1996Offshore Malawi-Turner.Pmd

C M Y K Offshore CichlidsofLakeMalawi Offshore Cichlids of Lake Malawi OFFSHORE CICHLIDS Lake Malawi is internationally renowned among evolutionary biologists and aquarium enthusiasts alike for its immense number of species of cichlid fishes, which display a dazzling of repertoire of structural diversity, feeding specialisations, and bril- liant colours. Almost all of the attention has focused on the rocky shore fish or mbuna, and it has been assumed that the offshore waters and the sandy or muddy shores harbour a relatively low- LAKE MALAWI diversity community dominated by non-cichlid fishes. This book, the first ever guide to the cichlid fishes of the offshore waters of Lake Malawi, shows that this habitat harbours a great diversity of little-known cichlid species, which dominate the catches of the commercial and artisanal food fisheries. How they evolved, how they continue to coexist, and how to manage George F. Turner their exploitation for food while conserving these unique species will be major challenges to scientists and policymakers. Aquarists will be fascinated by the wealth of previously-unknown brilliantly-coloured and bizarrely-shaped species. Information on distinguishing features, colour, size, distribution and abundance, commercial importance, diet, reproduction, and taxonomy are given for 199 species, 79 of which are presently undescribed. 186 colour and 44 black and white photo- graphs illustrate all species. Also included are figures showing the main distinguishing features of the fish, maps, a glossary of Turner George F. technical terms, a full bibliography and brief discussion of the evolution, ecology and conservation of these fishes. The author, Dr George Turner, has worked on African cichlid fishes for 13 years and has spent more than 3 years in Malawi. Most of the information collected in this book was obtained while working on the commercial fisheries of the southern lake for the UN Food and Agriculture Organisation from 1990 to 1992. He is presently lecturer in Ecology at the University of Southampton, England, and continues to carry out research on evolution, ecology, behaviour, taxonomy, conservation, and management of African freshwater fishes. ISBN 3-928457-33-0 C M Y K 2 Offshore Cichlids of Lake Malawi 1 2 Offshore Cichlids of Lake Malawi George F. Turner Department of Biology University of Southampton England, UK 3 Photo cover: Rhamphochromis 'long-fin yellow' ISBN 3-928457-33-0 Copyright © 1996. Cichlid Press. All rights reserved. No part of this publication may be repro- duced, stored in a retrieval system, or trans- mitted in any form or by any means—elec- tronic, mechanical, photocopying, record- ing, or otherwise—without prior permission of the author and the publisher. Cichlid Press, Ahornweg 3, D-31864 Lauenau. 4 Contents Chapter 1. Introduction ............................................................................ 7 Chapter 2. Methods ................................................................................. 10 Chapter 3. Habitats, fish communities and their exploitation ........ 12 Chapter 4. Introduction to the cichlid species. ................................... 20 Chapter 5. Tilapiines ............................................................................... 27 Chapter 6. Mbuna .................................................................................... 32 Chapter 7. Ncheni and Ndunduma ..................................................... 38 Chapter 8. Utaka ...................................................................................... 66 Chapter 9. Lethrinops and allied genera ............................................... 76 Chapter 10. Aulonocara and Alticorpus ................................................. 100 Chapter 11. Placidochromis hennydaviesae complex ............................. 113 Chapter 12. Miscellaneous barred species .......................................... 119 Chapter 13. Buccochromis ........................................................................ 129 Chapter 14. Mylochromis and other oblique-striped species ............ 133 Chapter 15. Otopharynx and other spotted species ............................ 152 Chapter 16. Protomelas and other horizontally-striped species ....... 190 Chapter 18. Nimbochromis and other blotched species ...................... 202 Chapter 19. Discussion ........................................................................... 209 Glossary ............................................................................................... 221 References ............................................................................................... 231 Index ............................................................................................... 236 5 6 Chapter 1 Introduction The purpose of the present book is cles & Trewavas 1989), before the in- to provide an introduction to the off- troduction of offshore research vessels shore cichlids of Lake Malawi and to or commercial trawlers allowed the give some assistance in their identifi- deeper regions of the lake to be ex- cation in the field. plored. Although further ad hoc collections and descriptions of a few spe- Since the pioneering work of Fryer cies have been made by Burgess & (1959), the inshore cichlid fishes of Axelrod (1973), Eccles & Lewis (1977, Lake Malawi, particularly the rocky 1978, 1979), Stauffer & McKaye (1986, shore species, have been internation- 1988), Konings (1990a, b, 1993) and ally recognised as an outstanding ex- Turner (1994a, b, c), at least a third and ample of rapid speciation, with the probably more than half of all offshore potential to provide us with critical species are not only lacking a formal insights into the whole evolutionary description, but have never been men- process. Malawian cichlids are also tioned in print. well-known as a tourist attraction at Many of the fishes covered in the the Lake Malawi National Park, and present work are sometimes found in are kept by thousands of aquarists all inshore habitats — often principally in over the world. The excellent publica- these areas — although all occur to tions of Ribbink et al. (1983) and Ko- some extent further offshore in waters nings (1989, 1990), based largely on difficult to survey with SCUBA equip- SCUBA surveys, provide a fairly com- ment, either because of depth or the prehensive coverage of the distribu- turbidity of the water. Such areas are tion, ecology, and distinguishing fea- also those which are easiest to fish with tures of the shallow water cichlids, mass-catching, nonselective gears such particularly those of the rocky shore. as beach seines and trawls. From an Although most inshore species have evolutionary biologist's point of view, still not been formally described, the the offshore cichlids are interesting as great majority can be easily identified they appear to be free (or at least freer and now have fairly well-established than rocky shore fishes) to move informal names. around the lake. Since most theories of Those species which cannot readily speciation assume that populations be collected by SCUBA divers remain have to be separated geographically, it very poorly known. The only substan- is a greater challenge to explain how tial work on the taxonomy and identi- these fishes have evolved into so many fication of the offshore cichlids is species. Consequently, among the largely based on studies of preserved fishes of Lake Malawi, the offshore specimens collected prior to 1930 (Ec- cichlids are (i) the most important for 7 human food, (ii) the most interesting lected several species of Diplotaxodon to evolutionary biologists, (iii) the spe- during the 1950s, D. S. C. Lewis made cies most likely to be in danger of ex- a large collection of Rhamphochromis in tinction, and (iv) the least known. the 1970s, and D. H. Eccles collected I would like to make it clear that the numerous Lethrinops and other off- present work should on no account be shore species. Even a few preliminary regarded as definitive. There are un- studies on these collections would doubtedly many mistakes. The collec- have been very valuable to me and tions were obtained opportunistically other workers on Lake Malawi. Even and not as part of a systematic survey now, very little of this material has been programme. All the specimens came worked on, many of the specimens from the southern part of the lake. This have been destroyed or their collection book gives a brief outline of what little labels lost. Many other major studies is known of those cichlid species which on Lake Malawi made no taxonomic I encountered during my research on collection at all, such as those funded the fisheries of southern Lake Malawi by FAO in the 1970s and 1980s, ODA and Lake Malombe in 1990-92. Of these in the 1980s and 1990s, and the current species, 83 were undescribed at the World Bank/ ICEIDA project. There- time I carried out the field work, al- fore, each new study of the commer- though 4 have subsequently been for- cial fisheries or offshore fishes has be- mally described by myself or Ad Ko- gun from a basis of limited knowledge nings. Of the undescribed species, I and researchers have either had to re- was able to reliably identify 11 of these peat previous work or more often have on the basis of temporary names as- just avoided trying to identify the signed to them in the collection of the haplochromine component of the field museum of the Monkey Bay Fish- catch. The great underestimation of the eries Station in Malawi, mostly by D. species richness

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