Fish Assemblages in European Lakes - Comparison of Sampling Methods and Analysis of Size Structure
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Fish assemblages in European lakes - Comparison of sampling methods and analysis of size structure DISSERTATION zur Erlangung des akademischen Grades Doctor rerum agriculturarum (Dr. rer. agr.) Eingereicht an der Landwirtschaftlich-Gärtnerischen Fakultät der Humboldt-Universität zu Berlin von Dipl. Biol. MATTHIAS EMMRICH Präsident/Präsidentin der Humboldt-Universität zu Berlin: Prof. Dr. Jan-Hendrik Olbertz Dekan/Dekanin der Landwirtschaftlich-Gärtnerischen Fakultät: Prof. Dr. Dr. h. c. Frank Ellmer Gutachter/Gutachterinnen: 1. Prof. Dr. Robert Arlinghaus 2. PD Dr. Thomas Mehner 3. Prof. Dr. Reiner Eckmann Tag der mündlichen Prüfung: 05.02.2013 Contents page List of papers V Author contributions VI Abstract (English) 1 Abstract (German) 2 1 Introduction 3 1.1 Sampling fish in lakes 4 1.1.1 Recreati onal angling 5 1.1.2 Scientific fish sampling 6 1.2 Size structure of lake fish assemblages 9 1.2.1 Anthropogenic influences of the size structure of lake fish assemblages 12 1.2.2 The role of spatial scale 13 2 Objectives 14 3 Methods and datasets 15 3.1 Sampling fish in lakes 16 3.1.1 Recreati onal angling 16 3.1.2 Scientific fish sampling 16 3.1.2.1 Multi -mesh gillnets 16 3.1 .2 .2 Trawling 18 3. 1. 2.3 Hydroacoustics 19 3.2 Size structure of lake fish assemblages 19 4 Main results 22 4.1 Sampling fish in lakes 22 4.2 Size structure of lake fish assemblages 24 5 Discussion 25 5.1 Sampling fish in lakes 25 5.2 Size structure of lake fish assemblages 29 6 Conclusions 31 Acknowledgement 32 References 34 Declaration of authorship 50 Appendix 51 Paper I 51 Paper II 67 Paper III 84 Paper IV 95 Paper V 115 List of papers This thesis is based on five papers, which are referred to in the text by their Roman numerals (I-V). Paper I Heermann, L., Emmrich, M., Heynen, M., Dorow, M., König, U., Borcherding, J., and Arlinghaus, R. (2013): Explaining recreational angling catch rates of Eurasian perch, Perca fluviatilis: the role of natural and fishing-related environmental factors. Fisheries Management and Ecology, in press. doi: 10.1111/fme.12000 Paper II Emmrich, M., Winfield, I.J., Guillard, J., Rustadbakken, A., Vergès, C., Volta, P., Jeppesen, E., Lauridsen, T.L., Brucet, S., Holmgren, K., Argillier C., and Mehner, T. (2012): Strong correspondence between gillnet catch per unit effort and hydroacoustically derived fish biomass in stratified lakes. Freshwater Biology, 2436-2448. doi: 10.1111/fwb.12022 Paper III Emmrich, M., Helland, I.P., Busch, S., Schiller, S., and Mehner, T. (2010): Hydroacoustic estimates of fish densities in comparison with stratified pelagic trawl sampling in two deep, coregonid-dominated lakes. Fisheries Research 105: 178-186. doi: 10.1016/j.fishres.2010.05.001 Paper IV Emmrich, M., Brucet, S., Ritterbusch, D., and Mehner, T. (2011): Size spectra of lake fish assemblages: responses along gradients of general environmental factors and intensity of lake-use. Freshwater Biology 56: 2316-2333. doi: 10.1111/j.1365-2427.2011.02658.x Paper V Emmrich, M., Pédron, S., Brucet, S., Winfield, I.J., Jeppesen, E., Volta, P., Argillier, C., Lauridsen, T.L., Holmgren, K., Hesthagen, T., and Mehner, T.: Differential pattern of size structure in European lake fish assemblages depending on elevation, latitude and species composition. Manuscript Papers I, II, III & IV are reprinted with permission of the publishers Maps were made with Natural Earth: Free vector and raster map data @ naturalearthdata.com V Author contributions Author of the thesis: Matthias Emmrich (ME) List of co-authors: Atle Rustadbakken (AR) Jost Borcherding (JB) Stéphanie Pédron (SP) Charlotte Vergès (CV) Kerstin Holmgren (KH) Susan Busch (SBu) Christine Argillier(CA) Lisa Heermann (LH) Susanne Schiller (SS) David Ritterbusch (DR) Malte Dorow (MD) Thomas Mehner (TM) Erik Jeppesen (EJ) Martina Heynen (MH) Torben L. Lauridsen (TLL) Ian J. Winfield (IJW) Pietro Volta (PV) Trygve Hesthagen (TH) Ingeborg P. Helland (IPH) Robert Arlinghaus (RA) Ulrike König (UK) Jean Guillard (JG) Sandra Brucet (SBr) Paper I This study consists of two parts: a single-lake study and a multi-lake study with different author contributions. LH & JB designed the single-lake study, LH & UK analysed the data (single- lake study), LH & MH wrote the paper (single-lake study), RA, ME & MD designed the multi-lake study, ME analysed the data (multi-lake study), ME & RA wrote the paper (multi-lake study). Paper II All authors contributed with data, ME & TM designed the study, ME analysed the data and wrote the paper. All co-authors revised the paper. Paper III All authors contributed with data, ME & TM designed the study, ME analysed the data and wrote the paper. All co-authors revised the paper. Paper IV DR created the database, ME contributed with data, ME & TM designed the study, ME & SBr analysed the data, ME wrote the paper. All co-authors revised the paper. Paper V All authors contributed with data, SP created the database, ME & TM designed the study, ME analysed the data and wrote the paper. All co- authors revised the paper. VI __________________________________________________________________________________ Abstract (English) Lake fish assemblages are increasingly exposed to environmental change in their habitats. The investigation of abiotic and biotic factors and their effects on the size structure of lake fish is essential for predicting the response of fish assemblages to environmental change. However, sampling of lake fish is challenging because sampling gears are selective. The quality and correspondence of fish catches from angling, gillnetting, trawling and hydroacoustics were analysed. Non-standardised catch data from recreational angling were of limited quality for a comparison of fish stocks. Vertical hydroacoustics is an efficient method to quantify fish biomass in stratified lakes. Sampling effort of multi-mesh gillnets can be reduced when fish abundance estimates are derived from contemporarily operating hydroacoustics. Trawling is useful to sample pelagic fish assemblages in deep lakes. The size structures of fish assemblages differed on a small and a large geographical scale along gradients of abiotic and biotic lake descriptors and differences in fish assemblage composition. At a small geographical scale assemblages in deep and less nutrient-rich lakes with high predator abundances were characterised by a higher proportion of large fish. Shallow nutrient-rich lakes with few predators were characterised by more medium-sized fish. At a large geographical scale thermal optima of fish generated two types of assemblages with different size structures. A high proportion of large salmonids was observed in coldwater lakes at high elevation sites in northern and southern Europe. Lowland lakes with cool- and warmwater fish were dominated by small-sized individuals. The results suggest that lowland lake fish assemblages are relatively robust against environmental change. Coldwater fish assemblages instead may suffer dramatic consequences from global warming as expected species shifts are likely to be accompanied by shifts in the size structure towards smaller individuals. Key words: lake fish, hydroacoustics, gillnet, trawl net, recreational angling, body size, size structure __________________________________________________________________________________ 1 __________________________________________________________________________________ Abstract (German) Fischgemeinschaften in Seen sind zunehmenden Umweltveränderungen unterworfen. Die Analyse des Einflusses abiotischer und biotischer Faktoren auf die Größenstruktur von Fischgemeinschaften ist entscheidend, um die Entwicklung von Seeökosystemen im Zuge von Umweltveränderungen vorhersagen zu können. Es ist jedoch schwierig Fische in Seen zu beproben, da Fanggeräte selektiv sind. Die Qualität und Vergleichbarkeit von Fischfängen durch Angler, Kiemennetze, Schleppnetze und Hydroakustik wurden untersucht. Anglerfänge eignen sich begrenzt für vergleichende Fischbestandsuntersuchungen. Vertikale Hydroakustik eignet sich für die Fischbiomasse- quantifizierung in geschichteten Seen. Der Beprobungsaufwand von Kiemennetzen kann reduziert werden, wenn zeitnah hydroakustische Untersuchungen statt finden. Schleppnetze eignen sich für die Beprobung von pelagischen Fischen in tiefen Seen. Die Größenstruktur von Fischgemeinschaften unterschied sich auf regionaler und überregionaler Ebene entlang abiotischer und biotischer Gradienten. Die regionale Studie zeigte, dass tiefe nährstoffarme Seen mit hohen Raubfischabundanzen durch mehr große Fische gekennzeichnet waren. Nährstoffreiche Flachseen mit wenigen Raubfischen zeigten höhere Anteile von mittleren Fischgrößen. Im überregionalen Vergleich führten Temperaturpräferenzen der Fischarten zu zwei Fischgemeinschaften, die sich in ihrer Größenzusammensetzung unterschieden. Ein hoher Anteil großer Salmoniden war typisch für hochgelegene Kaltwasserseen im Norden und Süden Europas. Flachlandseen mit Kühl- und Warmwasserfischen zeichneten sich durch eine Dominanz von kleinen Fischen aus. Das lässt vermuten, dass Fischgemeinschaften in Flachlandseen relativ robust gegenüber Umweltveränderungen reagieren. Kaltwasserfischgemeinschaften könnten im Zuge der Klimaerwärmung starken Änderungen unterliegen, da eine Veränderung in der Artenzusammen- setzung von einer Verschiebung in der Größenstruktur hin zu mehr kleinen Fischen begleitet sein wird. Schlagwörter: Fisch, See, Hydroakustik, Kiemennetz, Schleppnetz, Freizeitangelei, Körpergröße, Größenstruktur __________________________________________________________________________________