Stocking impact and migration pattern in an anadromous brown trout (Salmo trutta) complex: where have all the stocked spawning sea trout gone?

We monitored temporal changes in body size for three cohorts of a partial migratory, lake-migrating brown trout population. We tested if body mass differed between nonmigratory males, migrants, and other members of the cohort (females and immature males). We hypothesized that large-sized individuals would mature as nonmigratory males or migrate at younger ages than small-sized individuals. As previous studies have shown that female fecundity is influenced by body size and that more trout from the downstream section (D) of the stream migrated than from the upstream section (U), we hypothesized that there would be a greater proportion of mature males in D than U. We found that body size of males that reproduced was similar to migrants that migrated the subsequent spring and larger than other cohort members. Reproducing males had a larger body size than equal-aged males that delayed reproduction. Similarly, individuals that migrated had a larger body size than equal-aged individuals that migrated subsequently. The proportion of mature males was greater in D than in U. The fact that body size differentiation occurred late in ontogeny and that age of maturation and migration varied within cohorts suggests that the decision to mature or migrate might be conditionally dependent.

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Saltwater spawning grounds of sea-run brown trout (Salmo trutta) in tidal waters of a major Norwegian river

Environmental Biology of Fishes ◽

10.1007/s10641-021-01147-y ◽

2021 ◽

Author(s):

Sven-Erik Gabrielsen ◽

Robert J. Lennox ◽

Tore Wiers ◽

Bjørn T. Barlaup

Keyword(s):

Brown Trout ◽

Salmo Trutta ◽

Pink Salmon ◽

River Mouth ◽

Competitive Balance ◽

Spawning Grounds ◽

Sea Trout ◽

Spawning Areas ◽

Brown Trout Salmo Trutta ◽

Spawning Behaviour

AbstractSea-run brown trout (Salmo trutta) have a highly phenotypically plastic life history that allows them to be effective colonizers and competitors in freshwater. This paper documents a previously unknown spawning behaviour in a brackish, tidally influenced estuary 14 km from the mouth of the Vosso River, a major Atlantic salmon- and sea-run brown trout–producing river in western Norway. Putative spawning gravel was observed, and sea-run brown trout deposited eggs that hatched in April. Survival of recruits was high (> 95%) in the tidal spawning gravel. These areas are strongly tidally influenced with a peak of 23.17 psu recorded at the lowest spawning ground. The observation of spawning so far from the river mouth may be unique in such a system with a long estuary but provides important insight into the biology of sea trout. Invasion of pink salmon, also known to spawn in estuaries, may negatively affect the competitive balance of sea trout with other salmonids in rivers where sea trout populations rely on recruitment from these relatively extreme spawning areas. Restoration of estuaries that have been modified by dredging or channelization may be important to ensure quality and heterogenous habitat for sea trout spawning given that haline spawning grounds could contribute to population resilience.

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A comparison of trends in population size and life history features of Atlantic salmon (Salmo salar) and anadromous and non-anadromous Brown trout (Salmo trutta) in a single catchment over 116 years

Hydrobiologia ◽

10.1007/s10750-021-04751-2 ◽

2021 ◽

Author(s):

Colin E. Adams ◽

Hannele M. Honkanen ◽

Ellen Bryson ◽

Isabel E. Moore ◽

Malcolm MacCormick ◽

...

Keyword(s):

Time Series ◽

Atlantic Salmon ◽

Brown Trout ◽

Salmo Trutta ◽

Relative Proportion ◽

Population Trends ◽

Sea Trout ◽

Salmon Population ◽

Brown Trout Salmo Trutta ◽

Long Time

AbstractWe use a long time series of catch abundance from a recreational fishery over 116 years to look for population trends in Atlantic salmon, and anadromous (sea trout) and non-anadromous (brown) trout for a single catchment, Loch Lomond, west central Scotland. Year strongly predicted variation in catches but catch effort did not meaningfully increase explained variation. Salmon showed periods of increasing and decreasing trends, for sea trout and brown trout there was an overall declining trend. Since 1952, Lomond salmon population trends differed from both wider Scotland and southern Europe, indicating that the Lomond population is partially buffered from drivers of change in salmon populations more widely. In contrast Lomond sea trout showed a similar declining trend to that of populations from the wider west of Scotland over this period. The Lomond populations showed some evidence of shorter-term cycling patterns; the drivers for which are unknown. Body size in salmon and sea trout declined but increased in brown trout; salmon returned to freshwater later, and the relative proportion of all caught trout that were anadromous increased across the time series. This study shows a long and protracted period of fundamental change to populations of these two species over 116 years.

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Encapsulation and migration of PIT tags implanted in brown trout (Salmo trutta L.)

Aquaculture ◽

10.1016/j.aquaculture.2009.10.004 ◽

2010 ◽

Vol 298 (3-4) ◽

pp. 350-353 ◽

Cited By ~ 14

Author(s):

Cristina Gheorghiu ◽

Jillian Hanna ◽

John W. Smith ◽

D. Scott Smith ◽

Michael P. Wilkie

Keyword(s):

Brown Trout ◽

Salmo Trutta ◽

Pit Tags ◽

Brown Trout Salmo Trutta ◽

And Migration

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A continuum of life history tactics in a brown trout (Salmo trutta) population

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-057 ◽

2005 ◽

Vol 62 (7) ◽

pp. 1600-1610 ◽

Cited By ~ 62

Author(s):

Julien Cucherousset ◽

Dominique Ombredane ◽

Katia Charles ◽

Frédéric Marchand ◽

Jean-Luc Baglinière

Keyword(s):

Life History ◽

Brown Trout ◽

Salmo Trutta ◽

Environmental Variability ◽

Continuous Distribution ◽

Juvenile Growth ◽

Migratory Behaviour ◽

Brown Trout Salmo Trutta ◽

And Migration ◽

Pit Tagging

Life history tactics of the brown trout (Salmo trutta) population of the Oir River (Normandy, France) were studied using passive integrated transponder (PIT) tagging data of five consecutive cohorts (5900 individuals) monitored between 1995 and 2002. Results demonstrate that (i) life history traits vary among cohorts, chiefly caused by environmental variability, (ii) juvenile growth, particularly second-year growth, plays an important role in the determination of the growing environment and trout exhibit variable migratory behaviour (from remaining in the natal brook to migrating in the sea) related to their juvenile growth rate, and (iii) the description of life history tactics (including juvenile growth, fine-scale migratory behaviour, and reproduction) can be clarified. Tactics are expressed along a continuum in time (age to reproduce) and space (distance of migration). Flexible life history tactics varying with juvenile growth is consistent with previous studies, but the use of empiric data on growth and migration from PIT tagging allows refining the description of life history tactics, taking into account their continuous distribution in time and space.

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A comparison of the survival and migration of wild and F1-hatchery-reared brown trout ( Salmo trutta ) smolts traversing an artificial lake

Fisheries Research ◽

10.1016/j.fishres.2017.08.011 ◽

2017 ◽

Vol 196 ◽

pp. 47-55 ◽

Cited By ~ 7

Author(s):

Michael Schwinn ◽

Henrik Baktoft ◽

Kim Aarestrup ◽

Anders Koed

Keyword(s):

Brown Trout ◽

Salmo Trutta ◽

Artificial Lake ◽

Brown Trout Salmo Trutta ◽

And Migration

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Long-term monitoring of a brown trout (Salmo trutta) population reveals kin-associated migration patterns and contributions by resident trout to the anadromous run

BMC Ecology and Evolution ◽

10.1186/s12862-021-01876-9 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Eloïse Duval ◽

Øystein Skaala ◽

María Quintela ◽

Geir Dahle ◽

Aurélien Delaval ◽

...

Keyword(s):

Population Size ◽

Effective Population Size ◽

Brown Trout ◽

Salmo Trutta ◽

Anthropogenic Pressure ◽

Parentage Assignment ◽

Effective Population ◽

Migration Timing ◽

Brown Trout Salmo Trutta ◽

And Migration

Abstract Background In species showing partial migration, as is the case for many salmonid fishes, it is important to assess how anthropogenic pressure experienced by migrating individuals affects the total population. We focused on brown trout (Salmo trutta) from the Guddal River in the Norwegian Hardanger Fjord system, which encompasses both resident and anadromous individuals. Aquaculture has led to increased anthropogenic pressure on brown trout during the marine phase in this region. Fish traps in the Guddal River allow for sampling all ascending anadromous spawners and descending smolts. We analyzed microsatellite DNA markers from all individuals ascending in 2006–2016, along with all emigrating smolts in 2017. We investigated (1) if there was evidence for declines in census numbers and effective population size during that period, (2) if there was association between kinship and migration timing in smolts and anadromous adults, and (3) to what extent resident trout were parents of outmigrating smolts. Results Census counts of anadromous spawners showed no evidence for a decline from 2006 to 2016, but were lower than in 2000–2005. Estimates of effective population size also showed no trends of declines during the study period. Sibship reconstruction of the 2017 smolt run showed significant association between kinship and migration timing, and a similar association was indicated in anadromous spawners. Parentage assignment of 2017 smolts with ascending anadromous trout as candidate parents, and assuming that unknown parents represented resident trout, showed that 70% of smolts had at least one resident parent and 24% had two resident parents. Conclusions The results bear evidence of a population that after an initial decline has stabilized at a lower number of anadromous spawners. The significant association between kinship and migration timing in smolts suggests that specific episodes of elevated mortality in the sea could disproportionally affect some families and reduce overall effective population size. Finally, the results based on parentage assignment demonstrate a strong buffering effect of resident trout in case of elevated marine mortality affecting anadromous trout, but also highlight that increased mortality of anadromous trout, most of which are females, may lower overall production in the system.

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