Roles of discharge and temperature in recruitment of a cold‐water fish, the European grayling <i>Thymallus thymallus</i>, near its southern range limit

Bašić, Tea; Britton, J. Robert; Cove, Richard J.; Ibbotson, A.T.; Gregory, Stephen D.

doi:10.1111/eff.12405

Cited by 17 publications

(17 citation statements)

References 60 publications

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“…However, recruitment of grayling and trout was positively associated in an English chalk stream (Bašić, Britton, Cove, Ibbotson, & Gregory, 2018). Also, Alpine bullhead (Cottus poecilopus, Cottidae) is a strong competitor to juvenile brown trout where these species cooccur (Hesthagen & Heggenes, 2003;Holmen, Olsen, & Vøllestad, 2003).…”

Section: Interspecific Competitionmentioning

confidence: 99%

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

et al. 2019

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This paper reviews the life history of brown trout and factors influencing decisions to migrate. Decisions that maximize fitness appear dependent on size at age. In partly anadromous populations, individuals that attain maturity at the parr stage typically become freshwater resident. For individual fish, the life history is not genetically fixed and can be modified by the previous growth history and energetic state in early life. This phenotypic plasticity may be influenced by epigenetic modifications of the genome. Thus, factors influencing survival and growth determine life‐history decisions. These are intra‐ and interspecific competition, feeding and shelter opportunities in freshwater and salt water, temperature in alternative habitats and flow conditions in running water. Male trout exhibit alternative mating strategies and can spawn as a subordinate sneaker or a dominant competitor. Females do not exhibit alternative mating behaviour. The relationship between growth, size and reproductive success differs between sexes in that females exhibit a higher tendency to migrate than males. Southern populations are sensitive to global warming. In addition, fisheries, aquaculture with increased spreading of salmon lice, introduction of new species, weirs and river regulation, poor water quality and coastal developments all threaten trout populations. The paper summarizes life‐history data from six populations across Europe and ends by presenting new research questions and directions for future research.

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Section: Interspecific Competitionmentioning

confidence: 99%

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

et al. 2019

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“…The chalk streams of southern England, such as the Hampshire Avon or Dorset Frome, are renowned to have more stable flow and temperature regimes than more rain-fed rivers and are likely to behave quite differently (Basic et al, 2018;Solomon & Paterson, 1980). By opting to treat our sample rivers as random representatives of Wales, we precluded making river-specific inferences because our river-specific estimates will have reduced variance due to shrinkage (Harrison et al, 2018).…”

Section: Generalisation Across and Beyond Walesmentioning

confidence: 99%

“…They suggested that methods with strong assumptions about the form of density-dependence in recruitment, such as the Beverton-Holt model, were appropriate for single data-rich stocks (e.g. Baglinière, Marchand, & Vauclin, 2005;Basic, Britton, Cove, Ibbotson, & Gregory, 2018), but that more data-driven, statistical models were emergence conditions, which could be more common under future climate change.…”

Section: Introductionmentioning

confidence: 99%

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

et al. 2020

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1. Understanding the effects of density-dependent and density-independent factors on recruitment is often inhibited by difficulties quantifying their relative contributions in highly variable recruitment data. Use of data-driven statistical methods with data that include one or more extreme recruitment events could help overcome these difficulties. 2. Juvenile Atlantic salmon and trout abundances in Wales have declined over the last 2 decades, and 2016 was a notably poor recruitment year in rivers around southern Europe, including England and Wales. The 2016 recruitment crash coincided with extreme winter weather conditions, leading to speculation that unusually warm temperatures and high flows adversely affect salmonid recruitment and caused the 2016 crash, although this remains untested. 3. We developed data-driven statistical models to: (1) describe juvenile salmonid recruitment from density-dependent and density-independent factors; and (2) assess whether the density-independent factors probably contributed to the 2016 salmon recruitment crash. We compiled salmon and trout young-of-year juvenile abundances from electrofishing surveys, egg deposition estimates and river flow and air temperature data from 2001-2017 for seven Welsh rivers, broadly representative of rivers around Wales. We used river flow and air temperature data to derive ecologically and behaviourally meaningful density-independent explanatory variables. 4. Salmonid recruitment in Wales was best described using density-dependent and density-independent factors, especially for salmon: after accounting for a concave relationship with egg deposition, salmon juvenile abundance was reduced under (1) warmer spawning temperatures that might inhibit spawning, and (2) higher flood frequencies during pre-emergence and emergence that might washout eggs or alevins. Results were less clear for trout, perhaps because they are behaviourally more plastic. 5. Our findings provide empirical support for general and predictable effects of temperature and flow during spawning and emergence on salmonid-especially salmon-recruitment in Wales. Furthermore, we suggest that the 2016 salmon recruitment crash was caused-in part-by particularly inclement spawning and

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“…Recruitment from eggs to age 0 juveniles was estimated as a density-dependent function modified by explanatory variables, as there is evidence for a negative effect of conspecific densities on annual grayling recruitment in the River Wylye (Bašić et al, 2018).…”

Section: Ecological Process Equationsmentioning

confidence: 99%

Medium‐term environmental changes influence age‐specific survival estimates in a salmonid population

et al. 2021

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1. Human-induced environmental change is a major stressor on freshwater habitats that has resulted in the population declines of many freshwater species.Ontogenetic shifts in habitat use and associated (st)age-specific requirements mean that impacts of environmental stressors can influence (st)ages in a population differently, and yet relatively few studies of freshwater fish populations account for their detail.2. We aimed to identify environmental and biotic factors affecting survival estimated for six age-classes of a European grayling population in the River Wylye, UK over a 17-year period. We used a Bayesian age-structured state space model to estimate survival of grayling cohorts between subsequent life stages (eggs to age 5 adults) for 16 annual transitions (2003-2004 to 2018-2019), whilst accounting for imperfect sampling of the population. We quantified the effects of seasonal water flow and temperature, in-stream habitat and prey resource, and potential competitors and predators on survival between subsequent life stages. We used Bayesian variable selection to gauge their relative importance on survival.3. Grayling abundances declined during the study period (>75% in all age-classes), predominately driven by a loss of mature adults. Changes to seasonal flows negatively influenced their survival: increased days of summer low flow related to decreased survival of subadults and mature adults, and lower winter flows related to reduced recruitment of juveniles from eggs. Higher summer macrophyte cover negatively influenced juvenile and subadult survival and increasing days of high temperature in summer appeared detrimental to juvenile survival. Abundance of brown trout (a potential competitor and predator) did not negatively influence grayling survival. 4. Our results reveal the implications of environmental change on a salmonid population, where recent low summer flows and high temperatures, and below average winter flows, have negatively influenced grayling survival. These conditions appear to be becoming more frequent and persistent in our study river, which is towards the species' southern range limit, which could render the population vulnerable to climate change. Our study demonstrates how careful analysis of long-termThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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Roles of discharge and temperature in recruitment of a cold‐water fish, the European grayling Thymallus thymallus, near its southern range limit

Cited by 17 publications

References 60 publications

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

Medium‐term environmental changes influence age‐specific survival estimates in a salmonid population

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