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The inland water fishes of Africa

 | 
Didier Paugy
, 
Christian Levêque
, 
Olga Otero

Foreword

Didier Paugy, Christian Levêque et Olga Otero

Texte intégral

1Since 1992, the International Convention on Biodiversity has emphasized the need for conservation of species and natural environments. Much discussion has involved the biological diversity of tropical forests and terrestrial ecosystems, as well as the consequences, often negative, of human activity on the long-term evolution of these environments. Although freshwaters did not always receive enough attention, their present state is often worrying.

2Yet continental aquatic biodiversity displays interesting characteristics:

  • a relatively high rate of endemicity, particularly in lakes and rivers that were isolated for millions of years such as the East African great lakes, Lakes Baïkal, Biwa, and Titicaca, as well as the forest basins of the Amazon and the Congo, to name a few;
  • high genetic variability between populations of species with an enormous geographic distribution, but occupying hydrographic systems that have been isolated for more or less long periods;
  • a disproportionately large number of vertebrates in relation to the surface area occupied by continental waters (0.01% of the planet’s waters, for an area of around 1 or 2% of land mass).

3Out of some 30,000 known fish species, an estimated 12,800 are freshwater species. The inland waters of the African continent host no fewer than 3,000 fish species and many families of ancient origin.

4If we take into account all the other vertebrates (amphibians, reptiles, birds, and mammals) that depend heavily on continental waters to complete their life cycle, then at least a third of these vertebrates are present in the hydrosystems or largely depend upon them.

5The very concept of biodiversity presumes that we take an interest in the different levels of biological organization within a hierarchical system: genes, species, communities, and ecosystems. The backdrop of biodiversity has both spatial (stations, ecosystems, regions) and temporal (from the present to millions of years past) aspects. In other words, the diversity we see now is the legacy of the long evolutionary history of species, in an also-evolving climatic and geomorphological context. Research on palaeo-environments and the phylogeny of species help us reconstruct the dynamics of species evolution and distribution, which in turn allow us to interpret and explain the composition of local and regional fauna today.

6But biodiversity also encompasses the knowledge of the genetic diversity of species, especially for fragmented populations that are isolated from each other – the case of many widely-distributed species for whom watersheds are, in fact, equivalent to islands. This field, which emerged only in the 1980s with the development of molecular biology tools, is an area of research that has already yielded much new information and become of paramount importance in recent years.

7The diversity of biological traits is also a matter of interest. To some, these are adaptive responses to environmental conditions, though within the bounds of the constraints posed by phylogenetic characteristics. Biodiversity’s role in ecosystem function is also explored. Do all species play a useful role in ecosystem function? What consequences are derived from the disappearance or, conversely, the introduction of certain species? What are the roles and significance of key species and rare species? All these questions on biological diversity are, in themselves, fascinating research topics.

8In Africa, fishes were long preserved from anthropogenic impacts but are now endangered by human activities:

  • water planning and management (dams, dikes, channels, etc.);
  • industrial, urban, or non-point source pollution;
  • overexploitation of existing stocks;
  • introduction of exotic species.

9The conservation of aquatic biodiversity requires emergency measures practically everywhere in the world, including Africa where, for instance, the fauna of the East African lakes is seriously endangered.

10Fishes are in fact an excellent biological model for tackling questions raised by the myriad aspects of biodiversity:

  • this biological heritage, of global value, is the fruit of a long evolutionary history; Africa in particular has a large number of endemic species and numerous so-called “archaic” families;
  • a wide range of biological and ecological models are available thanks to the variety of life history, space occupation, and resource use strategies, and physiological and morphological adaptations;
  • the group is seriously threatened by human activity, either through fishing and the introduction of foreign species, or through physical (landscape planning) or chemical (pollution) changes that affect aquatic environments;
  • specific issues regarding fish protection are raised in the context of conservation biology;
  • fishes are an economic resource of utmost importance, be it though fishing or aquaculture (and the sole source of protein in some developing countries), or the activities surrounding it in the fields of sport fishing or aquariology.
  • fishes are an element of cultural diversity, and may be the subject of myth and tradition.

11Wise management of continental waters is a real economic issue for African countries. This book is a synthesis of multiple research activities on African aquatic ecosystems. It compiles the existing information on African fishes, which displays a broad diversity of biological models. It provides a synthesis of biological and ecological data needed to cope with conservation.

12Six main themes are developed in this book:

  • diversity of aquatic environments (p. 12 to p. 49);
  • origins and ecology (p. 51 to p. 188);
  • biology and evolution (p. 189 to p. 257);
  • population richness and community structure (p. 259 to p. 440);
  • impacts of human activities on fish species and populations (p. 441 to p. 478);
  • fishing and fish farming end the book (p. 479 to p. 545).

13With regard to fish biology, ecology, and populations of African continental waters, this book is the obvious sequel and companion to two other books that reviewed the state of taxonomic and faunistic knowledge, and that were published in 2003 (The fresh and brackish water fishes of West Africa) and 2007 (The fresh and brackish water fishes of Lower Guinea, West-Central Africa) as an initial contribution to the topic of ichthyofaunal diversity in the continental waters of Africa.

14The Scientific Editors

We dedicate this book to Rosemary Lowe-McConnell (1921-2014) who was a pioneer in the study of tropical fish and made a highly significant contribution to our understanding of the taxonomy, evolution and ecology to tropical fishes, particularly in Africa. Ro’s research (Ro is her nickname for friends) on tilapia, an important food source for many communities in the developing world, provided a valuable basis for further studies of fish farming in tropical waters. Tilapia is now a major food fish, stocked in lakes and dams, and cultivated in ponds worldwide (see later in this book).

Ro began her African scientific research in 1945 in Malawi (Lake Nyassa/Malawi). Later she went in Jinja, Uganda, at the East African Fisheries Research Organization, now the National Fisheries Resources Research Institute. Her main purpose was to study the biology of tilapia in the lakes of east Africa. Life in Africa had its challenges, but was fun, too, as described in Ro’s very readable book The tilapia trail. The life history of a fish biologist (2006).

Ro never actually retired and her work in the field never did end. She participated in many international conferences on ichthyology, limnology, and ecology, and produced more than 60 academic publications and published several books bringing together studies on the ecology of freshwater fishes from the tropics.

Acknowledgements

15It goes without saying that this book would not have been possible without the extraordinary participation of the 16 contributing authors.

16Special thanks are also due to a number of individuals whose additional efforts have been pivotal in bringing this book to fruition. In particular we would like to thank Emily Divinagracia (Publications Service, Royal Museum for Central Africa) for her outstanding translation and correction work on all the chapters.

17Our special thanks also go to Isabelle Gérard (Publications Service, Royal Museum for Central Africa), and Catherine Guedj and Thomas Mourier (IRD Éditions) for keeping us on course to publication.

Auteurs

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

A professorial lecturer at the University of Poitiers (Institute of Paleoprimatology, Human Paleontology: Evolution and Paleoenvironments). She studies the evolution and diversification of African fishes to reconstruct the relationships between their spread, diversification, and the paleoenvironment.

© IRD Éditions, 2017

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