1,721,030 research outputs found
Discharge, habitat complexity and social status: the influence of abiotic and biotic factors upon habitat suitability curves and the performance of juvenile Atlantic Salmon, Salmo salar
No full textPrevious instream flow models assume that hydraulic habitat (based upon abiotic criteria) is the dominant factor in governing fish positions in a stream environment. However, fish utilisation of instream habitats within a specific range of water velocities has been shown by a number of scientific studies to be both density dependent and to vary with discharge. This paper will investigate how social dominance (a biotic factor) of 1+ Atlantic salmon, interacts with habitat complexity and discharge in affecting fish performance and position choice in relation to velocity. The study was undertaken using a 32 metre length of flume, partitioned into sixteen 1 m2 chambers, which were landscaped with natural stream gravel and fed by water from a typical Scottish salmonid river. This paper will present the results and discuss how the findings are important in terms of the utilisation of hydraulically defined habitat
The response of migrating juvenile Chinook salmon smolts to instream structure associated with
No full textIn-channel placement of structure to enhance habitat complexity and connectivity for stream-dwelling salmonids
No full textInfluence of corrugated boundary hydrodynamics on the swimming performance and behaviour of juvenile common carp (Cyprinus carpio)
Full text linkTo facilitate the upstream passage of small fish, corrugated culverts are often preferred over smooth pipes, due to the lower edge and mean cross sectional water velocities created. This benefit could be lost if greater intensities of turbulence induced by wall roughness cause instability and increase the energetic expense of fish locomotion. Common carp (Cyprinus carpio) swimming performance and behaviour were evaluated in a flume using four wall roughness treatments: smooth (control), small (SC), medium (MC), and large (LC) corrugations, dependent on corrugation wavelength and amplitude. Individual fish (n = 128, mean ± S.D. total length [TL] = 86 ± 8 mm) swam at a mid-channel velocity of 0.5 m s?1 for 30 min or until fatigue. Swimming performance was quantified by: (a) success (completion of 30 min trial) or failure; and (b) the time to fatigue (endurance) of those that failed. To evaluate behaviour, fish head positions were tracked manually every second. Occupancy of the area within the MC and LC troughs (concave area where velocity was lowest) was recorded and the relationships between trough occupation and (i) TL and (ii) success tested. Differences were tested for between successful and failed individuals, and among treatments, for the following dependent variables: the total distance moved, the mean distance from the flume wall occupied (FishD), and mean velocity (FishU) and turbulent kinetic energy (FishTKE) experienced. Treatment did not influence frequency of success (38–58% per treatment) or time to fatigue. During the MC and LC treatments, troughs were occupied for part of the trial by 56 and 55% of individuals, respectively. Trough occupation was independent of TL in both treatments, and more common for successful fish than failures in the LC treatment. For successful fish, the total distance moved did not differ among treatments. Successful FishD varied among treatments and was higher for the LC (mean ± S.E. = 93.2 ± 22.3 mm) than the SC (33.5 ± 2.8 mm) treatment. Despite the availability of lower velocity areas, median successful FishU was higher in the LC treatment (0.51 m s?1) than in any other (median = 0.47 m s?1, 0.44 m s?1 and 0.47 m s?1 in the MC, SC, and control treatments, respectively). Treatment did not influence successful FishTKE which was consistently low (median = 5.3–7.7 J m?3 per treatment). Although occupation of the MC and LC troughs occurred, many individuals spent little time here, and areas with lower TKE were often occupied. Under the experimental conditions created, this study does not support the assumption that low velocity areas created by wall corrugations will improve culvert passage
The feasibility of reintroducing burbot (Lota lota) to the British Isles
No full textThe last confirmed capture of a burbot (Lota lota) in a UK river, was on the 14th of September 1969, in the Old West River at Aldreth, Cambridgeshire (Marlborough, 1970). Despite sporadic reports of subsequent captures, it is generally accepted that the species has been extirpated from the British Isles. However, Dr Paul Kemp, Dr Patrick Osborne and PhD student Tom Worthington from the International Centre for Ecohydraulic Research are researching whether it is feasible to reintroduce the burbot back to the British Isles. The research will follow the structure of the International Union for the Conservation of Nature and Natural Resources (IUCN) guidelines on species reintroduction (IUCN, 1998). The overall aims of the project are to investigate the causes of the burbot’s extinction in the UK, determine whether these factors are still prevalent and whether any future risks threaten the species. Opinion is divided over the reasons for the loss of this species; climate change, overfishing, pollution and habitat destruction have all been advanced as possible causes. However, no research has been carried out to fully quantify the burbot’s decline. This study will examine the role of changes in water temperature, habitat connectivity and river discharge in the burbot’s extinction
Response of migrating Chinook salmon (Oncorhynchus tshawytscha) smolts to in-stream structure associated with culverts. [In special issue: Riverine Hydroecology: Advances in Research and Applications. Selected Papers from the Tenth International Symposium on Regulated Streams, Stirling, August 2006]
No full textPoorly designed culverts can impede upstream movements of fish under high flows when excessive water velocities create adverse conditions. Improvement in upstream fish passage efficiency may occur with placement of structures within culverts that increase hydraulic complexity and provide resting areas. The effects of structural modification on downstream migrants, however, are unknown. To address this gap in knowledge, the behaviour of Chinook salmon (Oncorhynchus tshawytscha) smolts was assessed in an experimental laboratory flume. Under light and dark conditions, fish were observed as they encountered either an unmodified aluminium channel (control) or one of two treatments: an intermediate substrate (treatment channel lined with corrugated sheet) or a complex substrate (addition of cobbles to the intermediate treatment). More smolts passed the control channel than the treatment channels. Even with control of the variation in flow between channels, under light conditions more fish than expected passed the control channel when paired with the complex treatment. Smolts more frequently rejected both treatments than the control channel when light, and the complex treatment when dark, by swimming upstream against the flow after entry. The majority of fish moved through the flume facing downstream, although a greater proportion faced upstream when dark than when light, and entered the control channel. Velocity of downstream movement (ground velocity) was greater through the control channel than for the treatment routes, and slower than the mean water velocity, and under the dark condition. When mean water velocities were taken into account, the net velocity through the control channel was not significantly different to the intermediate, and lower than the complex channel. Juvenile Chinook salmon determined fine-scale variation in structural complexity and exhibited avoidance behaviour in the presence and absence of visual stimuli. Hydraulic stimuli influenced route selection exhibited by migratory juvenile salmonids
Efficacy of a side-mounted vertically oriented bristle pass for improving upstream passage of European eel (Anguilla anguilla) and river lamprey (Lampetra fluviatilis) at an experimental Crump weir
No full textGlobally, populations of diadromous anguilliform morphotype fish, such as eel and lamprey, have experienced substantial declines, partly as a result of habitat fragmentation caused by river infrastructure. In the UK, a new configuration of hydraulically unobtrusive bristle pass (side-mounted and vertically oriented) has been developed to help upstream moving European eel (Anguilla anguilla) negotiate gauging weirs. The efficacy of vertically oriented bristle passes remains untested, despite their potential as a low-cost low-maintenance solution to improve habitat connectivity at low-head structural barriers worldwide. This study assessed the ability of small (82–320 mm) and large (322–660 mm) European eel and adult (291–401 mm) river lamprey (Lampetra fluviatilis) to pass upstream over an experimental Crump weir installed in a large open-channel flume with (treatment) and without (control) side-mounted vertically oriented bristle passes under three different hydraulic regimes. Both species were highly motivated to explore their surroundings and move upstream during the trials. Under flooded control conditions, passage efficiency (the total number of times fish passed the structure as a percentage of total attempts) and passage success (the number of fish that passed the structure as a percentage of those that attempted) were high, delay was short, and number of failed attempts before passage was low for both species. When difference in head was at its greatest (230 mm) and velocity and its variation downstream were high (maximum u and ?: 2.43 ms?1 and 0.66 ms?1, respectively), the upstream movement of small eel and lamprey was blocked, and passage efficiency and success for large eel low (4.6% and 17.2%, respectively). For large eel that successfully passed, delay was long, and number of failed attempts before upstream passage was high. When bristle passes were installed, passage efficiency for small (91.5%) and large eel (56.7%), and passage success for large eel (76.5%) and lamprey (36.7%) was higher, while delay and the number of attempts before passage was lower for both species. Bristle passes helped European eel and river lamprey pass a small experimental Crump weir, although interspecific variation in efficacy was evident
Seaward migrating juvenile pacific salmon avoid conditions of rapid hydraulic transition and overhead cover.
No full textThe behaviour of seaward migrating juvenile Pacfic salmonids: implications for enhanced fish passage
No full textIn an effort to restore populations of migratory salmonids on the Columbia River, attempts have been made to aid fish passage and enhance survival at the HEP projects. The guidance efficiencies associated with mechanical structures designed to divert fish away from turbines towards alternative routes of passage are often much lower than expected. Site-specific macro-scale studies that use remote tracking technology have traditionally provided the evidence on which our understanding of fish passage is based. Recent research, however, suggests that fish react to localized environmental factors that operate at a fine-scale. There is a need to integrate information collected across scales to develop on existing models of fish passage that presently are based on assumptions that may or may not be true. We conducted a series of fine-resolution flume experiments at McNary dam, on the Columbia River, to assess the influence of hydraulic transition and overhead cover on the behavior of seaward migrating juvenile Pacific salmonids. Smolts passing through the flume were given a choice of passage route that varied based on rates of velocity acceleration, flow, and overhead cover. Direct observation of behavior revealed that individuals elicit strong avoidance behavior when they encounter areas where hydraulic conditions change rapidly or are covered. Further, the behavioral response varies with species and fork length. Our findings have implications relevant to diversion structure design and culvert passage
- …
