This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/jfb.14346 Assortative aggression among males in a sympatric pair of Labeotropheus from Lake Malaŵi, Africa Michael J. Pauers a,b,c* and Jacob A. Grudnowski b a Section of Vertebrate Zoology, Milwaukee Public Museum, 800 W. Wells Street, Milwaukee, WI, 53233 b University of Wisconsin-Milwaukee at Waukesha, 1500 N. University Drive, Waukesha, WI, 53188 c School of Freshwater Sciences, University of Wisconsin-Milwaukee, 600 E. Green field Avenue, Milwaukee, WI, 53204 *Corresponding Author: mjpauers@gmail.com; +001 414 278 6947 Funding This article is protected by copyright. All rights reserved.