- Winston Churchill Memorial Trust

Fish Counting
Technology for
Sustainable Fisheries
Management.
Report of a Winston Churchill Memorial Trust
Travelling Fellowship to Norway, Iceland, Alaska
and Canada in 2005.
By Jim Gregory
Historical distribution of the Atlantic Salmon, Salmon salar.
Introduction
The Atlantic Salmon, a mighty fish and a
mighty symbol. It’s momentous migratory
life cycle inspires awe and respect. It’s
mere presence can give a river an almost
iconic status with an association of a
clean and pristine environment. Equally
its absence or decline can signal quite
the opposite. No other freshwater fish in
Britain has such a strong connection with
the environment in the consciousness of
the public. There is no better symbol of
the health of a river system. Protecting
its habitat and encouraging its
distribution through cleaner water,
improved farming practises, over coming
barriers to migration and managing
historical spawning areas is very good
news for all river life. But more than
this, it can give people that connection
with their environment, inspiring more
active participation in outdoor activities.
Maybe even inspire them to take up
fishing and get outdoors in the first
place. Angling participation programs,
though not for salmon, have helped get
vulnerable young people off crime, out
of trouble, and away from play stations.
But it is also a mighty symbol of the
ability of an ecosystem to recover. The
salmon has had a rough time over the
years. The Industrial Revolution was bad
news for a species that suddenly found
itself migrating through conduits for the
effluent produced by the great industrial
processes. By the start of the 1980s, the
Thames, Tyne, Mersey, Taff and other
once great salmon rivers had been devoid
of salmon for over a hundred years. But
with the decline of industry, better
water quality and an improving
environment, these rivers and many like
them have seen the return of this great
fish. The salmon can be seen as a beacon
of hope for an environmentally troubled
generation. So, there is a lot riding on
the back of the salmon.
New threats, same dangers.
But times are changing. Though the
decline of industry has let salmon back in
on some rivers, its legacy of climate
change is felt acutely by the king of fish.
The thirst for water for agriculture,
potable supply and other demands on
water intensify. Exploitation is still an
issue. Salmon are just clinging on in
many of our once great rivers with
populations well below their potential.
The number of salmon eggs being laid in
many of our famous salmon rivers is
barely enough to maintain the current
populations. These therefore remain
perilously vulnerable and as a
consequence exploiting this resource
through the recreational rod fishery and
commercial fishing interests is something
that has to be done very carefully.
Fundamental to this careful approach is
accurate and comparable knowledge of
fish numbers.
How Many Salmon?
The number of adult salmon coming back
to a river system is therefore a very
important indicator of the health of that
population. Not just as an indicator of
the number of eggs deposited, but also
the timing of those movements, the
response to environmental cues like flow
and temperature. The size of fish is also
important since the bigger the fish the
more eggs they will both lay and
fertilise.
One fish, two fish, red fish, blue fish.
Counting fish in a river is difficult.
Salmon at least make it easier by
actively migrating and therefore have to
pass a fixed point on the lower reaches
of a river in order to spawn. But it is not
a precise art. There are problems. These
are:
1. Downtime
2. Efficiency
3. Species Apportionment
4. Reporting
Many other countries face problems with
counting fish, whether that is atlantic
salmon or the 6 species of pacific
salmon, and my Churchill Fellowship set
out to visit four of them.
Sites visited in Norway, Iceland, Alaska and
Canada.
The Fellowship had the following aims:
Aims and Objectives
1. To examine the techniques and
Technology used to automatically
count migratory salmon in rivers,
specifically sonar, infra-red,
resistivity and video counters.
2. To see how data is analysed from
counting systems to produce a
consistent output.
3. How is this data used to manage
fisheries sustainably
4. Look for opportunities that could
benefit UK fishery management.
Only the first of these aims is reported
here. The others have been reported
separately through my role as Senior
Technical Specialist with the
Environment Agency in technical reports,
presentations and video diary.
Fish Counting On the Edge!
Alaska and the Pacific Salmon
My story starts in Alaska, a state of
gigantic proportions, over a fifth the size
of the entire US, with the highest
mountain in North America and salmon
runs that are measured in the millions.
The economic importance of salmon
commercially means that managing it is
vital and the resources available to
monitor it dwarfs anything in the UK. But
the range of methods employed to count
salmon goes from edge to edge on the
technology spectrum.
The Salcha River, in Central Alaska is a
typical example of how counting has
been carried out on over 30 rivers. A
tributary of the Tanana, which in turn
runs into Yukon, the Salcha has a run of
chum and Chinook salmon and a
recreational fishery.
A view upstream and downstream on the River
Salcha, Alaska.
A human fish counter takes up her vigil of Salcha
river salmon at an Alaskan fish counting tower.
The drive for technology.
Many Alaskan rivers are glacial fed.
These carry the fine particles, and
sediment eroded by the ice fields of
Alaska and this gives the rivers a
distinctive blue tint.
Fish are counted here with the piece of
technical equipment pictured below.
The Kenai River, Alaska.
The common Tallywhacker.
A white canvas sheet is stretched across
a 40 metre width of the river to
silhouette fish as they pass over it. A
string of lights suspended from a wire
above it provide lighting during darkness.
For 10 to 15 minutes every hour, 24
hours a day for up to 2 months, a person
ascend the counting tower, dons a pair of
polarising glasses, takes hold of a
tallywhacker and counts off each fish
that passes.
The glacial river Kenai on the Kenai
Peninsular South West of Anchorage, is a
massive draw for Anglers in search of
coho, sockeye and Chinook salmon.
The two important species to count here
are the sockeye, which are the major
commercial species with catches
measured in the millions, and Chinook,
which brings in the headlines for the
river as having the biggest specimens in
the world. Counting these visually in the
high sediment load of a glacial river is
impossible. But listening for salmon is
not.
Sonar
Sonar systems transmit pulses of sound
into the water column and “listen” for
the returning echoes from, amongst
other things, fish. Since the 1970’s, sonar
counting systems have been used on
many Alaskan rivers and on the Kenai to
count sockeye salmon. The system can
not discriminate between species, but a
behavioural trait is utilised to distinguish
sockeye from other species; their spatial
distribution across the river.
Chinook are large powerful fish, with the
energy and strength to easily swim
against the flow of the Kenai. Sockeye
are much smaller and conserve energy by
migrating close to the banks of the river,
in the slower flowing water. The sonar
operators can concentrate their counting
effort on the first six metres from both
banks of the river. The salmon travel so
close that they build a small weir to
force the fish out from the bank by at
least a few metres and count them as
they move back to shore.
A fish deflection weir on the river Kenai, built to
force fish out from the shore and make them
easier to detect using sonar.
This equipment has provided an estimate
of the sockeye run size for over 30 years.
The big issue though is that the hardware
is slowly dieing. Alaska had over 30 sites
using this single beam Bendix system. It
is no longer produced and, increasingly,
existing systems have to be cannibalised
in order to keep others operational.
The Bendix sonar fish counting system; A 1970’s
original that’s still in use in Alaska.
So, the search has been on for over 8
years to find a replacement system. But
this search had some strict parameters:
Everything the existing counter said was
the truth and any new system that said
something different was incorrect.
Fish counting is never an absolute. In the
UK we have been storing up many
problems for our selves by reporting
figures in a form which effectively says;
“in 2004, 567 salmon entered the river”.
Not 568 or 560, but 567. The notion that
a counter can count all the fish and
nothing but the fish is ridiculous. But
that’s exactly what we have been
training people to expect. As we improve
things by giving an appraisal of errors
and presenting confidence interval
around figures, so it looks as if we are
suddenly very uncertain. But this
problem is nothing compared to the
Alaskan problem.
For the last 30 years, the sonar counter
on the Kenai has given THE definitive run
size of sockeye. Commercial fishing
operations have opened and closed as a
consequence and profits have been made
or lost. So, if a different technique was
used that came up with radically
different figures from the existing system
and therefore cast doubt on the figures
from previous years, then it is feared
that this could undermine credibility and
call into question previous management
decisions. Most people now except that
the existing sonar is fine as an index
from year to year. But other methods are
less likely to suffer from the same faults.
The previous pictures were obtained
from a high frequency acoustic system
which gives almost video quality images
for inspection and identification of
objects underwater. This is being trialled
along side the Bendix system. But in the
land where the tallywhacker roams free,
the images seen are still counted by eye.
However, these systems are not made or
supported anymore and contain obsolete
components that make keeping them
operational evermore difficult. Hence
they are looking again for alternative
technology. Sonar is still the answer but
much has changed since the 1970’s.
Dual Frequency Identification Sonar (DIDSON).
Sonar image of salmon detected by DIDSON. The
solid objects at 5 to 6 metres are the fish. This
can be played like a video image to observe fish
behaviour.
In contrast to the sockeye counting
system, the Chinook counter, which is
operated by a different division of the
Alaska Department of Fish and Game,
have always gone for the best
information/technology available for its
results. They have embraced split beam
acoustics when that was developed in
the early 1990’s, and have adopted the
newer technology.
Alternative High Resolution Systems
The success of DIDSON has encouraged
other companies to market their high
resolution sonar systems. Blueview
Technologies produce multibeam sonar
systems for mounting on Remote
Operated Vehicles (ROVs) and were
looking at breaking into the fisheries
market. I attended a trial of their system
which is still in the development stage
for fisheries applications.
Hey! It even looks like a fish! Imaging with sound
using the DIDSON system.
Edge of Innovation/simplicity
Norway and the Atlantic Salmon.
With approximately 667 Atlantic
salmon rivers, several of the world’s
largest individual populations, and
some of the world’s largest specimens
of wild Atlantic salmon, Norway remains
the world’s leading producer of the
species.
Endangered
Categorisation of Norway’s salmon rivers.
(23 %)
In Norway, fish are counted a little
differently. By far the most ubiquitous
tool for counting fish in Norway is the
mechanical fish counter.
A mechanical fish counter from Norway, out of
water (top) and under water (bottom) with
provision for camera mounts.
Typically this is installed on fish passes
or fish ladders built to enable fish to
ascend an obstruction on the river. The
metal bars are forced aside as a fish
pushes through, causing a mechanical
count of fish to be made. This has won a
Norwegian award for innovation and is
installed on over 60 sites throughout
Norway. Many are linked to a camera to
give video or still images from each fish
passing through the pass. This works very
well in areas that have little debris and
weed to collect on and block the
machine. So the northern rivers of
Norway are ideally suited to this type of
counting system.
More Innovation – Video!
Counting adult salmon as they return to
the river to spawn is easy compared with
trying to count the young salmon (smolt)
as they leave the river. Counting these
10 to 15 cm fish as they migrate in
tightly packed shoals has proved near
impossible with conventional counting
techniques. So in many cases, smolt
monitoring is carried out by trapping and
physically handling fish. The clear waters
and light nights of Northern Norway
allow smolts to be counted by sight using
underwater video cameras, saving the
fish from the stress and potential
damage of trapping.
A private consultancy in Norway has
taken to deploying up to 60 underwater
cameras across a width of the River Orkla
and connecting a motion detector unit to
each one. The output of that motion
detection process is then watched by
(several) temporary workers with our old
friend the (atlantic) tallywhacker in
hand. I was introduced to an excellent
motion detector for fisheries application
and have subsequently introduced it into
the UK. The Digital Video Motion
Detector (DVMD), produced by Radiant is
now used all over the UK in Fisheries
applications as a consequence.
This air tight box contains cameras and
lighting to illuminate fish that pass
within a metre of it.
Edge of Crisis
Canada, Horsefly River.
The mighty River Fraser, at 850 miles
long, is one of the biggest in North
America. It flows into the Strait of
Georgia in the South West of Canada and
five species of pacific salmon make their
spawning migration up it.
That little black box. Digital Video Motion
Detection.
More Video!
South East Alaska
Video is being increasingly used In Alaska
too. Alaska is remote, so many fish
counting sites require crews to camp out.
Remote cameras are could in some cases
provide an answer to this labour
intensive monitoring. On smaller
streams, some sites use a reflective
white board on the riverbed to silhouette
fish, and a temporary weir structure to
guide them over it. Cameras then either
record this on site or rely it back to a
fixed location and out comes the
tallywhacker.
The sockeye salmon fishery is worth a
fortune. This fishery is managed by a
series of models which predicts the run
size based on smolt output and previous
years run size. This run size is measured
each year by a combination of fish
counters, creel surveys and
mark/recapture studies. Sockeye spawn
in lakes or rivers off lakes and one of the
most productive rivers in the Fraser
system is the Horsefly River that runs
into Horsefly lake. Every year on this site
a study is undertaken to capture adult
sockeye, weigh, measure and tag them.
They spawn and die several weeks later
and the catchment is walked repeatedly
to establish the proportions of tagged
and untagged fish. From this, a total run
size can be calculated.
Some sites use fish weirs to push fish
past a temporary viewing window.
The Horsefly River and fish tagging crew.
Prefabricated camera and lighting box.
The DIDSON was attached to the base of the
structure on the left and aimed across the weir
gap.
Tagging sockeye salmon
This is very labour intensive and
expensive (c. $500K). So, in 2005 a trial
of everybody in fisheries current flavour
of the month, DIDSON was being tested.
Weir across the Horsefly
A 10 metre gap in the weir was left for fish to
pass through and be counted by DIDSON.
Around 500,000 sockeye were estimated
to have run the river according to the
DIDSON, but this was a more difficult
tallywhacking job. Each video clip was
watched three time; once to count fish
in the range 0 to 5 metres going up
stream, then again in the 5 to 10 metres
range upstream, then a third time 0 to
10 metres counting all the downstream
movement. At time of writing, the
comparison with the mark/recapture
estimate was still undergoing work.
But not everything revolves around
Tallywhackers
Edge of memory
The first automatic fish counters to gain
a wide use in Britain were the resistivity
counters. No chance of tallywhacking
from these as they worked by creating a
small electric field between three
stainless steel electrode strips placed in
a water filled tube. As a fish swam
through, the electrical resistance of the
water showed a characteristic change.
Then some one took this idea and put it
on the face of a weir, so removing the
requirement to get fish to swim through
a narrow tube. These resistivity or
conductivity counters are now the most
ubiquitous counters in the UK with over
40 sites. The efficiency of this system
depends on fish swimming very close to
the electrodes, which is why they are
placed on weir faces. Tube counters have
not been used in England and Wales for
about fifteen years.
The resistivity counting strips are under the
bridge on the right hand side
This has been validated for a summer in
1998 and it was found to have an
upstream efficiency of over 90%.
The white heat of fish counting technology. A
1960’s resistivity fish counting unit from the UK.
There is something quintessentially
British about Resistivity counters. The UK
must have over 40 resistivity sites and
Ireland a further 30. But they are rare to
find away from here. However, I did
come across one in Norway on the River
Orkla. This was different to the
deployments in the UK as it was based on
a flat bed with over a metre of water
over it.
Resistivity counters have also migrated
to the west coast of Canada, carried by
Don McCubbing, a Brit who had worked
with the system in the UK. Through him,
several flat-bed resistivity sites have
been commissioned such as these
pictured here on the Merret River.
Flat bed resistivity counter, Canada.
The River Orkla, Norway, immediately upstream
of the counting site.
These are deployed to count steel head
trout as they migrate up these smaller
streams to spawn in April time. At this
time of year the depth of water here can
be 0.5 metres. A camera is used in
conjunction with the counting system in
side aspect to attempt some validation
and the clarity of water is such that fish
can be seen across almost the entire
width of the stream. The cameras have
been found to be necessary to interpret
some of the graphical outputs of the
counters. Fish behaviour and water
depths at this site make camera work
essential to fully understand the fish run.
beam pattern and forms an outline of the
objects shape.
Picture of vaki stuff from the poster
A more traditional resistivity couting weir on the
Merret River, Canada.
The resistivity tube counter is proving it
still has a place in fishery management
after all these years. They have been
deployed at the fish exit of passes on a
number of spawning tributaries, mainly
to monitor Chinook salmon like this one
on the Bonepart river, a tributary of the
Fraser system.
It was great to see resistivity counters
alive and well in Canada.
Counting on the Edge of the World.
Iceland.
Like Norway, the pristine water of low
productivity means little organic debris
load and therefore little to block in river
grids and sluices. A type of fish counter
has developed here which takes
advantage of that. The infra-red
counters used here are all produced by a
company called Vaki Dng and many are
operated by them for the Icelandic
Institute of Freshwater. The system uses
a series of infrared beams to create an
unbroken grid between transmitter and
receiver. When an object does pass
through this infrared grid it breaks the
Due to attenuation of infrared in water,
there is a limitation on the distance
between transmitting and receiving
diodes of about 0.5 metres. This
separation distance makes the system
ideally suited to small fish passes such as
this one in Northern Iceland near the
town of Akureyi.
Infrared counting frame installed on at the top of
two rivers in Iceland.
But where such a pass does not exist, fish
have to be persuaded to swim through
the narrow aperture of the infrared
system. In many UK rivers, this would
create a serious maintenance problem,
possible flood risk and be a magnate for
curious members of the public and petty
vandals. But in these high latitudes, it is
a perfectly manageable deployment.
An Icelandic river, outside of Reykjavik, with
grids leading fish into an Infrared counting
system.
Camera system can be deployed here to
aid interpretation of the silhouettes and
this system is by far the easiest and
quickest to verify and produce a count.
Species apportionment is carried out on a
sizing basis and there is little overlap in
size distribution between the 5 species of
freshwater fish present!
Video counting developments
A number of companies in Iceland
manufacture underwater lighting and
camera equipment. There are others who
deal exclusively with fisheries operation
and others with image analysis. I talked
through our aims in England and Wales to
develop a new type of fish counter using
these skills and knowledge and
established an informal collaboration.
This is reported in a later Environment
Agency R&D report.
On the Edge of the World
Alaska
This place seemed like the edge of the
world. Close to Fairbanks deep in
Alaska’s interior, on the Tanana river, a
tributary of the Yukon, an hours fast
boat ride down river took me to a fish
wheel.
Alaskan fish wheel on the Tanana River.
Fish wheels are ancient and very
effective fish capture devises that use
the river flow to power a fish basket to
“scoop” fish out of the water. These fish
wheels were a common sight on the river
20 years ago when a thriving fishery for
the chum salmon existed, mainly to
harvest the roe. But the fishery has
since collapsed and many people blame
that on the fish hatchery at Valdez in
Prince William. I went to see the
hatchery but they were too busy to talk
to me as the team were shovelling dead
pink and chum salmon off the beaches
and harbour. The hatchery regularly over
produces fish to avoid leaving the fishery
short during a poor salmon year. But in a
good year there are far too many fish for
both the fishery and for the spawning
streams of Prince William Sound. It was
this vast number of wasted, rotting fish
that gave the town of Valdez such a
distinctive aroma. The town’s people had
got them to do something about it,
hence the shovelling of dead fish. Their
routine over production has led to the
state law on banning roe harvest in
PrinceWilliam Sound being lifted, leading
to huge amounts of roe saturating the
Japanese market. It was this that forced
the closure of the Tanana fishery and
now the only fish wheels are turning for
subsistence fishing. Or to cold smoke for
sled dog winter feed which amounts to
the same thing.
targets are automatically selected by the
system and stored for a user to review
later that day. The tags on the fish can
clearly be seen and the proportion of
marked to unmarked fish used to give an
estimation of the run size.
An image grabbed from the fish wheel counting
system, Alaska.
A live chum salmon, unsmoked.
Slow smoked chum salmon on in a smoke house
on the banks of the Tanana.
But a few wheels have been used for
fishery monitoring purposes. The site I
visited was identical to a site 30kms
further down stream where fish were
captured and tagged. This site was the
recapture site, but instead of trapping
and handling the fish, video cameras
were placed above fish channel and this
was connected to a computer and image
analysis software. Still images of fish
Products and benefits
To examine the techniques and
Technology used to automatically count
migratory salmon in rivers, specifically
sonar, infra-red, resistivity and video
counters.
The stars of the show were sonar and
video applications. There were two stars
of the show for considering application in
the UK. These were video applications
and the Didson sonar acoustic camera.
Underwater video is used extensively in
the UK to validate existing fish counters.
The range in hardware observed during
the fellowship has direct relevance to UK
use and many of the camera type,
motion detection systems and lighting
arrangements have been adopted here.
The chance to meet and speak with
manufacturers and software developers
has proved valuable both as it has helped
to learn from and inform the
development process we are undergoing
here, but we are also working with some
companies met during the Fellowship.
This is reported in Environment Agency
report.
The DIDSON is a new and emerging
technique. It is also a very expensive tool
to buy. So the opportunity to see it
operating at three different sites was
unique. The high numbers of fish passing
per hour, the river widths and huge
resources defined the limitations of the
system in a way that we would not have
been able to do. A full report on this is
available in Environment Agency report.
The key analysis of accounting for
downtime, counter efficiency and
species apportionment, so important to
UK fish counting is dealt with in a
subsequent report.
Personal Development
The whole Fellowship year has been such
a landmark event in my life. The trip
itself was fantastic for me personally and
enabled me to make contact with people
and see techniques that I would never
have the opportunity to do. And I have
implemented many of the techniques and
hardware tricks discovered. But beyond
that, it has given me a status within my
rather specialised job that I did not
foresee and has given me enormous
confidence. I will be eternally grateful to
all at the Winston Churchill Memorial
Trust for giving me this opportunity.