Master Thesis Population characteristics of a Baltic sea trout spawning cohort from a small North German river: Age composition, spawning experience, growth and temporal genetic diversity Hauke Kramer Westring 312, 24116 Kiel Martrikelnummer: 1010221 September 2018 Erstgutachter Prof. Dr. Günther B. Hartl, Zoologisches Institut der Christian-Albrechts-Universität zu Kiel, Am Botanischen Garten 1-9, 24118 Kiel Zweitgutachter Prof. Dr. Oscar Puebla, Geomar Helmholtz-Zentrum für Ozeanforschung Kiel, Düsternbrooker Weg 20, 24105 Kiel 2 Table of content Table of content .................................................................................................................................3 1 Abstract ......................................................................................................................................6 2 Zusammenfassung ......................................................................................................................8 3 Introduction .............................................................................................................................. 10 3.1 Salmo trutta: species facts, taxonomy, anadromy and broadscale distribution .................. 11 3.2 Fine-scale distribution, lifecycle and reproduction ............................................................. 12 3.2.1 Spawning run ............................................................................................................. 12 3.2.2 Nesting, mating, fertilization and kelt return to the sea.............................................. 12 3.2.3 Egg development, hatching, alevin, fry and parr stage................................................ 13 3.2.4 Smolt: Age and size .................................................................................................... 13 3.2.5 Maiden individuals, repeated spawners and “Überspringer” ...................................... 14 3.3 Scale Reading .................................................................................................................... 15 3.4 Temporal genetic diversity................................................................................................. 16 3.5 Management options ........................................................................................................ 16 3.6 This study .......................................................................................................................... 17 3.7 Scientific research questions.............................................................................................. 18 3.7.1 Age of an individual fish ............................................................................................. 18 3.7.2 Returning fish for spawning ....................................................................................... 18 3.7.3 Growth of the individual fish ...................................................................................... 18 3.7.4 Genetic information ................................................................................................... 18 4 Material and Methods............................................................................................................... 19 4.1 River of interest ................................................................................................................. 19 4.1.1 Farver Au in Schleswig-Holstein, Germany ................................................................. 19 4.1.2 Abiotic conditions ...................................................................................................... 19 4.2 Field Work ......................................................................................................................... 20 4.2.1 Electrofishing ............................................................................................................. 20 4.2.2 Size and weight measurements .................................................................................. 21 4.2.3 Genetic fin clip tissue sample ..................................................................................... 22 4.2.4 Stable isotopes sample .............................................................................................. 22 4.2.5 Scale sampling ........................................................................................................... 22 4.2.6 T-Bar Tags .................................................................................................................. 22 4.3 Scale Reading .................................................................................................................... 23 4.3.1 Sample Selection........................................................................................................ 23 4.3.2 Scale preparation ....................................................................................................... 23 3 4.3.3 Interpretation of sea trout scales ............................................................................... 24 4.3.4 Notation .................................................................................................................... 26 4.3.5 Back-calculation ......................................................................................................... 27 4.3.6 Difficulties in scale reading ......................................................................................... 27 4.3.7 Validation .................................................................................................................. 28 4.4 Genetic analysis ................................................................................................................. 28 4.4.1 Sample selection ........................................................................................................ 28 4.4.2 Gene extraction, PCR and Sequencing ........................................................................ 28 4.4.3 Genotyping ................................................................................................................ 29 4.4.3 Population analysis .................................................................................................... 29 4.5 Statistical methods for data analysis .................................................................................. 30 4.5.1 D’Agostino & Pearson normality test ......................................................................... 30 4.5.2 One-way ANOVA ........................................................................................................ 30 4.5.3 Mann-Whitney U Test ................................................................................................ 30 4.5.4 T-Test ........................................................................................................................ 30 4.5.5 Kruskal-Wallis test ..................................................................................................... 30 4.5.6 ROUT test .................................................................................................................. 30 5 Results ...................................................................................................................................... 31 5.1 Electro fishing .................................................................................................................... 31 5.1.1 Total capture ............................................................................................................. 31 5.1.2 Length frequency ....................................................................................................... 31 5.2 Scale reading ..................................................................................................................... 33 5.2.1 Sample selection ........................................................................................................ 33 5.2.2 Smolt age ................................................................................................................... 34 5.2.3 Sea age ...................................................................................................................... 34 5.2.4 Spawning Marks......................................................................................................... 36 5.2.5 Age and length of first-time spawners ........................................................................ 37 5.2.6 Growth ...................................................................................................................... 38 5.2.7 Recaptures ................................................................................................................. 45 5.2.8 Silvery fish ................................................................................................................. 46 5.3 Temporal genetic diversity................................................................................................. 47 5.3.1 STRUCTURE results – Sample ordered by the year of birth ......................................... 47 5.3.2 Effective population size – Sample ordered by the year of birth ................................. 48 5.3.3 STRUCTURE results – Sample ordered by spawning cohorts ....................................... 48 5.3.4 Effective population size – Sample ordered by spawning cohorts ............................... 49 5.3.5 Calculated Fst-values – sample ordered by spawning cohort ...................................... 49 4 6 Discussion ................................................................................................................................