06/03/2006 - Today (Monday
6 March 2006), the Environment Agency starts
work on a major refurbishment of the fish
pass at Shrewsbury Weir.
The work is necessary because an increased
flow of water over the fish pass demonstrates
that the structure of the fish pass (but
not the weir) is failing.
The first step is to drain the water from
the fish pass and carry out a survey. We
will create a dry working area by installing
sheet piles across the front and pumping
out any remaining water.
During the survey we will carry out a thorough
visual and structural inspection. We will
then use the information gathered during
the surveys to prepare detailed drawings
and a design for refurbishment.
We hope to be able to carry out the refurbishment
works immediately afterwards, if possible,
but we must leave the site before the end
of May, when salmon begin to return to the
spawning grounds upstream.
Adult salmon return to breed in the river
where they were spawned. Fish passes make
it easier for salmon to negotiate obstacles
such as weirs.
There are several different types of fish
pass but the fish pass at Shrewsbury Weir
consists of a series of pools, which divide
the large fall of water at the structure
into several smaller falls. They dissipate
the energy of the falling water and provide
resting areas for ascending fish.
Fisheries and Recreation Team Leader, Mike
Exeter says: "With salmon populations
declining, it is very important that the
fish can get back to their spawning grounds
upstream so that they have the best chance
to breed. We have a duty to ensure that
the fish pass is in good condition. Having
identified that there seems to be a problem,
we will do our best to refurbish the fish
pass in time for this year’s salmon run
at the end of May."
More information
Salmon remember the scent of their home
river and will return after a number of
years at sea to breed in the river where
they were spawned. They lay their eggs in
gravel in shallow water in November and
December. The eggs lie buried in the gravel
until March or April, depending on the water
temperature. The young fish spend about
two years in the stream, then make their
way to the sea, where they mature, eventually
coming back to their home river as adults
to begin the breeding cycle again.
In order for the populations to thrive,
they need to be able to get back to their
spawning grounds upriver. Unfortunately,
many man-made obstructions such as dams,
weirs and mills, restrict this access
The Salmon and Freshwater Fisheries Act
1975 required new obstructions, or those
rebuilt for more than half their width,
to include a fish pass. Each fish pass design
must be suitable for the relevant fish species
and size and be easy for the fish to find.
It should generally be positioned at the
natural point where fish congregate.
