Great cormorant (<i>Phalacrocorax carbo sinensis</i>) predation on adult anadromous brown trout (<i>Salmo trutta</i>)

Källo, Kristi; Birnie‐Gauvin, Kim; Jepsen, Niels; Aarestrup, Kim

doi:10.1111/eff.12701

Cited by 11 publications

(3 citation statements)

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“…While it is unclear which factors affect the documented patterns of straying, several hypotheses can be formulated, with the causes possibly differing among rivers. For example, in river Villestrup, where the spawning population is large (Birnie‐Gauvin et al., 2018; Källo, Birnie‐Gauvin, Jepsen, et al., 2023) and competition for mates and adequate spawning habitat is likely high, it may be more beneficial for smaller fish originating from Villestrup to stray to non‐natal rivers, where they may have a better chance of spawning successfully. In contrast, for individuals originating from river Valsgaard, the decreased likelihood for larger individuals to return to their natal river may suggest that the size of the river limits the inclination for larger sea trout to return.…”

Section: Discussionmentioning

confidence: 99%

“…While similar patterns of straying towards larger rivers have also been reported in other systems (Degerman et al, 2012;Unwin & Quinn, 1993), straying seems to occur predominantly towards rivers close to the natal river (Berg & Berg, 1987;Jonsson et al, 2003), disparate from the results of this study. However, as all the rivers in Mariager fjord are within the distance over which straying has been documented to commonly occur (60-80 km; Bekkevold et al, 2020;Jonsson et al, 2003) Källo, Birnie-Gauvin, Jepsen, et al, 2023) and competition for mates and adequate spawning habitat is likely high, it may be more beneficial for smaller fish originating from Villestrup to stray to non-natal rivers, where they may have a better chance of spawning successfully. In contrast, for individuals originating from river Valsgaard, the decreased likelihood for larger individuals to return to their natal river may suggest that the size of the river limits the inclination for larger sea trout to return.…”

Section: Assigning Spawning Adult Sea Trout To Their Natal Riversmentioning

confidence: 99%

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Otolith microchemistry combined with genetics reveal patterns of straying and population connectivity in anadromous brown trout (Salmo trutta)

Källo,

Birnie‐Gauvin,

Baktoft

et al. 2023

Ecology of Freshwater Fish

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Salmonids are well known for their natal homing behaviour, meaning they return to breed in the same area where they originated. However, not all individuals return to their natal breeding grounds—a behavioural trait known as straying. The prevalence of straying is difficult to explore and therefore quantitative estimates for straying are seldom reported. In this study, otolith microchemistry and genetics were combined to investigate patterns of straying over ecological and evolutionary time, respectively, between neighbouring rivers flowing into Mariager fjord, Denmark. Otolith microchemistry was used to determine the river of origin for sea trout (Salmo trutta) upon their return to freshwater and 288 SNP markers were used to determine genetic structure among the rivers in the fjord. In this system, where the distance between rivers is short, otolith microchemistry achieved 80% accuracy in assigning juvenile brown trout to their natal river, thus allowing us to determine that approximately 43% of the adult sea trout had returned to non‐natal rivers to spawn, with a similar proportion of strayers and natal homers in all of the rivers. Genetic analysis further supported that there was substantial gene flow among individuals originating from different rivers, indicating that sea trout in Mariager fjord make up one population. The findings obtained from otolith microchemistry and genetics complement each other and provide further evidence that sea trout in this system migrate to non‐natal rivers and spawn there, which consequently affects the genetic structure of the population.

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Section: Discussionmentioning

confidence: 99%

Section: Assigning Spawning Adult Sea Trout To Their Natal Riversmentioning

confidence: 99%

Otolith microchemistry combined with genetics reveal patterns of straying and population connectivity in anadromous brown trout (Salmo trutta)

Källo,

Birnie‐Gauvin,

Baktoft

et al. 2023

Ecology of Freshwater Fish

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“…The situation is different elsewhere in Scandinavia and continental Europe, where cormorants have denser populations with larger breeding colonies. In Danish rivers, vulnerable populations of sea-run brown trout Salmo trutta and grayling Thymallus thymallus are exposed to a high predation pressure from the sinensis subspecies (Jepsen et al 2018, Källo et al 2023.…”

Section: Introductionmentioning

confidence: 99%

Combining biometrics and genetics to distinguish two subspecies of the Great Cormorant Phalacrocorax carbo carbo and P. c. sinensis at an inland lake in southeast Norway

Grøndahl,

Johnsen

2024

Ornis Norv.

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Cover photo: Adult Great Cormorant of the subspecies Phalacrocorax carbo sinensis in breeding plumage. Photo: Frode Falkenberg. Great Cormorants Phalacrocorax carbo are now regularly seen in inland watercourses in southeast Norway, after the P. c. sinensis subspecies first established breeding colonies in coastal south Norway in 1996. Although both the sinensis and carbo subspecies occur, the ratio between them is unknown. We tested the accuracy of subspecific identification based on biometrics and genetic analyses in 75 Great Cormorants that drowned in fishing nets in a lake in southeast Norway during the period 2009-2020. Primarily based on the gular pouch angle (GPA), we classified 40 individuals to the carbo subspecies and 35 individuals to the sinensis subspecies. Eight of the carbo individuals and 14 of the sinensis individuals were within the overlapping range of GPA and were therefore classified to subspecies by supplementary measurements (bill depth minimum and bill length). Genetic analyses were based on seven polymorphic microsatellite markers. Assuming one panmictic population, we performed Structure analyses to separate the genotypes into two assumed genetic clusters. The two clusters, carbo and sinensis, could only be separated when adding information about morphological subspecies identities for the carbo, sinensis and carbo/sinensis groups. The sinensis and the carbo/sinensis groups belonged almost entirely to one genetic cluster, whereas the carbo group consisted of individuals with varying proportions of mixed ancestry. Furthermore, we found significant genetic differentiation between the carbo and sinensis groups, and between the carbo and the carbo/sinensis groups, but no significant differentiation between the sinensis and the carbo/sinensis groups. Our results suggest that gene flow is more common from sinensis into carbo than vice-versa, and that the use of GPA < 73° has limitations for the identification of Great Cormorant subspecies in areas where both forms occur. We conclude that the numbers of carbo vs. sinensis individuals in our sample were 32 and 43, respectively.

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Stream Salmonids on the Cormorant (Phalacrocorax carbo) Menu

Jepsen,

Rasmussen

2024

Fish &Amp; Fisheries Series

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Great cormorant (Phalacrocorax carbo sinensis) predation on adult anadromous brown trout (Salmo trutta)

Abstract: However, migration between habitats also encompasses a level of risk, as increased mortality is often associated with such movements

Cited by 11 publications

References 78 publications

Otolith microchemistry combined with genetics reveal patterns of straying and population connectivity in anadromous brown trout (Salmo trutta)

Otolith microchemistry combined with genetics reveal patterns of straying and population connectivity in anadromous brown trout (Salmo trutta)

Combining biometrics and genetics to distinguish two subspecies of the Great Cormorant Phalacrocorax carbo carbo and P. c. sinensis at an inland lake in southeast Norway

Stream Salmonids on the Cormorant (Phalacrocorax carbo) Menu

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