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81.
嘉陵江下游鱼类资源现状调查 总被引:8,自引:2,他引:6
2003年5月至10月对嘉陵江下游的鱼类资源进行了调查,并对该水域鱼类资源变动的原因进行了探讨。计调查226船次,统计渔获物1153kg,测量鱼类标本19378尾。共记录鱼类92种,隶属于5目14科61属,其中有13种为该水域新记录。结果表明嘉陵江水域生态环境的变化导致鱼类物种组成、种群结构发生了变化;珍稀鱼类、洄游性或半洄游性鱼类的种群数量急剧减少甚至绝迹,如中华鲟、达氏鲟、白鲟、胭脂鱼、等。 相似文献
82.
A.C.B. OLIVEIRA L.A. MARTINELLI M.Z. MOREIRA & J.E.P. CYRINO 《Aquaculture Nutrition》2008,14(1):10-13
Estimation of the apparent digestibility coefficient ADC(%) of C3 and C4 plants in experimental diets for fingerlings of tambaqui (Colossoma macropomum, Cuvier, 1818) was calculated by applying chromic oxide (Cr2O3) external marker methodology and by a proposed mathematical expression based on the isotopic composition (δ13C). A total of 240 tambaqui fingerlings each weighing ±48.2 g and measuring ±9.8 cm were maintained in eight 500‐L aquariums specially designed for faeces collection. The ADC(%) of the C3 and C4 diets did not differ significantly between the two methods, producing results of 75.6%; 76.2% and 74.4%; 72.8%, respectively. The ADC(%) results obtained by isotopic method presented less variation than by chromic oxide. The proposed mathematical expression for calculating the ADC(%) based on δ13C values offers an alternative methodology, which can reduce errors and diminish the effort required to collect biological material. However, it is important to note that this method is limited to analysis of diets or food items with distinct isotopic signals. 相似文献
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Abstract – The native and non-native freshwater fish species richness as well as the proportion of native fish species to overall fish species were examined to test a hypothesis of a spatial linkage between the distributions of dams and non-native fishes based on survey data collected in rivers and streams in Hokkaido, Japan. Non-native fish species have steadily increased in Hokkaido since the mid 1970s, as indicated by the decreasing proportion of native fish species per fish survey. Non-native species richness was significantly higher in areas above dams (i.e., reservoirs and their inlet streams) compared to areas without dams. As a result, the proportion of native fish species was lower above dams. This proportion was lower in developed and agricultural areas compared with forest areas, although both native and non-native species richness were higher in areas with development and agriculture. Non-native cyprinids, catfish and snakehead occurred primarily in a particular river basin with the largest drainage area, the longest history of reclamation and highest human population in the island. Non-native salmonids on the other hand, occurred in forest areas at higher elevations and their occurrence was associated with the existence of dams. There was a spatial linkage between the distribution of dams and non-native species, although it was applicable only to salmonids. The management of dams and reservoirs needs a strategy to prevent further expansion of exotic salmonids such as rainbow and brown trout. These species can be a significant threat to native Japanese salmonids as a result of various biological mechanisms. 相似文献
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86.
Aloyce R Kaliba Charles C Ngugi John Mackambo & Kwamena K Quagrainie 《Aquaculture Research》2007,38(11):1129-1136
Economic profitability of Nile tilapia production in Kenya was analysed using a model that simulated individual fish growth and took fish population dynamics in the pond into account. The results suggest that the currently practiced mixed‐sex tilapia culture is economically unsustainable. It is suggested that research and extension efforts be geared towards developing monosex Nile tilapia production systems. Nile tilapia culture with African catfish predation should be viewed as an intermediate step towards all‐male Nile tilapia culture. This will allow accumulation of both physical and human capital to support all‐male tilapia culture. Under all‐male culture, economic returns are high enough to justify investment in Nile tilapia culture using borrowed capital. However, the success of monosex culture will depend on the availability and affordability of quality fingerlings and low‐cost fish feeds. The results have a wide application in Sub‐Saharan Africa where mixed‐sex Nile tilapia culture is common. 相似文献
87.
Abstract Salmonid fishways have been used in many countries for non-salmonid fishes, including Australia, but generally with poor results. Trapping the entrance and exit of a 1:9 gradient salmonid fishway on the Murray River confirmed very poor passage of native fish, with <1% of the most abundant species ascending. Fifty years of fish passage monitoring showed the numbers of three native species declining by 95–100% and non-native fish becoming dominant. Fishways are now being designed for native fish and being quantitatively assessed, but daily flow management also needs to be addressed. The ecological model for passage of potamodromous fishes has changed from passing adults of a few species to one that incorporates the whole fish community, specifically: immature fish of large-bodied species that dominate numbers migrating upstream; a diverse range of movement strategies; and small-bodied species, crustaceans and low numbers of less-mobile species. 相似文献
88.
Processes of collating a European fisheries database to meet the objectives of the European Union Water Framework Directive 总被引:1,自引:0,他引:1
U. BEIER & E. DEGERMAN A. MELCHER C. ROGERS H. WIRLÖF 《Fisheries Management and Ecology》2007,14(6):407-416
Abstract FIsh Database of European Streams, a common database for the FAME project, was merged using existing data on electric fishing and environmental data. FIsh Database of European Stream is a relational database with eight tables. Metrics based on classification of fish species into guilds were calculated, and provided in separate tables. FIsh Database of European Stream contained information about 150 freshwater fish species, from 12 countries, 17 ecoregions, 40 main river regions, 2651 rivers and 8228 sites. Examples of data coverage and use are given. Relationships between environmental variables were illustrated using principal component analysis, which resulted in three environmental components – latitude, size and altitude. Environmental component scores were correlated with fish metrics used in the European Fish Index. Results exemplify how fish guilds reflect gradients in environmental variation. Benefits and problems concerning standardisation and data availability at the global level are discussed. 相似文献
89.
Consumer perception versus scientific evidence of farmed and wild fish: exploratory insights from Belgium 总被引:2,自引:2,他引:0
Wim Verbeke Isabelle Sioen Karen Brunsø Stefaan De Henauw John Van Camp 《Aquaculture International》2007,15(2):121-136
The increasing number of marketable fish being supplied from aquaculture is a response to the increasing demand for healthy
food and is filling the gap left by depleting natural fish stocks. Little is known about the awareness and perception of the
consumer in terms of farmed fish versus fish from capture fisheries. The consumer's subjective point of view is of overriding
importance for the production system and product acceptance as well as for future market success. In this paper consumer perception
in Belgium is explored and compared against scientific evidence of farmed versus wild fish. Primary data were collected through
a consumer survey (April 2003) and focus group discussions (May 2004) with Belgian consumers. The majority of the consumer
sample reported no perceived differences between farmed versus wild fish. However, mean perception scores were slightly in
favour of wild fish on the attributes taste, health and nutritious value, in particular among consumers aged 55 years and
older. The availability of farmed fish was perceived to be better than that of wild fish, while the consumer's perception
of safety did not differ between farmed and wild fish. The focus group discussions indicated that consumers’ opinions and
beliefs about farmed fish are mainly based on emotion and image transfer from intensive terrestrial livestock production rather
than on awareness and factual knowledge of aquaculture.
相似文献
John Van CampEmail: |
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