Paul S. Kemp

Habitat requirements of Atlantic salmon and brown trout in rivers and streams

The distributions and abundances of trout and salmon are strongly influenced by their habitat. The habitat includes both abiotic and biotic factors, which interact in complex webs. Habitat probably has strongest effects during population bottlenecks, when the standing stock approaches the carrying capacity of the environment. Various approaches to modelling interactions between habitat and population density and mean weight have been explored, but further work is needed in this area of investigation. The importance of depth, current, substrate, cover, and to a lesser extent, temperature and oxygen availability to the various stages of the life cycles of salmon and trout are briefly reviewed. By drawing on published data, it is possible to define broad ranges of acceptable conditions for the life stages of each species. However, it is not possible to partition this variation into between-population differences, within-population preferences, within-population tolerances, and effects of interactions between habitat variables. To pursue this important issue further, a structured approach using experimentation both in the field and in suitable laboratory systems is recommended. There is abundant evidence that habitat requirements of salmon and trout overlap. Trout tend to out-compete salmon except often in areas of particularly fast flows and, perhaps, remote from the river bank. The habitat requirements of year classes of salmon and trout overlap and therefore, there is scope for interactions between them depending on the spatial arrangement of habitats and the occurrence of bottlenecks. It is particularly important to understand where the bottlenecks to production lie and to focus on these in the first instance. Otherwise, there is a risk of manipulating habitat that is already in excess, or increasing numbers of a population that will subsequently be constrained, e.g., by over-wintering habitat. For this reason, it is prudent to accept that although manipulations of habitat may appear to be beneficial when considered locally, they should be measured and assessed where possible in terms of the production of returning adults and/or high quality smolts. Because of the complexity of interactions between salmon, trout, and the animals that eat them, it is at present difficult, or impossible, to derive good predictive models of the effects of manipulating habitats under many circumstances.

The role of dopaminergic imaging in patients with symptoms of dopaminergic system neurodegeneration

Diagnosis of neurological and psychiatric conditions associated with disturbances of dopaminergic functioning can be challenging, especially in the early stages, and may be assisted with biomarkers such as dopamine system imaging. Distinguishing between Alzheimers disease and dementia with Lewy bodies is a major diagnostic challenge. Clinical diagnosis of Parkinsons disease is straightforward with classic presentation, but accurate distinction among Parkinsonian variants may be difficult; non-Parkinsons disease conditions are commonly misdiagnosed as Parkinsons disease, and ~20% of patients with Parkinsons disease are not clinically diagnosed despite coming to medical attention. Early and accurate diagnosis is desirable to improve management. Imaging of the dopamine transporter using single-photon emission computed tomography may be of particular utility in this regard. Abnormal imaging indicates underlying nigrostriatal neurodegeneration, supportive of a diagnosis of Parkinsons disease, atypical parkinsonism or dementia with Lewy bodies, and identifies patient groups in whom dopaminergic therapy may be beneficial. Normal imaging supports diagnosis of a condition not involving nigrostriatal neurodegeneration such as Alzheimers disease, essential tremor or drug-induced parkinsonism and hence a different therapeutic approach. In patients in whom there was diagnostic uncertainty between degenerative parkinsonism and non-degenerative tremor disorders, baseline imaging with the dopamine transporter ligand [(123)I]ioflupane (DaTscan™) has shown 78% sensitivity and 97% specificity with reference to clinical diagnosis at 3 years, versus 93% and 46%, respectively, for baseline clinical diagnosis. In a Phase III trial of [(123)I]ioflupane in patients with initial clinical diagnosis of probable or possible dementia with Lewy bodies or non-Lewy body dementia, mean specificity for excluding non-Lewy body dementia (predominantly Alzheimers disease) was 90.4%. Using clinical diagnosis as a reference against which to assess sensitivity and specificity of dopamine transporter imaging is a limitation, but definitive diagnosis via pathological confirmation is generally not feasible. In a series of patients with post-mortem brain examination, imaging using [(123)I]ioflupane has demonstrated higher sensitivity (88%) and specificity (100%) for differentiating dementia with Lewy bodies from non-Lewy body dementia than clinical diagnosis (75% and 42%, respectively). Dopaminergic system imaging may be particularly valuable in patients with clinically inconclusive parkinsonism or a clinical diagnosis of possible dementia with Lewy bodies; it is not helpful in differentiating between Parkinsons disease and atypical parkinsonism, although postsynaptic dopaminergic imaging may be of utility. Other potential uses of dopamine transporter imaging include identification of patients with premotor Parkinsons disease, monitoring disease progression in testing novel therapeutics, and as an inclusion criterion for entry into clinical trials.

Dopamine transporter imaging with [(123)I]FP-CIT SPECT: potential effects of drugs

Background[123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-{4-iodophenyl}nortropane ([123I]FP-CIT) single photon emission computed tomography (SPECT) is a frequently and routinely used technique to detect or exclude dopaminergic degeneration by imaging the dopamine transporter (DAT) in parkinsonian and demented patients. This technique is also used in scientific studies in humans, as well as in preclinical studies to assess the availability of DAT binding in the striatum. In routine clinical studies, but also in scientific studies, patients are frequently on medication and sometimes even use drugs of abuse. Moreover, in preclinical studies, animals will be anesthetized. Prescribed drugs, drugs of abuse, and anesthetics may influence the visual interpretation and/or quantification of [123I]FP-CIT SPECT scans.DiscussionHere, we discuss the basic principle of how drugs and anesthetics might influence the visual interpretation and/or quantification of [123I]FP-CIT SPECT scans. We also review drugs which are likely to have a significant influence on the visual interpretation and/or quantification of [123I]FP-CIT SPECT scans. Additionally, we discuss the evidence as to whether frequently prescribed drugs in parkinsonian and demented patients may have an influence on the visual interpretation and/or quantification of [123I]FP-CIT SPECT scans. Finally, we discuss our recommendations as to which drugs should be ideally withdrawn before performing a [123I]FP-CIT SPECT scan for routine clinical purposes. The decision to withdraw any medication must always be made by the specialist in charge of the patient’s care and taking into account the pros and cons of doing so.

Fine-Scale Behavioral Responses of Pacific Salmonid Smolts as They Encounter Divergence and Acceleration of Flow

Abstract We assessed fine-scale behavioral responses of the smolts of four Pacific salmonid species to open and constricted channels in a flume. Natural migrants encountered two geometrically similar parallel channels with different hydraulic conditions representing constricted and open treatments. Observation of route selection under alternate discharge scenarios provided evidence of behavioral choice by smolts. As expected, the majority of smolts passed through the open channel in a ratio consistent with flow. After controlling for the influence of flow, both initial channel selection and subsequent channel rejection was higher for the constricted channel; rejection was probably due to fish detecting an area of rapidly accelerating flow. The majority of smolts traveled downstream headfirst and faster than the mean midcolumn water velocity. Those that faced the flow passed at a slower rate and tended to select the open treatment. The few yearling Chinook salmon Oncorhynchus tshawytscha and coho salmon O....

Response of downstream migrant juvenile Pacific salmonids to accelerating flow and overhead cover

Mechanical structures designed to divert or guide juvenile migrant salmon at dams often work less effectively than expected. This likely results from a lack of understanding of fish behaviour. In order to address this, a series of experiments was conducted at McNary dam, USA, to assess the influence of hydraulic transition and overhead cover on the behaviour of seaward migrating juvenile Pacific salmon. Fish passing through a flume encountered a choice of route that varied based on hydraulic factors and overhead cover. Direct observation revealed that individuals elicited strong avoidance behaviour when they encountered areas where hydraulic conditions changed rapidly or were covered. Our findings have implications relevant to fish pass design and culvert restoration in Europe. Critically, improvement of current fish pass design and development of alternative mechanisms that effectively block fish access to, and divert fish away from poor passage routes, requires consideration of the behavioural component of fish migration.

Value of Semiquantitative Analysis for Clinical Reporting of 123I-2-β-Carbomethoxy-3β-(4-Iodophenyl)-N-(3-Fluoropropyl)Nortropane SPECT Studies

Clinical 123I-2-β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (123I-FP-CIT) SPECT studies are commonly performed and reported using visual evaluation of tracer binding, an inherently subjective method. Increased objectivity can potentially be obtained using semiquantitative analysis. In this study, we assessed whether semiquantitative analysis of 123I-FP-CIT tracer binding created more reproducible clinical reporting. A secondary aim was to determine in what form semiquantitative data should be provided to the reporter. Methods: Fifty-four patients referred for the assessment of nigrostriatal dopaminergic degeneration were scanned using SPECT/CT, followed by semiquantitative analysis calculating striatal binding ratios (SBRs) and caudate-to-putamen ratios (CPRs). Normal reference values were obtained using 131 healthy controls enrolled on a multicenter initiative backed by the European Association of Nuclear Medicine. A purely quantitative evaluation was first performed, with each striatum scored as normal or abnormal according to reference values. Three experienced nuclear medicine physicians then scored each striatum as normal or abnormal, also indicating cases perceived as difficult, using visual evaluation, visual evaluation in combination with SBR data, and visual evaluation in combination with SBR and CPR data. Intra- and interobserver agreement and agreement between observers and the purely quantitative evaluation were assessed using κ-statistics. The agreement between scan interpretation and clinical diagnosis was assessed for patients with a postscan clinical diagnosis available (n = 35). Results: The physicians showed consistent reporting, with a good intraobserver agreement obtained for the visual interpretation (mean κ ± SD, 0.95 ± 0.029). Although visual interpretation of tracer binding gave good interobserver agreement (0.80 ± 0.045), this was improved as SBRs (0.86 ± 0.070) and CPRs (0.95 ± 0.040) were provided. The number of striata perceived as difficult to interpret decreased as semiquantitative data were provided (30 for the visual interpretation; 0 as SBR and CPR values were given). The agreement between physicians’ interpretations and the purely quantitative evaluation showed that readers used the semiquantitative data to different extents, with a more experienced reader relying less on the semiquantitative data. Good agreement between scan interpretation and clinical diagnosis was seen. Conclusion: A combined approach of visual assessment and semiquantitative analysis of tracer binding created more reproducible clinical reporting of 123I-FP-CIT SPECT studies. Physicians should have access to both SBR and CPR data to minimize interobserver variability.

Experimental quantification of the swimming performance and behaviour of spawning run river lamprey Lampetra fluviatilis and European eel Anguilla anguilla.

Using a large-scale open-channel flume, the swimming ability and behaviour of individual adult European eel Anguilla anguilla and river lamprey Lampetra fluviatilis, species that exhibit anguilliform locomotion, were quantified under complex hydraulic conditions created by a 0·2-0·3 m high under- or overshot weir during four discharge regimes. Fishes were allowed to approach the weirs from both up- and downstream. All fishes passed the undershot weir, independent of discharge and direction of movement, and under high flow (mean ±S.E. 194·63 ± 6·48 l s(-1)) moved upstream against velocities that ranged between 1·75 and 2·12 m s(-1), suggesting greater maximum swimming capability than previously reported. In comparison, passage efficiency during upstream movement was lower for the overshot weir for both L. fluviatilis and A. anguilla. Downstream moving A. anguilla took longer to pass the over- than undershot weir. This study describes a methodology to attain realistic measures of swimming ability and behavioural performance required to develop multispecies fish passage criteria.

Lamprey Spawning Migration

During recent decades, new insights regarding the spawning migration of lampreys have been gained due to advances in technology and growing interest in this key life history phase. The development of miniaturized active and passive transmitters has led to detailed information on the timing and extent of lamprey migrations. These tools, together with sophisticated laboratory experiments, have provided fertile ground for studies of lamprey migratory physiology and behavior. New molecular tools have been applied to questions of population structure and philopatry, while the identification of lamprey pheromones has illuminated heretofore unimagined mechanisms of migration and orientation. Interest in spawning migration has been spurred by the growing need to restore native lamprey populations and the equally pressing need to control invasive sea lamprey in the Laurentian Great Lakes. While important advances in anadromous lamprey biology have been achieved, gaps remain in our understanding of marine movements, species-specific differences, mechanisms of orientation, and the factors controlling passage success. Moreover, with the exception of the landlocked sea lamprey in the Great Lakes, research on the spawning migrations of the strictly potamodromous species (i.e., those that are parasitic in fresh water and the non-parasitic “brook” lampreys) is sorely lacking, seriously compromising our ability to assess what constitutes barriers to their migration.

Response of seaward migrating European eel (Anguilla anguilla) to manipulated flow fields

Anthropogenic structures (e.g. weirs and dams) fragment river networks and restrict the movement of migratory fish. Poor understanding of behavioural response to hydrodynamic cues at structures currently limits the development of effective barrier mitigation measures. This study aimed to assess the effect of flow constriction and associated flow patterns on eel behaviour during downstream migration. In a field experiment, we tracked the movements of 40 tagged adult European eels (Anguilla anguilla) through the forebay of a redundant hydropower intake under two manipulated hydrodynamic treatments. Interrogation of fish trajectories in relation to measured and modelled water velocities provided new insights into behaviour, fundamental for developing passage technologies for this endangered species. Eels rarely followed direct routes through the site. Initially, fish aligned with streamlines near the channel banks and approached the intake semi-passively. A switch to more energetically costly avoidance behaviours occurred on encountering constricted flow, prior to physical contact with structures. Under high water velocity gradients, fish then tended to escape rapidly back upstream, whereas exploratory ‘search’ behaviour was common when acceleration was low. This study highlights the importance of hydrodynamics in informing eel behaviour. This offers potential to develop behavioural guidance, improve fish passage solutions and enhance traditional physical screening.

Physical modelling of water, fauna and flora: knowledge gaps, avenues for future research and infrastructural needs

Physical modelling is a key tool for generating understanding of the complex interactions between aquatic organisms and hydraulics, which is important for management of aquatic environments under environmental change and our ability to exploit ecosystem services. Many aspects of this field remain poorly understood and the use of physical models within eco-hydraulics requires advancement in methodological application and substantive understanding. This paper presents a review of the emergent themes from a workshop tasked with identifying the future infrastructure requirements of the next generation of eco-hydraulics researchers. The identified themes are: abiotic factors, adaptation, complexity and feedback, variation, and scale and scaling. The paper examines these themes and identifies how progress on each of them is key to existing and future efforts to progress our knowledge of eco-hydraulic interactions. Examples are drawn from studies on biofilms, plants, and sessile and mobile fauna in shallow water fluvial and marine environments. Examples of research gaps and directions for educational, infrastructural and technological advance are also presented.