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1.
Abstract – European eel Anguilla anguilla is in strong decline. We assessed the relative impact of fisheries and hydropower during the downstream migration of silver eel in the River Meuse in the Netherlands using radio-telemetry. For this, 16 fixed detection stations (Nedap Trail-System® ) were used, each covering the entire river width, including all outlets to sea, and two covering the entrances of the two hydropower stations present. In September 2002, 150 silver eels were surgically implanted with Nedap-transponders and released at the catch site. Of these, 121 started to migrate downstream of which 37% successfully reached the North Sea. Hydropower mortality was at least 9% and assessed to be 16–26%. Fisheries mortality was at least 16% (reported recaptures) and estimated to be 22–26%. A clear difference was found in passage behaviour at hydropower stations, where 40% showed recurrence, in contrast to the river stations where this hardly occurred, indicating a hesitation to pass the turbines. Also a difference was found in diurnal pattern; 63% of the eels that passed through the turbines did so during the first 5 h of the night, whereas for the stations on free-flowing sections this was only 35%. 相似文献
2.
Abstract Selective opening of the Patea hydroelectric dam spillway gates was examined for its potential to provide safe downstream passage for sexually mature (silver) eels in New Zealand. During autumn 2000, one of the spillway gates at the 82-m high Patea Dam was opened for 2.5 h and a large fyke net set across the river about 1.5 km below the dam. Fifty one live endemic longfin eels Anguilla dieffenbachii (Gray), 60 live shortfin eels Anguilla australis (Richardson), and eight dead shortfin eels were captured. All but three of the eels caught were downstream migrants, and aside from the dead eel, only a small portion (5%) had external signs of injury. It was likely that the majority of the eels captured passed over the spillway, but some may have originated from the section of river between the dam and the net or gone through the turbines. To further test the ability of eels to survive passage over the spillway, three controlled spills were made in autumn 2001 and 102 eels released immediately upstream of the partially opened spillway gates. A net stretched across the base of the concrete spillway was used to recover the eels. Most of the eels recovered from the spillway had low levels of injury. However, during the third controlled spill, 10 wild migrant eels were also caught with none showing any external signs of injury. This indicated that the damage noted on the recovered eels were the result of handling rather than passage over the spillway. It was concluded that selective opening of hydroelectric dam spillway gates can provide safe downstream passage for migrant eels. 相似文献
3.
Abstract – The downstream migration of European silver eels in the River Frémur was examined to determine the potential effects of the numerous migration barriers that exist on waterways in western France. The Frémur has a 14 m high dam which creates a 3 × 106 m3 water supply reservoir, 6 km from tidal limit. Based on 8-year records (1996–2004) of migrant silver eels captured in a Wolf trap located about 1 km below the dam, the influence of this dam on the migration was examined. These records indicate that 91% of silver eels were captured when the dam was overtopped (i.e. when the water reservoir was full). The timings of the overflow periods varied greatly between years mainly because they are function of the duration of the filling period which in turn is dependent on the level of summer water abstraction and annual hydrological conditions. Consequently, migration periods occurred at variable dates (between November and April) which is late in comparison with nonobstructed European river systems (generally between August and December). During overflow periods the migration of silver eels increased markedly during rain events (increasing river flow). This indicates that flow flushes, are essential so that settled silver eels can orientate themselves and pass over the dam. The hypothesis of a 'dam effect' that could stop temporarily or permanently some of silver eels in the reservoir is discussed. Finally, the influence of the migration delays on the condition of silver eels is considered. 相似文献
4.
Jonathan D. Bolland Leona A. Murphy Robert J. Stanford Natalie V. Angelopoulos Nicola J. Baker Rosalind M. Wright Jake D. Reeds Ian G. Cowx 《Fisheries Management and Ecology》2019,26(1):76-85
Downstream passage of European eel Anguilla anguilla (L.) in catchments with pump(s) for water level management is a major concern. Catchment‐wide acoustic telemetry revealed silver eels quickly migrated downstream through unobstructed reaches (n = 12; mean ± SD = 17.9 ± 1.9 km/day). Fourteen of 17 acoustic‐tagged eels detected at the pumping station (82.1%) retreated back upstream and ten (58.8%) passed through pumps after delays (9.5 ± 11.0 days). Multi‐beam sonar imaging across the intake screen (55‐mm gaps) revealed that peaks in migration occurred during the nights preceding the new moon but 76.7% retreated back upstream. All passive integrated transponder (PIT)‐tagged eels recaptured (n = 56) downstream of a large (2.23‐m diameter) mixed flow pump survived but 96.5% had minor injuries, reduced physical condition and/or abnormal behaviour. By contrast, 64.7% of PIT‐tagged eels recaptured (n = 17) downstream of a small (0.8‐m diameter) axial flow pump died. No acoustic‐tagged eels that passed through the small axial flow pump (n = 10) performed onward migration at sea, unlike “control” eels released downstream (n = 11). This evidence may help develop effective remediation measures, such as operational changes, to maximise escapement of catadromous eel species at pumping stations. 相似文献
5.
Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam 
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下载免费PDF全文 Daniel Nyqvist Larry A. Greenberg Elsa Goerig Olle Calles Eva Bergman William R. Ardren Theodore Castro‐Santos 《Ecology of Freshwater Fish》2017,26(4):707-718
Passage of fish through hydropower dams is associated with mortality, delay, increased energy expenditure and migratory failure for migrating fish and the need for remedial measures for both upstream and downstream migration is widely recognised. A functional fish passage must ensure safe and timely passage routes that a substantial portion of migrating fish will use. Passage solutions must address not only the number or percentage of fish that successfully pass a barrier, but also the time it takes to pass. Here, we used radiotelemetry to study the functionality of a fish bypass for downstream‐migrating wild‐caught and hatchery‐released Atlantic salmon smolts. We used time‐to‐event analysis to model the influence of fish characteristics and environmental variables on the rates of a series of events associated with dam passage. Among the modelled events were approach rate to the bypass entry zone, retention rates in both the forebay and the entry zone and passage rates. Despite repeated attempts, only 65% of the tagged fish present in the forebay passed the dam. Fish passed via the bypass (33%), via spill (18%) and via turbines (15%). Discharge was positively related to approach, passage and retention rates. We did not detect any differences between wild and hatchery fish. Even though individual fish visited the forebay and the entry zone on multiple occasions, most fish passed during the first exposures to these zones. This study underscores the importance of timeliness to passage success and the usefulness of time‐to‐event analysis for understanding factors governing passage performance. 相似文献
6.
Abstract A 100-mm diameter bypass was installed in the dam face at a small hydropower station on the Mokau River, New Zealand, and its use by downstream migrating silver eels, Anguilla spp., was monitored by trapping at the outlet in autumn 2002 and 2003. In addition, a passive integrated transponder system was used to monitor passage over the spillway. Migrant eels were able to find the bypass, with 544 and 744 eels recorded using it in 2002 and 2003 respectively. Although the bypass was the sole means of safe passage at low flow, migrant eels passed down the spillway in preference to the bypass when the dam was overtopped during floods. A combination of spilling and small diameter bypasses would provide safe downstream passage at hydroelectric facilities for silver eels, so long as entrainment and impingement at the intake screens can be prevented. 相似文献
7.
Abstract – We used logistic models to analyse the longitudinal distribution patterns of yellow European eels in the Loire catchment (France). Our models for predicting the presence of yellow eels supported contrasting spatial patterns according to the size of individuals and catchments. The smallest eels (mainly <150 mm and secondly 150–300 mm) were confined to downstream areas, but rapidly colonised upstream reaches. By contrast, larger eels were distributed further inland but tended to become more sedentary. In addition, a higher density of barriers to migration in the Maine catchment (a large catchment within the Loire catchment) probably delayed the upstream colonisation compared with the rest of the Loire catchment. These results suggest that logistic models may be a useful and efficient tool: (1) for the assessment of eel status and trends in freshwater systems; and (2) for the assessment of the consequences of local perturbations or conversely improvement of colonisation. 相似文献
8.
Philip M. Harrison Eduardo G. Martins Dirk A. Algera Trina Rytwinski Brent Mossop Alf J. Leake Michael Power Steven J. Cooke 《Fish and Fisheries》2019,20(3):403-418
Potadromous fishes are vulnerable to involuntary entrainment through hydropower turbines. However, turbines can also provide a downstream passage route for potadromous fish. Here, we review evidence for turbine entrainment and passage in potadromous fish, and evaluate the effects of these processes on upstream and downstream populations. We develop conceptual frameworks and metrics to quantify vulnerability to turbine entrainment removals, and to quantify the efficiency of turbines as a downstream passage route. We highlight factors that influence these processes and provide case‐studies demonstrating their applicability. We found that juvenile potadromous fish are being entrained through turbines at rates high enough to impact upstream populations. Given that juvenile passage survival is often high, we argue that turbines provide an important downstream passage route for potadromous fish. We show that entrainment vulnerability is likely a function of interactions between in‐reservoir fish behaviour, habitat configuration and operations and thus not well captured by passage mortality estimates. Similarly, we show that while passage mortality can limit downstream passage efficiency, passage success is also dependent on reservoir and forebay navigation, along with survival and fitness in the downstream river. We advocate for a shift in focus away from estimates of passage mortality and injury, which have previously accounted for the majority of turbine passage research. Instead, we recommend an approach that focusses on quantification of the factors that influence downstream passage efficiency and entrainment vulnerability. Moreover, we highlight the need to better understand the broader scale impacts of these events on upstream and downstream populations. 相似文献
9.
Abstract – The downstream migration of juvenile salmonids has previously been considered predominantly passive. It has been argued that passive displacement during periods of darkness is, partially at least, a result of an inability to maintain a fixed position in the absence of visual cues. In this study, behaviour of juvenile Pacific salmonids was assessed under conditions of light and dark as they passed through an artificial channel and encountered a submerged weir. Results indicated that when light, fish formed schools and actively explored the channel. Conversely, when dark (infrared illumination only) they did not form schools, but maintained randomly distributed positions holding station against the flow. As a consequence, more fish approached and either passed, or rejected, the weir when light. The majority of fish that passed the weir did so within the first minute of each trial. Fish predominantly passed through the channel facing downstream and changed orientation prior to passing tail first over the weir crest in the presence and absence of visual cues. The orientation switch was less common when dark. This study shows, at a fine-resolution scale, that downstream movement of juvenile salmonids can be inhibited as fish exhibit alternative behaviours in the absence of visual cues. Downstream movement was not predominantly passive. Fish passage design should not be based on the assumption that downstream migration is passive. 相似文献
10.
Jenna Vergeynst Ine Pauwels Raf Baeyens Ans Mouton Tom De Mulder Ingmar Nopens 《Ecology of Freshwater Fish》2021,30(1):73-87
Migrating fish species are worldwide in decline due to several global changes and threats. Among these causes are man‐made structures blocking their freshwater migration routes. Shipping canals with navigation locks play a dual role in this. These canals can serve as an important migration route, offering a short cut between freshwater and the sea. In contrast, the navigation locks may act as barriers to migration, causing delays and migration failures. To better understand these issues for downstream migrating fish, we studied the behaviour of European eels (Anguilla anguilla) in the Albert Canal at two scales. The mid‐scale contained a 27‐km canal pound confined by two navigation lock complexes, in which we released and tracked 86 silver eels. The small scale was a 200 × 150 m area just in front of the most downstream complex of the canal pound, where we analysed the behaviour of 33 eels in relation to the flow field resulting from a computational fluid dynamics (CFD) model. This paper discusses the factors influencing fish behaviour, and the relation between these behaviours on both scales. On the mid‐scale, migration efficiency resulted from a combination of intrinsic behaviour and flow in the canal pound. Also on the small scale, intrinsic behaviour influenced the success to pass the navigation lock. Increasing the flow would create more attraction and passage opportunities and hence facilitate migration through shipping canals, but only if this flow guides the fish through safe passage routes. 相似文献
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12.
Abstract – Larval stage duration of the sea lamprey, Petromyzon marinus , in the River Mondego is estimated to last for 4 years. The number of annuli provides reliable age estimates when compared with length–frequency distributions analysis. The growth rate of the sea lamprey ammocoetes displays strong seasonal patterns, and reaches its highest value during the first 2 years of larval stage. About 69% of the length increment between hatching and metamorphosis is attained at the end of the second year. There is a longitudinal gradient associated with ammocoete distribution along the river. Relative abundance of ammocoetes decreases downstream from the Açude-Ponte dam, the first obstruction encountered by the adult sea lampreys in their upstream spawning migration along the River Mondego. 相似文献
13.
Josef Knott Melanie Mueller Joachim Pander Juergen Geist 《Ecology of Freshwater Fish》2020,29(1):74-88
Hydropower structures hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on timing and extent of natural patterns of fish downstream movement is necessary. So far, migration behaviour of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of nonmigratory species or medium-distance migrators. In this study, movement patterns of 39 fish species captured by stownets while transiting hydropower facilities in four impounded rivers were assessed and compared with the fish community composition directly upstream of the hydropower plants assessed by electrofishing. Strong differences between the fish community composition inhabiting the upstream sides of the dams and the fish detected in downstream passage were evident. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught during the night (2.9 fish/hr) than during the day (1.3 fish/hr). Topmouth gudgeon, European grayling and pike-perch mostly moved downstream during the night, whereas roach, spirlin and bleak were the most frequent downstream moving fish during daytime. Downstream fish movement was positively related with turbidity, water temperature and discharge. The strong differences in seasonal and diurnal fish movement patterns suggest that fish damage can be strongly reduced by adaptive turbine and corridor management, for example by shutting down turbines at peak movements. 相似文献
14.
The upstream migration of European eels, Anguilla anguilla (L.), was studied during 1991–1993 in the Rivers Severn and Avon using traps mounted on weir or sluice barriers. Only pigmented elvers and juvenile eels were trapped at the tidal limits, catches being equivalent to about 0.8% of the commercial glass eel catch in the lower estuary. First catches were made as temperatures rose above 10–11 °C. Pigmentation-stage analyses and body size data indicated that estuarine migration was slow and that natural mortality was probably very high. Relatively more eels were trapped in the Severn compared with the Avon, but in both rivers the number of immigrants decreased rapidly upstream of the tidal limits, whilst the average size and age increased. The number and severity of weir and sluice barriers to be surmounted exerted a greater effect than distance alone. Recapture rates of marked eels were low (1–2%), implying variable migratory tendencies and/or high mortality. Mean migration rate in the non-tidal rivers was 0.64 ± 0.6 km day–1 and some eels were not recaptured until one or two years after release. Speed of migration increased with temperatures above 15–16 °C. Relationships between migration dynamics, barriers and the scarcity of upriver stocks of eels and distorted population structures in the two rivers are discussed. Recommendations are made for the provision of passes and/or stocking to enhance migration and recruitment. 相似文献
15.
P. M. Bizzotto A. L. Godinho V. Vono B. Kynard H. P. Godinho 《Ecology of Freshwater Fish》2009,18(3):461-472
Abstract – Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the 'nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam. 相似文献
16.
Behavioural transition during the estuarine migration of wild Atlantic salmon (Salmo salar L.) smolt
F. Martin R. D. Hedger J. J. Dodson L. Fernandes D. Hatin F. Caron F. G. Whoriskey 《Ecology of Freshwater Fish》2009,18(3):406-417
Abstract – Ultrasonic telemetry and hydrodynamic modelling were used to study the migratory behaviour of 54 wild Atlantic salmon ( Salmo salar ) smolt captured in freshwater during their downstream migration and tracked in 2 years through a shallow estuary system. A high-density, fixed array of receivers provided detailed spatial and temporal resolution of behaviour in the second year of study. Smolt migration in the river occurred mostly at night and downstream migration was slower during the day. In the estuary, smolt moved seaward on ebbing tides and landward on flooding tides. The effect of current velocity was greater during the night than during the day. We documented for the first time that current velocity and diurnal period only accounted for approximately one-third of the variation in smolt ground speeds in the estuary, indicating that smolt movements were far less passive than previously reported. Smolt energetic status had no effect on smolt swimming behaviour or migratory performance. With an increase in salinity, smolt seaward movements during flooding tides were more frequent, and overall seaward ground velocity increased. The increase in salinity experienced by the smolt during their migration through the leading edge of saltwater intrusion thus induced a behavioural transition from a more passive, fluvial migration to a more active- and seaward-oriented migration. 相似文献
17.
Olvin Alior van Keeken Ralf van Hal Hendrik Volken Winter Tony Wilkes Arie Benjamin Griffioen 《Fisheries Management and Ecology》2021,28(1):76-90
European eel, Anguilla anguilla (L.), migrating to sea encounter many man-made structures that can hamper and delay migration or induce mortality. Three pumping stations in Friesland, the Netherlands, were covered with acoustic receivers. Ninety-three silver eels tagged with acoustic transmitters were released in the polders upstream of the stations and 89% were detected passing a pumping station. The majority of silver eels passed the stations within a day after arriving at the station. Four silver eels stayed for longer than 2 weeks before passage, and 18 were detected at the receiver downstream the pumping station for more than one day, with detections up to several weeks. These detections probably indicated a dead eel, but could also indicate a live eel remaining at the site. Most of the silver eels passed the pumping stations within a day after release, so fish-friendly pumps will benefit the migrating population most. In the Netherlands, there are several thousand pumping stations. Installing fish passages near these stations is not feasible due to high costs. Prioritising all these sites in relation to the degree of blockage, mortality rates and its relative importance for migratory fish, can maximise the effectiveness of measures and mitigation taken. 相似文献
18.
Abstract Worldwide, populations of catadromous eels are in decline. Knowledge on downstream migration patterns is needed to mitigate damage caused by hydroelectric stations. Silver eel migration and its relation with environmental factors were investigated using data from a fishery located in the lower reaches of a large catchment (110 000 m2 ). Migration days, indicative of different proportions (50%, 75% and 95%) of the annual run of eels (i.e. represented by the annual catch), were predicted using discriminant analyses. Efficiency of prediction was 58–95% depending on the proportion of the run targeted. The onset of migration was correlated with sunshine hours, August temperature and discharge. Julian days (i.e. photoperiod) was significantly correlated with migration days, indicating between-year similarity in the dynamics of the runs. The size of migrants varied within the migration season, reflecting differences in their initial spatial distribution. 相似文献
19.
Peter Davies J. Robert Britton Andrew D. Nunn Jamie R. Dodd Chris Bainger Randolph Velterop Jonathan D. Bolland 《水产资源保护:海洋与淡水生态系统》2021,31(9):2560-2574
- River ecosystems are often fragmented by artificial structures, such as weirs. For anadromous species, these structures can impede access to upstream spawning sites and ultimately lead to severe population declines.
- This study focused on the freshwater spawning migration of the sea lamprey, Petromyzon marinus, an anadromous species threatened by habitat fragmentation across its native range. To quantify the cumulative impacts of multiple weirs on upstream-migrating adults, and to explore the environmental factors affecting migratory movements, passive acoustic telemetry was applied to 56 individuals during their spawning migration in the heavily fragmented River Severn basin, UK.
- While 89% of tagged sea lamprey passed the first weir upstream of the release site on the main river, only 4% passed the fifth weir. For 85% of migrants, the upstream extent of migration was immediately downstream of a weir. Individuals that passed weirs upstream of the release site (n = 50) took 21.6 ± 2.8 days to reach their most upstream location, experiencing cumulative passage times at weirs of 15.7 ± 2.8 days; these delays constituted a median of 84% of total upstream movement times.
- Multistate models showed that the weir passage rates of sea lamprey in tidal and non-tidal areas increased significantly when downstream river level and discharge were elevated. Upstream-to-downstream changes in direction were frequent downstream of weirs, but rare in unobstructed river sections.
- The results provided evidence for a cumulative effect of multiple weirs on sea lamprey movements, substantially delaying upstream migrants and limiting their spawning to atypical habitat. The results also demonstrated the crucial roles of high tides and elevated discharge events in enabling weir passage. Although the Severn Estuary features conservation designations for sea lamprey, this study reveals that barriers are inhibiting their upstream migration, a problem that should be addressed to assist sea lamprey conservation.
20.
The yellow European eel (Anguilla anguilla L.) may adopt a sedentary lifestyle in inland freshwaters
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