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Published by the Food and Agriculture
Organization of the United Nations in
arrangement with DVWKMany fish species
undertake more or less extended migrations
as part of their basic behaviour. Amongst
the best known examples in Europe are
salmon (Salmo salar) and sturgeon
(Acipenser sturio), which often swim
several thousands of kilometres when
returning from the sea to their spawning
grounds in rivers. In addition to these
long-distance migratory species other fish
and invertebrates undertake more or less
short-term or small-scale migrations from
one part of the river to another at
certain phases of their life cycles.Fish
passes are of increasing importance for
the restoration of free passage for fish
and other aquatic species in rivers as
such devices are often the only way to
make it possible for aquatic fauna to pass
obstacles that block their up-river
journey. The fish passes thus become key
elements for the ecological improvement of
running waters. Their efficient
functioning is a prerequisite for the
restoration of free passage in rivers.
However, studies of existing devices have
shown that many of them do not function
correctly. Therefore, various
stakeholders, e.g. engineers, biologists
and administrators, have declared great
interest in generally valid design
criteria and instructions that correspond
to the present state-of-the-art of
experience and knowledge.The present
Guidelines first refer to the underlying
ecological basics and discuss the general
requirements that must be understood for
sensible application of the complex
interdisciplinary matters. These general
considerations are followed by technical
recommendations and advice for the design
and evaluation of fish passes as well as
by proposals for choosing their hydraulic
dimensions correctly and testing the
functioning. Fishways can be constructed
in a technically utilitarian way or in a
manner meant to emulate nature. Bypass
channels and fish ramps are among the more
natural solutions, while the more
technical solutions include conventional
pool-type passes, slot passes, fish lifts,
hydraulic fish locks and eel ladders. All
these types are dealt with in this book.
Furthermore, particular emphasis is laid
on the importance of comprehensive
monitoring.These Guidelines deal with
mitigation of the upstream migration only
as data on improvement of downstream
passage was scarce at the time of the
preparation of the first edition,
published in German in 1996. Therefore,
the complex theme of downstream migration
is only touched on but not developed in
depth.
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