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1.
We studied the effects of acidification on female sexual behavior in brown trout (Salmo trutta) and compared the results with those in hime (land-locked sockeye) salmon (Oncorhynchus nerka) (Kitamura and Ikuta, 2000). The results were similar to those of sockeye salmon. Spawning brown trout were extremely sensitive to the acidity of ambient water, and nest-digging behavior was severely inhibited (p<0.05) by very slight acidification (pH below 6.4). However, there were some differences between the two species. Female trout and salmon showed almost no digging below pH 5.0 and 6.0 (Kitamura and Ikuta, 2000), respectively. When the ambient water was returned to nearly neutral (pH6.6) conditions, digging in hime salmon reappeared in 4 of the 6 fish tested (Kitamura and Ikuta, 2000), whereas digging in brown trout reappeared in all 6 fish tested. The above-mentioned differences in behavioral response between the two species appear to reflect the species difference in terms of vulnerability to acidification (Ikuta et al., 1992). Avoidance of slightly acidic water in selection of spawning site or cessation of spawning behavior in weakly acidic environments may be the most potent cause of the reduction of salmonid populations in the early stages of acidification.  相似文献   

2.
Mature male and female rainbow trout were treated with low pH (Av. 4.5) sulfuric acid water for 1 or 2 weeks. Percentage of eyed embryos in eggs from control, 1-week-treated and 2-week-treated females were 100%, 80% and 0%, respectively. Low pH exposure of male trout induced 11% deformation in embryos fertilized with their sperm. In order to clarify the physiological mechanism of the effects of low pH exposure, sex hormone levels were compared. In female fish, plasma sex hormones levels showed no difference among the groups, but egg contents of 1720-dihydroxy-4-pregnen-3-one, which induces oocyte maturation, were significantly lower in low pH exposed groups. Acidified male fish showed higher plasma levels of the spermiation inducing hormone, 11-ketotestosterone. Effects on eggs were manifested under pH lower than 5. Under continual rearing of land-locked sockeye salmon in acid water, the effects on the oocyte were observed in those adult females which were exposed to acidic condition for more than 1 week before the timing of ovulation. These results suggest that low pH affects oocyte maturational events occurring just 1 week before ovulation, and that acid stress affects the endocrinological mechanisms of final maturation in fish gametocytes. Thus, acidification of the aquatic environment may reduce the reproductive activity of fish at rather low acidity levels.  相似文献   

3.
The pro-oxidative activity of trout hemoglobin was significantly increased at low pH (2.5-3.5) in a washed fish muscle (WFM) system. It was found that the more unfolded the hemoglobin was the more exposed its heme group was, which increased its pro-oxidative activity. The amount of oxidation products produced (TBARS) were, however, lower at low pH vs neutral pH. At pH 10.5-11, the pro-oxidative activity of hemoglobin was greatly suppressed. The conformation of hemoglobin was significantly more stable at high pH as compared to pH 7 as judged by its visible absorption spectrum. Hemoglobin readjusted from low pH to pH 7 had a higher pro-oxidative activity (i.e., more rapid oxidation) in WFM than native hemoglobin at pH 7, even though TBARS values were lower than in the untreated sample at pH 7. The results suggest that the WFM becomes slightly more susceptible to oxidation after low pH treatment but also produces less TBARS. The increased pro-oxidative activity after pH readjustment correlated well with an incomplete recovery in the native structure on pH readjustment. A longer unfolding time and a lower pH led to a less refolded hemoglobin with increased pro-oxidative activity. Hemoglobin was less pro-oxidative at low pH in the presence of 500 mM NaCl. The presence of salt did, however, increase the pro-oxidative properties of hemoglobin after readjustment to pH 7. The treatment of washed fish muscle at alkaline pH followed by adjustment to pH 7 led to a slight delay in hemoglobin-mediated lipid oxidation in WFM as compared to native hemoglobin at pH 7. The results suggest that WFM becomes less susceptible toward oxidation after pH readjustment from alkaline pH. These results clearly show that for muscle protein extraction/isolation processes requiring highly alkaline or acidic conditions, alkaline conditions are preferred if the lipid oxidation originating from hemoglobin is to be minimized.  相似文献   

4.
An accidental release of non-toxic waste from decommissioned wood pulp industry in the River Numedalslågen, Southern Norway, occurred in the upper part of the accessible stretches for anadromous fish during a study of migration behaviour of radio tagged Atlantic salmon (Salmo salar, n=32, body length 51–99 cm). The fish had completed the migration phase and initiated the resident phase characterised by little movement until spawning. When the wooden fibres and pulp were released, 16 of 32 (50%) salmon showed an immediate avoidance response. Six (19%) salmon moved upstream and 10 (31%) salmon moved downstream. Of the salmon moving downstream, eight (25%) moved all the way to sea (average 14.8 km). Four re-entered the River Numedalslågen, two entered a neighbouring river and two were not recorded later. Fish moving downstream but without moving to the sea, moved on average 5.3 km during the episode, whereas those moving upstream moved on average 6.7 km. All fish recorded after the episode (n=30) survived until the spawning season. The study demonstrates that fish in nature may show an evident avoidance response, even to non-toxic contaminants. For Atlantic salmon, the size of the spawning population may be reduced by fish leaving the river (13% left the river and never came back). Moreover, the dispersal of salmon to other rivers may increase, and the distribution of the spawning population within the contaminated river may shift.  相似文献   

5.
Freshwater suspensions of pulp fiber in concentrations exceeding 1000 ppm at 15°C are acutely lethal to sockeye salmon fingerlings. Limited adaptation of such fish to fiber is possible but injury, at least in the short term, is irreversible. The acute lethality of various toxicants associated with industrial pulps is synergistically enhanced by the presence of fiber, and pulp storage up to 158 days at 15°C had no significant effect on the acute lethality. Highly purified fibers are less toxic in fresh than in sea water. The sensitivity to fiber of fish from two sources did not differ significantly.  相似文献   

6.
In Norway, a variable pH target (pH 6.2–6.4 during most of the year, but 6.4 during the smoltification period) is used to reduce the cost of liming salmon rivers. Here we test the adequacy of this liming strategy. Atlantic salmon presmolts exposed to sublethal acidic water (pH 5.9, <25 µg Ali·L?1) for more than 3 months showed impaired sewater tolerance, elevated gill-Al concentrations, severe gill tissue changes, elevated blood plasma glucose concentrations, but no effect on blood plasma chloride. It is usually assumed that smolt will recover from prior aluminum (Al) exposure if water quality is restored. Recovery rate is here used as an indirect measure of water quality improvements achieved after treating acid water (pH 5.8, 85 µg Ali·L?1) with lime to reach pH-target levels of 6.0 – 6.3. Fish were exposed in a channel-tank set-up for >210 hrs in water aged from 1 minute up to 2 hours after treatment (in a flow through system). More Al was eliminated from the gills when the fish were exposed to pH 6.3 than to pH 5.8 or 6.0, and when water was aged after pH increase. Recovery, defined as return of normal gill morphology, blood homeostasis and establishment of seawater tolerance was achieved within 210 hrs in channels treated with lime to pH 6.3, while a similar recovery was not obvious at lower pH values. Liming to pH 6.3 detoxified Al better than pH 6.1.  相似文献   

7.
Automated stream dosers that deliver a wet slurry of calcite were installed in 1987 on two Maryland Coastal Plain streams subject to acidic pulses during rainstorms to evaluate the use of stream liming technology to maintain suitable water quality for early life stages of anadromous fish. Results of water quality sampling during baseflow conditions and hydrologic events indicated that significant changes in water chemistry occurred at the upstream (untreated) site during elevated flows on each stream. Observed responses in stream chemistry during the events included declines in pH, acid neutralizing capacity (ANC), and Ca, and increases in monomeric Al concentrations. With the addition of calcite, stream chemistry conditions at the downstream (treated) sites during each event were similar to those observed during baseflow. In situ bioassay experiments indicated that survival of yellow perch eggs and newly-hatched larvae may be enhanced by stream liming.  相似文献   

8.
鱼游泳能力对体长的响应及其在鱼道设计中的应用   总被引：4，自引：4，他引：0  
为了探讨鱼类体长对游泳能力的影响并为鱼道水流的设计提供参考,该研究在封闭水槽中使用"递增流速法"测试了海南省某水利枢纽鱼道目标对象的游泳能力,并用Origin软件进行了数据统计分析,得到了试验鱼感应流速、临界游泳速度和爆发游泳速度的直线回归方程和Kaplan-Meier曲线。结果表明:1)随着试验鱼体长增大,相对感应流速、临界游泳速度和爆发游泳速度(体长/s)均减小,体长和鱼类速度的相关关系可用直线方程表示,且数据经过对数变换后的直线方程拟合效果比未经过对数变换的拟合效果更好,其中R2由0.664～0.725提高至0.907～0.933。2)根据鱼道设计规范、导则及文献,结合本工程目标过鱼对象的感应流速、临界游泳速度和爆发游泳速度(m/s),建议本工程鱼道进口诱鱼流速控制在0.35～0.47 m/s,池室流速控制在0.21～0.59 m/s,竖缝流速控制在0.57～0.74 m/s,出口断面至下一个池室之间的流速控制在0.21～0.50 m/s。鱼类体长对相对游泳速度(体长/s)产生了负面影响,鱼类游泳速度及其变化规律可对鱼道水流设计值提供参考。  相似文献   

9.
Liming detoxifies aluminum in a time-dependent process following the increase in pH. Transformation of Ali into non-reactive or colloidal forms of Al reduces toxicity. To investigate the effects of pH on the detoxification rate, Atlantic salmon (Salmo salar) parr were exposed in four identical channel-tank setups differing only in mixing ratio (30:70, 16:84 or 6:94) between acid (pH 5.6, total Ali 90 µg Al·L?1) and non-acid water (pH 6.3, total Ali 3 µg Al·L?1). Two channels had identical mixing ratio (30:70), but differed with respect to pH (6.0 or >6.4) due to addition of lime. Fish were exposed for 140 hrs. in waters aged from 1 minute and up to 4 hours after mixing. Ali decreased within minutes after mixing at pH 6.4. The detoxification process required hours at pH 6.0. Al accumulation onto fish gills and fish homeostasis was related to Ali. The data suggest that the detoxification process, and therefore the water body affected by ongoing polymerization, was strongly influenced by pH, where a pH target for liming set at pH 6.4 detoxified water faster than a pH target of pH 6.0.  相似文献   

10.
Given the extent of biological invasions in industrialized countries, our understanding of the determinants of overall patterns of biological invasions could gain most from consideration of why exotic species are absent from some areas, rather than from distribution patterns of exotic species. Fish communities were sampled at 381 sites representing 221 rivers in the Adour-Garonne stream system (116 000 km2, SW France). Very few rivers were not colonized by exotic fish species, however, on a local basis, only 33% of the sampling sites hosted exotics. Using General Linear Modelling, we found that patterns of exotic fish (occurrence, number of species, proportion within assemblage) responded to both land-use and physical variables, whereas patterns of native fish only responded to the local meso-scale characteristics of each stream reach from headwaters to mouth. All fish communities were susceptible to invasion regardless of native species richness, and higher native species richness did not decrease the opportunity for establishment by exotic species. The likelihood that exotic fish are absent primarily increased with elevation and with lower human influence upon the land cover, while human-impacted landscapes (agricultural and urban areas) were more likely to host exotic fish and higher numbers of exotic species. In light of urban and agricultural development, our ability to detect responses of exotic species to landscape alterations using a combination of simple physical and land cover variables exemplifies a cost-effective technique for assessing areas at greater invasion risk in large stream systems.  相似文献   

11.
Responses to low pH of perch, Perca fluviatilis, from a naturally acid and a neutral lake were compared by 24 hr exposures to pH 4.6, 4.1 and 3.8 and by 72 hr exposures to pH 4.5. Plasma osmolality and plasma concentrations of Na and chloride decreased in fish from both lakes during acid exposures. Significant differences between the populations were observed at pH 4.1 and 4.5. Hematocrits of the fish from the acid lake increased rapidly and at higher pH compared with those of fish from the neutral lake. This was interpreted as an adaptation to their normal acidic environment, connected with the maintenance of red cell oxygen affinity. The perch from the acid lake maintained their muscle water balance at lower pH better than did the fish from the neutral lake.  相似文献   

12.
The Hudson River Foundation convened a conference to evaluate evidence pertaining to the roles played by acid deposition and stream acidification in the decline of anadromous fish populations along the Atlantic coastal plain. The stimuli for the conference were that (1) some populations of Atlantic salmon, American shad, hickory shad, alewives, blueback herring and striped bass as well as a few species resident in coastal streams (yellow perch and white perch) are in a state of severe decline along portions of the east coast of North America; (2) several of these species have declined more or less simultaneously since about 1970; and (3) severe episodic pH depressions are observed in some streams of the Chesapeake Bay system. For example, the pH of Lyons Creek decreased from 7.0 to 5.9 in 1 hr during a rain event, returning to 7.0 a day later. After discussing several possible mechanisms for these observations, the conferees agreed that a combination of factors including stream and river acidification, toxic metals and organic compounds, eutrophication and overfishing appears to be contributing to the reduction in fish stocks. The essential point resulting from the conference is that the acid deposition hypotheses for stream acidification and declines of anadromous fish populations, a potential mechanism that has received very little attention heretofore, was shown to be viable for these coastal areas. Specific recommendations for research were agreed upon by the conferees.  相似文献   

13.
The present study is mainly focusing on mortality variations of fish due to changing Alchemistry of mixing zones. An artificial mixing zone was made by pumping water from a limed stream and an acidic tributary into a mixing channel. Atlantic salmon (Salmo salar L.) parr were exposed to the mixed water, limed stream water, and acidic tributary water. Mortality, blood haematocrit and plasma Cl?-concentration were recorded. Neither mortality, nor changes in haematocrit and plasma Cl? were observed when fish were exposed to limed water, while in both acidic and mixed water, mortalities and loss of plasma Cl? were observed. The highest mortality rates were found within the initial part (0 to 20 s) of the mixing zone. Blood haematocrit increased only in fish exposed to acidic tributary water. Our results shows that changes in Al-chemistry and subsequent Al-polymerization occur when acidic tributary water is mixed with limed stream water. We have also demonstrated that the toxicity which can arise in mixing zones are greater than in the original acidic water before mixing. The variations in mortality observed are associated with the quality and quantity of Al-polymerization as well as ageing of the polymers.  相似文献   

14.
河道内鱼类上溯路径不唯一,聚集位置更是难以预测,对鱼类上溯行为进行有效引导有助于提升过鱼设施进口的效率。为此,该研究提出了一种导鱼堰的概念和设计方法,结合姚家坪水电站的过鱼设施,利用流场三维数值模拟、鱼类洄游（active fish migration,AFM）模型和实鱼试验对导鱼堰的效果进行评估。结果表明：姚家平水利枢纽工程的导鱼堰上下游水面落差为0.36～0.40 m,过堰水流流速可达1.5～2.8 m/s,形成阻鱼的屏障,并在导鱼堰下游侧形成了诱导鱼类向集鱼渠进鱼口游动的唯一低流速上溯通道,鱼类聚集点趋于唯一,验证了导鱼堰方案的合理性。利用鱼类洄游模型对导鱼堰的导鱼效果进行预测,结果表明,下游高水位和低水位2种工况下,90%以上的鱼类游动路径均表现出相似的规律,鱼类沿河道右岸和导鱼堰下游侧的低流速通道上溯,并最终聚集在集鱼渠的进鱼口处。放鱼试验中试验个体全部进入集鱼渠,结果进一步证实导鱼堰可以有效引导鱼类游动路线,并在集鱼渠进鱼口处形成唯一的聚集区。本文提出的导鱼堰丰富了生态水工建筑物的形式,可为过鱼设施进口的水力设计及下游河道的局部整治提供参考。  相似文献   

15.
As part of the Shenandoah National Park: Fish in Sensitive Habitats (SNP: FISH) project, movements of blacknose dace (Rhinichthys atratulus) and brook char (Salvelinus fontinalis) were examined during exposure to artificial acidification in paired channels of a laboratory stream. The objective of this study was to determine the ability of the fish to avoid depressions in the ambient pH and recognize and use a neutral-pH microhabitat refuge during acute reductions. Fish preference for a particular channel was statistically predictable based on the delivery of food. We tested fish avoidance behavior by manipulating food and the delivery of a pulse of acidified water. Both blacknose dace and brook char avoided the acid pulse (ambient pH reduced from 7.2 to 5.1) by sheltering in the pH-neutral refuge. Extensive field sampling in refuge microhabitats before and during episodic acidification is needed to determine changes in the distributional patterns of these species associated with acid precipitation events.  相似文献   

16.
Reintroduction of extirpated populations creates a unique context that can exacerbate the effects of interactions among species. Thus, reintroduced populations may be particularly vulnerable to predators and competitors, including native species with which they historically coexisted. In this study, we evaluated the effect of native fishes on survival of reintroduced Atlantic salmon (Salmo salar) in the Connecticut River basin, where the native salmon population is extinct. Juvenile salmon are stocked annually in many Connecticut River tributaries. We sampled salmon reintroduction sites across tributaries with different fish communities to determine whether native fish reduce the success of salmon reintroductions (N = 19 site-years). Increased density of slimy sculpin (Cottus cognatus), a native generalist predator, was associated with reduced recruitment of reintroduced salmon. Salmon first-summer survival declined with increased sculpin density across sites, and low first-summer survival led to reduced densities of overyearling salmon the subsequent year. Hierarchical partitioning analysis showed that the negative relationship between sculpin and salmon was independent of potentially confounding variation in other fish community or habitat characteristics. Negative effects of native, historically-sympatric species, particularly generalist predators, can impede restoration of extirpated populations.  相似文献   

17.
Data pertaining to the transport of fluvial sediment sampled in detail during a five hour long event in a small upland stream channel in the extremely arid Southern Negev are presented. Considerations based on comparative evaluations of water discharge, stream power, total and fractional sediment concentration, and total and fractional sediment discharge suggest that bedload transport in channels of even very small upland catchments practically devoid of continuous alluvial cover takes place in waves, which are not a priori related to any water discharge characteristic, but rather reflect some intrinsic feature of watershed dynamics, such as slope-channel topographic contrasts or fluvial bifurcation. The regular spacing of pools and riffles and of gravel bars in the more alluvial reaches downstream may therefore be initiated from upstream.  相似文献   

18.
Investigations in the southern part of the Scandinavian mountain range have shown a direct correlation between snowpack pH and the lowest pH in small streams. In streams with catchments <100>2 a snowpack pH below 4.8 resulted in a stream pH below 5.5. As the snowpack pH in the southern mountain range is 4.0–4.6, lower values to the south and at high altitudes, large areas are affected by acid deposition. The acidity of the snowpack is released almost directly into the streams during thaw, due to the large snowpack, rapid thaw, steep terrain and thin soils. The acidification of the snow has lead to an extensive fauna depletion, especially in smaller streams without upstream lakes. The abundance of benthos in acidified streams in the municipality of Härjedalen (11.000 km2) is today only one tenth of the abundance before acidification. Fish populations have declined to the same extent, and several acid-sensitive species have been lost. It is concluded that mountain streams and fauna are extremely sensitive to acidification, and that even large reductions of emissions will be insufficient.  相似文献   

19.
The Kusurisambetsu River is a tributary of the Noboribetsu River. These rivers flow through Hokkaido Prefecture, Japan. Because the upper reaches of the river are acidified by a caldera lake and basin, the river water contains aluminum in high concentration, together with iron and sulfate. The drainage area at the lower reaches is not acidified. Therefore, the acidified water of the river is neutralized by the alkalinity of water from the drainage area. The water at the mouth is neutral in pH, although about 1 mg/L of aluminum is detected. Heavy rainfall occurred in Autumn 1993, and many adult salmon were killed at the lower reaches of the river. This prompted study of the neutralization process of river water, the Al concentration change, and the influence of rainfall. Determination of Al found total Al concentration to be roughly constant at the mouth of the Noboribetsu River. However, the concentration of monomeric Al varied with pH, which varied according to rainfall and flow volume. Monomeric Al showed a minimum concentration of roughly pH 6.0. At pH of greater than 6.0, the presence of some kinds of polymeric Al is determined by filtration fraction. This suggests that the death of salmon is caused by monomeric Al when conditions are acidic. Liming test of the river water confirmed that the monomeric Al that was toxic under acidic conditions became non-toxic under alkaline conditions.  相似文献   

20.
Acidification is one of the most serious environmental problems in Norway. International agreements to reduce emissions are the only acceptable solution to the acidification problem. The “Sulphur Protocol”, signed in Oslo in 1994, will certainly improve matters, but southern Norway will have large acidified areas for decades. Norwegian environmental authorities therefore carry out liming as a temporary alleviatory measure to reduce damage for freshwater ecosystems. In 1995, about NOK 92 mill, was spent on liming. Acidification has wiped out the salmon in 25 rivers, and they are threatened in another 28 rivers. Because of varying water flow and rapidly changing water quality, liming a Norwegian salmon river is a huge operation demanding sophisticated equipment. Eleven rivers carrying anadromous fish are being limed in 1995. The largest is the River Audna where liming has meant that a salmon stock could be reintroduced. Most rivers are limed using automatic lime dosers. The most sophisticated ones control the amount of lime using pH sensors and water flow to neutralize major episodes of acidic water flow, which regularly occur in Norwegian rivers.  相似文献   

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