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Book review – Bleher’s Discus Vol. 1

by Joseph S. Nelson


I love books on fishes, human history, natural history, and exploration, and when a book combines all of these subjects it is truly a joy to read. I do mean read—this extraordinary work is far more than a reference book, it is a rich source of information that is truly enjoyable to read. There is much for those who, apart from wanting information on the discus itself, wish to learn more about those ichthyologists and aquarists of former years involved in making the discus so well known. Heiko Bleher has done a wonderful job in combining coverage of the history of 19th century and onward of Austria and other parts of Europe and of South America relevant to events leading to the discovery and subsequent collections of the discus. He gives the reader scientific and practical information on a fish on which there is an abundance of literature. Discus are a member of the family Cichlidae, the third most species rich family of fishes in the world. The three species of discus now recognized occur in the central Amazon basin, a region with the highest freshwater species diversity in the world. Discus are one of the foremost aquarium fishes that there has ever been. They are variously known as “The aristocrat of the aquarium”, a term as explained by Heiko coined by William T. Innes in the 1930’s, and later as the “King of the Amazon”. Heiko has published extensively on discus (including a book in 1982) and on other fishes and he has a wealth of experience in exploration. The book is Heiko! No-one else could have written such a book.

This book is the result of almost 50 years of research. Many interesting and previously unpublished facts are given, and it is a synthesis of a vast literature, much of it poorly known. The book has an abundance of historical artwork and pictures. In all, there are roughly 5000 photographs, paintings, and illustrations of fishes, people, and landscapes, and numerous maps. Apart from captivating information on the discus and items related to it, the book is also rich in historical anecdotal information on such items as the history of the very first “Sacher Torte”, the European discoverer of the Indians arrow-poison, Sir Walter Ralegh, and a German expedition up the Rio Jari under swastika flag in 1935-1937. Readers are left with no doubt about the discus having a magic-like attraction. It is not surprising that such a wonderful fish should involve so many scientists and others in interesting events and attract the highly dynamic and adventurous Heiko Bleher to be its biographer in this masterful book.
Following the Introduction is a helpful section “How to use this book”, giving the reader an overview of what lies ahead. Chapter 1, the first of five chapters, covers the history of discovering the three species of discus. Heiko gives much credit and coverage to the indigenous peoples, the first to know the discus. He drives home the often neglected fact that aboriginals knew the fish well. Discus were first collected by Europeans in an Austrian expedition. The history of what was happening in Europe and in South America relative to exploration in South America and fish collecting is presented. The circumstances of the many expeditions of the Austrian Johann B. Natterer to South America, the first in 1817 with others on the first overseas expedition of the Austrian navy, and the routes in South America, eventually leading to the discovery of the discus in 1832, involves much intrigue. The first species was then described by Johann Jakob Heckel in 1840. The reader is also introduced to European ichthyologists such as Rudolf Kner, Franz Steindachner, and Johann Bapt. de (von) Spix. Similar historical treatment is given in discussing the discovery of the second species, in which the famous Swiss ichthyologist Louis Agassiz played a major part. This is followed by discoveries in the 20th century, where amongst others, we are introduced to Herbert R. Axelrod, Harald Schultz, and to W. T. Innes (whose book “Exotic aquarium fishes” I have from when a teenager). We also get a glimpse at the fascinating life of Heikos’ mother, Amanda Flora Hilda Bleher, the first commercial female fish-collector. Much of Heiko’s own experiences are described. Detailed treatment is given to the importation of the first live discus to the USA in 1932 and subsequent attempts to establish a flourishing trade by air flights under pioneering conditions, primarily after WWII. In good form, Heiko delivers excellent conservation messages, and we can all feel the pain that the poor aboriginals suffered while explorations and exploitations were undertaken.
Chapter 2 in discussing the taxonomy of discus, presents more information about Heckel, the person who described the first species of discus, developed ichthyology in Austria, and is best known for his work describing cichlids collected by Natterer. The original description of the first species is reproduced as is that of the second species, described by Jacques Pellegrin in 1904. I must confess to not previously knowing much of this French ichthyologist who described many new taxa and was one of our most prolific workers, living until 1944. One of the interesting but poorly known stories of aggressive competition in describing fish species in relatively recent times is narrated. This involves Leonard P. Schultz, long with the University of Washington and the National Museum of Natural History (Washington, DC, where he was in charge of their Division of Fishes) and Herbert R. Axelrod, founder of Tropical Fish Hobbyist Publications. George S. Myers, a world famous ichthyologist at Stanford University, and another but unnamed ichthyologist, apparently had a manuscript description of a new species of tetra that we know as the Cardinal Tetra. In Heiko’s words, Axelrod had his good friend Schultz describe it instead and in great haste, naming it after Axelrod. Schultz (not to be confused with Harald Schultz) is well known for many systematic studies, including a 1960 review of the discus genus in which he recognized two species, one with two new subspecies that he described. The Swedish ichthyologist Sven Kullander, the most prolific living cichlid systematist, sunk Schultz’s subspecies in a 1986 book discussing taxonomic problems of upper Amazonian cichlids. This move is accepted by Heiko except, in light of more recent information than was available in 1986, one subspecies is now recognized at the species level. The chapter concludes with Heiko’s critical comments on Symphysodon taxonomy and supporting the recognition of three species; this was in part with the assistance of the recently deceased Jacques Géry, who is well known for his work on characoids. In a separate publication, while acknowledging the need for more taxonomic study using nuclear DNA, Bleher et al. (2007) found three clades of Symphysodon using mtDNA and based on knowledge of their biology recognized them as valid species: Symphysodon discus Heckel, 1840, the Heckel Discus; S. aequifasciatus Pellegrin, 1904, the Green Discus; and S. haraldi Schultz, 1960, the Brown Discus. The latter species was originally described as a subspecies of Symphysodon aequifasciata and considered a synonym of S. aequifasciata by Sven Kullander in his earlier works, it was elevated to species level by J. Géry and H. Bleher in 2004. Hybrids were found of Symphysodon discus x S. haraldi and Fig. 26 of Bleher et al. (2007) suggests that S. haraldi is paraphyletic.
Chapter 3 treats the distribution of the three species of discus and their colour variants and presents 11 maps. Heiko awakens us to the gross misleading statements in the past on locality records of a fish that collectors often want to keep secret or where they wish to exaggerate their collecting abilities. Sadly, we discover that there is so much misleading information (for example, apparently discus have not been collected in the Rio Madeira and yet 38 variants are reported from this one river).
Chapter 4 deals with the many colour varieties of discus in nature. There are 46 pages of colour photographs dealing with variation in each of the three species. In making this a valuable scientific contribution, only photographed fish are shown where the place of capture could be confirmed by Heiko, usually because he collected the fish and took the picture (trade information, apparently is often faked, must surely create a dilemma in trying to enforce laws dealing with endangered populations). One wonders how much of this bewildering colour variation within each species is the result of natural selection adapting the morphs to differing environments or to dietary or other non-genetic effects.
Chapter 5, by far the longest one, is on the natural habitats of discus and on collectors. It leads off with much fascinating history, geography (including descriptions of the development of such cities as Belém and Manaus), ecological description of the very different water types, development (logging, rubber production, etc), aboriginal and other human interest stories (such as on the slaves), European scientific travelers such as Alexander von Humboldt and so many others, cultural events, and of course much on the discus and other fishes. Throughout all, presented under eight geographic areas, we get many tales of Heiko’s own exciting travels and experiences. Following this is a valuable section presenting previously unpublished detailed evidence that each of the three species has its own preferred requirements for living and spawning for such water parameters as pH, temperature, and conductivity. The chapter ends with detailed information on discus nutrition in the wild (e.g., vegetable material, algae, invertebrates), on discus communities (aquatic comrades and predators), and a section on the history of fish collecting (interestingly, going back to the time of Cro-Magnons in Europe).
There is a useful seven page glossary that covers English, Portuguese, and Brazilian terms and those of indigenous Indian tribes. The nine page References includes publications in numerous languages and is up to date. The Index is divided into four parts: General; Flora and Fauna (helpfully, pages with pictures of fishes have the page number in bold except for the very numerous discus variants, while names of higher taxa are in bold); People; and Places. Lastly, there is an overview of the author’s interesting life and work (he went on his first discus hunt when seven) from his birth in a bunker in the ruins of Frankfurt on Main in 1944 to currently being managing editor of “Aqua, journal of ichthyology and aquatic biology”. I digress here to encourage readers to look at the new Aqua website: His highly adventurous mother was a world traveler and collector of fishes and plants (now we know where Heiko gets his unique features!) and her father, Adolf Kiel, was a famous pioneer of the modern aquarium and known as the “father of water plants”. Heiko got into collecting fishes and plants as a very young boy by accompanying his mother on trips to Africa, throughout Europe, and into the depths of the South American jungle (and living with native Indian tribes). Lastly, there is a one page errata including missing references.
“Bleher’s Discus” Vol. 1, already available in seven languages, is an outstanding book that I highly recommend as one suited to a wide audience of readers with wide interests, from those interested primarily in the wonderful discus and aquarium fishes in general to varied aspects of natural history and exploration of South America. We will look forward to Vol 2, dealing with breeding the discus (and the history of attempts to breed it), cultivated forms of discus, history of classification of the discus, development of discus exhibition, advice on keeping discus, the future of discus, listing of discus clubs and associations world wide, discus on the Internet, and discus products.

BLEHER, H., STÖLTING, K. N., SALZBURGER, W. & MEYER, A. 2007. Revision of the genus Symphysodon Heckel, 1840 (Teleostei: Perciformes: Cichlidae) based on molecular and morphological characters. aqua, International Journal of Ichthyology 12 (4): 133-174.

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