Search

Background and Aims In 2020 we reported the ACE Index in acute colitis which used biochemical and endoscopic parameters to predict steroid non-response on admission in patients with acute ulcerative colitis [UC]. We aimed to validate the ACE Index in an independent cohort. Methods The validation cohort comprised patients screened as eligible for inclusion in the CONSTRUCT study, a prospective, randomized, placebo-controlled trial which compared the effectiveness of treatment with infliximab vs ciclosporin in patients admitted with acute UC. The CONSTRUCT cohort database was reviewed at The Edinburgh IBD Unit and the same biochemical and endoscopic variables and cut-off values as those in the derivation cohort were applied to the validation cohort. Results In total, 800 patients were identified; 62.5% [55/88] of patients with a maximum ACE Index of 3 did not respond to intravenous [IV] steroids (positive predictive value [PPV] 62.5%, negative predictive value [NPV] 79.8%). Furthermore, 79.8% [158/198] of patients with an ACE Index of 0 responded to IV steroids [PPV 79.8%, NPV 62.5%]. Receiver operator characteristic [ROC] curve analysis produced an area under the curve [AUC] of 0.663 [ p  < 0.001]. Conclusions We have now reported and externally validated the ACE Index in acute colitis in a combined cohort of over 1000 patients from across the UK. The ACE Index may be used in conjunction with clinical judgement to help identify patients admitted with active UC who are at high risk of not responding to IV steroids. Further studies are required to improve objectivity and accuracy of assessment. [ABSTRACT FROM AUTHOR]

Central Valley Chinook must pass through the San Francisco Estuary as juveniles and again as maturing adults. Much attention has been given to the effects on Chinook of management of the freshwater part of the estuary, and the Sacramento–San Joaquin Delta, and especially to the effects on Chinook of diversions of water from the Delta. Here, I review available information on juvenile Chinook in and around the estuary that seems most relevant to management of the estuary and of Chinook. Most naturally produced juvenile fall Chinook enter the estuary as small fish (

Protected evolutionarily significant units (ESUs) of salmonids require objective and measurable criteria for guiding their recovery. In this report, we develop a method for assessing population viability and two ways to integrate these population-level assessments into an assessment of ESU viability. Population viability is assessed with quantitative extinction models or criteria relating to population size, population growth rate, the occurrence of catastrophic declines, and the degree of hatchery influence. ESU viability is assessed by examining the number and distribution of viable populations across the landscape and their proximity to sources of catastrophic disturbance.Central Valley spring-run and winter-run Chinook salmon ESUs are not currently viable, according to the criteria-based assessment. In both ESUs, extant populations may be at low risk of extinction, but these populations represent a small portion of the historical ESUs, and are vulnerable to catastrophic disturbance. The winter-run Chinook salmon ESU, in the extreme case, is represented by a single population that spawns outside of its historical spawning range. We are unable to assess the status of the Central Valley steelhead ESU with our framework because almost all of its roughly 80 populations are classified as data deficient. The few exceptions are those populations with a closely associated hatchery, and the naturally-spawning fish in these streams are at high risk of extinction. Population monitoring in this ESU is urgently needed.Global and regional climate change poses an additional risk to the survival of salmonids in the Central Valley. A literature review suggests that by 2100, mean summer temperatures in the Central Valley region may increase by 2-8°C, precipitation will likely shift to more rain and less snow, with significant declines in total precipitation possible, and hydrographs will likely change, especially the the southern Sierra Nevada mountains. Warming at the lower end of the predicted range may allow spring-run Chinook salmon to persist in some streams, while making some currently utilized habitat inhospitable. At the upper end of the range of predicted warming, very little spring-run Chinook salmon habitat is expected to remain suitable.In spite of the precarious position of Central Valley salmonid ESUs, there are prospects for greatly improving their viability. Recovering Central Valley ESUs may require re-establishing populations where historical populations have been extirpated (e.g., upstream of major dams). Such major efforts should be focused on those watersheds that offer the best possibility of providing suitable habitat in a warmer future.

Effective conservation and recovery planning for Central Valley steelhead requires an understanding of historical population structure. We describe the historical structure of the Central Valley steelhead evolutionarily significant unit using a multi-phase modeling approach. In the first phase, we identify stream reaches possibly suitable for steelhead spawning and rearing using a habitat model based on environmental envelopes (stream discharge, gradient, and temperature) that takes a digital elevation model and climate data as inputs. We identified 151 patches of potentially suitable habitat with more than 10 km of stream habitat, with a total of 25,500 km of suitable habitat. We then measured the distances among habitat patches, and clustered together patches within 35 km of each other into 81 distinct habitat patches. Groups of fish using these 81 patches are hypothesized to be (or to have been) independent populations for recovery planning purposes. Consideration of climate and elevation differences among the 81 habitat areas suggests that there are at least four major subdivisions within the Central Valley steelhead ESU that correspond to geographic regions defined by the Sacramento River basin, Suisun Bay area tributaries, San Joaquin tributaries draining the Sierra Nevada, and lower-elevation streams draining to the Buena Vista and Tulare basins, upstream of the San Joaquin River. Of these, it appears that the Sacramento River basin was the main source of steelhead production. Presently, impassable dams block access to 80% of historically available habitat, and block access to all historical spawning habitat for about 38% of the historical populations of steelhead.

This monograph presents an extensive review of the biology and management of Chinook salmon and steelhead in the Central Valley of California. Relevant data and publications on these populations are summarized and discussed in the context of the wider professional literature, with emphasis on the importance of evolutionary considerations in the assessment of populations and in their management, the need to manage populations together with their environments, and the contradiction between maintaining a major hatchery program to support a mixed-stock ocean fishery and trying to maintain or restore populations adapted to natural or semi-natural habitats. Recommendations are presented for management and monitoring—for example for a thorough review of hatchery operations, for more emphasis on monitoring individual-based factors such the physiological condition and growth rates of juveniles, and for simulation of major restoration actions and monitoring programs. The 17 chapters cover major conceptsin salmon biology and conceptual foundations for management, and Central Valley Chinook and steelhead populations and their habitat, growth and migration, habitat use, harvest, hatcheries, modeling, monitoring, and management.

Eight large Federal hydro-power dams were constructed between the 1930's and 1970's on the mainstem lower Columbia and Snake Rivers, U.S.A. The dams included fishways that enabled effective upstream passage of adult salmonids to Snake River basin spawning areas, but they lacked any facilities for protection of juvenile salmonids migrating downstream to the ocean. Prior to completion of the dam complex, early studies on mortality of juvenile salmon passing through turbines suggested that Snake River salmon stocks could not survive the cumulative mortalities to populations offish that would have to pass downstream through turbines at all eight dams. This led to a more than 30-yr field effort conducted primarily by NOAA's National Marine Fisheries Service personnel to devise, test, and recommend for installation effective screening systems for turbine intakes at dams to decrease mortality of downstream migrating juvenile salmonids. This paper provides a history of the extensive research to accomplish this goal., Background Pacific Northwest's Columbia River drains a watershed of 680,000 [km.sup.2], and historical flows in the lower river ranged from 1,400 to 28,300 [m.sup.3]/s, with the peak flows primarily resulting [...]

Are smolt-to-adult return rates (SARs) for wild steelhead (i.e., sea-run rainbow trout, Oncorhynchus mykiss) and wild Snake River spring--summer Chinook salmon (Oncorhynchus tshawytscha) related to changes in the Columbia River plume at the time that juvenile migrants enter the ocean? We used three-dimensional (3D) numerical models of the baroclinic circulation in the Columbia River estuary--plume--shelf system to simulate within-season variation in plume size and location, comparing the results with SARs for each day that juvenile salmon entered the ocean for 1999-2003. We found that steelhead benefited from the plume environment at a narrow window of time around their ocean entry. However, when large-scale ocean conditions turned unfavorable, the contribution of local plume conditions to the overall variability in steelhead survival became not significant. A similar evaluation revealed that the plume did not affect survival of Chinook salmon, at least at the fine scale of variability considered. The differential response between the two species is consistent with observed and previously reported behavioral characteristics they exhibit. We speculate that steelhead mainly use the plume to move quickly away from coastal habitats and the predation pressures associated with this environment, for a more direct migration than Chinook salmon to ocean habitats in the Gulf of Alaska. Resume: Les taux de survie du saumoneau a l'adulte (SARs) des truites arc-en-ciel anadromes (Oncorhynchus mykiss) sauvages et des saumons chinook (Oncorhynchus tshawytscha) de printemps--ete de la Snake sont-ils relies aux changements dans le panache du Columbia au moment ou les jeunes saumons penetrent dans l'ocean? Nous avons utilise des mode les numeriques tridimensionnels (3D) de la circulation baroclinique dans le systeme estuaire--panache--plate-forme du Columbia pour simuler la variation au cours de la saison de la taille et de la position du panache, en associant les resultats aux SAR pour chaque jour ou les jeunes saumons ont penetre dans la mer en 1999-2003. Les truites arc-en-ciel anadromes ont tire benefice de l'environnement du panache pendant une courte periode au moment de leur arrivee dans l'ocean. Cependant, lorsque les conditions oceaniques a grande echelle sont devenues defavorables, la contribution des conditions du panache local a la variabilite globale de la survie des truites arc-en-ciel anadromes est devenue non significative. Une evaluation similaire a montre que le panache n'affecte pas la survie des saumons chinook, au moins a l'echelle fine de la variabilite consideree. Les reponses differentes des deux especes sont en accord avec les caracteristiques comportementales observees presentement et signalees anterieurement chez elles. Nous croyons que les truites arc-en-ciel anadromes utilisent le panache pour s'eloigner rapidement des habitats cotiers et des pressions de predation qui leur sont associees, afin de migrer plus directement que les saumons chinook vers les habitats oceaniques dans le golfe de l'Alaska. [Traduit par la Redaction], Introduction The Endangered Species Act listing of many evolutionarily significant units of eastern Pacific Ocean salmon (Oncorhynchus spp.) has prompted extensive research into possible causes for their declines. Although most [...]

Fish have evolved intrinsic flight responses, allowing pre-emptive avoidance of potentially threatening situations. To direct downstream migrant fish away from deleterious conditions at dams and other barriers, mechanical devices such as travelling screens and fish bypass systems are often installed. However, field observations suggest that if these structures create areas of rapidly accelerating flow, they do not effectively guide the fish. We studied the avoidance behaviour of actively migrating fall Chinook salmon (Oncorhynchus tshawytscha) smolts in controlled experiments of low-, medium-, and high-flow accelerations. We measured the response velocity ([V.sub.R]) and the velocity gradient (VG) over body length. Although [V.sub.R] varied significantly with flow conditions and increased with increasing water temperature, the median VG at the instant at which smolts displayed an avoidance response was similar over the range of accelerating flows tested. Results from this study present the first quantitative information about the avoidance behaviour of fish to flow acceleration and should provide data needed to help engineers and biologists develop effective systems to alleviate anthropogenically altered flow regimes. Furthermore, the devised experimental setup provides a valuable means to test the effects of accelerating flow on any downstream migrant fish species. Resume: Les poissons ont developpe au cours de leur evolution des reactions intrinseques de fuite qui leur permettent d'eviter de facon preventive les situations menacantes. On installe souvent dans les barrages et autres barrieres des structures mecaniques, telles que des grilles mobiles et des voies d'evitement pour les poissons, afin de diriger les poissons qui migrent vers l'aval loin des conditions deleteres. Cependant, les observations sur le terrain laissent croire que si ces structures creent des zones de debit en acceleration rapide, elles ne reussissent pas a orienter les poissons efficacement. Nous etudions le comportement d'evitement de saumoneaux du saumon chinook (Oncorhynchus tshawytscha) d'automne en phase de migration active au cours d'experiences controlees dans des conditions d'acceleration faible, moyenne et elevee du debit. Nous avons mesure la vitesse qui elicite une reaction [V.sub.R] et le gradient de vitesse VG le long du corps. Alors que les [V.sub.R] varient de facon significative en fonction des conditions de debit et augmentent en fonction des temperatures croissantes, le VG median au moment ou les saumoneaux montrent une reaction d'evitement est semblable dans toute la gamme de debits en acceleration testes. Les resultats de notre etude apportent les premiers renseignements quantitatifs sur le comportement d'evitement des debits en acceleration chez les poissons; ils de[V.sub.R]aient fournir les donnees necessaires aux ingOnieurs et aux biologistes pour mettre au point des systemes efficaces pour attenuer les effets des modifications anthropiques des regimes de debit. De plus, le montage experimental que nous avons imagine fournit une methode interessante pour tester les effets des debits en acceleration sur toute espece de poisson lors de sa migration vers l'aval. [Traduit par la Redaction], Introduction Construction of dams, weirs, and other barriers on rivers and streams may substantially alter the natural flow regimes and migratory corridors under which fishes evolved (Williams 2008). Migratory fishes [...]