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1.
Although a large number of fish species have been introduced into Guangdong Province in Southern China, a few species, such as tilapia (Tilapia spp.), North African catfish Clarias gariepinus Burchell, mrigal carp, Cirrhinus mrigala (Bloch) and the sucker mouth catfish (Hypostomus sp.), have established natural populations and can be considered “successful invaders” in large rivers. The specific mechanisms underlying these contrasting results among different introduced fish species remain understudied. The relationship between multiple abiotic–biotic factors and the success of four invasive species was investigated using survey data for the Guangdong Province river ecosystem. In contrast to previous studies that have considered species‐specific traits, the focus was on economic, ecological and anthropogenic factors to predict invasion success. Four main predictive indicators were found: (1) successful invaders were of low or no commercial value; (2) successful invaders tolerated a wide range of environmental conditions, including poor water quality; (3) biodiversity loss accelerated the growth of non‐native populations; (4) human disturbance facilitated population growth and spread of invasive fish species. To lessen the impacts of invasive fish species, the selection of breeding species and breeding areas, maintenance of water quality and reduction in water pollution, protection of the diversity of fish species and reduction of human interference should be addressed.  相似文献   

2.
The Philippines has vast freshwater resources for cage culture of fish. Two tilapia species, Tilapia mossambica and Tilapia nilotica, are cultured commercially in cages in several lakes.Field testing for cage culture of Tilapia nilotica, the preferred species, is described. A pilot commerical cage farm has been established.The major problems affecting development are the short supply of quality fingerlings, the lack of a standard commercial feed, and the increasing costs of cage construction. Recommendations for resolving these problems are given.  相似文献   

3.
由于特殊的地理环境和良好的气候条件,海南省已成为我国外来生物入侵的重灾区之一,许多外来淡水生物在海南均有分布。2016-2018年,对万泉河、南渡江、昌化江等海南主要河流外来淡水生物的种类和分布进行了初步调查。经过调查发现,目前海南共有43种外来淡水水生生物,其中鱼类31种、爬行类2种、两栖类1种、软体动物2种、甲壳动物3种,淡水植物4种。海南省外来淡水生物的主要入侵途径是水产养殖引种,主要危害是捕食和竞争。根据调查结果提出了健全管理制度、加大科学研究和人才培养、加强宣传等防控策略。  相似文献   

4.
Tilapia culture in rural communities in the state of Yucatan, Mexico, has been increasing in recent decades. Polyculture of tilapia with other more commercially valuable species provides an opportunity to substantially improve the economic yields of rural producers. The economic viability of implementing Nile tilapia with Australian redclaw crayfish in polyculture was analyzed using profitability indicators such as internal rate of return (IRR) and net present value (NPV). A bioeconomic model was developed to simulate three production densities, accounting for investment recuperation in time horizons of 5, 10 and 15 years. Simulations showed a notable improvement in profitability when farms adopt the polyculture strategy, particularly over the 5-year horizon. Nile tilapia with Australian redclaw crayfish polyculture shortens investment return time and buffers risk related to changes in tilapia sale price. Of the three studied polyculture combinations the optimum outcome was achieved with medium redclaw crayfish density.  相似文献   

5.
1. Development of effective conservation strategies for freshwater biodiversity must take account of the trade‐off between species preservation and human use of ecosystem goods and services. The latter cannot be prevented, and attempts to manage ecosystems that focus solely on maximizing biodiversity will fail. 2. A compromise position of management for ecosystem functioning and human livelihoods — rather than preservation of every species — will provide a better basis for biodiversity conservation. This has implications for the management of exotic species. 3. There are some situations, in lentic habitats in Sri Lanka, for example, where the establishment of exotics has increased fishery yields without apparent detriment to native biodiversity. The Sepik River in Papua New Guinea provides another illustration of potential compromises between human livelihoods and biodiversity conservation. 4. The Sepik supports a relatively unproductive fishery. Two fish stocking projects (in 1987–93 and 1993–97), representing a partnership between the Papua New Guinea Government and the United Nations (UNDP/FAO), led to the introduction of a suite of exotic fish into the Sepik. Species were selected on the basis of their potential to occupy niches not filled by native fish. Unfortunately, the outcomes of these introductions are poorly documented, although there is preliminary evidence both of increased human use of exotic fish as well as declines of some native species associated with the spread of exotics. 5. Better understanding of the results of the Sepik fish introductions is important, because the pressures of burgeoning human populations in most of tropical Asia make it impossible to preserve near‐pristine environments such as the Sepik. While attempts to conserve natural or near‐natural systems must remain a priority, there is a need to develop strategies for the management of damaged or degraded ecosystems, which may contain exotics, with the aim of maintaining ecosystem functioning and, if possible, maximizing the persistence of native biodiversity. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

6.
Fish introductions, particularly in areas of high biological diversity and endemism, represent a major threat for biodiversity. In the Balkan Peninsula, 60 fish species have been introduced to date, of which 36 have become naturalized in inland waters. Since the Balkans are one of the world's 35 biodiversity hot spots, this large presence of alien fish species poses a serious threat for the stability of freshwater ecosystems and the survival of the native ichthyofauna and of aquatic biodiversity in general. The motivation for the introductions, and the historical timeline, varies among the Balkan states. Despite recent attempts to implement and align legislation aimed at preventing the introduction of potentially invasive species, and the implementation of rigorous controls of introductions and increased protection of open waters, the majority of current introductions remain intentional, primarily via aquaculture. This review article provides a historical overview of freshwater fish introductions, the motivation behind them and the current distribution of alien freshwater fishes in the Balkans. The ecological implications and future perspectives concerning alien fish species in the region are also discussed.  相似文献   

7.
This is the first controlled experiment to quantify the effect of introduced tilapia on indigenous species. This experiment was conducted in small earthen ponds (100 m2) to assess the impact of mixed‐sex or all‐male Nile tilapia (Oreochromis niloticus) on small indigenous species (SIS) commonly found in south Asia, mola (Amblypharyngodon mola), chela (Chela cachius) and punti (Puntius sophore). Ponds were fertilized, then stocked with 0.56 fish m?2 of water surface area in the mixed‐sex and all‐male tilapia treatments and 0.42 fish m?2 in the treatment without tilapia. No additional nutritional inputs were applied after stocking. Treatments were: mixed‐sex tilapia with SIS, mono‐sex male tilapia with SIS and SIS without tilapia (control). All treatments were stocked with 14 fish per species. All species reproduced during the 21‐month culture duration. The number of recruits varied by species, Tilapia reproduced in greater numbers than SIS. Tilapia numbers at harvest were the highest (451 ± 25/100 m2) in the mixed‐sex treatment compared with mola (221 ± 22/100 m2), chela (94 ± 8/100 m2) and punti (100 ± 7/100 m2). The number of mola was higher (399 ± 33/100 m2) in the all‐male tilapia treatment. There was reduction in the number of mola and chela in the treatment containing mixed‐sex tilapia. Gut content analysis combined with water sampling revealed that all fish species fed selectively. Significant interspecies dietary overlap was found between Nile tilapia and SIS and among SIS. Thus, there is potential for tilapia to compete with indigenous fish species when space and other resources are limiting, but a longer duration study with varying level of management is needed to determine how successfully tilapia competes with locally adapted SIS.  相似文献   

8.
Abstract. This paper examines the digestibility of different feed mixtures by three species of fish: carp, Cyprinus carpio L., tilapia, Oreochromis aureus × O. niloticus , and African catfish, Clarias gariepinus (Burchell 1822). Protein from poultry sources was digested better by tilapia than by carp or catfish, but no significant difference was found in the case of protein mainly from fish meal. Carp showed the best ability to digest fats, followed by catfish, with tilapia having the least ability. Tilapia digested carbohydrate better than the other two species, however, whether from wheat or corn sources. The same pattern applies to the digestibility of energy.  相似文献   

9.
Tilapia are the second most farmed fish worldwide and their production has quadrupled over the past decade due to ease of aquaculture, marketability and stable market prices. Tilapia aquaculture must adopt sustainable practices (such as polyculture) for continuing increased production and improved sustainability. This article reviews tilapia polyculture around the world and discusses its benefits, strategies and practices. Tilapia polyculture improves feed utilization, enhances water quality, increases total yield and profit. Further investment will increase these gains. Research on tilapia polyculture in China was also summarized and addressed that polyculture in semi‐intensive systems was a way of improving sustainability for tilapia aquaculture.  相似文献   

10.
南海北部灯光罩网渔获组成及其对渔业资源的影响   总被引：10，自引：2，他引：8  
近年来,灯光罩网在南海区迅速发展,给南海区北部沿岸浅水域幼鱼资源增大了捕捞压力.为了查明南海区灯光罩网渔业的渔获组成及其对渔业资源的影响,2006年4月27日～5月2日在阳江沿海水域进行了灯光罩网海上渔获组成调查.研究结果表明:(1)主捕对象是趋光性鱼类和头足类,枪乌贼Loligo sp.、带鱼Trichiurus haumela、蓝圆鲹Decapterus maruadsi、康氏马鲛Scomberomorus commerson、刺鲳Psenopsis anomala、乌贼Sepia sp.、赤鼻棱鳀Thrissa kammalensis、乌鲳Formio niger、杜氏棱鳀Thryssa dussumieri和竹筴鱼Trachurus japonicus是南海北部灯光罩网的常见渔获种类;(2)幼鱼渔获比例高,损害海洋渔业资源严重;(3)网目尺寸小、灯光照度大和近岸渔场是导致幼鱼渔获比例高的主要成因.笔者建议规定最小网目尺寸和加强渔具管理.  相似文献   

11.
Abstract In less-developed countries, fisheries enhancement using stocking is a common practice to manage reservoirs for biomass production. In many cases, there appears to be little control over whether the stocking activity is appropriate or necessary. Cuban reservoir fisheries have been usually managed to maximize fish biomass. Blue tilapia have been introduced and supplemented in reservoirs, and Chinese carp are introduced and maintained in reservoirs throughout the entire island. Supplemental stocking with introduced fish species is a usual practice to manage large and medium-sized reservoirs. Small and very small reservoirs have been managed as semi-intensively enhanced fisheries with carp and tilapia stocking. The main purposes of the present paper are to study the factors contributing to the outcome of stocking programmes in reservoirs and to test the hypotheses that supplementary stocking for self-sustained fish populations usually cannot contribute to increase fish yield. Yield and stocking data by groups of fish species were available for Cuban reservoirs. Total fish yield was only slightly related to total fish stocking density for the complete set of reservoirs. However, this result was mainly because of the relationship between total yield and cyprinid stocking for semi-intensively-used reservoirs. Tilapia yield was not significantly related to tilapia stocking for both extensively and semi-intensively-used reservoirs. However, yield and stocking for cyprinids were highly related for both reservoir subsets. Therefore, cyprinid stocking was effective in certain reservoirs, but tilapia stocking was not effective in any reservoir. Moreover, tilapia stocking was a superfluous activity for reservoirs where tilapia have an adequate natural reproduction cycle.  相似文献   

12.
ABSTRACT

India is a very populous country with more than one billion people. In order to provide food for this growing population, serious environmental problems may result. Despite many benefits from the green, blue, and silver revolutions adopted in India, there has been much concern resulting from intensive agricultural practices that led to environmental problems in both terrestrial and aquatic ecosystems. Increasing demand for aquatic resources also caused inland fisheries to decrease over the past few decades. The location of aquaculture projects, landscape destruction, soil and water pollution by pond effluents, over-exploitation of important fish stocks, depletion in biodiversity, conflicts over agriculture and aquaculture among various stakeholder groups over resource and space allocation, and international fish trade controversies have threatened the long-term sustainability of fisheries and aquaculture industries. The subject of sustainable aquaculture has not been adequately projected in terms of current aquaculture practices aimed to boost a rural economy. This review briefly describes the key issues of aquaculture unsustainability in terms of intensive aquaculture, nutrient enrichment syndrome, soil and groundwater salinization, destruction of mangroves, loss of biodiversity, marine pollution and loss of fish stock, use of aquachemicals and therapeutics, hormone residues, etc. The strategies for sustainability have been highlighted with respect to rice-cum-fish culture, carp polyculture, integrated farming with livestock, rural aquaculture, intensification of small farms, wastewater-fed aquaculture, crop rotation, probiotics, feed quality, socioeconomic considerations, environmental regulations and fisheries acts, transboundary aquatic ecosystems, impact of alien species, ethical aspects of intensive aquaculture, responsible fisheries, and environmental impact assessment. A suggested model outlines the feedback mechanisms for achieving long-term sustainability through improved farm management practices, integrated farming, use of selective aquachemicals and probiotics, conservation of natural resources, regulatory mechanism, and policy instruments.  相似文献   

13.
罗非鱼（Tilapia）原产于非洲，具有雄性率高、生长快、易繁殖、食性杂、抗逆性强、病害少、群体产量高和肉质鲜美等特点，已成为国际鱼类贸易中的重要品种之一。罗非鱼是联合国粮农组织推荐养殖的优良品种，也是最具产业化发展条件的品种，发展罗非鱼苗种生产有利于提升广西特别是南宁对东盟各国的影响力。目前广西水产研究所罗非鱼良种场为广西最大的优质罗非鱼苗种生产单位，该场年生产供应优质罗非鱼苗种达到8000万尾以上，销往广东、海南、福建、云南、贵州、湖南、湖北、河北等10多个省市，并远销越南和缅甸，客户评价很高，信誉良好。  相似文献   

14.
A study was conducted to assess the effects of common carp and the African catfish on growth and reproduction of the native tilapia Oreochromis shiranus in Malawi. The study was done from 1 May to 1 October 2018 at the National Aquaculture Centre (NAC), Zomba. Four triplicated treatments were used: O. shiranus + carp (T1), O. shiranus + catfish (T2), O. shiranus + carp + catfish polyculture (T3) and O. shiranus monoculture (T4). Fish were stocked at uniform density of 0.8 fish/m2. Data collection was done once every month. Results showed that O. shiranus mean weight gain (%), specific growth rate (% body weight/day), average daily gain (g fish?1 day?1) and condition factor (g/cm3) were highest in T3 and lowest in T1 and T4 treatments. T3 had better water quality regime and higher tilapia biomass than T1 and T4 treatments. Tilapia fry production (no. fry pond?1 day?1) was highest in T4 but did not significantly differ (p > .05) between T2 and T3 treatments. It is concluded that the farming of common carp in aquatic ecosystems containing the African catfish may not adversely affect growth and reproduction of O. shiranus and that the polyculture of the African catfish, common carp and tilapia can be adopted to mitigate the potential adverse effects of carp on the environment and improve tilapia growth.  相似文献   

15.
The freshwater characiform fish Prochilodus lineatus is a detritivorous species that has its native distribution area in South America but has been imported to China for aquaculture purposes. This is the first time that it is being reported in Vietnam, both from aquaculture and captured from a river channel. According to local authorities, the species is becoming increasingly important in local aquaculture and its spread can be expected. Keeping in mind the high biomass production in the rivers of its native distribution area, a successful establishment of P. lineatus into Vietnamese fresh waters may exert serious impacts on the local ecosystems.  相似文献   

16.
Nile tilapia, Oreochromis niloticus, is one of the most popular freshwater aquaculture species in developing countries. Although formulated feed provides higher fish yield, it is expensive. Therefore, fertilizer-based fish culture using natural food sources is generally implemented in developing countries. The aim of this study was to identify the major natural foods contributing to tilapia growth in fertilizer-based fish ponds. The stomach contents of tilapia in a fertilizer-based fish pond in Lao PDR were analyzed to estimate their feeding behaviors; stable isotope ratios of carbon and nitrogen in the potential food organisms and suspended solids were measured and compared with the ratios in the fish muscle tissues. Further, the feed efficiency of chironomid larvae was compared with that of chlorella and formulated feed in a laboratory feeding experiment. Consequently, chironomid larvae were identified as the main contributors to tilapia growth in the fertilizer-based fish pond. In conclusion, benthic larvae of insects belonging to the family Chironomidae are confirmed to be a natural food source for tilapia in the fertilizer-based fish pond.  相似文献   

17.
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18.
Co-infections commonly arise when two or multiple different pathogens infect the same host, either as simultaneous or as secondary concurrent infection. This potentiates their pathogenic effects and leads to serious negative consequences on the exposed host. Numerous studies on the occurrence of the bacterial, parasitic, fungal and viral co-infections were conducted in various tilapia species. Co-infections have been associated with serious negative impacts on susceptible fish because they increase the fish susceptibility to diseases and the likelihood of outbreaks in the affected fish. Co-infections can alter the disease course and increase the severity of disease through synergistic and, more rarely, antagonistic interactions. In this review, reports on the synergistic co-infections and their impacts on the affected tilapia species are highlighted. Additionally, their pathogenic mechanisms are briefly discussed. Tilapia producers should be aware of the possible occurrence of co-infections and their effects on the affected tilapia species and in particular of the clinical signs and course of the disease. To date, there is still limited information regarding the pathogenicity mechanisms and pathogen interactions during these co-infections. This is generally due to low awareness regarding co-infections, and in many cases, a dominant pathogen is perceived to be of vital importance and hence becomes the target of treatment while the treatment of the co-infectious agents is neglected. This review article aimed at raising awareness regarding co-infections and helping researchers and fish health specialists pay greater attention to these natural cases, leading to increased research and more consistent diagnosis of co-infectious outbreaks in order to improve control strategies to protect tilapia when infected with multiple pathogens.  相似文献   

19.
Periodicity and timing of opaque zone formation in otoliths of introduced redbelly tilapia, Tilapia zillii (Gervais), in Crater Lake Nkuruba, Uganda, were validated using marginal increment. Age and growth were assessed through readings of biannuli in thin‐sectioned sagittal otoliths. Deposition of opaque zone formation in T. zillii otoliths was bimodal (March–May and September–November), corresponding to two seasonal peaks of precipitation characteristic of this equatorial region. Ages of T. zillii ranged from 2 to 8 years, with fish gillnetted offshore having a faster growth and attaining larger size‐at‐age than fish captured inshore in minnow traps, suggesting that use of multiple gears is needed when estimating the growth of T. zillii. Total instantaneous mortality (Z), estimated using catch curve analysis, was 0.74 for gillnetted fish and 0.71 for trapped fish. These estimates were at the low end of the total mortality reported for other tilapia species. Natural mortality (M) was estimated as 0.52–0.54 by applying Rikhter and Efanov's maximum age at maturity and Hoenig's maximum age methods, respectively. Fishing mortality (F) in Lake Nkuruba was 0.17–0.22, indicating a low exploitation level in the lake.  相似文献   

20.
Understanding drivers of freshwater fish assemblages is critically important for biodiversity conservation strategies, especially in rapidly developing countries, which often have environmental protections lagging behind economic development. The influences of natural and human factors in structuring fish assemblages and their relative contributions are likely to change given the increasing magnitude of human activities. To discriminate natural and human drivers of fish diversity and assemblage patterns in developing countries with rapid socio‐economic development, a dataset of 908 freshwater fish species and 13 metrics including three categories of both natural (i.e., biogeographic) and human drivers (i.e., economic growth, inland fisheries) in China were analysed with machine learning algorithms (i.e., self‐organizing map, random forest). Here, we found that biogeographic drivers explained 21.8% of the observed fish assemblage patterns in China and remained stronger predictors when compared to human drivers (i.e., 15.6%, respectively). Freshwater fish species richness was positively correlated to rainfall, air temperature, surface water area and inland fisheries production but negatively correlated with urbanization. In addition, the strong structuring effects of climatic variables on Chinese fish richness patterns suggested that the fish assemblages could be particularly vulnerable to climate change. Our results showed that natural biogeographic factors still dominate in driving freshwater fish assemblage patterns despite increased human disturbances on aquatic ecosystems in a rapidly developing country. These findings consequently suggested that we should consider both natural (e.g., climate) and human (e.g., urbanization, inland fisheries) factors when establishing aquatic conservation strategies and priorities for developing countries that are experiencing rapid socio‐economic changes.  相似文献   

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