Eawag Annual Report 2021

LEHREN
23
Christoph Vorburger, Eawag
What can be done to protect native crayfish?
Photo Crayfish play an important
role in river ecosystems:
these omnivorous creatures
decompose leaf litter or the
remains of dead fish.
Native species of crayfish – formerly widespread – have now almost completely disappeared
from large rivers in Switzerland. To help preserve surviving populations,
Eawag is reaching out to experts with a practice-oriented (PEAK) course.
PEAK
Programme
Crayfish are among the largest invertebrates found in
Swiss waters, but people’s knowledge of these nocturnal
river dwellers remains limited. For thousands
of years, native species such as the stone, whiteclawed
and noble crayfish were widely distributed
throughout Europe. Today, these species have almost
completely disappeared from large waterbodies in
Switzerland. What exactly has happened? And what
measures is Switzerland taking to support the surviving
populations?
Dramatic decline
These questions were discussed by practitioners
attending a PEAK course in Tolochenaz (by Lake Geneva)
entitled “Protection of native crayfish.” It was
explained that, in many waterbodies, there is a lack
of natural structures to provide shelter for crayfish.
Also problematic is the contamination of rivers with
pesticides and heavy metals.
The situation deteriorated sharply when, from the
19th century onwards, North American species such
as the signal or red swamp crayfish were introduced
to Europe. These invasive species not only outcompeted
native crayfish for habitat, but also brought crayfish
plague to Europe.
Enhancement measures
Today, native crayfish are only to be found in the upper
reaches of certain rivers, surviving in largely isolated
residual populations. However, according to Christoph
Vorburger, Head of the Aquatic Ecology department,
Adjunct Professor at ETH Zurich and organiser of the
PEAK course on crayfish, “It is possible for waters
to be enhanced in such a way that they become habitable
for crayfish again. To preserve the remaining
populations, there is a need for protection efforts –
and dialogue with practitioners, which we facilitate
through our course.”