Characteristics of the Sea Trout
            <i>Salmo trutta</i>
            (L.) Stock Collapse in the River Ewe (Wester Ross, Scotland), in 1988‐2001

Butler, John R.; Walker, Amanda

doi:10.1002/9780470996027.ch4

Cited by 13 publications

(25 citation statements)

References 20 publications

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“…A gradual decrease in marine growth rates was also detected from scale analyses of sea trout from a Scottish river adjacent to salmon farms (data from 1980 to 1989−1990, 1992−1993, and 1997−2001) (Butler & Walker 2006). Thus, from 1980 to the period 1997−2001, maximum sea age was reduced from 11 to 5 yr.…”

Section: Osmoregulatory Problems and Physiological Stress Responsesmentioning

confidence: 84%

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Thorstad¹,

Todd²,

Uglem³

et al. 2015

Aquacult. Environ. Interact.

127

142

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Salmon farming increases the abundance of salmon lice, which are ectoparasites of salmonids in the sea. Here we review the current knowledge on the effects of salmon lice on wild sea trout. Salmon lice feed on host mucus, skin and muscle, and infestation may induce osmoregulatory dysfunction, physiological stress, anaemia, reduced feeding and growth, increased susceptibility to secondary infections, reduced disease resistance and ultimately mortality of individual sea trout. Wild sea trout in farm-free areas generally show low lice levels. In farm-intensive areas, lice levels on wild sea trout are typically higher, and more variable than in farm-free areas. Lice on wild sea trout are found at elevated levels particularly within 30 km of the nearest farms but can also extend to further ranges. Salmon lice in intensively farmed areas have negatively impacted wild sea trout populations by reducing growth and increasing marine mortality. Quantification of these impacts remains a challenge, although population-level effects have been quantified in Atlantic salmon by comparing the survival of chemically protected fish with control groups, which are relevant also for sea trout. Mortality attributable to salmon lice can lead to an average of 12−29% fewer salmon spawners. Reduced growth and increased mortality will reduce the benefits of marine migration for sea trout, and may also result in selection against anadromy in areas with high lice levels. Salmon lice-induced effects on sea trout populations may also extend to altered genetic composition and reduced diversity, and possibly to the local loss of sea trout, and establishment of exclusively freshwater resident populations.

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Section: Osmoregulatory Problems and Physiological Stress Responsesmentioning

confidence: 84%

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Thorstad¹,

Todd²,

Uglem³

et al. 2015

Aquacult. Environ. Interact.

127

142

View full text Add to dashboard Cite

show abstract

“…This contrast may reflect differences in sampling strategy between countries: Irish sea trout were captured in inner estuaries or river mouths and had returned prematurely from the sea, whereas the majority of sea trout in the Scottish samples were captured in sweep nets at sea. Premature return of lice-infested sea trout to freshwater has been reported in Ireland since lice epizootics have been recorded (Whelan 1991 and later in Scotland (Butler & Walker 2006, HattonEllis et al 2006. Bjørn et al (2001) found that sea trout and Arctic char that returned prematurely to freshwater had higher relative infection intensities than fish caught at sea at the same time, and commented that premature return of the most infected fish to freshwater may therefore be triggered to reduce the physiological consequences of the infection (Bjørn & Finstad 1997.…”

Section: Sampling Effectsmentioning

confidence: 99%

“…This compares to a 14% reduction in the weight of a sea trout of mean length in the present study. Butler & Walker (2006) also recorded a decrease in marine growth rates for River Ewe (Scotland) sea trout close to salmon farms, and concluded that the decline in growth was at least partly caused by salmon lice epizootics emanating from the farms. demonstrated that a significant reduction in sea trout marine growth in the Burrishoole system in western Ireland was most likely linked to premature return to freshwater of lice-infested sea trout.…”

Section: Sub-lethal Impactsmentioning

confidence: 99%

Aquaculture and environmental drivers of salmon lice infestation and body condition in sea trout

Shephard¹,

MacIntyre²,

Gargan³

2016

Aquacult. Environ. Interact.

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“…This was reflected in the River Ewe rod catch, with significant changes in the body mass distribution of fish between 1971− 1980 and 1992−2001, with the mean falling from 0.54 to 0.34 kg over the time period. Taken together, the changes in the River Ewe stock structure could be related to declines in marine growth and survival, which were deduced to have been at least partly attributable to salmon lice epizootics emanating from salmon farms in the adjacent coastal waters of the marine embayment of Loch Ewe (Butler & Walker 2006). Harris (2006) commented that the structure and composition of a sea trout population will determine its ability to withstand and recover rapidly from any adverse factors in both the freshwater and marine environments.…”

Section: Discussionmentioning

confidence: 99%

“…Butler & Walker (2006) recorded a collapse in sea trout rod catch in the River Ewe/Loch Maree system in Wester Ross, Scotland, in 1988, with an apparently unprecedented reduction in marine growth and survival reflected in marked shifts in the population structure before and after the collapse. Between 1980Between and 1997Between −2001, maximum sea age fell from 11 to 5 yr and marine growth rates declined.…”

Section: Discussionmentioning

confidence: 99%

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

Gargan¹,

Kelly²,

Shephard³

et al. 2016

Aquacult. Environ. Interact.

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The demographic and life history characteristics of sea trout Salmo trutta L. populations can be changed by a range of pressures in both freshwater and marine environments. Few long-term monitoring programmes are in place to assess temporal change in population dynamics. We analysed a 20 yr time series (1985−2004) using 15 sea trout population response variables in the Erriff River, western Ireland. Over this period, when time was considered as a categorical variable comprising 4 sequential periods of 5 yr, important life history changes were observed. The most dramatic of these changes corresponded with the period immediately after the commencement of salmon farming in the local estuary, with significant decreases in the number and length of sea 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. We found a significant positive relationship between the number of salmon lice Lepeophtheirus salmonis in the local salmon farm and the number of lice found on sea trout collected contemporaneously in local rivers. Results of this long-term monitoring programme demonstrate that significant changes in sea trout population structure with respect to quantitative life history traits can occur over a relatively short time period and suggest that the introduction of salmon farming into the local estuary most likely contributed to the observed changes in sea trout population dynamics.

show abstract

Characteristics of the Sea Trout Salmo trutta (L.) Stock Collapse in the River Ewe (Wester Ross, Scotland), in 1988‐2001

Cited by 13 publications

References 20 publications

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Effects of salmon lice Lepeophtheirus salmonis on wild sea trout Salmo trutta—a literature review

Aquaculture and environmental drivers of salmon lice infestation and body condition in sea trout

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

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