characteristics of 121 one-year-old juvenile silver carp （Hypophthalmichthys molitrix） and bighead carp （Aristichthys nobilis） bred during the 1950s ...Multivariate analysis was adopted to analyze 30 morphometrical characteristics of 121 one-year-old juvenile silver carp （Hypophthalmichthys molitrix） and bighead carp （Aristichthys nobilis） bred during the 1950s （＂the former population＂） and 2008 （＂the current population＂） and collected from the middle reach of the Yangtze River. The average discriminant accuracies of the former and current silver and bighead carp population were 94.2% and 98.0%, respectively. Discriminant analysis also revealed that significant differences in morphology occurred between the former and current populations of both carp in overall characteristics. One-way analysis of variance indicated that between former and current populations, silver carp showed highly significant differences （P0.01） in twelve of their characteristics and significant differences （P0.05） in eight of their characteristics, while bighead carp showed highly significant differences （P0.01） in eight of their characteristics and significant differences （P0.05） in eight of their characteristics. Six head morphology variables of the current silver and bighead carp were significantly or highly significantly larger than the former populations; fourteen characteristics of silver carp and ten characteristics of bighead carp of the current populations, mainly reflecting truck and tail morphology, were significantly or very significantly smaller than the former populations. Our results indicate that silver and bighead carp have developed a larger head and smaller truck and tail during the last 50 years. Due to such morphological changes, it seems apparent that the heads of these fish species need to be considered in regards to human diets, particularly in relation to economic and nutritious value.展开更多
On May 12, 2008, an earthquake of 8.0 magnitude on the Richter scale and its numerous aftershocks devastatingly hit Wenchuan County and its nearby region along the Longman Mountains in Sichuan Province, China. The hea...On May 12, 2008, an earthquake of 8.0 magnitude on the Richter scale and its numerous aftershocks devastatingly hit Wenchuan County and its nearby region along the Longman Mountains in Sichuan Province, China. The heavy ruined area was up to 30,000km2 and 13% of its land surface was denuded by the extremely terrible quakes. The mountain collapses, landslides and debris flows induced by the earthquake not only scared the landscape at the immense scale, but also poured L66-billion-m3 sediment combined with offscourings and rubble into the Yangtze River and its breaches. This amount of sediments is 3 times more than the normal amount discharged into the Yangtze River, and will significantly increase sediment transportation of rivers and decrease storage capacities of reservoirs downstream. The dramatic increase in sediment load will imperil the engineering safety and impact the operation of the giant Three-Gorge Hydro-power Station if no proper prevention measures are taken.展开更多
基金National Natural Science Foundation of China (30630051)Aquaculture E-Institute of Shanghai Universities(03E009)Shanghai Leading Academic Discipline Project(S30701)
文摘Multivariate analysis was adopted to analyze 30 morphometrical characteristics of 121 one-year-old juvenile silver carp （Hypophthalmichthys molitrix） and bighead carp （Aristichthys nobilis） bred during the 1950s （＂the former population＂） and 2008 （＂the current population＂） and collected from the middle reach of the Yangtze River. The average discriminant accuracies of the former and current silver and bighead carp population were 94.2% and 98.0%, respectively. Discriminant analysis also revealed that significant differences in morphology occurred between the former and current populations of both carp in overall characteristics. One-way analysis of variance indicated that between former and current populations, silver carp showed highly significant differences （P0.01） in twelve of their characteristics and significant differences （P0.05） in eight of their characteristics, while bighead carp showed highly significant differences （P0.01） in eight of their characteristics and significant differences （P0.05） in eight of their characteristics. Six head morphology variables of the current silver and bighead carp were significantly or highly significantly larger than the former populations; fourteen characteristics of silver carp and ten characteristics of bighead carp of the current populations, mainly reflecting truck and tail morphology, were significantly or very significantly smaller than the former populations. Our results indicate that silver and bighead carp have developed a larger head and smaller truck and tail during the last 50 years. Due to such morphological changes, it seems apparent that the heads of these fish species need to be considered in regards to human diets, particularly in relation to economic and nutritious value.
基金carried out under the auspices of the public project of the Ministry of Water Conservancy of China (200801073, 2007SHZ0901034)the Knowledge Innovation Project of the Chinese Academy of Science (KZCX1-YW-08)
文摘On May 12, 2008, an earthquake of 8.0 magnitude on the Richter scale and its numerous aftershocks devastatingly hit Wenchuan County and its nearby region along the Longman Mountains in Sichuan Province, China. The heavy ruined area was up to 30,000km2 and 13% of its land surface was denuded by the extremely terrible quakes. The mountain collapses, landslides and debris flows induced by the earthquake not only scared the landscape at the immense scale, but also poured L66-billion-m3 sediment combined with offscourings and rubble into the Yangtze River and its breaches. This amount of sediments is 3 times more than the normal amount discharged into the Yangtze River, and will significantly increase sediment transportation of rivers and decrease storage capacities of reservoirs downstream. The dramatic increase in sediment load will imperil the engineering safety and impact the operation of the giant Three-Gorge Hydro-power Station if no proper prevention measures are taken.
