Metabolic rates and feeding behaviour of sprat, Sprattus sprattus L. Dissertation Zur Erlangung der Würde des Doktors der Naturwissenschaften des Fachbereichs Biologie, der Fakultät für Mathematik, Informatik und Naturwissenschaften, der Universität Hamburg vorgelegt von LAURA MESKENDAHL aus Radevormwald, Deutschland Hamburg 2013 Genehmigtvom Fachbereich Biologie der FakultdtfUr Mathematik, lnformatik und Naturwissenschaften an derUniversitdt Hamburg aufAntrag von Professor Dr. A. TEMMING WeitererGutachter der Dissertation : ProfessorDr. C. MOLLMANN Tagder Disputation: 25. Januar 2013 Hamburg,den 15. Januar 2013 $G ' ProfessorDr. J. Fromm Vorsitzenderdes Promotionsaussch usses Biologie TABLE OF CONTENTS Summary .................................................................................................................................... 1 Zusammenfassung ..................................................................................................................... 5 1 General introduction ......................................................................................................... 9 1.1 Sprat and its ecological role ....................................................................................... 9 1.2 Feeding ecology of sprat and herring....................................................................... 10 1.2.1 Functional response ............................................................................................. 11 1.2.2 Foraging-related swimming activities .................................................................. 11 1.3 Fish bioenergetics ..................................................................................................... 13 1.3.1 Metabolic rates .................................................................................................... 14 1.3.2 Specific dynamic action (SDA) .............................................................................. 16 1.3.3 Egestion and excretion ......................................................................................... 17 1.3.4 Temperature and body mass effects on metabolic rates .................................... 18 1.4 Specific goals of the thesis ....................................................................................... 19 1.5 References ................................................................................................................ 20 2 Manuscript 1: Effects of temperature and body mass on metabolic rates of sprat, Sprattus sprattus L. .................................................................................................................. 29 2.1 Introduction .................................................................................................................... 30 2.1 Material and Methods .............................................................................................. 31 2.1.1 Fish capture and maintenance ............................................................................. 31 2.1.2 Experimental Set-up ............................................................................................. 32 2.1.3 Experimental Design ............................................................................................. 32 2.1.4 Data analysis ......................................................................................................... 33 2.1.5 Determination of metabolic level ........................................................................ 33 2.1.6 Effect of body mass and temperature ................................................................. 34 2.1.7 Comparison of data .............................................................................................. 35 2.2 Results ...................................................................................................................... 35 2.2.1 Metabolic level ..................................................................................................... 35 2.2.2 Body mass effect .................................................................................................. 37 2.2.3 Temperature effects ............................................................................................. 38 2.3 Discussion ................................................................................................................. 38 2.3.1 Determination of metabolic level ........................................................................ 38 2.3.2 Temperature effects ............................................................................................. 41 2.3.3 Body mass effect .................................................................................................. 42 2.4 Acknowledgments .................................................................................................... 44 2.5 References ................................................................................................................ 44 i 3 Manuscript 2: Energy costs of spontaneous swimming in sprat, Sprattus sprattus L., at different water temperatures ................................................................................................. 49 3.1 Introduction .............................................................................................................. 50 3.2 Materials and Methods ............................................................................................ 52 3.2.1 Fish capture and maintenance ............................................................................. 52 3.2.2 Respirometry and experimental design ............................................................... 53 3.2.3 Image acquisition ................................................................................................. 54 3.2.4 Automated fish tracking ....................................................................................... 56 3.2.5 Determination of swimming speeds and direction changes................................ 57 3.2.6 Calculation of oxygen consumption rates ............................................................ 58 3.2.7 Data selection ....................................................................................................... 59 3.2.8 Model selection .................................................................................................... 60 3.3 Results ...................................................................................................................... 61 3.3.1 Swimming characteristics ..................................................................................... 61 3.3.2 Spontaneous swimming costs .............................................................................. 62 3.4 Discussion ................................................................................................................. 66 3.4.1 Fish behaviour and tank effects ........................................................................... 66 3.4.2 Classification of spontaneous active metabolic rates .......................................... 67 3.4.3 Metabolic costs for swimming and direction changes......................................... 68 3.4.4 Temperature effects ............................................................................................. 69 3.5 Acknowledgements .................................................................................................. 70 3.6 References ................................................................................................................ 70 4 Manuscript 3: Functional responses of juvenile herring and sprat in relation to different prey types ................................................................................................................. 75 4.1 Introduction .............................................................................................................. 76 4.2 Materials and Methods ............................................................................................ 78 4.2.1 Capture and maintenance of experimental fish .................................................. 78 4.2.2 Prey types ............................................................................................................. 78 4.2.3 Experimental setup .............................................................................................. 79 4.2.4 Data analyses ........................................................................................................ 80 4.3 Results ...................................................................................................................... 84 4.3.1 Experimental procedure ....................................................................................... 84 4.3.2 Feeding behavior .................................................................................................. 84 4.3.3 Feeding time for A. tonsa and Artemia nauplii .................................................... 86 4.3.4 Functional responses ............................................................................................ 86 4.4 Discussion ................................................................................................................. 89 4.4.1 Experimental procedure ....................................................................................... 89 4.4.2 Feeding behavior .................................................................................................. 89 4.4.3 Functional response