How to Estimate the Reproductive Success of European Silver Eels -- Silvering -- Seasonal Evolution and Individual Differences in Silvering Eels from Different Locations -- Silvering: Metamorphosis or Puberty? -- Silver Eel Migration and Behaviour -- Performance -- High Pressure Resistance and Adaptation of European Eels -- Acclimation to Seawater in the European Eel Anguilla anguilla: Effects of Silvering -- Calcitonin Gene-Related Peptide (CGRP), a New Endocrine Factor Involved in the Complex Multi-hormonal Control of the Gill Osmoregulation: Evidence from Studies in the European Eel, Anguilla anguilla -- Energy Requirements of European Eel for Trans Atlantic Spawning Migration -- Impact of the Swim-Bladder Parasite on the Health and Performance of European Eels -- Maturation and Reproduction -- Effects of Swimming on Silvering and Maturation of the European Eel, Anguilla anguilla L. -- The Gonadoliberin(S)-Gonadotropin(S) Axis in the Eel: Expression and Regulation Under Induced Maturation and Sex Steroid Feedbacks -- Dopamine Inhibition of Eel Reproduction -- Artificial Maturation and Reproduction of the European Eel -- Testis Development, Sperm Quality Evaluation and Cryopreservation in the European Eel -- Environmental Effects -- The Effect of PCBs on the Spawning Migration of European Silver Eel (Anguilla anguilla L.) -- Impact of Eel Viruses on Recruitment of European Eel -- Evolutionary Consequences of Eel Migration -- Proximate and Ultimate Control of Eel Continental Dispersal -- Synthesis -- Reproduction Capacity of European Eels. The European eel Anguilla anguilla is a common fish species in West European countries supporting several thousands of small-scale fisheries. In June 2007, it has been listed in Annex B of CITES after the 99% decline in recruitment observed over the last decades. A European Council Regulation was issued on September 2007 to arrest the collapse of the eel stock. In this book, we discuss the factors that may contribute to the collapse of the European eel population. With respect to conservation measures two important aspects have to be considered: quality and quantity of escaping silver eels. Clearly, a poor condition of the silver eels can never be compensated by large numbers. Qualitative parameters were thus far hardly available for management applications. The main goal of this book is to provide useful quality parameters for migrating silver eels, indicating their contribution to recruitment. The process of migration and maturation also provides information about the natural conditions for eel reproduction. Therefore, this book will also be very useful for eel aquaculture; it may provide tools for reproduction as well as for suppression of precocious maturation. An integrative approach regarding eel maturation requires a combination of ecology and physiology. In this book we included both aspects, and we hope that this will contribute to the restoration of the European eel population.