Fisheries survey report of the
Soham Lode
Cambridgeshire and Bedfordshire – Fisheries Monitoring Programme
2014
Summary
The 2014 survey cycle recorded several specimen sized chub and some strong, if localised, roach
populations. The increase in roach, when compared to the previous survey in 1997, has resulted in a
significant increase in both stock density and biomass and perhaps unsurprisingly catches were linked to
areas of channel which offered suitable habitat and provided the most cover and protection from
predators.
Seventeen species plus one hybrid were recorded over the 2 sites surveyed, including bitterling a non
native species. Species caught included:
Bitterling [Rhodeus sericeus]
Bleak [Alburnus alburnus]
Bullhead [Cottus gobio]
Chub [Leuciscus cephalus]
Common bream [Abramis brama]
Dace [Leuciscus leuciscus]
European eels [Anguilla anguilla]
Gudgeon [Gobio gobio]
Perch [Perca fluviatilis]
Pike [Esox lucius]
Roach [Rutilus rutilus]
Rudd [Scardinius erythrophthalmus]
Ruffe [Gymnocephalus cernuus]
Silver bream [Abramis bjoerkna]
Spined loach [Cobitis taenia]
Stone loach [Barbatula barbatula]
Tench [Tinca tinca]
Ro x Cb hybrid [Rutilus rutilus x Abramis brama]
Density and standing crop pie charts with percentage values and colour key:
Species density composition (>99mm)
Species standing crop composition (>99mm)
Density and standing crop of individual fish species are calculated using the number / weight of fish in
each site and then a mean (average) calculated for the reach, in this case five sites. Density is reported
as the number of individuals of that particular species that might be found in 100m2 of the river.
Similarly, standing crop is the weight, or grams, of that fish species that might be found in the same
area.
The average density (number of fish in a given area) of all species >99mm over the two sites increased
from 11.96 Ind./100m2 in 1997 to 27.90 ind./100m² in 2014.
Total average standing crop (weight of fish in a given area) of all species >99mm also increased from
973.4 g/100m2 in 1997 to 1597.0 g/100m² in 2014.
Site locations
Introduction to Environment Agency fisheries surveys
The Environment Agency has a statutory duty to maintain, improve and develop fisheries. Our policy is
to do this in a way that maximises the social, recreational and economic benefits arising from the
sustainable exploitation of the fish stocks that underpin fisheries. To help deliver this duty, we have a
National Fisheries Monitoring Programme (NFMP) to describe the status of our fish populations and
inform our fisheries management to meet international (WFD, Eel regulations, ICES reporting), national
and local data needs.
Sites are regularly reviewed to maintain a representative sample of fish populations and the water body
as a whole in order to retain a comparable dataset. Sites designated for the national fisheries
monitoring programme cannot be altered, unless there is a valid health and safety concern or there has
been a review of policy during the monitoring period.
Survey methodology
The sites were sampled using electric fishing methodology, which uses the physiological effect of an electric
field in water to attract and immobilise fish. Electrodes, immersed in the water, stimulate a fishes nervous
system so that it swims towards the operator, or is unable to swim away, and can be caught. Image 1 shows
the typical components of an electric fishing system.
Image 1
In shallow streams it is generally possible to wade upstream within the channel using generator powered
equipment towed within a small boat. When rivers deepen or site depth is variable, electric fishing from a
boat using generator powered equipment is often the preferred method. The boat is manoeuvred
downstream via an electric or petrol outboard engine or on ropes by an operative on either bank
controlling the speed, direction and channel positioning.
Stop nets are positioned across the channel isolating the survey site preventing fish from migrating into and
out of the survey area. The electric fishing operation is repeated until a 50% reduction in the total number
of fish caught has been achieved.
Fish are measured to the nearest millimetre and scales taken for age, growth and other statistical
analyses at the National Fish Laboratory in Brampton. Results are reported utilising fish greater than
99mm as this method has been shown to be inefficient below 99mm.
Current survey data
Total number and largest (mm) fish captured during the 2014 survey cycle for key species.
Site Name
Soham Cotes
Barway
Roach
No.
Largest
550
14
591
2
Perch
No.
Largest
84
183
32
175
Chub
No.
Largest
14
503
2
181
Rudd
No.
Largest
5
229
Pike
No.
Largest
7
584
8
653
Roach were the most common fish over the two sites, with a maximum density estimate of 23.14
individuals for every 100m2 of river surveyed, equivalent to a 83% share of the total population.
Gudgeon were subdominant with 6%, followed by perch contributing 4% to the overall population.
Mean density of fish (>99mm) from Soham Lode 2014
Roach are also the dominant species’ by weight with a mean standing crop estimate of 766.9g for every
100m2 of the river or 48% share of the overall biomass. Pike were subdominant with 348.1g/100m2,
followed by chub with a standing crop estimate of 288.8g/100m2.
Mean standing crop of fish (>99mm) from Soham Lode 2014
Historic survey data
Historic density data is available for the key angling species between 1987 and 2014. Fish populations
were seemingly at their strongest during the initial 1987 survey with a combined density estimate of
71.81 ind./100m². However, this data should be viewed with caution as the survey occurred during late
October and may have coincided with a large winter aggregation, as the bulk of these fish were caught
from a single site.
Historic density of fish (>99mm) from Soham Lode 1987 – 2014
The subsequent survey in 1990 recorded a significant decline in fish density (97%) with this result
primarily attributed to a reduction in the number of roach. The corresponding fisheries report seems to
suggest that two consecutive droughts had resulted in poor water quality within the channel, with
insufficient flows to dilute sewage treatment work effluent resulting in noticeably high ammonia
readings.
The 1990 fisheries report concluded:
During the drought conditions of the previous two years, flows from the River Snail have been reduced
and in the late summer of 1990 the source springs dried up completely. This effectively meant there was
no dilution of water coming down the No. 1 Public Drain. Therefore any deleterious discharge incidents
did not receive any immediately dilution from the River Snail and could therefore have a potentially
harmful effect for a greater distance downstream. In the week preceding the fishery surveys of Soham
Cotes and Barway on the Lode, a total ammonia level of 5.157 mg/l was recorded at Barway compared
with values of close to 0.1 mg/l in the two preceding months. Although this would not be directly toxic
to fish, it is likely that cyprinids such as roach may have avoided such water and this could account for
their absence at the Barway site. The poor fish population recorded in 1990 was a result of fish becoming
displaced to the adjacent River Great Ouse whereby avoiding the poor quality water. Evidence to
support the theory of avoidance of poor water quality in 1990 is backed up by the stocking of over 1200
roach at Barway in early September 1990 of which none were recorded in the survey a couple of weeks
later.
Site level survey data
Site: Soham Cotes
Survey Date: 20/05/2014
Species density composition (>99mm)
Roach were the most abundant species present
at Soham Cotes during 2014 recording a density
estimate of 25.93 individuals for every 100m²,
equivalent to 79% of the overall catch. In total
550 roach were caught with the largest fish
captured measuring 193mm in length. Gudgeon
were subdominant with 10%, followed by perch
with 6%.
Historic species density data (>99mm)
Site: Barway
Survey Date: 22/05/2014
Species density composition (>99mm)
Despite recording seventeen species of fish in
2014, the bulk of the catch at Barway comprised
of roach (88%) with a similar sized catch to that
recorded at Soham Cotes. Numerically speaking,
perch were subdominant with 32 followed by
bleak and silver bream with 9 individuals each.
Historic species density data (>99mm)
Supporting evidence
Following several high profile fish mortalities associated with pumping stations across Anglian Region, a
joint investigation was carried out between the Environment Agency and Hull International Fisheries
Institute (HIFI) to ascertain a semi quantitative estimate as to the number of fish utilising pump
chambers as refuge and to gauge the behavioural pattern once the pumps have been initiated.
Fish are naturally attracted to these manmade structures as the large pump chambers offer fish, notably
silver fish, an area of refuge from predators. In some circumstances these structures are the only habitat
suitable for fish populations to utilise, however there is the risk that fish become entrained within the
pumps’ machinery once water transfers begin, which may result in serious damage or mortality.
At the confluence of Soham Lode and the River Great Ouse is Soham Lode Pumping Station. This
structure prevents excess water from entering the lode from the adjacent River Great Ouse during
periods of high flow, whilst also maintaining water levels within the lode for operational requirements.
Following a successful investigation at Bottisham Lode Pumping Station in 2012, it was decided to repeat
the process in early 2013 at Soham Lode Pumping Station. Two weeks prior to a planned seine netting
operation, Fisheries, Biodiversity & Geomorphology team and HIFI installed DIDSON monitoring
equipment.
DIDSON (Dual Frequency Identification Sonar) is an underwater acoustic camera system which transmits
pulsed sound waves and converts the returning echoes into near video quality images. This equipment is
often utilised for observing fish behaviour in natural environments and around manmade structures,
identifying fish species, sizing fish and calculating numbers present.
The survey involved two seine netting operations, the first during daylight hours to isolate the fish
within the pump chambers and remove any fish from within a 100m survey area and the second at night
once the fish had vacated the pumping station.
Once processed, all of the fish caught during the daylight netting were released upstream of the top
stop net to prevent them from re-entering the survey area and influencing the night netting survey
results. The catch was dominated by roach, with both perch and pike sub-dominant. The results of this
investigative survey are displayed below:
Species
Roach
Perch
Pike
Bitterling
Rudd
Common bream
Ruffe
Silver bream
Dace
Bullhead
Chub
Total
No. Caught
651
9
9
4
3
1
1
1
1
1
1
682
Density (All Fish)
81.38
1.13
1.13
0.50
0.38
0.13
0.13
0.13
0.13
0.13
0.13
85.25
Density (>99mm)
0.50
0.38
1.13
2.00
Approximately 2 hours after darkness, the fish within the pump chambers emerged (evident via the
DIDSON monitoring equipment) and a seine net was wrapped around these fish preventing any from reentering the pumping station. As with the previous daylight survey, the catch was primarily dominated
by roach, with perch subdominant followed by common bream. The results of this investigative survey
are displayed in below:
Species
Roach
Perch
Common bream
Bitterling
Ruffe
Gudgeon
Pike
Rudd
Silver bream
Dace
3-spined stickleback
Bleak
Total
No. Caught
16964
128
7
5
5
5
4
3
2
1
1
1
17126
Density (All Fish)
2120.50
16.00
0.88
0.63
0.63
0.63
0.50
0.38
0.25
0.13
0.13
0.13
2140.75
Density (>99mm)
696.13
9.75
0.25
0.13
0.50
0.13
706.88
The fisheries data obtained through this investigation have highlighted the importance of pumping
stations as a place of refuge when habitat is limited and the significance of correct protocols and the
implementation of fish deterrents prior to the operation of pumps in order to prevent significant fish
mortalities.
Night netting operation
Additional information
If any angling matches are held throughout this river length then angling clubs are encouraged to
provide match results to feed into the Environment Agencies Match Catch Database which analyses
angler catches to assess fishery performance. The output of this database can also be used as
supporting evidence to assist analysis of routine survey results. Match return cards and more
information on the Match Catch Database can be obtained from Fisheries Analysis and Reporting Officer
Chris Middleton [email protected]
Before you go fishing don’t forget:
 You must have a validEnvironment Agency rod licence and permission from the fishery owner;
 You must comply with thefisheries byelaws;
 The coarse fish close season (15th March to 15th June inclusive) applies to all rivers, streams and
drains in England and Wales but not most stillwaters. Stillwater fishery owners can still have their
own close season and rules, so please check with them before setting out.
Report illegal fishing:
If you see any fishing, netting or trapping you think may be illegal, please do not tackle it yourself. Call
us immediately on 0800 80 70 60 and tell us:
 Exactly where the alleged offence is taking place;
 What is happening;
 How many people are involved and their descriptions;
 The registration numbers of any vehicles involved.
If you prefer to remain report an environmental crime anonymously call Crimestoppers on 0800 555
111 or https://crimestoppers-uk.org/give-information/give-information-online/.
Next survey
Spring 2020.