TABLE OF CONTENTS Pages Symposium 1 - the National Sea ...

Recirculation Systems for Farming Eel in
Western Europe: Towards a Certified
Environmental Performance
Andries Kamstra
Netherlands Institute for Fisheries Research (RIVO)
IJmuiden, The Netherlands
Peter Rand Kees Kloet
Danish Institute for Fisheries Hesy Bergambacht bv
Technology and Aquaculture (DIFTA) Bergambacht,
Hirtshals, Denmark The Netherlands
Andre Aarnink
Institute of Agricultural and Environmental
Engineering (IMAG)
Wageningen University, The Netherlands
Present status of eel farming in recirculation systems
Eels are considered a delicacy in some countries in Western Europe and have
traditionally fetched high prices, in the near past in the order of 8-10 US$/kg. The high
value and decreasing landings from fisheries have been a strong impetus for developing
eel culture over the last 30 years. Eels need a water temperature of 23 to 25 °C for
optimal growth. Given the climate in Western Europe, farming of eel is only an option
using warm effluent from power stations or recirculation technology. Although some
of the early initiatives were utilising warm effluent in a flow-through mode, this
approach has been virtually abandoned because it proved not to be reliable. The first
recirculation systems for eel were built at the end of the seventies. Slowly and with
much difficulty eel farming has expanded, mainly in Denmark and The Netherlands, to
a business comprising approximately 100 farms with a production of 6700 tonnes in
1999.
Although other species like sea bass, sea bream, turbot, sturgeon and African catfish
are reared in recirculation systems occasionally, farming of eel is still the backbone for
application of recirculation technology in Western Europe.
Developments in design and management of systems
To our knowledge, no studies are available which compare long-term technical
performance of systems at a commercial level. Studies available usually cover
instantaneous performance or only a certain aspect of performance (Gousset, 1990;
Heinsbroek & Kamstra, 1990). Moreover, failure or success of certain systems in the
strict technical sense is often difficult to disentangle from other factors regarding for
example the management of the fish or the economic peformance.
In the early days a range of techniques was used for removal of suspended solids:
sedimentation bassins, swirl separators, fixed-bed upflow filters and some mechanical
filtration. Today, only microscreens are used, which have shown strong technical
development. Fine solids (bioflocs) are sometimes removed with upflow filters or UV;
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