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1.
Hatcheries often produce bold fish that are maladapted to survive in the wild, as absence of predators and selection for fast growth tend to favour risk-taking behaviors. Not surprisingly, losses of hatchery fish through predation can be high immediately after release and this may account for the failure of many ex-situ fish conservation programmes. For supportive-breeding to be useful, it is essential that released fish are able to display natural behaviors. We compared the performance of juvenile Atlantic salmon reared in environmentally-enriched tanks receiving natural prey and subjected to simulated predator attacks with fish reared under standard hatchery conditions while keeping densities constant. No differences were detected between controls and environmentally enriched fish in survival, final size or nutritional status. Yet, changes in rearing conditions had rapid and marked effects on risk-taking behavior. Environmentally enriched fish were 2.1 times less willing, and took significantly longer to leave shelter, than controls within two weeks of enrichment. Thus our study indicates that it is possible through environmental enrichment to modify at least one component of fishes’ behavior known to have clear adaptive implications, i.e. the propensity of hatchery-reared fish to take excessive risks. Ex-situ conservation could therefore benefit from rearing fish in naturalized, structurally complex environments with natural prey to promote the development of more natural behaviors. 相似文献
2.
Eric R. Buhle Kirstin K. Holsman Mark D. Scheuerell Andrew Albaugh 《Biological conservation》2009,142(11):2449-2455
Efforts to conserve depleted populations of Pacific salmon (Oncorhynchus spp.) often rely on hatchery programs to offset losses of fish from natural and anthropogenic causes, but their use has been contentious. We examined the impact of a large-scale reduction in hatchery stocking on 15 populations of wild coho salmon along the coast of Oregon (USA). Our analyses highlight four critical factors influencing the productivity of these populations: (1) negative density-dependent effects of hatchery-origin spawners were 5 times greater than those of wild spawners; (2) the productivity of wild salmon decreased as releases of hatchery juveniles increased; (3) salmon production was positively related to an index of freshwater habitat quality; and (4) ocean conditions strongly affect productivity at large spatial scales, potentially masking more localized drivers. These results suggest that hatchery programs’ unintended negative effects on wild salmon populations, and their role in salmon recovery, should be considered in the context of other ecological drivers. 相似文献
3.
4.
北京昌平区农业景观野生蜂多样性的时空动态分布 总被引：1，自引：0，他引：1
近年来,由于生境质量的下降和生境丧失,野生蜂多样性急剧下降,严重威胁传粉服务和农业的可持续发展。为揭示野生蜂在农业景观镶嵌体中的时空分布格局及不同生境对野生蜂保护的重要性,本研究于2016年4—9月采用网捕法调查了北京昌平农业景观4种主要生境类型(人工林、自然灌木林、荒草地和桃园)中的野生蜂,分析不同生境类型中野生蜂多样性及其时间动态变化特征。结果表明:野生蜂及其中的大体长蜂和独居蜂的物种数和个体数,以及中体长蜂的个体数均在自然灌木林中最高,人工林中小体长蜂个体数最多,野生蜂总个体数和总物种数均在桃园中最低。在不同月份,所有功能群野生蜂均在自然或半自然生境中最高,5月桃园中最低,原因可能与桃园中对地表杂草的集约化管理有关。多度最大的4个优势物种依次为黄胸彩带蜂、铜色隧蜂、黄芦蜂和隧淡脉隧蜂,其在生境间的时间动态特征不同。调查的4种生境均为野生蜂提供了可利用资源,但自然生境和半自然生境的作用更大;其中,自然灌木林维持了较多具有较高潜在传粉效率的中体长和大体长野生蜂,具有更高的保护价值。为了促进该地区农业景观中不同功能群野生蜂多样性及传粉服务,需提高生境类型的多样性,同时在野生蜂活动高峰季节采取低集约化的生境管理方式。 相似文献
5.
滇东南南瓜传粉昆虫密度对生境丧失的差异性响应 总被引：2，自引：1，他引：1
响应多样性理论认为不同传粉蜂对环境胁迫的响应尺度和过程在时空上存在差异,然而目前尚不清楚我国重要农林生态系统传粉蜂对环境胁迫的响应规律。试验以云南省文山州广南县南瓜农田生态系统为研究对象,根据农田景观中自然半自然生境数量和面积的变化梯度和离自然半自然生境的距离梯度选择南瓜样地,抽样调查南瓜样地内熊蜂密度和蜜蜂密度。解译卫星影像获取土地类型数据,分析熊蜂密度和蜜蜂密度同自然半自然生境面积百分率和耕地面积百分率的相关系数,在最大相关系数对应的空间尺度下探索蜜蜂密度和熊蜂密度对生境丧失的响应规律。研究发现,熊蜂密度随自然半自然生境面积百分率的增加而显著增加,但蜜蜂密度并不受自然半自然生境面积的影响。同时,熊蜂密度随耕地面积百分率的增加而显著下降,但蜜蜂密度不受耕地面积的影响。此外,熊蜂密度随离自然半自然生境的距离增加而显著下降,但蜜蜂密度不受距离作用的影响。由此可见,云南省文山州南瓜传粉熊蜂和蜜蜂多度对生境丧失表现出多样的响应规律。熊蜂和蜜蜂对生境丧失的差异性响应可能是保障该区域南瓜受粉的重要机制。 相似文献
6.
We compared the behaviour of wild and captive-bred butterfly splitfins (Ameca splendens), an endangered freshwater fish, to investigate whether captive breeding results in the behavioural divergence of wild and captive individuals. In a first experiment, we examined whether the captive environment allows for the similar expression of behaviours observed in wild fish. The foraging, courtship and aggressive behaviour of fish in their natural habitat (in Mexico) was compared with that of their counterparts that have been bred at London Zoo, UK, for 40 years. These in situ observations revealed that wild fish were preoccupied with searching for food whereas captive fish engaged more in aggressive interactions. In a subsequent laboratory experiment we compared the behaviour of wild-caught and captive-bred fish under standard conditions in two novel habitats: structured (enriched) and unstructured (bare) aquaria. Overall, captive-bred butterfly splitfins displayed higher levels of aggression than wild-caught fish. The relationship between aggression and habitat structure was influenced by density; captive-bred males were more aggressive when observed in structured habitats than unstructured ones, but only when they were stocked at a high density. We also found an effect of tank structure on foraging behaviour, with individuals spending more time foraging in unstructured tanks than structured tanks. There was no effect of captive breeding or habitat structure on courtship behaviour.Our findings suggest that captive environments can promote the development of aggressive behaviour which may affect the suitability of captive-bred fishes for reintroduction into the wild. 相似文献
7.
基于水下机器视觉的大西洋鲑摄食行为分类 总被引：6，自引：6，他引：0
根据鱼群摄食行为状态进行水产养殖精准投喂控制,是有效提高饵料利用率降低水体污染的关键技术。目前,大多数基于机器视觉的鱼类摄食行为研究都是在实验室对真实养殖环境进行模拟并采用水上摄像机获取数据,由于光照条件和养殖环境的影响,该数据无法反映大西洋鲑在实际生产状况下的摄食行为,因此应用范围有限。为解决此问题,该研究提出一种基于真实工厂化养殖环境的鱼类摄食行为分类算法。该算法使用水下观测方式并采用视频序列作为样本,首先利用变分自动编码器对视频序列样本进行逐帧编码以产生所有帧对应的高斯均值和方差向量,分别联立所有均值和方差向量得到均值特征矩阵和方差特征矩阵。然后将特征矩阵输入到卷积神经网络中,实现对鱼群的摄食行为分类。试验结果表明,在真实的工厂化养殖环境下,该研究所提出的方法综合准确率达到了89%,与已有的基于单张图像的鱼类摄食行为分类方法相比,综合准确率提高了14个百分点,召回率提高了15个百分点。研究结果可为基于鱼类摄食行为的鱼饵精准投喂控制提供参考。 相似文献
8.
Populations living on the periphery of a species range are subjected to intense habitat pressures that stress their vulnerability to threats. South Iberian brown trout (Salmo trutta) populations are located on the southwestern boundary of the species range in Europe. This region has been described as a contact zone between Atlantic and Mediterranean populations in other fish species, and allozyme data detected natural hybridization between native Atlantic and Mediterranean brown trout in this area. Nevertheless, native pattern of populations relationships are threatened by hybridization with exogenous hatchery fish. Allozyme data and complete mtDNA control region sequences were used to analyse the ongoing processes of human mediated hybridization between native and hatchery brown trout in this region. Estimates of the persistence of hatchery genes detected a high level of introgression in some of the sampled locations (hatchery ancestry more than 25% in GF-1, GF-2 and GF-3), but results differed from both kinds of markers. The low intrapopulation diversity (Hs = 0.051) indicated that genetic drift could explain discrepancies between markers. At individual level, the complementary use of both markers detected more hatchery origin fish than those detected by the use of a single technique. Based on these results, the importance of considering a large number of genetic markers to evaluate introgression accurately is emphasized. The ability of the current management policies to the protection and conservation of marginal populations that retain complex and special evolutionary histories such as those studied is also questioned. 相似文献
9.
采用机器视觉和傅里叶频谱特征的循环水养殖鱼类摄食状态判别 总被引：2，自引：2，他引：0
为精准判别工厂化循环水养殖池中鱼类摄食行为动态,实现精准投喂,该研究提出一种基于傅里叶频谱特征提取并通过支持向量机分类的鱼类摄食行为判断方法。首先,对采集到的工厂化循环水养殖池中鱼群的摄食影像作水花前景提取,并从空域转化至频域;然后,在频域内构建环形滤波器,通过频谱滤波确定特征向量提取范围(更明显表征图像灰度变化剧烈程度的频谱区域),并提取区间内幅值,以此表征鱼类摄食欲望的强弱,从而可以实现鱼类摄食行为的判断。统计每一区间所得幅值样本之和并以此构建特征向量集,并将所得特征向量训练支持向量机。结果表明,该研究所提出的方法在工厂化养殖鱼类摄食行为判断方面具有很好的效果,判断准确率可达99.24%,研究结果能以极高准确率判断鱼类摄食行为,为指导精确投喂提供科学依据。 相似文献
10.
循环水养殖模式下鱼生长对水环境因子的响应模型构建 总被引：2，自引：0，他引：2
为探究鱼类生长对水环境的响应,预测鱼类在养殖水环境多因子协同作用下的生长速度,进行了室内曝气推流循环水养殖罗非鱼试验,试验持续周期为8周。结果表明,在一定范围内,随着溶解氧质量浓度的增加,鱼的食物转化效率和特定生长率均有所提高;随着非离子氨质量浓度的增加,鱼的食物转化效率和特定生长率均有所降低;而亚硝酸盐质量浓度由于变化不大且均处于安全质量浓度范围,该试验中对鱼的食物转化效率和特定生长率未产生显著影响。基于这一系列试验结果对罗非鱼特定生长率进行了非线性拟合,建立了鱼的生长预测模型,R2为0.82,并通过实测数据验证了模型的有效性和普适性。预测模型表明,养殖初始鱼质量、养殖密度、非离子氨以及亚硝酸盐质量浓度的增加,均会导致鱼生长速度减缓,而提高溶解氧质量浓度则可以提高鱼生长速度。该预测模型虽然是在曝气推流循环养殖模式下获得的,但对其他养殖模式同样适用,使鱼生长对水环境因子的响应变得可测,为促进养殖鱼类的健康发展、养殖系统的优化和养殖效益的提高提供了便利和参考。 相似文献
11.
K.H. Chorlton I.D. Thomas D.W. Bowen V.P. Carnide 《Genetic Resources and Crop Evolution》2000,47(2):157-162
The Plant Genetic Resources Unit of the Institute of Grassland and Environmental Research, U.K., and the Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro, Portugal, carried out a joint plant collecting expedition in Portugal in May 1995. Seven regions of Portugal were explored from the north to the south. A diverse range of habitats was sampled covering different altitudes, management systems and ecological conditions, where semi-natural grassland and wild unmanaged grassland was found. Vegetative samples of forage grass and legume populations were collected wherever possible. Seed samples were collected in the absence of live plants and from farmers' stores. Detailed collection site data was recorded at every site. 113 populations of Lolium spp., Festuca spp., Agrostis spp., Dactylis spp. and Briza spp. and 53 populations of Trifolium spp., Medicago spp. and Lupinus spp. were collected from 115 sites. It was possible to find traditional agricultural systems throughout Portugal but they are changing in response to European Union farming policies. For example, Lolium multiflorum Lam. is still intercropped with maize, although seed production of this crop on the farm is no longer permissible and, therefore, local land races are being replaced by commercial varieties. These changes to traditional agricultural systems are contributing to a major loss of genetic diversity. 相似文献
12.
H. H. Zahran 《Biology and Fertility of Soils》1991,12(1):73-80
Summary The Rhizobium-legume symbiosis in arid ecosystems is particularly important for locations where the area of saline soils is increasing and becoming a threat to plant productivity. Legumes, which are usually present in arid ecosystems, may be adapted to fix more N2 under saline conditions than legumes grown in other habitats.Legumes are known to be either sensitive or moderately resistant to salinity. The salt sensitivity can be attributed to toxic ion accumulations in different plant tissues, which disturb some enzyme activities.Among the basic selection criteria for salt-tolerant legumes and rhizobia are genetic variability within species with respect to salt tolerance, correlation between accumulations of organic solutes (e. g., glycine betaine, proline betaine, and proline) and salt tolerance, and good relationships between ion distribution and compartmentation, and structural adaptations in the legumes.Salt stress reduces the nodulation of legumes by inhibiting the very early symbiotic events. Levels of salinity that inhibit the symbiosis between legumes and rhizobia are different from those that inhibit the growth of the individual symbionts. The poor symbiotic performance of some legumes under saline conditions is not due to salt limitations on the growth of rhizobia.Prerequisites for a successful Rhizobium-legume symbiosis in saline environments include rhizobial colonization and invasion of the rhizosphere, root-hair infection, and the formation of effective salt-tolerant nodules.The possibility of exploring the Rhizobium-legume symbiosis to improve the productivity of saline soils is reviewed in this paper. 相似文献
13.
Supportive breeding is an important tool in conservation management, but its long-term genetic consequences are not well understood. Among the factors that could affect the genetics of the offspring is sperm competition as a consequence of mixed-milt fertilizations - which is still a common practice in many hatcheries. Here, we measured and combined the relevant factors to predict the genetic consequences of various kinds of hatchery-induced sperm competition. We drew a random sample of male Coregonus zugensis (an Alpine whitefish) from a hatchery program and quantified their in vitro sperm potency by integrating sperm velocity during the first minute after activation, and their in vitro milt potency by multiplying sperm potency with milt volume and sperm cell density. We found that not controlling for sperm density and/or milt volume would, at a constant population size, decrease the variance effective number of male breeders Nem by around 40-50%. This loss would decrease with increasing population growth rates. Partial multi-factorial breeding and the separate rearing of in total 799 batches of eggs revealed that neither sperm nor milt potency was significantly linked to egg survival. Sperm and milt potency was also not significantly correlated to other potential quality measures such as breeding tubercles or condition factor. However, sperm potency was correlated to male age and milt potency to male growth rate. Our findings suggest that hatchery-induced sperm competition not only increases the loss of genetic variation but may also induce artificial selection, depending on the fertilization protocol. By not equalizing milt volume in multi-male fertilization hatchery managers lose relatively more genetic variation and give fast-growing males a reproductive advantage, while equalizing milt volume reduces the loss of genetic variation and favors younger males who may have fast sperm to compensate for their subdominance at the spawning place. 相似文献
14.
在鱼类养殖过程中,饲料成本是主要养殖成本,如何做到合理投喂是减少养殖成本、提高养殖效益的关键。智能投喂是基于各类传感器获取环境和鱼群的各类信息,结合相关算法模型进行决策的投喂方式,是提高鱼类养殖投喂效率的重要手段。目前,鱼类的智能投喂已经取得了一些成果,但由于复杂多变的养殖环境和鱼类行为的不确定性,实现鱼类智能投喂仍面临挑战。该研究综述了鱼类养殖智能投喂的应用与进展,包括基于计算机视觉技术的鱼类摄食行为分析与饲料检测,声学技术、其他传感器技术和生物模型在智能投喂中的应用与发展。此外,分析了投饵机和投喂系统的研究现状,并总结了目前研究存在的问题。今后,要进一步加强水产、工学、信息等多学科的交叉融合,对鱼类图像、声音、生长规律与生物特征等多种信息进行综合分析应用,以提高投喂系统对多场景和多种养殖方式的适应性。 相似文献
15.
Andrew M. Griffiths Jonathan S. Ellis Darryl Clifton-Dey Gonzalo Machado-Schiaffino Dylan Bright Eva Garcia-Vazquez Jamie R. Stevens 《Biological conservation》2011,144(11):2733-2738
Since the 1970s, when major improvements to the water quality were made, the River Thames has been subject to a high-profile project aimed at restoring Atlantic salmon to the catchment. Whilst initially successful, with hundreds of salmon returning each year in the late 1980s, the number of adults returning to the river has declined steeply again in recent years, reaching a low in 2005 when no salmon were recorded. Using a baseline of genetic information gathered from 3830 salmon from throughout their southern European range, and incorporating samples from the hatchery fish used to stock the Thames, all 10 tagged hatchery fish captured in 2003 and all 16 returning untagged adult salmon captured between 2005 and 2008 were assigned to their most likely river of origin. The results suggest that untagged salmon currently ascending the river originate not from exogenous fish stocked into the Thames, but predominantly from other rivers in southern England. This highlights the potential for natural processes of recolonisation to operate in rivers where salmon have become locally extirpated. These findings also underscore several important considerations when undertaking species restoration projects: (i) previous causes of declines must be sufficiently ameliorated to allow new/translocated individuals to thrive, (ii) introduced individuals should originate from a stock that is closely related to the extirpated population, according to the principles of contemporary conservation biology, and (iii) dispersal and gene-flow from neighbouring populations may play a significant role in establishing new populations. 相似文献
16.
Jean-Marie Prosperi Eric Jenczewski Michel Angevain Joëlle Ronfort 《Genetic Resources and Crop Evolution》2006,53(4):843-856
One hundred and three natural populations of Medicago L. were collected in Spain, mainly from roadsides, non-irrigated or grazed lands. This germplasm was evaluated at Montpellier
(France) with control cultivars and Spanish landraces under completely random block design, replicated four times, and observed
for 64 qualitative or quantitative characters. Differences between natural populations and cultivated controls are highly
significant, but gene flow occurs between wild and cultivated compartment and hybrid populations were identified. On the basis
of multivariable analysis, the accessions were grouped into four clusters depending on their proximity with the cultivated
pool to facilitate their management and ex situ conservation. The relationship between environment of the site of collection and phenotypic characteristics of the natural
populations was also discussed. Different policies of conservation of these genetic resources are suggested to avoid their
disappearance even when they disappeared from the other regions of the western Mediterranean. Spanish wild pool of alfalfa,
also called ‘Mielga’, appears of great interest for the breeding of alfalfa because it contains a large diversity of characteristics
(prostrate habit, rhizomes) linked to tolerance to grazing or drought environment. With the need for more sustainable systems
in agriculture, the erosion of natural habitats and the necessity for rehabilitation of degraded ecosystems, the importance
of this wild pool is really inestimable. 相似文献
17.
Ex situ collections in botanic gardens have great potential in contributing to the conservation of rare plants. However, little is known about the effects of cultivation on the genetic diversity and fitness of garden populations, about genetic changes due to unconscious selection and potential adaptation to the artificial conditions. We compared the genetic variability and fitness of the rare, short-lived perennial Cynoglossum officinale from 12 botanic gardens and five natural populations in Germany. Genetic variability was assessed with eight nuclear microsatellites. Plants were grown in a common garden and performance was measured over 2 years. Mean genetic diversity was very similar in botanic garden and natural populations. However, four of the garden populations exhibited no genetic variability at all. Moreover, the genetic diversity of garden populations decreased with increasing duration of cultivation, indicating genetic drift. Plant performance from natural and garden populations in terms of growth, flowering and seed production was similar and in garden populations only seed mass was strongly related to genetic diversity. Several lines of evidence indicated genetic changes in garden populations in response to cultivation. Seed dormancy was strongly reduced in garden populations, and in response to nutrient addition garden plants increased the size of their main inflorescence, while wild plants increased the number of inflorescences. These changes could be maladaptive in nature and reduce the suitability of garden populations as a source for reintroductions. We suggest that botanic gardens should pay more attention to the problem of potential genetic changes in their plant collections. 相似文献
18.
Nathalie Cassagne Thierry Gauquelin Marie-Claude Bal-Serin Charles Gers 《Pedobiologia》2006,50(2):127-134
Our study compared the soil collembolan community at three semi-natural sites (a beech forest, a beech–fir forest and a fir stand) and three managed sites (Norway spruce, beech–fir and fir). Collembola were extracted from a total of 60 samples with a Berlese–Tullgren funnel, counted and identified to species level. A total of 7187 specimens, representing 51 species and 37 genera, were collected. There were significant differences between managed and natural forests (t-test, P=0.000). The communities and their population densities were significantly lower in the managed site: 51 species with 708,498 ind m−2 in the semi-natural forests to 36 species and 306,042 ind m−2 in the managed stands. The endemic component suffered a particularly severe decrease in species richness and abundance (57% and 71% lower in the managed forests, respectively). These species with narrow distribution and small local populations are doubly vulnerable to alterations of environmental conditions. They are very sensitive to loss of their natural habitat owing to human intervention and thus represent useful indicators of tolerance to environmental stress. We highlight the need to take endemic species into consideration in studies on the conservation of biodiversity because they are most at risk of extinction. Semi-natural forests are refuges for endemic species and should be protected. 相似文献
19.
Owing to the extensive development of road networks, millions of animals are killed annually. This impact on the natural environment has been questioned: is there a selection of victims in the car collisions? and do road-kills, as do predators, influence a population by eliminating individuals in poor condition? We compared road-killed individuals to those killed by predators in SE Poland in three bird species: Yellowhammer Emberiza citrinella, Barn Swallow Hirundo rustica, and Chaffinch Fringilla coelebs. We applied ptilochronology, in which the width of feather growth bars represents an individual’s relative nutritional condition. Our results show that the analyzed species were in significantly better body condition than those killed by raptors. Our study does not concur with previous studies which concluded that weaker individuals are more vulnerable on the road. Raptors select prey in poor condition, but road-killed individuals are in significantly better condition, so apparently road-kill results in the random elimination of healthy individuals. The conservation implications of this study are far-reaching; future road construction and safety regulations must take wildlife into consideration. If these human-created habitats are killing a significant proportion of the healthier part of natural populations in a non-selective manner, this could result in situations where fragmented populations could be driven to a critical stage, and/or the situation of declining or endangered populations worsened further. 相似文献
20.
基于光流法的鱼群摄食状态细粒度分类算法 总被引：1，自引：1，他引：0
对鱼群摄食状态的细粒度分类有利于更精细地描述鱼群的摄食行为。该研究基于工厂化的循环养殖池环境提出了一种利用光流法进行特征提取的鱼群摄食状态细粒度分类算法。算法对鱼群的巡游视频进行摄食状态分类,首先通过光流法提取视频内鱼群的帧间运动特征,其次构建了一个帧间运动特征分类网络对该特征进行细粒度分类,最后基于投票策略确定视频的最终类别。试验结果表明,该研究算法在投票阈值设置为50%的情况下,视频准确率达98.7%;在投票阈值设置为80%的情况下,视频准确率为91.4%。在不同的投票阈值设置下,该算法的视频准确率始终保持在90%以上,说明其分类鲁棒性较强。相较于实验室养殖环境,基于工厂化养殖环境对鱼群的摄食状态所展开的算法研究实际应用性更强,可为精细描述鱼群摄食行为,实现精准投饵自动控制提供参考。 相似文献