Limnol. Oceanogr., 52(6), 2007, 2715–2718 E 2007, by the American Society of Limnology and Oceanography, Inc. The role of insectivorous fish in fostering the allochthonous subsidy of lakes Thomas Mehner, 1 , Jan Ihlau, 2 and Hendrik Do¨rner 3 Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mu¨ ggelseedamm 310, P.O. Box 850 119, D-12561 Berlin, Germany Michael Hupfer Chemical Laboratory, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mu¨ ggelseedamm 301, P.O. Box 850 119, D-12561 Berlin, Germany Franz Ho¨lker 3 Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mu¨ ggelseedamm 310, P.O. Box 850 119, D-12561 Berlin, Germany Recently, Wurtsbaugh (2007) commented on our earlier report in which we quantified the nutrient subsidy by a facultative insectivorous fish (bleak, Alburnus alburnus) feeding on terrestrial insects in a 0.12 km 2 lake (Großer Va¨tersee, Germany) (Mehner et al. 2005). We showed that the annual consumption rate of bleak consisted of about 84% terrestrial insects. We estimated that the allochtho- nous phosphorus included in these insects represented about 2.1% of the lake’s internal total phosphorus (TP) concentration, whereas excretion of P by fish was equivalent to about 11% of the mean epilimnetic soluble reactive phosphorus (SRP) concentration. Accordingly, we concluded that the lake studied was only weakly subsidized by allochthonous phosphorus stored in insects. Based on a decay model with varying parameters that calculated the spatial distribution of the daily fallout of terrestrial insects into lakes, we concluded that the subsidy by terrestrial insects to fish consumption and lake nutrient pools was likely most important in small, oligotrophic lakes sur- rounded by forests. Wurtsbaugh identified three possible shortcomings in our analyses. First, he argues that insects consumed by fish 3 Present address: European Commission, DG Joint Research Centre (JRC), Institute for the Protection and Security of the Citizen (IPSC), Agriculture and Fisheries Unit, TP 051, I-21020, Ispra, Italy. 2 Present address: Institut fu¨ r Systematische Zoologie, Museum fu¨ r Naturkunde, Humboldt-Universita¨ t, Invalidenstraße 43, D- 10115 Berlin, Germany. Acknowledgments Discussions with Wayne Wurtsbaugh helped clarify the arguments. Michael Vanni made constructive suggestions to improve the manuscript. Peter Kasprzak provided unpublished data from Lake Großer Va¨ tersee. Doug Beare checked the language. The study was financially supported by grants from the German Research Foundation (DFG) (Me 1686/4-1 and 4-2). 1 Corresponding author (mehner@igb-berlin.de). 2718–2721 2718 Mehner et al.