Extreme inefficiency of two conventional, technical fishways used by European river lamprey (Lampetra fluviatilis)

In recent years, fishways have increasingly been designed and installed with the intention to not only provide economically important fishes, such as salmonids, with free passage at barriers, but also for other elements of the migratory fish community. However, in Europe and North America, large numbers of conventional technical fishways exist, for which the efficacy and suitability for non-salmonid species is often inadequately known. Using passive integrated transponder (PIT) telemetry, this study evaluated the efficacy of two such conventional, technical fishways (pool and weir and plain Denil baffle) located on the Yorkshire River Derwent, north-east England, for the threatened anadromous European river lamprey Lampetra fluviatilis, an anguilliform swimmer, over the upstream migration and spawning seasons. For lamprey that entered the fishways, 0.0% and 5.0% passage efficiencies were recorded for Denil (n = 1) and pool and weir (n = 1) fishways, respectively, over the entire study period. The pool and weir fishway exhibited poor attraction efficiency (42.6%) compared to the Denil fishway (91.8%), and lamprey took significantly longer to locate the pool and weir fishway, probably as a result of ineffective attraction flow. Most lamprey detected at the fishway entrances were recorded within 24 h of release and returned mostly during high flow events on up to 12 separate dates over a 150 day period. Under these conditions, these fishways were unsuitable for river lamprey. Emphasis is placed upon the increased need for a thorough consideration of the entire migratory fish community during the inception of fishway designs, and that post-construction, strategic evaluation of fishways should be actively supported and encouraged to advance the provision of effective multi-species fishways

Reduced flow impacts salmonid smolt emigration in a river with low-head weirs

The impacts of large dams on the hydrology and ecology of river systems are well understood, yet the impacts of low-head structures are poorly known. While impacts of small weirs on upstream-migrating fish have long been mitigated by fish ladders, it is assumed that downstream migration of surface-oriented fishes is unaffected under natural flow regimes. To test this, the effects of low-head weirs and the influence of river flow on the migration of brown trout (Salmo trutta) smolts in the River Tweed, UK, were examined. Movements of acoustic tagged smolts were quantified in 2010 and 2011 using automatic listening stations and manual tracking throughout the migration route. In both years, smolts exhibited major losses, most likely due to predators, with escapement rates of 19% in 2010 and 45% in 2011. Loss rates were greater in 2010 when flows were frequently below Q95 (20% of study period) compared to 2011 when more typical flows predominated (0% of study period below Q95). Smolts experienced significantly longer delays at weirs during 2010 than 2011, associated with the different hydrographs during emigration as well as weir design. Flow comparisons within the study periods and historical records show that low flows experienced in 2010 were not unusual. The swimming behaviour of smolts in relation to flow conditions differed between years, with smolts in 2010 increasing their rate of movement in relation to increasing flow at a faster rate than smolts in 2011. This is the first study to demonstrate river flow impacts on the migration success of wild salmonid smolts at small weirs. Because small weirs are common in rivers and because spring-summer low-flow periods may become more frequent with climate change (based on UKCIP09 models) and altered river hydrology, further research and improved management is needed to reduce the impacts of low river flows in combination with low-head weirs on salmonid smolt migration

Evaluating the effectiveness of restoring longitudinal connectivity for stream fish communities: towards a more holistic approach

A more holistic approach towards testing longitudinal connectivity restoration is needed in order to establish that intended ecological functions of such restoration are achieved. We illustrate the use of a multi-method scheme to evaluate the effectiveness of ‘nature-like’ connectivity restoration for stream fish communities in the River Deerness, NE England. Electric-fishing, capture-mark-recapture, PIT telemetry and radio-telemetry were used to measure fish community composition, dispersal, fishway efficiency and upstream migration respectively. For measuring passage and dispersal, our rationale was to evaluate a wide size range of strong swimmers (exemplified by brown trout Salmo trutta) and weak swimmers (exemplified by bullhead Cottus perifretum) in situ in the stream ecosystem. Radio-tracking of adult trout during the spawning migration showed that passage efficiency at each of five connectivity-restored sites was 81.3–100%. Unaltered (experimental control) structures on the migration route had a bottle-neck effect on upstream migration, especially during low flows. However, even during low flows, displaced PIT tagged juvenile trout (total n = 153) exhibited a passage efficiency of 70.1–93.1% at two nature-like passes. In mark-recapture experiments juvenile brown trout and bullhead tagged (total n = 5303) succeeded in dispersing upstream more often at most structures following obstacle modification, but not at the two control sites, based on a Laplace kernel modelling approach of observed dispersal distance and barrier traverses. Medium-term post-restoration data (2–3 years) showed that the fish assemblage remained similar at five of six connectivity-restored sites and two control sites, but at one connectivity-restored headwater site previously inhabited by trout only, three native non-salmonid species colonized. We conclude that stream habitat reconnection should support free movement of a wide range of species and life stages, wherever retention of such obstacles is not needed to manage non-native invasive species. Evaluation of the effectiveness of fish community restoration in degraded streams benefits from a similarly holistic approach

Convergent discrete numerical solutions of strongly coupled mixed parabolic systems

This work has been partially supported by the Spanish D.G.I.C.Y.T. grant BMF 2000-0206-C04-04Jódar Sánchez, LA.; Casabán, M. (2003). Convergent discrete numerical solutions of strongly coupled mixed parabolic systems. UTILITAS MATHEMATICA. 63:151-172. http://hdl.handle.net/10251/161860S1511726

Energetically efficient behaviour may be common in biology, but it is not universal: a test of selective tidal stream transport in a poor swimmer

Selective tidal stream transport (STST) is a common migration strategy for a wide range of aquatic animals, facilitating energetically efficient transport, especially of species considered poor swimmers. We tested whether this mechanism applies during the upstream migration of a poor swimmer, the European river lamprey Lampetra fluviatilis, in a macrotidal estuary. Lamprey (n = 59) were acoustically tagged and tracked in a 40 km section of the River Ouse estuary (NE England) in autumn 2015. Against expectations, lamprey did not use STST and migrated upstream during flood, ebb and slack tide periods. Lamprey also migrated during both day and night in most of the study area, probably due to the high turbidity. The global migration speed (all individuals, over the entire track per individual) was (mean ± SD) 0.15 ± 0.07 m s-1. The migration speed varied significantly between tidal periods (0.38 ± 0.04 m s-1 during flooding tides, 0.12 ± 0.01 m s-1 during ebbing tides and 0.28 ± 0.01 m s-1 during slacks). It was also higher in areas not affected by tides during periods of high freshwater discharge (0.23 ± 0.08 m s-1) than in affected areas (0.17 ± 0.14 m s-1). If the energetic advantages of STST are not employed in macrotidal environments, it is likely that the fitness costs of that behaviour exceed potential energy savings, for example due to increased duration of exposure to predation. In conclusion, STST is evidently not universal in relatively poor swimmers; its use can vary between species and may vary under different conditions

Personality, density and habitat drive the dispersal of invasive crayfish

There is increasing evidence that personality traits may drive dispersal patterns of animals, including invasive species. We investigated, using the widespread signal crayfish Pacifastacus leniusculus as a model invasive species, whether effects of personality traits on dispersal were independent of, or affected by, other factors including population density, habitat, crayfish size, sex and limb loss, along an invasion gradient. Behavioural traits (boldness, activity, exploration, willingness to climb) of 310 individually marked signal crayfish were measured at fully-established, newly-established and invasion front sites of two upland streams. After a period at liberty, recaptured crayfish were reassessed for behavioural traits (newly-established, invasion front). Dispersal distance and direction of crayfish movement, local population density, fine-scale habitat characteristics and crayfish size, sex and limb loss were also measured. Individual crayfish exhibited consistency in behavioural traits over time which formed a behavioural syndrome. Dispersal was both positively and negatively affected by personality traits, positively by local population density and negatively by refuge availability. No effect of size, sex and limb loss was recorded. Personality played a role in promoting dispersal but population density and local habitat complexity were also important determinants. Predicting biological invasion in animals is likely to require better integration of these processes

Adaptive management in the context of barriers in European freshwater ecosystems

Many natural habitats have been modified to accommodate for the presence of humans and their needs. Infrastructures – such as hydroelectric dams, weirs, culverts and bridges – are now a common occurrence in streams and rivers across the world. As a result, freshwater ecosystems have been altered extensively, affecting both biological and geomorphological components of the habitats. Many fish species rely on these freshwater ecosystems to complete their lifecycles, and the presence of barriers has been shown to reduce their ability to migrate and sustain healthy populations. In the long run, barriers may have severe repercussions on population densities and dynamics of aquatic animal species. There is currently an urgent need to address these issues with adequate conservation approaches. Adaptive management provides a relevant approach to managing barriers in freshwater ecosystems as it addresses the uncertainties of dealing with natural systems, and accommodates for future unexpected events, though this approach may not be suitable in all instances. A literature search on this subject yielded virtually no output. Hence, we propose a step-by-step guide for implementing adaptive management, which could be used to manage freshwater barriers

Is current floodplain management a cause for concern for fish and bird conservation in Bangladesh’s largest wetland?

Worldwide, water regulatory structures have impacts on aquatic ecological connectivity. This study determined the effects of current sluice management on the fish community in the Baral River, a major connection to the largest wetland (Chalan Beel) in Bangladesh. It also examines wider problems for biodiversity conservation (particularly waterbirds) in that wetland, which has shrunk to 30% of its former dry-season size in 50 years. During the flood period, the peak breeding time for native floodplain fishes, sluices were in undershot operation (open by 16–60% of water depth). During this time, fish abundance and species richness were 229% and 155% higher respectively at sites upstream of the sluices, despite similar habitat upstream and downstream. Outside this period, when sluices were fully open, abundance and species richness were similar upstream and downstream. Fish samples were dominated by fry, which are susceptible to damage by sluices. Twenty (41.7%) of 48 fish species captured in this study are classed as threatened in Bangladesh and their abundance was significantly lower downstream of the sluices. Two alien species, Aristichthys nobilis and Hypophthalmichthys molitrix, were recorded, probably escapees from local aquaculture activities. Twenty-five species of wetland birds were recorded in the Chalan Beel. From interviews, 64% of these species appear to have decreased in the last 20 years, together with 11 more species that may have become locally extinct over this period. This suggests that widespread ecological disruption is occurring. Improved water management (e.g. gate opening height and duration) or modification (e.g. fish pass) of the Baral sluices is needed, to meet biodiversity and fisheries needs, rather than just for flood control and crop production. Improved hydrological and ecological connectivity and habitat protection are needed, as are a cessation of destructive fishing and seasonal fish ranching practices that currently provide synergistic pressures

Modelling fine scale route choice of upstream migrating fish as they approach an instream structure

This study used pattern-oriented modelling (POM) to investigate the space use and behavioural response of upstream migrating European river lamprey (Lampetra fluviatilis) to the two-dimensional hydrodynamic conditions created by an instream structure (triangular profile gauging weir). Passive Integrated Transponder (PIT) and acoustic telemetry were used to map the spatial-temporal distribution patterns of lamprey as they migrated upstream. Acoustic Doppler velocimetry and computer modelling were used to quantify the hydrodynamic environment. In adherence with the POM methodology, multiple movement models, incorporating increasingly complex environmental feedback mechanisms and behavioural rules were created and systematically assessed to identify which factors might reproduce the observed patterns. The best model was a spatially explicit Eulerian-Lagrangian Individual Based Model (IBM) that included two simple behaviours: 1) tortuous non-directed swimming when in low flow velocity (< 0.1 m s−1) and 2) persistent directed (against the flow) swimming in moderate to high flow velocity (≥ 0.1 m s−1). The POM indicated that flow heterogeneity was an important influence of lamprey space use and that simple behavioural rules (i.e. two separate movement behaviours in response to flow velocity) were sufficient to reproduce the main movement pattern observed: avoidance of flow recirculating regions near the banks. The combination of field telemetry, hydrodynamic modelling and POM provided a useful framework for systematically identifying the key factors (hydrodynamic and behavioural) that governed the space use of the target species and would likely work well for investigating similar relationships in other aquatic species