The Mediterranean, Black, and Caspian Seas, the rivers and canals that connect them, and the enormous volume of shipping in the region, represent a conduit for aquatic invasion, whose consequences are only now beginning to be understood. This book provides an up-to-date overview of jelly invasions in the Ponto-Caspian which have affected local ecosystems since the early 1980s, contrasting that with other biological invasions, in search of underlying principles.

What have we learnt about the Nile since the mid-1970s, the moment when Julian Rzoska decided that the time had come to publish a comprehensive volume about the biology, and the geological and cultural history of that great river? And what changes have meanwhile occurred in the basin? The human popu- tion has more than doubled, especially in Egypt, but also in East Africa. Locally, industrial development has taken place, and the Aswan High Dam was clearly not the last major infrastructure work that was carried out. More dams have been built, and some water diversions, like the Toshka lakes, have created new expanses of water in the middle of the Sahara desert. What are the effects of all this on the ec- ogy and economy of the Basin? That is what the present book sets out to explore, 33 years after the publi- tion of "The Nile: Biology of an Ancient River". Thirty-seven authors have taken up the challenge, and have written the "new" book. They come from 13 different countries, and 15 among them represent the largest Nilotic states (Egypt, Sudan, Ethiopia, Uganda, and Kenya). Julian Rzoska died in 1984, and most of the - authors of his book have now either disappeared or retired from research. Only Jack Talling and Samir Ghabbour were still available to participate again.

What have we learnt about the Nile since the mid-1970s, the moment when Julian Rzoska decided that the time had come to publish a comprehensive volume about the biology, and the geological and cultural history of that great river? And what changes have meanwhile occurred in the basin? The human popu- tion has more than doubled, especially in Egypt, but also in East Africa. Locally, industrial development has taken place, and the Aswan High Dam was clearly not the last major infrastructure work that was carried out. More dams have been built, and some water diversions, like the Toshka lakes, have created new expanses of water in the middle of the Sahara desert. What are the effects of all this on the ec- ogy and economy of the Basin? That is what the present book sets out to explore, 33 years after the publi- tion of "The Nile: Biology of an Ancient River". Thirty-seven authors have taken up the challenge, and have written the "new" book. They come from 13 different countries, and 15 among them represent the largest Nilotic states (Egypt, Sudan, Ethiopia, Uganda, and Kenya). Julian Rzoska died in 1984, and most of the - authors of his book have now either disappeared or retired from research. Only Jack Talling and Samir Ghabbour were still available to participate again.

This book contains a collection of papers dealing with various aspects of the biology and aquaculture of the large branchiopod crustacea; the Anostraca, Conchostraca, and Notostraca. Included are many of the papers presented at the Second International Large Branchiopod Symposium convened in Ulm, Germany, 30 July--3 August 1993. Additional manuscripts contributed by colleagues who were unable to attend are also included. A special feature of this volume is a checklist of the Anostraca, including information on distribution, location of type material, taxonomic problems, and literature references.

This book IS an attempt to review the state-of-the-art in the fields of limnology and of marine biology in the Sudan. The need for it became apparent while we were doing some joint field work in the Nile Valley and along the Red Sea coast. We feel that several reasons justify its publication. Firstly, a vast amount of information is being gathered year after year by the staff of the Hydrobiological Research U nit of the University of Khartoum, in conjunction with the faculties of Medicine and Agriculture of this university; much of this information fails to find an outlet to the scientific literature. Secondly, we did not want to restrict our book to the Nile Valley. The Nile is such a vital life artery to the Sudan that it has dominated limnological efforts in this country, to the neglect of other geographical areas. The same holds true for the field of marine biology, which lags far behind, despite the existence of a marine field laboratory at Suakin and a research institute at Port Sudan. It is hoped that both will develop considerably in the near future.

Our knowledge of the limnology of the waters situated, roughly, between the tropics of cancer and of capricorn, has depended for a long time on the expedition-approach, and therefore developed in a rather irregular, haphazard way, with the personal incentive of a small number of individuals as the main driving force. Things slowly started to change in the 1950s, and at an accelerating rate in the 1960s and 1970s. The IBP, and later the SCOPE and MAB programs, whatever their shortcomings are or may have been, promoted in-depth research of a small number of tropical lakes. For one thing, they showed the need for the creation of in situ limnological research institutes. When, in the 1970s, limnological research facilities or their nuclei began to appear in the tropical zones of all continents, an interesting phenomenon occurred: while most of the young native limnologists had received their training in advanced centres or courses held in the temperate (and developed) climatic zones, quite a few of their former supervisors or their associates became interested in warm lakes and rivers as well, using the new or newly expanded local institutes. We are, today, still in this phase and it is, apparently, expanding even further. Although not all experiments of this kind lead to happy marriages, a few were quite successful, and several papers contained in the present volume are hoped to reflect this.

The Mediterranean, Black, and Caspian Seas, the rivers and canals that connect them, and the enormous volume of shipping in the region, represent a conduit for aquatic invasion, whose consequences are only now beginning to be understood. This book provides an up-to-date overview of jelly invasions in the Ponto-Caspian which have affected local ecosystems since the early 1980s, contrasting that with other biological invasions, in search of underlying principles.