Temporal variation in sea trout Salmo trutta life history traits in the Erriff River, western Ireland

Gargan, Patrick; Kelly, Fiona; Shephard, Samuel; Whelan, Ken

doi:10.3354/aei00211

Cited by 20 publications

(19 citation statements)

References 39 publications

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“…In inland waters, the mean length of fish in the catch or assemblage has also been identified as the simplest and most direct indicator of the state of a multispecies fishery (Welcomme, 1999). LBI are assumed to reflect the impacts of size-selective fishing pressure (Froese, 2004;Rochet & Trenkel, 2003;Shin, Rochet, Jennings, Field & Gislason, 2005), but may capture other processes, for example, sea lice infestation of sea trout (Gargan, Kelly, Shephard & Whelan, 2016), that can also curtail size distribution.…”

Section: Length-based Methods-indicatorsmentioning

confidence: 99%

Inland fish stock assessment: Applying data‐poor methods from marine systems

Fitzgerald

Delanty

Shephard

2018

Fisheries Management Eco

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Inland fisheries can be diverse, local and highly seasonal. This complexity creates challenges for monitoring, and consequently, many inland fish stocks have few data and cannot be assessed using methods typically applied to industrial marine fisheries. In such situations, there may be a role for methods recently developed for assessment of data‐poor fish stocks. Herein, three established data‐poor assessment tools from marine systems are demonstrated to highlight their value to inland fisheries management. A case study application uses archived length, catch and catch‐per‐unit‐effort data to characterise the ecological status of an important recreational brown trout stock in an Irish lake. This case study is of specific use to management of freshwater sport fisheries, but the broader purpose of the paper was to provide a crossover between marine and inland fisheries science, and to highlight accessible data‐poor assessment approaches that may be applicable in diverse inland systems.

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Section: Length-based Methods-indicatorsmentioning

confidence: 99%

Inland fish stock assessment: Applying data‐poor methods from marine systems

Fitzgerald

Delanty

Shephard

2018

Fisheries Management Eco

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“…All fish were checked weekly for morphological indicators of smolting from March to June in each of 2017 and 2018, the period corresponding to the natural migratory period in the wild for this population (Gargan et al, ). Wild smolts typically migrate out of the Erriff system aged between 1+ and 4+, with the large majority doing so aged 2+ or 3+ (approximately equal numbers of each; Gargan et al, ). Smolting is a precursor to downstream migration in several salmonines, and comprises a number of morphological, behavioural and physiological changes.…”

Section: Methodsmentioning

confidence: 99%

“…Immature fish (unconfirmed sex at the time of sampling) were later genotyped to determine genotypic sex using a microsatellite sex marker. The natural spawning period for the wild population‐of‐origin is in late autumn/early winter, and the migratory period is in the spring (Gargan et al, ). Since freshwater maturation generally precludes migration in brown trout (Dȩbowski & Dobosz, ; Dellefors & Faremo, ; Jonsson, ), any fish showing signs of maturing without having migrated to sea are considered to be on a non‐anadromous trajectory, while smolts which undertake marine migrations are immature.…”

Section: Methodsmentioning

confidence: 99%

Food and temperature stressors have opposing effects in determining flexible migration decisions in brown trout (Salmo trutta)

Archer

Hutton

Harman

et al. 2020

Global Change Biology

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With rapid global change, organisms in natural systems are exposed to a multitude of stressors that likely co-occur, with uncertain impacts. We explored individual and cumulative effects of co-occurring environmental stressors on the striking, yet poorly understood, phenomenon of facultative migration. We reared offspring of a brown trout population that naturally demonstrates facultative anadromy (sea migration), under different environmental stressor treatments and measured life history responses in terms of migratory tactics and freshwater maturation rates. Juvenile fish were exposed to reduced food availability, temperatures elevated to 1.8°C above natural conditions or both treatments in combination over 18 months of experimental tank rearing. When considered in isolation, reduced food had negative effects on the size, mass and condition of fish across the experiment. We detected variable effects of warm temperatures (negative effects on size and mass, but positive effect on lipids). When combined with food restriction, temperature effects on these traits were less pronounced, implying antagonistic stressor effects on morphological traits. Stressors combined additively, but had opposing effects on life history tactics: migration increased and maturation rates decreased under low food conditions, whereas the opposite occurred in the warm temperature treatment. Not all fish had expressed maturation or migration tactics by the end of the study, and the frequency of these 'unassigned' fish was higher in food deprivation treatments, but lower in warm treatments. Fish showing migration tactics were smaller and in poorer condition than fish showing maturation tactics, but were similar in size to unassigned fish. We further detected effects of food restriction on hypo-osmoregulatory function of migrants that may influence the fitness benefits of the migratory tactic at sea. We also highlight that responses to multiple stressors may vary depending on the response considered. Collectively, our results indicate contrasting effects of environmental stressors on life history trajectories in a facultatively migratory species. K E Y W O R D S anadromy, antagonistic interaction, aquatic, brown trout, climate change, multiple stressors, partial migration, Salmo trutta | 2879 ARCHER Et Al. S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Archer LC, Hutton SA, Harman L, et al. Food and temperature stressors have opposing effects in determining flexible migration decisions in brown trout (Salmo trutta). Glob Change Biol. 2020;26:2878-2896. https ://doi.

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“…It has been suggested that an increase in marine mortality and a reduction in sea growth due to lice or other factors affecting trout in the marine environment can result in a population shift in lifehistory strategy (Thorstad et al 2015). Gargan et al (2016) showed significant changes in quantitative life-history traits in the trout population in the Erriff River, western Ireland, after the establishment of salmon farming in the local estuary. These changes included a reduction in the number and size of trout kelts, the estimated number of eggs deposited, the sea trout rod catch, the proportion of older (1+ and 2+ sea age) fish and the frequency of repeat spawners.…”

Section: Consequences For Populationsmentioning

confidence: 99%

Impacts of salmon lice on mortality, marine migration distance and premature return in sea trout

Llinares

Bøhn

Karlsen

et al. 2020

Mar. Ecol. Prog. Ser.

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Brown trout Salmo trutta (L.) is a facultative anadromous species, where a portion of individuals in populations with access to the sea perform migrations to use the richer feeding resources. We investigated the effect of salmon lice Lepeophtheirus salmonis (Krøyer 1837) infestation on the survival and behaviour of wild trout post-smolts (average fork length = 180 mm) during their marine migration. Comparisons of the marine migratory behaviour were made between an artificially infested group (n = 74) and a control group (n = 71) in an area with low natural lice infestation pressure. Artificial infestation was estimated to cause 100% prevalence and a mean intensity of 65 lice fish-1 (mean relative intensity of 2.4 lice g-1 fish). Survival analysis showed limited statistical power but revealed lice-induced mortality, with an estimated hazard ratio of 2.73 (95% CI = 1.04-7.13) compared to the control group, when data from a previous pilot study were included. Surviving individuals in the infested group additionally responded by residing closer to fresh water while at sea, and by prematurely returning to fresh water. On average, infested fish returned to fresh water after only 18 d at sea, while control fish spent on average 100 d at sea. The residency in the inner part of the fjord and the premature return to fresh water represent an adaptive behavioural response to survive the infestation, at the probable cost of reduced growth opportunities and compromised future fitness.

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Temporal variation in sea trout Salmo trutta life history traits in the Erriff River, western Ireland

Cited by 20 publications

References 39 publications

Inland fish stock assessment: Applying data‐poor methods from marine systems

Inland fish stock assessment: Applying data‐poor methods from marine systems

Food and temperature stressors have opposing effects in determining flexible migration decisions in brown trout (Salmo trutta)

Impacts of salmon lice on mortality, marine migration distance and premature return in sea trout

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