Priv.-Doz. Dr. Thomas Mehner

Vice Head
Dept.4 Biology and Ecology of Fishes
12561 Berlin, Mueggelseedamm 310

Research area:

Evolutionary ecology of fishes

Genetic structure of vendace (Coregonus albula) populations in lakes of north-east Germany
(In cooperation with Kirsten Pohlmann, Mike Monaghan, Che Elkin und Jörg Freyhof)

Recent studies revealed the occurrence of endemic vendace species in two north-east German lakes. We analyse the genetic structure of vendace populations in about 50 lakes in that area to explore, whether (a) other lakes also inhabit endemic species, (b) recommendations can be given for further fisheries management of local vendace stocks.

The impact of climate variability on recruitment, life history, and physiology of sympatric pairs of ciscoes (Teleostei: Coregonus spp.) in lakes

(DFG Me 1686/5-1 to 5-3, with Jörg Freyhof, within the priority program AQUASHIFT) in co-operation with Susan Busch.

Recently, it has been speculated that global warming trends may favor year-class strengths of spring-spawning in opposition to autumn-spawning fish species. The mechanisms behind were assumed to be a differential timing of the hatching of fish and the spring peak of the zooplankton as food for the small fish, and a variable recruitment due to temperature-sensitive adaptations of the life cycle. Here, we compare the timing of hatch and early recruitment of a sympatric pair species of ciscoes in a deep lake whereby one species spawns in autumn, and the other in spring. In this postglacial lake, speciation and divergence have occurred during the last 10,000 years. The ecological, behavioural and physiological differences between both species (except for the spawning time) are assumed to be low. By following the growth, feeding, distribution and physiological performance of the early life stages of both species, we want to test whether the spring-spawning species is indeed better adapted to the anticipated earlier ice break and higher spring water temperatures due to global warming. Furthermore, the predation risk against piscivorous fish is estimated for both species by inspecting the stomach content of littoral predatory fish.

As the next step, we are developing individual-based models to simulate the adaptive value and the consequences of global warming on verticla migrations of coregonids.

Size spectra and functional diversity of fish assemblages in lakes as potential indicator of ecological integrity

Subproject within the EU-project WISER (Water bodies in Europe: Integrative systems to assess ecological status and recovery)

(In co-operation with Matthias Emmrich)

Recent tests provided weak evidence only that measures of structural diversity of fish assemblages correlate with ecological integrity of Europen lakes. We will test size spectra and measures of functional diversity of fishes as alternatives. The results will become an integral part of a Pan-European evaluation system of lake integrity by their fish assemblages.

Secondary production, stable isotopes and matter flow between zooplankton, macroinvertebrates and fishes in shallow lakes and their coupling to the terrestrial surroundings.

Subproject 4 within the project TERRALAC (founded by WGL)

(In co-operation with: Kristin Scharnweber and Dr. Jari Syväranta)

We are going to analyse the coupling between aquatic and terrestrial ecosystems by allochthonous particulate organic carbon.in two shallow lakes, differing in their state between macrophyte or phytoplankton dominance. This subproject aims to measure secondary production, stable isotopes, matter flow and insect exchange between water and land.

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Recent papers (since 2006): For full list since 1990 click here

98. Lewin, W.-C., Huckstorf, V., Mehner, T. & Wolter, C. (2010): When no catches matter: coping with zeros in environmental assessments. Ecological Indicators (in press).

97. Mehner, T. (2010): No empirical evidence for community-wide top-down control of prey fish density and size by fish predators in lakes. Limnology and Oceanography 55: 203-213.

96. Helland, I.P., Vøllestad, L.A., Freyhof, J. & Mehner, T. (2009): Morphological differences between two ecologically similar sympatric fishes. Journal of Fish Biology 75: 2756-2767.

95. Mehner, T., Pohlmann, K., Elkin, C., Monaghan, M.T. & Freyhof, J. (2009): Genetic mixing from enhancement stocking in commercially exploited vendace populations. Journal of Applied Ecology 46: 1340-1349.

94. Huckstorf, V., Lewin, W.-C., Mehner, T. & Wolter, C. (2009): Performance level and efficieny of two differing predator-avoidance strategies depend on nutritional state of the prey fish. Behavioral Ecology and Sociobiology 63: 1735-1742.

93. Kobler, A., Klefoth, T., Mehner, T. & Arlinghaus, R. (2009): Coexistence of behavioural types in an aquatic top predator: a response to resource limitation? Oecologia 161: 837-847.

92. Busch, S. & Mehner, T. (2009): Hydroacoustic estimates of fish population depths and densities at increasingly longer time scales. International Review of Hydrobiology 94: 91-102.

91. Ohlberger, J., Staaks, G., Petzoldt, T., Mehner, T. & Hölker, F. (2008): Physiological specialization by thermal adaptation drives ecological divergence in a sympatric fish species pair. Evolutionary Ecology Research 10: 1173-1185.

90. Mehner, T., Diekmann, M., Gonsiorczyk, T., Kasprzak, P., Koschel, R., Krienitz, L., Rumpf, M., Schulz, M. & Wauer, G. (2008): Rapid recovery from eutrophication of a stratified lake by disruption of internal nutrient load. Ecosystems 11: 1142-1156.

89. Ohlberger, J., Mehner, T., Staaks, G. & Hölker, F. (2008): Is ecological segregation in a sympatric species pair of coregonines supported by divergent feeding efficiencies? Canadian Journal of Fisheries and Aquatic Sciences 65: 2105-2113.

88. Ohlberger, J., Mehner, T., Staaks, G. & Hölker, F. (2008): Temperature-related physiological adaptations promote ecological divergence in a sympatric species pair of temperate freshwater fish, Coregonus spp. Functional Ecology 22: 501-508.

87. Mehner, T., Padisak, J., Kasprzak, P., Koschel, R. & Krienitz, L. (2008): A test of food web hypotheses by exploring time series of fish, zooplankton and phytoplankton in an oligo-mesotrophic lake. Limnologica 38: 179-188.

86. Brämick, U., Diekmann, M., Lemcke, R. & Mehner, T. (2008): Assessing shifts in fish assemblage composition in German large lakes by literature data and commercial catch statistics. Fundamental and Applied Limnology 171: 87-103.

85. Helland, I.P., Harrod, C., Freyhof, J. & Mehner, T. (2008): Coexistence of a pair of pelagic planktivorous coregonid fish. Evolutionary Ecology Research 10: 373-390.

84. Mehner, T., Ihlau, J., Dörner, H., Hupfer, M. & Hölker, F. (2007): The role of insectivorous fish in fostering the allochthonous subsidy of lakes. Limnology and Oceanography 52: 2718-2821.

83. Mehner, T., Holmgren, K., Lauridsen, T.L., Jeppesen, E. & Diekmann, M. (2007): Lake depth and geographical position modify lake fish assemblages of the European 'Central Plains' ecoregion. Freshwater Biology 52: 2285-2297.

82. Kasprzak, P., Benndorf, J., Gonsiorczyk, T., Hülsmann, S., Koschel, K., Krienitz, L., Mehner, T., Schulz, H. & Wagner, A. (2007): Reduction of nutrient loading and biomanipulation as tools in water quality management: Long-term observations on Bautzen Reservoir and Feldberger Haussee (Germany). Lake and Reservoir Management 23: 410-427.

81. Mehner, T., Kasprzak, P. & Hölker, F. (2007): Exploring ultimate hypotheses to predict diel vertical migrations in coregonid fish. Canadian Journal of Fisheries and Aquatic Sciences 64: 874-886.

80. Hölker, F., Dörner, H., Schulze, T., Haertel-Borer, S.S., Peacor, S. & Mehner, T. (2007): Species-specific responses of planktivorous fish to the introduction of a new piscivore: implications for prey fitness. Freshwater Biology 52: 1793-1806.

79. Helland, I.P., Freyhof, J., Kasprzak, P. & Mehner, T. (2007): Temperature sensitivity of vertical distributions of zooplankton and planktivorous fish in a stratified lake. Oecologia 151: 322-330.

78. Lewin, W.-C., Arlinghaus, R. & Mehner, T. (2006): A review of documented and potential biological impacts of recreational angling: insights for management and conservation. Reviews in Fisheries Science 14: 305-367.

77. Dörner, H., Schulze, T., Mehner, T. & Hölker, F. (2006): Experimental evaluation of temperature-dependent mortality in tagged fish. Journal of Fish Biology 69: 1255-1260.

76. Schulze, T., Dörner, H., Hölker, F. & Mehner, T. (2006): Determinants of habitat choice in a large planktivorous fish. Journal of Fish Biology 69: 1136-1150.

75. Schulze, T., Baade, U., Dörner, H., Eckmann, R., Haertel-Borer, S., Hölker, F. & Mehner, T. (2006): Response of the residential fish community to introduction of a new predator type in a mesotrophic lake. Canadian Journal of Fisheries and Aquatic Sciences 63: 2202-2212.

74. Mehner, T. (2006): Prediction of hydroacoustic target strength of vendace (Coregonus albula) from concurrent trawl catches. Fisheries Research 79: 162-169.

73. Schulz, M., Freyhof, J., Saint-Laurent, R., Ostbye, K., Mehner, T. & Bernatchez, L. (2006): Evidence for independent origin of two spring-spawning ciscoes in Germany (Salmoniformes: Coregonidae). Journal of Fish Biology 68 (Supplement A): 119-135. Appendix table

72. Garcia, X.-F., Diekmann, M., Brämick, U., Lemcke, R. & Mehner, T. (2006): Correlations between type-indicator fish species and lake productivity in German lowland lakes. Journal of Fish Biology 68: 1144-1157.

71. Mehner, T. (2006): Individual variability of diel vertical migrations in vendace (Coregonus albula) explored by stationary vertical hydroacoustics. Ecology of Freshwater Fish 15: 146-153.

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Lecture "Fish behaviour and evolution", 60 hours

Humboldt-University Berlin, Faculty of Agriculture and Horticulture

Lecture "Fish ecology", 30 hours, Institute for Hydrobiology, Dresden University of Technology

Aquatic Ecology
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Freshwater Biology
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Limnologica
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