EN 17233:2021

SLOVENSKI STANDARD
01-september-2021
Kakovost vode - Navodilo za ocenjevanje učinkovitosti sistemov ribjih prehodov in
s tem povezanih metrik s telemetrijo
Water quality - Guidance for assessing the efficiency and related metrics of fish passage
solutions using telemetry
Wasserbeschaffenheit - Anleitung zur Beurteilung der Wirksamkeit und zugehöriger
Kennwerte von Fischaufstiegshilfen mittels Fernmessung
Recommandations pour l’évaluation par télémétrie de l’efficacité des dispositifs de
franchissement piscicole et d'indicateurs associés
Ta slovenski standard je istoveten z: EN 17233:2021
ICS:
13.060.99 Drugi standardi v zvezi s Other standards related to
kakovostjo vode water quality
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 17233
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2021
EUROPÄISCHE NORM
ICS 13.060.99
English Version
Water quality - Guidance for assessing the efficiency and
related metrics of fish passage solutions using telemetry
Qualité de l'eau - Recommandations pour l'évaluation Wasserbeschaffenheit - Anleitung zur Beurteilung der
par télémétrie de l'efficacité des dispositifs de Wirksamkeit und zugehöriger Kennwerte von
franchissement piscicole et d'indicateurs associés Fischaufstiegshilfen mittels Fernmessung
This European Standard was approved by CEN on 18 January 2021.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17233:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Principle and field of application . 9
5 Equipment . 10
5.1 General . 10
5.2 Calibration and system checks . 10
5.2.1 General . 10
5.2.2 Acoustic telemetry . 10
5.2.3 Radio telemetry . 10
5.2.4 PIT telemetry . 11
5.2.5 Multiple tagging scenarios . 11
6 Experimental design . 11
6.1 Pre-planning . 11
6.2 Sample size . 13
6.3 Timing and duration of investigations . 13
6.4 Baseline, control and reference investigations . 14
6.5 Receiver positions. 14
6.5.1 General . 14
6.5.2 Available fish (f ) . 16
a
6.5.3 FPS attraction efficiency (η ) . 16
a
6.5.4 FPS entrance efficiency (η ) . 17
e
6.5.5 FPS passage efficiency (η ) . 17
p
6.5.6 Overall FPS efficiency (η ) . 18
fps
6.5.7 Impediment passage efficiency (η ) . 18
ip
6.5.8 Fallback and Delay . 18
6.5.9 Further information . 18
6.6 Capture, tagging and release of fish . 19
6.6.1 General . 19
6.6.2 Source fish. 20
6.6.3 Motivation . 20
6.6.4 Capture of fish . 20
6.6.5 Handling and tagging of fish . 21
6.6.6 Release of fish . 22
6.7 Data acquisition from additional equipment . 22
7 Post processing and data analysis . 23
8 Quality control and quality assurance . 23
8.1 General . 23
8.2 Quality control . 23
8.3 Quality assurance . 23
9 Reporting . 24
9.1 General . 24
9.2 Introduction and objectives . 24
9.3 Study site. 24
9.3.1 General . 24
9.3.2 Waterbody information . 24
9.3.3 Impediment description . 24
9.3.4 FPS description . 25
9.4 Equipment and methods . 25
9.5 Results . 26
9.6 Discussion. 26
9.7 Conclusions/recommendations . 26
Annex A (informative) Suitability and limitations of telemetry methods . 27
Annex B (informative) Complementary data provided by mobile tracking . 31
Annex C (informative) Estimates of sample size . 32
Annex D (informative) Examples of receiver positions in telemetry studies . 36
Bibliography . 45
European foreword
This document (EN 17233:2021) has been prepared by Technical Committee CEN/TC 230 “Water
analysis”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2021, and conflicting national standards shall
be withdrawn at the latest by October 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Introduction
Fish passage solutions (FPS) are measures to help fish pass a cross-river obstacle or impediment in
upstream and/or downstream directions. The ideal solution, from a global-ecological perspective,
would be to re-establish natural river connectivity by decommissioning or removing the obstacle which
would at the same time eliminate or reduce any impounded section and allow unimpeded sediment
transport. In the last two decades or so, the number of constructed upstream FPS has increased
significantly at least in some parts of the world, and the range of proposed FPS designs has also
increased. However, despite careful control of FPS design both pre-and post-construction, the
performance of FPS needs comprehensive field monitoring for the following reasons: FPS designs
globally rely on laboratory experiments that need validating in situ; the efficiency of initially well-
designed FPS may be modified by changes to the environment (e.g. discharge, river morphology) and
require improvement; and the efficiency for new target species or life stages that were not considered
during the initial design process could be necessary. In addition, whilst the design of FPS for some
species and life stages is well advanced (e.g. adult migratory salmonids), the requirements of other
species and for downstream migration are not fully understood. Only systematic, reproducible
monitoring studies assessing the performance of FPS will enable us to improve and develop current fish
pass designs.
In general terms, FPS monitoring is the activity of assessing by appropriate means the degree of success
(or failure) of fish overcoming an impediment and dealing with the conditions of an implemented FPS.
FPS monitoring can serve several purposes:
— It can help to determine the appropriateness of the chosen design of a FPS by providing data about
the effectiveness (assessment or count of the number and type of fish successfully negotiating the
FPS in relation to the fish community present) and/or the efficiency (percentage of available fish
attempting to pass an impediment(s) that find, enter and successfully negotiate, the FPS) for fish
that have to cross the impediment. As a result, a documented well-functioning solution can serve as
an example for a solution in a similar river type with a similar fish community. Any reduction in
performance should be carefully analysed, and the reasons for failures identified and addressed
through adjustments, i.e. by structural changes (e.g. modifications of the design of [different parts
of] the pass) or by operational solutions (e.g. by optimizing the attraction to the entrance, by
adapting the discharge through the pass or by adapting the operation of the turbines).
— Technical information which is indispensable for the design development or optimization of future
FPS can be gathered along with the observations of fish behaviour.
— Provided that appropriate methods are used, FPS monitoring can support informed management of
fish populations upstream or downstream of the impediment, e.g. supporting EU eel regulations,
Directive 2000/60/EC (Water Framework Directive) or direct management of freshwater fishery
resources, and the general biodiversity in the river.
FPS monitoring studies can provide several layers of information. Methods for assessing FPS
effectiveness are not covered by this document. These include; trapping, video, acoustic cameras, direct
observation/online surveillance, physiological telemetry (e.g. EMG (electromyogram), accelerometry
and heart rate), eDNA (environmental Deoxyribonucleic Acid), Catch Per Unit Effort (CPUE) and flume
studies (see [10] and [11] for further information about these methods). These methods do not provide
information on the numbers of fish approaching the impediment that are available to pass, therefore
the failure rate cannot be assessed.
If efficiency needs to be addressed, measures of the proportion of fishes passing successfully, relative to
those attempting, is crucial, together with evidence concerning passage-related delay, mortality or
other health impacts [2]. For this purpose, telemetry (acoustic, radio and Passive Integrated
Transponder [PIT] tagging) techniques that enable estimation of a percentage of fish that passed the
impediment in relation to the number of fish approaching the impediment to pass, have major
advantages over other methods. Acoustic and radio telemetry methods are typically applied in medium
to large sized river systems. For smaller sized rivers with lower depths PIT telemetry is often a more
suitable approach. Telemetry methods can be costly procedures for fish-pass monitoring and are
inherently associated with implantation, surgery and therefore animal welfare and always require an
animal testing approval. Some aspects of efficiency (FPS passage efficiency) can be also gathered by
other methods (capture–mark-recapture [CMR], traps in combination with electric-fishing) in certain
situations, mainly in smaller rivers. However, these other methods are not covered in this document.
It should be noted that telemetry methods used in isolation usually look only at a single species and/or
fish of a limited size range (e.g. adults, sub-adults) and are therefore unsuitable to judge the overall FPS
performance for the whole fish community and age classes present. In addition, other highly relevant
aspects of fish passage related to FPS performance (number of species, size classes etc.) cannot be
assessed by telemetry methods and can be much better assessed by using other methods in
combination. A fully comprehensive monitoring programme should ideally target the whole range of
species and fish sizes present, therefore requiring a multi-method approach.
Telemetry techniques involve the tagging of individual fish and subsequent tracking of these individuals
as they approach an impediment and either pass or fail to pass. The proportion of fish that successfully
negotiate the FPS can be calculated and further information about the point of failure derived from the
tracking information e.g. a high attraction efficiency but low passage efficiency can highlight possible
problems concerning the hydraulic conditions within the FPS. This detailed information has the
potential to be used to improve current fish pass designs if enough comparable monitoring information
can be collected to allow detailed assessments of the performance of fish passes for different species or
of different fish pass designs. Currently, however, due to non-standardized monitoring methods,
definitions and protocols, data from fish pass efficiency monitoring studies using telemetry across
Europe are not directly comparable.
This document on assessing the efficiency and related metrics of FPS deals exclusively with telemetry as
an agreed method for the judgement of the efficiency (attraction efficiency, entrance efficiency, passage
efficiency, and overall FPS efficiency) of a FPS to achieve highly standardized and comparable results
for selected species and age classes.
1 Scope
This document specifies standardized methods for assessing the efficiency and related metrics of fish
passage solutions using telemetry techniques that allow individual fish approaching an impediment to
be monitored.
It covers studies using fish that have been electronically tagged with acoustic, passive integrated
transponder or radio tags in order to provide a variety of defined passage efficiency metrics and
includes both upstream and downstream passage of fish.
It provides recommendations and requirements for equipment, study design, data analysis and
reporting. Selected literature with references in support of this document is given in the Bibliography.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
NOTE 1 Not all definitions listed below are necessarily applicable to all studies. Only those which are relevant
to the aims and objectives of the study in question are required.
NOTE 2 This document defines efficiency metrics in the following terms.
3.1
fish passage solution
FPS
any device, structure or mechanism which is designed or managed to facilitate the safe movement of
fish in an upstream and/or downstream direction when overcoming one or several impediments
3.2
FPS performance
overall capability of the FPS to meet its design objective
Note 1 to entry: The design objective will include objectives related to the target fish community, target species,
attraction and passage efficiencies and effectiveness.
3.3
available fish
f
a
number of tagged fish approaching the impediment
Note 1 to entry: The point at which fish are considered to be approaching the impediment will be site specific.
Once past this point, fish are assumed to be motivated to pass.
3.4
overall FPS efficiency
η
fps
percentage of available fish attempting to pass an impediment(s) that find, enter and successfully
negotiate, the FPS
Note 1 to entry: Encompasses attraction, entrance and passage efficiencies.
3.5
FPS attraction efficiency
η
a
percentage of available fish that are attracted to the FPS entrance
3.6
FPS entrance efficiency
η
e
percentage of fish attracted to the FPS entrance that subsequently enter
3.7
FPS passage efficiency
η
p
percentage of fish entering the FPS that successfully negotiate and exit the FPS
3.8
overall FPS passage time
time from first approach of fish to an impediment to exit from the FPS
3.9
FPS attraction time
time from first approach of fish to an impediment to arrival at the entrance area of the FPS
3.10
FPS entrance time
time from first arrival of fish at the FPS until first entrance
3.11
FPS passage time
time from first entrance of fish to FPS until exit
3.12
FPS effectiveness
assessment or count of the number and type of fish successfully negotiating the FPS in relation to the
fish community present
3.13
number of attempts
count of the number of times each tagged fish entered the FPS until successful negotiation and exit from
the FPS
3.14
fall-back
percentage of fish that move back downstream/upstream after ascending/descending an impediment
(whether by FPS or other route)
3.15
impediment passage efficiency
η
ip
proportion of fish attempting to pass an impediment that successfully negotiate it, by any route
3.16
overall impediment passage time
time from fish first approach to an impediment to successful passage, by any route
3.17
telemetry
use of electronic tags such as radio and acoustic transmitters, data storage tags, pop-up satellite
archival tags and PIT-tags to obtain information on free-ranging fish
4 Principle and field of application
Impediments to fish migration and associated FPS occur in freshwater and transitional water bodies
within a wide range of habitat types ranging from shallow headwaters to deep, wide lowland rivers;
busy urban environments to remote rural locations. The telemetry techniques covered by this
document enable monitoring in all of these, although no single method can be used across the whole
range of water body types.
Fish passage efficiency encompasses attraction, entrance into, and successful passage through, the FPS.
In order to evaluate the efficiency of FPS, it is necessary to be able to identify individual fish
approaching the impediment that are available to pass so that the success or failure of each fish is
known. Individual detection is best provided by telemetry.
Telemetric methods for assessing the efficiency of FPS that are covered by this document are:
— acoustic telemetry;
— radio telemetry;
— Combined Acoustic Radio Transmitters (CART);
— PIT telemetry;
— permutations of the above.
The suitability and limitations of these methods are summarized in Annex A.
Each of these techniques involves the electronic tagging of individual fish and positioning of receiver
units to track individual fish as they approach and pass (or fail to pass) an impediment. The positioning
of receiver units as described in this document allows relevant aspects of FPS efficiency (attraction,
passage, overall) to be assessed, depending on the specific aims and objectives of the study.
Guidance is provided on the selection of appropriate monitoring equipment, the experimental design of
FPS monitoring studies and data collection (see Clause 6), data processing procedures (see Clause 7),
quality control and assurance (see Clause 8), and presenting the results in a standard reporting format
(see Clause 9) to provide essential fish passage efficiency and delay metrics.
5 Equipment
5.1 General
In order to provide near-continuous detection performance and precise detection times, telemetric
determination of FPS performance will involve the use of automated receiver systems and
antenna/hydrophone arrays. The choice of telemetry method and associated equipment is based on
many factors, including study objectives, environmental factors such as channel depth and width, target
fish species and size and sample size. Annex A (Table A.1) summarizes the suitability and limitations of
the different telemetry methods for assessing the efficiency of fish passes.
5.2 Calibration and system checks
5.2.1 General
Thorough calibration and tuning of the receiving equipment is crucial to ensure the collection of good
quality, accurate data. It is essential that the detection range of the receiving equipment is fully mapped
and understood. Regular system checks shall be performed to take into account changing conditions
that can modify receiver detection ranges; for example temperature, entrained air and electromagnetic
fields. Data on tag failure rates should be obtained from the manufacturer or, better, tested for a subset
under experimental conditions; this enables one variable for tag loss during tracking to be quantified.
Similarly, careful quality controls need to be placed upon false positive records of tags, which can occur
due to signal processing errors and tag identification (ID) code collisions.
Tagged fish should be scanned prior to release to confirm that the tags are functioning; this is true for
all telemetry tag types. The likely effects of tag ID code collisions, or cycle period between reception
frequencies (used in some radio applications) relative to antenna range, on tag detection probability
shall be considered and incorporated into experimental design. The percentage period during the study
for which the remote array was functioning effectively shall be recorded; this is particularly important
for PIT stations since tag range is low, and in all but small streams, manual tracking to determine the
fate of PIT tagged fish is difficult (cf. radio, acoustic with battery-powered transmitters).
5.2.2 Acoustic telemetry
A detailed detection efficiency test shall be performed at the beginning of the study with test tag(s) of
the power output to be used and repeated where possible during the study. Detection ratios of test tags
within the hydrophone array should be recorded. Actual detection efficiency of tagged fish should be
back-calculated from known routes and reported. “Tag drags” (moving a tag within the array) should be
conducted to test the tracking capability of the system.
Reference acoustic-transmitters should be placed at several depths in known locations under typical
experimental conditions and the accuracy and precision of reported transmitter positions calculated. It
is a good idea to retain one or more reference transmitters (‘sentinel’ tags) for the duration of the study.
The detection range of each hydrophone should be determined under the range of experimental
conditions likely to be experienced.
5.2.3 Radio telemetry
A detailed signal strength map around antennas should be generated at the beginning of the study for
the tags to be used. Logger data should be analysed and signal strengths from several loggers (if
present) used to create a signal strength map that enables the position of the fish to be pinpointed. The
same approach should be used where one receiver is multiplexing multiple antennas.
Detection ratios of test tags within the antenna fields should be recorded. Actual detection efficiency of
tagged fish should be back-calculated from known routes and reported.
Radio-transmitters should be placed at several depths in known locations during known periods of time
and the accuracy and precision of reported transmitter positions calculated.
Reference transmitters can be used to compensate for variations in disturbance and the resulting signal
strength recorded. It is a good idea to retain one or more reference transmitters (‘sentinel’ tags) for the
duration of the study.
5.2.4 PIT telemetry
Because of the small range of PIT antennas, thorough testing with tags of the size and type to be used is
vital. Range and detection efficiency tests should be conducted over the possible extent of experimental
conditions for all tag orientations and for multiple as well as single tags (tag proximity can block
detection of other tags). This should include testing of tags passed at the same speed for which fish
passage through the detection field may be expected.
Regular tests of antenna efficiency should be carried out by manual checks or by automated sentinel
(check) tags and recorded. Actual detection of tagged fish should be back-calculated from known routes
and reported.
5.2.5 Multiple tagging scenarios
To overcome limitations of individual telemetry methods fish could be tagged with multiple tags,
provided fish welfare is not compromised. For example, both acoustic and PIT tags could be used for
fish moving through a wide and deep river and a narrow and shallow FPS. Acoustic telemetry will
enable fish approach to the obstruction be tracked, while PIT telemetry will enable movements inside
the pass to be studied.
6 Experimental design
6.1 Pre-planning
The following points shall be considered prior to conducting a study:
— Aims and objectives shall be clearly defined, as these will determine the study design. These could
be partially pre-determined by a request to monitor a particular location, species, age/size class or
catchment.
— Potential collaborative partners should be identified at an early stage in the planning process in
order to maximize the value and outcomes of the study.
— The study site may be predetermined at the outset of the study. If not, then the most strategic or
important site shall be identified.
— Site logistics. The operational and physical aspects and limitations of the site shall be identified.
This should include:
— safety of operators and equipment;
— potential for vandalism;
— impacts of flooding;
— availability of a power supply;
— access conditions;
— predator numbers/density;
— local sources of noise or other potential interference.
— The discharge variability of the study site shall be assessed in advance to ensure that the study
objectives are achievable and that the target metrics can be measured across the range of interest.
— The range of environmental conditions over which the efficiency of the FPS will be assessed e.g.
discharge, temperature, shall be selected.
— Ownership of the site shall be determined and the relevant access permissions obtained.
— Approvals and permits. Relevant approvals and permits for the work shall be obtained from the
appropriate authorities, including the approvals for animal experiments required to undertake fish
tagging (see 6.6.5).
— The time and spatial scales of the study shall be determined e.g. single year/many years; single
site/whole catchment.
— Potential target species. Information on potential target species shall be assessed and, if
information is lacking or scarce, efforts shall be made to improve knowledge through active
sampling and/or local experience.
— Selected target species. The target species and life stage shall be selected based on the aims and
objectives of the study. The following factors shall be considered:
— Whether the chosen species are representative of the entire fish community/assemblage.
— Behaviour and seasonality of migratory behaviour of the investigated age class.
— Sample size. Whether a sufficient number of fish of the species in question can be caught (without
causing injury or affecting behaviour) to provide a statistically robust sample size (see 6.2 and
Annex C), including sub-samples sufficient to perform quantitative analyses of size-classes, gender
effects, effects of fish origin, or other sub-sampling groups relevant for the study objectives.
Collaboration with partners in possession of local knowledge may be important to achieve this.
Sample size also refers to animal welfare issues and the three ‘R’s (see 6.6.5).
— Whether a proxy species (i.e. taxonomically related species) could be used if insufficient numbers
of target species are available. It shall be noted that this approach require considerable species
insights to draw robust comparative conclusions.
— Tagging method. Methods appropriate to the site (e.g. river width and depth), target species, life
stage and objectives of the study shall be selected. Consideration should be given to the available
budget and the limitations of each method (see Annex A).
— Pilot study. It may be necessary to carry out a pilot study before the full scale study to test the
feasibility of the study design and methods. Further, whenever possible, post-tagging mortality and
tag-retention shall also be evaluated.
— Control and baseline investigations. A control, baseline or reference investigation may be
appropriate depending on the aims and objectives of the study. All existing baseline or control
information shall be reviewed.
— Statistical analyses shall be planned prior the study taking place, with appropriate input.
6.2 Sample size
Sample size is important and shall be considered at the pre-planning stage. Non-statistical
considerations shall be taken into account. These include:
— availability of fish for capture. If the sample size is too small it is better actually not to do the study
if nothing of value will come out of it;
— conservation status of the target species;
— time available;
— application of the 3 ‘R’s — especially ‘Reduce’ — in the context of animal welfare legislation (see
6.6.5).
Statistical considerations depend on the study aims, objectives and design and include:
— whether the proposed study is explorative, descriptive or comparative;
— the required precision or statistical power of the result;
— likely variability in the data;
— how many tagged fish are likely to be lost, either through poaching, legal fishing gear, predation,
natural mortality, encounters with deadly/injurious mechanical events or by leaving the study area.
The appropriate sample size shall be calculated taking all of these factors into account. Descriptive
studies may often lead to comparative studies. The sample size estimation shall also take this into
account and be sufficiently large for analysis of future questions, however the principles of the 3 ‘R’s
(see 6.6.5) shall be considered throughout. The final sample size shall be a careful balance between
statistical power and animal welfare considerations.
Approaches to sample size estimation are provided in Annex C.
6.3 Timing and duration of investigations
Timing should cover the active periods of movement of the targeted species based on available regional
species knowledge and local knowledge on migrations and movements.
Ideally investigations should cover the entire migratory/movement cycle of the targeted species,
including early, mid- and late runners, where possible.
Timing shall provide representative information on the daily cycle of activity.
Depending on the aims of the study, the fish capture and release programmes should not be a single
event, because key points may be missed (e.g. related to flow, water temperature) if the study is based
on a single release. Instead there should be multiple releases throughout the seasons and the effect of
seasonal timing should be factored in as part of the study design.
Investigations should, if possible, cover representative annual and inter-annual variations in water
discharges, temperatures and other relevant parameters affecting migrations, movements and FPS
efficiency.
Emphasis shall be placed on developing robust study designs that minimize duration of animal handling
to meet animal welfare considerations.
6.4 Baseline, control and reference investigations
A hierarchical approach should be adopted to source data for FPS efficiency comparisons:
1) A baseline study at the treatment site should be conducted before a FPS is constructed or altered to
establish the status quo before any changes are made. Post construction or post-change efficiency
estimates can then be compared to the pre-construction information.
2) A control study is where two groups are used for comparison purposes. One group is exposed to the
experimental ‘treatment’ e.g. presented with the FPS, while the control group is not exposed to the
treatment e.g. passage through an unimpeded reach in the same waterbody. Ideally, FPS efficiency
and overall impediment passage time should be compared with the percentage and time of
motivated fish that successfully negotiate the unobstructed reach. The results from the two groups
are compared to determine the effect of the treatment, based on the selected species and sample
size. Care shall be taken to select fish that are equally motivated and to select an adequate control
reach, as fish from the same species at the same time of year may behave differently if captured in
different locations within the same river network.
3) In extreme cases, a nearby catchment with similar habitat may be used - termed a reference site.
Consider using a Before-After, Control-Impact (BACI) sampling design if possible and appropriate,
which incorporates both baseline and control studies into the experimental design.
It is important to distinguish the behaviour of tagged, living fish from the patterns of movement of
drifting dead fish. Corpses of dead fish should therefore be marked and released at the study site as
control samples to identify the scale of passive drift. Tagged fish, which perish whilst passing a FPS, may
not necessarily become stationary. Dead fish may drift several kilometres upstream (due to vortices,
tide, predation, etc.) and downstream, potentially influencing the size of the study area. Consequently it
is important to ensure tagged living fish which are moving in a quite passive way with the flow are not
confused with drifting dead fish, which shall not be considered in efficiency calculations.
6.5 Receiver positions
6.5.1 General
It is important to determine the aims of the study and, if using a fixed telemetry array, ensure that the
receiver/antenna positions are based on meeting these aims. The following scenario illustrates what
can be done under basic conditions for upstream and downstream movement studies, but the set-up
should be modified to take into consideration different fish passage routes e.g. sluice gates or scenarios
where the tail race outflow is some distance downstream of the dam, turbines, bypass, navigation lock
and spillway. Attraction, entrance and passage efficiencies may need to be calculated for each route.
Examples of more complex receiver positions are presented in Annex D.
Table 1 — Purpose and location of receiver/antenna equipment required to assess FPS
efficiency metrics. Numbers correspond to receiver positions in Figure 1 schematic
Receiver location and purpose
1 2 3 4 5 6
Information
Fish Fish Approach Entry to FPS exit Fish beyond

required
moving moving in to FPS FPS influence of
away from direction impediment
FPS of FPS
Available fish D R
FPS attraction
D R R
efficiency
FPS entrance efficiency R R
Passage efficiency R R D
Overall FPS efficiency D R R D
R — Required for metric calculation
D — Desirable for data interpretation
a) Upstream
b) Downstream
Key
A release site
B impediment
FPS fish passage solution
1 to 6 location of receiver equipment
NOTE The numbers correspond to the receiver positions in Table 1. The shaded areas represent the detection
area for each receiver. Flow is left to right.
Figure 1 — Schematic showing location of receiver equipment for upstream and downstream
FPS efficiency estimates at an idealised simple site
6.5.2 Available fish (f )
a
For upstream studies, position receiver/antenna equipment downstream of the impediment to assess
the number of fish available to pass (Table 1 and Figure 1). For downstream studies, the receiving
equipment shall be upstream of the impediment. Available fish corresponds to the number of tagged
fish detected at receiver 2. Once fish are detected here they are assumed to be motivated to pass
(see 6.6.3).
6.5.3 FPS attraction efficiency (η )
a
For upstream studies, position receiver/antenna equipment within the detectable range of the FPS
entrance and downstream of the impediment to identify the number of available fish and the number
attracted to the FPS entrance (Receiver 3 in Table 1 and Figure 1). The distance between the two and
the number of receivers/antennas used depend on the size of waterbody and the aims of the study. For
downstream studies, the receiving equipmen
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