Research
Activities
| Division of Population
Biology, Institute of Zoology, University of Berne, Switzerland. |
| Contact person (name and e-mail): |
| Persons working on brown trout
population genetics: |
| Maya Mezzera, Bruno
Schneider (University of Zurich), Carlo R. Largiadèr, Adolf Scholl |
| General research topics of the
laboratory: |
| Conservation and
Management, Phylogeography, Reproduction biology , Population structure. |
| General description of research on
brown trout population genetics: |
| A major research topic of
our laboratory is the conservation and management of brown trout. In particular, we study
the genetic effects on local populations through introductions of hatchery trout (or
through exchanges of wild trout across major watersheds). Another important topic is the
phylogeography of brown trout since we depend on correct identification of the
autochthonous form for the study of interactions between introduced and native trout.
Because of the long tradition of intensive stocking of brown trout populations and because
natural exchanges of fish communities across major watersheds (e.g. Black Sea - Atlantic
Sea) could have occurred in Switzerland after the last glaciations, we started to carry
out phylogeographic studies on less „disturbed" freshwater species (e.g. Cottus
gobio) in order to infer natural colonisation patterns of the Alpine region by
different brown trout forms. Furthermore, some of our studies address the relationship
between migratory Lake trout and sedentary trout and the mating system of brown trout. Protein electrophoresis, microsatellites, mtDNA PCR-RFLP are the
major molecular tools that are employed in these studies. |
| List of projects (brown trout) for
the past 3 years: |
 Study #1 |
| Researcher: |
Maya Mezzera (M.Sc.
student), Adolf Scholl (supervisor), Carlo R. Largiadèr (co-supervisor) |
| Source of project
funding: |
Fisheries administrations of diverse
Swiss cantons & in house. |
| Topic: |
Stocking effects. |
| Objective: |
To compare introgression rates between
different age classes in a stocked population and to assess genetic incompatibilities
between introduced and native trout forms. |
| Design: |
Samples from age classes 0+, 1+.,2+ and
a reference sample from the local hatchery strain used for stocking were analysed at
„diagnostic" loci. Reciprocal crosses between native and hatchery trout were
reared under hatchery conditions. |
| Methodology: |
Protein electrophoresis. |
| Trout population: |
Resident population (& Hatchery
stock). |
| Origin of samples: |
Switzerland, Mediterranean Sea Basin
(& Atlantic Basin). |
| Status: |
Started in Nov. 1994 and was completed
in June 1996. |
| Study #2 |
| Researcher: |
Maya Mezzera (PhD student),
Adolf Scholl (supervisor), Carlo R. Largiadèr (co-supervisor) |
| Source of project
funding: |
Federal Office of Environment, Forests
and Landscape (FOEFL) of Switzerland. |
| Topic: |
Stocking effects, stocking efficiency,
selective angling. |
| Objective: |
To study selective fishing pressure by
anglers on native and introduced trout and their hybrids. |
| Design: |
The genetic composition of trout
samples caught by anglers is compared with samples obtained by electrofishing. Several
factors such as time of capture, angling technique, age, body size are included into the
analysis. |
| Methodology: |
Single locus microsatellite DNA. |
| Trout population: |
Resident population. |
| Origin of samples: |
Switzerland, Mediterranean Sea Basin. |
| Status: |
Started in 1997 as part of M.M.’s
PhD thesis, will be completed in 1999. |
| Study #3 |
| Researcher: |
Maya Mezzera (PhD student),
Adolf Scholl (supervisor), Carlo R. Largiadèr (co-supervisor) |
| Source of project
funding: |
Federal Office of Environment, Forests
and Landscape (FOEFL) of Switzerland. |
| Topic: |
Stocking effects , stocking efficiency. |
| Objective: |
To assess „survival rates" of
different genotype classes (native and introduced trout and their hybrids) by studying the
temporal variation of admixture and introgression rates within cohorts of a stocked
population. |
| Design: |
The population is regularly re-sampled
over a period of three years and the genetic composition of all subsamples of the same
cohort is compared. |
| Methodology: |
Single locus microsatellite DNA. |
| Trout population: |
Resident population (& Hatchery
stock). |
| Origin of samples: |
Switzerland, Mediterranean Sea Basin
(& Atlantic Basin). |
| Status: |
Started in 1997 as part of MM PhD
thesis, will be completed in 2000. |
| Study #4 |
| Researcher: |
Carlo R Largiadèr |
| Collaborators: |
René Guyomard and Arnaud Estoup,
Laboratoire de Génétique des Poissons, INRA, F- 78352 Jouy-en-Josas (France); Alexis
Champignuelle; Station d’Hydrobiologie Lacustre, INRA, F-74203 Thonon-les-Bains
(France) |
| Source of project
funding: |
Swiss National Science Foundation &
in house. |
| Topic: |
Reproduction biology. |
| Objective: |
To study polyandry, intraspecific redd
superimposition and assortative mating between native and introduced trout. |
| Design: |
Polyandrous redds were detected and
analysed based on the genotype composition of egg samples and on the corresponding
maternal genotype Redd superimposition and assortative mating between native and
introduced trout were assessed by analysing the distribution of egg-genotypes within and
among a large number of redds, respectively. |
| Methodology: |
Single locus microsatellite DNA,
mtDNA-RFLP. |
| Trout population: |
Resident population. |
| Origin of samples: |
France, Mediterranean Sea Basin. |
| Status: |
Started in 1995 during CRL’s
postdoctoral stay at the Laboratoire de Génétique des Poissons (INRA) in Jouy-en-Josas
(France). |
| Study #5 |
| Researcher: |
Carlo R Largiadèr |
| Collaborators: |
René Guyomard and Arnaud Estoup,
Laboratoire de Génétique des Poissons, INRA, F- 78352 Jouy-en-Josas (France); Alexis
Champignuelle; Station d’Hydrobiologie Lacustre, INRA, F-74203 Thonon-les-Bains
(France) |
| Source of project
funding: |
Swiss National Science Foundation &
in house. |
| Topic: |
Stocking effects. |
| Objective: |
To study cytonuclear introgression
patterns on a microgeographic scale in a stocked population. |
| Design: |
A small creek (25 km) was divided into
14 sectors of about equal length and trout samples from each sector and three reference
samples from the main river were genetically analysed and compared. |
| Methodology: |
Single locus microsatellite DNA,
mtDNA-RFLP. |
| Trout population: |
Resident population. |
| Origin of samples: |
France, Mediterranean Sea Basin. |
| Status: |
Started in 1995 during CRLs
postdoctoral stay at the Laboratoire de Génétique des Poissons (INRA) in Jouy-en-Josas
(France) and will be completed in 1998. |
| Study #6 |
| Researcher: |
Bruno Schneider (PhD
student), Carlo R Largiadèr |
| Collaborators: |
Vinzenz Ziswiler (supervisor) |
| Source of project
funding: |
University of Zurich. |
| Topic: |
Stocking effects, gene diversity, gene
flow, temporal variation. |
| Objective: |
To study the genetic relationship
between migratory and stream resident populations of Lake Zurich. |
| Design: |
Within this system two trout morphs can
be distinguished by their growth pattern The genetic composition of samples of
„slow" (presumably resident trout) and „fast" growing individuals
(presumably migratory trout) are compared within and among localities. |
| Methodology: |
Single locus microsatellite DNA. |
| Trout population: |
Resident population, potamodromous. |
| Origin of samples: |
Switzerland, Atlantic North Sea Basin. |
| Status: |
Started in 1997 and will be completed
in 1998. |
Publications (brown trout genetics)
 Journal
papers:
- Estoup, A, Largiadèr, C R , Perrot, E & Chourrout, D (1996) Rapid one-tube DNA
extraction for reliable PCR detection of fish polymorphic markers and transgenes Mol
Mar Biol Biotech, 5, 295-298.
- Largiadèr, C R& Scholl, A (1994) Untersuchungen zur genetischen Variabilität bei
einheimischen Forellen Mitteilungen zur Fischerei, 52, 35-45.
- Largiadèr, C R & Scholl, A (1996) Effects of stocking on the genetic diversity of
brown trout populations of the Adriatic and Danubian drainages in Switzerland J Fish
Biol, 47 (Supplement A), 209-225.
- Largiadèr, C R & Scholl, A (1996) Cellulose acetate electrophoresis for screening
transferrin polymorphism in brown trout (Salmo trutta) populations In Advances
in Life Sciences: Endangered Freshwater Fish in Europe (Kirchhofer, A & Hefti, D,
eds), pp 199-202. Basel/Switzerland: Birkhäuser Verlag.
- Largiadèr, C R & Scholl, A (1996) Genetic introgression between native and
introduced brown trout (Salmo trutta L) populations in the Rhône River basin Mol
Ecol, 5, 417-426.
- Largiadèr, C R, Guyomard, R & Roche, P (1996) Evidence for natural reproduction of
Atlantic salmon (Salmo salar L) in a French tributary of the Rhine based on genetic
analysis of eggs collected from redds Bulletin Français de la Pêche et de la
Pisciculture 343, 183-188.
- Largiadèr, C R, Scholl, A & Guyomard, R (1996) The role of natural and artificial
propagation on the genetic diversity of brown trout (Salmo trutta L) of the upper
Rhône drainage In Advances in Life Sciences: Endangered Freshwater Fish in Europe (Kirchhofer,
A & Hefti, D, eds), pp 181-197. Basel/Switzerland:
Birkhäuser Verlag.
- Mezzera, M, Largiadèr, C R & Scholl, A (1997) Discrimination of native and
introduced brown trout in the River Doubs (Rôhne drainage) by number and shape of parr
marks J Fish Biol, 50, 672-677.
Theses (eg, PhD and MSc theses):
- Mezzera, M (1996) Untersuchungen über die Hybridisierung zwischenautochthonen Forellen
und eingestzten Zuchtforellen im Doubs Diploma Thesis, University of Berne.
- Largiadèr, C R (1995) Genetische Differenzierung der Forellen (Salmo trutta L)
in der Schweiz und der Einfluss von Besatz auf die Lokalpopulationen PhD Thesis,
University of Berne.
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