Hypoxia-based habitat compression of tropical pelagic fishes   总被引：2，自引：0，他引：2  

ERIC D. PRINCE  C. PHILLIP GOODYEAR 《Fisheries Oceanography》2006,15(6):451-464

Large areas of cold hypoxic water occur as distinct strata in the eastern tropical Pacific (ETP) and Atlantic oceans as a result of high productivity initiated by intense nutrient upwelling. We show that this stratum restricts the depth distribution of tropical pelagic marlins, sailfish, and tunas by compressing the acceptable physical habitat into a narrow surface layer. This layer extends downward to a variable boundary defined by a shallow thermocline, often at 25 m, above a barrier of cold hypoxic water. The depth distributions of marlin and sailfish monitored with electronic tags and average dissolved oxygen (DO) and temperature profiles show that this cold hypoxic environment constitutes a lower habitat boundary in the ETP, but not in the western North Atlantic (WNA), where DO is not limiting. Eastern Pacific and eastern Atlantic sailfish are larger than those in WNA, where the hypoxic zone is much deeper or absent. Larger sizes may reflect enhanced foraging opportunities afforded by the closer proximity of predator and prey in compressed habitat, as well as by the higher productivity. The shallow band of acceptable habitat restricts these fishes to a very narrow surface layer and makes them more vulnerable to over‐exploitation by surface gears. Predictably, the long‐term landings of tropical pelagic tunas from areas of habitat compression have been far greater than in surrounding areas. Many tropical pelagic species in the Atlantic Ocean are currently either fully exploited or overfished and their future status could be quite sensitive to increased fishing pressures, particularly in areas of habitat compression.  相似文献   

公路对天山马鹿（Cervus elaphus songaricus）种内遗传分化的影响     

周璨林  ;艾萨江·图合提  ;阿米拉·阿布来提  ;日沙来提·吐尔地  ;艾斯卡尔·买买提  ;马合木提·哈力克 《中国养羊》2014,(6):5-9

为研究公路对大型哺乳动物造成的影响,分别采集新疆省道110、203、303公路两侧的天山马鹿粪便样本,采用5个微卫星位点进行个体识别后利用Arlequin3．11进行遗传距离、基因多样性、杂合度等测定分析。结果表明：5个微卫星均具有很好的多态性,5地区中松树塘与寒气沟、白石头马鹿的遗传距离最远,松树塘马鹿的基因杂合度、基因型数量均最低;小西沟与白杨沟马鹿之间遗传距离为负值,其基因杂合度、基因型无显著性差异（P〉0．05）。说明公路对栖息地的分割状态不同,会导致种群的遗传情况改变。当公路仅深入栖息地没有将栖息地割裂时,公路两旁种群无差异;当栖息地被公路完全隔绝,则该栖息地内动物的基因杂合度、基因型数量降低;使用中的公路对临近种群的隔绝效果强于废弃旧公路。  相似文献   

The status of Arctic charr Salvelinus alpinus in Britain and Ireland     

P. S. Maitland  I. J. Winfield  I. D. McCarthy  F. Igoe 《Ecology of Freshwater Fish》2007,16(1):6-19

Abstract –  The Arctic charr occurs in lakes across Britain and Ireland and was previously described here as 15 separate species. Most authorities now agree that all these stocks belong to a single polymorphic species complex Salvelinus alpinus (L.). This fish is given little protection in British and Irish law and there has been a steady loss of natural populations in recent years in all the countries concerned. A few new stocks have been created either intentionally or accidentally. In Scotland, only a small proportion of the 258 recorded natural populations has been studied and at least 12 of these are now extinct. There are at least four introduced populations originating from native Scottish stocks, but the fate of stocks introduced from Canada for aquaculture is uncertain. In England, there are eight extant populations in Cumbria and four others extinct. The status of introduced stocks in England is uncertain but there is probably one population surviving in Yorkshire. In Wales, eight lakes with resident Arctic charr populations have been recorded, three of these populations are natural, one is extinct and four have been introduced. In Ireland, of the 74 known populations, approximately 30% are extinct. There is no evidence to indicate that introduced stocks (some of them from Iceland) in a small number of lakes have survived there. A range of factors is involved in the extinction of populations and these include pollution, eutrophication, acidification, afforestation, engineering, exploitation, aquaculture, introductions and climate change. Much research remains to be done and unique stocks of this valuable species will continue to be lost unless positive action is taken through local conservation management backed by appropriate national legislation.  相似文献   

Competitive interactions between native and exotic salmonids: a combined field and laboratory demonstration   总被引：4，自引：0，他引：4  

S. Blanchet  G. Loot  G. Grenouillet  S. Brosse 《Ecology of Freshwater Fish》2007,16(2):133-143

Abstract –  We studied the impact of two exotic salmonid species (brook trout, Salvelinus fontinalis and rainbow trout, Oncorhynchus mykiss ) on native brown trout ( Salmo trutta fario ) habitat, growth and survival. Habitat selection and vertical distribution between young-of-the-year of the three species were examined in a stream aquarium under different sympatric and allopatric combinations. In addition, similar species combinations were introduced in a Pyrenean mountain stream (southwest France) in order to extend laboratory results to growth and apparent survival. Both laboratory and field results indicated that rainbow trout significantly affected native brown trout habitat selection and apparent survival. On the contrary, brown trout habitat, growth and apparent survival were hardly affected by brook trout. These results support the idea that rainbow trout negatively influence native brown trout, and that competition could influence the outcome of fish biological invasions in freshwater ecosystems.  相似文献   

Linking habitat selection, emigration and population dynamics of freshwater fishes: a synthesis of ideas and approaches     

T. E. McMahon  W. J. Matter 《Ecology of Freshwater Fish》2006,15(2):200-210

Abstract –  The consequences of individual behaviour to dynamics of populations has been a critical question in fish ecology, but linking the two has proven difficult. A modification of Sale's habitat selection model provides a conceptual linkage for relating resource availability and individual habitat selection to exploratory behaviour, emigration and population-level responses. Whole-population experiments with pupfish Cyprinodon macularius that linked all factors along this resource to population continuum lend support to this conceptual model, and illustrate that emigration may be much more common in fish populations than considered in most individual- or population-based models. Accommodating emigration can enhance the ecological appropriateness of behavioural experiments and increase confidence in extrapolation of experimental observations to population-level effects. New experimental designs and advancing technologies offer avenues for assessing population consequences of habitat selection and emigration by individual fish. Emigration often is the key linkage between individual behaviour and population responses, and greater understanding of the underlying factors affecting this often-overlooked demographic parameter could offer new approaches for management and conservation of fishes.  相似文献   

Cascading effects of introduced Nile perch (Lates niloticus) on the foraging ecology of Nile tilapia (Oreochromis niloticus)     

G. N. Bwanika  L. J. Chapman  Y. Kizito  J. Balirwa 《Ecology of Freshwater Fish》2006,15(4):470-481

Abstract –  Nile tilapia ( Oreochromis niloticus L.) is the dominant of the introduced tilapiines in many East African lakes and has flourished in the presence of introduced Nile perch ( Lates niloticus L.). We explored the hypothesis that O. niloticus exhibits increased omnivory in response to a decline in abundance of haplochromine cichlids. First, we quantified variation in habitat use and diet of O. niloticus in Lake Nabugabo, Uganda. Second, we compared the diet of O. niloticus in lakes with (Nabugabo, Victoria) and without (Mburo, Wamala, Nyamusingiri, Kyasanduka) introduced Nile perch. In Lake Nabugabo, a higher level of phytoplanktivory was observed in small juveniles than in larger fish and in wetland ecotone areas where haplochromines were most abundant. An omnivorous diet dominated by detritus and invertebrates was recorded for O. niloticus in lakes Nabugabo and Victoria, while a predominantly herbivorous diet was characteristic of O. niloticus in lakes without Nile perch. Availability of a broad food base in lakes where inshore insectivores have been reduced may explain the increased omnivory recorded in lakes Nabugabo and Victoria.  相似文献   

Changes in rhodopsin-porphyropsin ratio of chum and pink salmon     

Ei-ichi?HasegawaEmail author 《Fisheries Science》2005,71(5):1091-1097

ABSTRACT:   In order to investigate the changes in rhodopsin-porphyropsin ratio of chum salmon and pink salmon in relation to the change in their habitat, the ratios were analyzed in individual fish prior to stocking, during the sea run, homing, and upstream migration. The ratio in both the species gradually increased during the sea run. However, the ratio decreased after upstream river migration. Moreover, in the sea, the rhodopsin-porphyropsin ratio of chum salmon was always slightly higher than that of pink salmon. The largest difference in the individual variation was observed in the individuals caught with a set net placed near the mouth of a home river.  相似文献   

The yellow European eel (Anguilla anguilla L.) may adopt a sedentary lifestyle in inland freshwaters     

P. Laffaille  A. Acou  J. Guillouët 《Ecology of Freshwater Fish》2005,14(2):191-196

Abstract – We analysed the movements of the growing yellow phase using a long-term mark–recapture programme on European eels in a small catchment (the Frémur, France). The results showed that of the yellow eels (>200 mm) recaptured, more than 90% were recaptured at the original marking site over a long period before the silvering metamorphosis and downstream migration. We conclude that yellow European eels >200 mm may adopt a sedentary lifestyle in freshwater area, especially in small catchment.  相似文献   

`Ocean triads' in the Mediterranean Sea: physical mechanisms potentially structuring reproductive habitat suitability (with example application to European anchovy, Engraulis encrasicolus)     

Vers N. Agostini  & Andrew Bakun 《Fisheries Oceanography》2002,11(3):129-142

Summaries of maritime weather reports and mean seasonal satellite-sensed ocean colour distributions for the Mediterranean Sea are used to identify characteristic configurations of physical mechanisms promoting (i) nutrient enrichment, (ii) concentration of larval food distributions, and (iii) local retention of eggs and larvae. Five subbasin scale `ocean triads', hypothesized to be particularly favourable groupings, are identified in the Aegean Sea, the Gulf of Lions and nearby Catalan Coast, the Alboran Sea, the Straits of Sicily/Tunisian Coast, and the Adriatic Sea. These are examined in relation to available knowledge of anchovy spawning grounds. All areas are characterized by patterns of linked wind-driven Ekman upwelling and downwelling. All areas except the Straits of Sicily are found to have inputs of less saline surface waters offering raised nutrient concentrations, enhanced upper layer stability, and frontal density contrasts, and to have areas where the characteristic rate of turbulent mixing energy input by the wind fall below a reference intensity level. All areas, except the Sicilian Channel/Tunisian Coast, also contain abundant locally reproducing anchovy populations.  相似文献   

基于四大家鱼产卵需求的汉江中下游生态流量研究     

张辉  曾晨军  李婷  何术锋  莫康乐  杨培思  陈求稳 《水生态学杂志》2022,43(3):1-8

针对汉江中下游梯级电站开发后水文节律变化造成四大家鱼栖息地生境质量降低的问题,分别通过几种常用水文学法和栖息地模型计算了汉江中下游河道最小生态流量和四大家鱼产卵适宜生态流量,并在最小生态流量的基础上,结合四大家鱼产卵适宜生态流量以及生态水文特征在5-8月进行了脉冲设计,综合确定出了满足四大家鱼产卵需求的生态流量过程。结果表明,Lyon法和7Q10法最适宜汉江中下游最小生态流量的计算,流量为294~863 m3/s;通过栖息地模型计算,彭市和仙桃江段四大家鱼产卵适宜生态流量为1233~3950 m3/s;流量日涨幅在139.1~534.8 m3/s,持续5 d的涨水过程可为四大家鱼产卵提供良好的条件。该研究从考虑四大家鱼产卵需求的角度,为汉江中下游梯级电站的生态调度提供科学参考。  相似文献