Technical, Logistical, and Economic Considerations for the Development and Implementation of a Scottish Salmon Counter Network: Scottish Marine and Freshwater Science Vol 7 No 2

Executive Summary

Chapter 1 - Introduction

Atlantic salmon ( Salmo salar) are culturally and economically important to Scotland. Salmon are now the target of large conservation actions due to growing concerns about their population status and the potential impacts of human activities on their productivity. To adequately assess the current and future status of salmon populations, accurate estimates of their population sizes are needed. In Scotland, electronic fish counter technology has been the cornerstone methodology used to accurately assess salmon population sizes. Marine Scotland Science ( MSS) seeks to expand the current counter distribution to include new counter sites throughout Scotland. An expanded network will provide valuable information for salmon fisheries management, sustainable marine planning, the development of renewable energy, and the growth of aquaculture.

Planning and implementing a counter network requires knowledge of the technical constraints, engineering requirements, operational protocols and economic costs. This report was commissioned by MSS to address a knowledge gap in the technical, logistical and economic understanding in the development of a Scottish salmon counter network. The overall objective of this report was to inform the future development of a fish counter network for Scotland. Specific objectives of this report were:

1. Technical Constraints and Installation Costs. Assess the technical benefits and limitations, and economic costs of deploying different counter technologies in different environmental settings, including a consideration of engineering requirements.

2. Automating Counts and Quality Control. Assess the opportunities for automating signal processing and quality control associated with different counter technologies, considering existing processes and protocols where these can be identified.

3. Operational Costs. Determine the costs of maintaining and validating the various counter options in the range of environmental contexts explored, including the costs of data processing and validation.

4. Integration of Technological and Economic Considerations to Determine Choice of Counter Technology. Combine data collated from Objectives 1-3 to produce an economic and technical optimization model to inform the choice of counter options in particular environments.

The report meets these objectives in seven detailed chapters. Chapter 1 provides a review of the limitations and benefits of fish counter technologies. Chapter 2 discusses installation and operation considerations (Obj. 1). Chapter 3 explores software for automating counts and quality control of data (Obj. 2). This chapter evaluates the cost and effectiveness of Echoview software for semi-automating counts using mulitbeam sonar technology among other proprietary counter software, new methods for data management (FishCounter R package), and explores species identification models for estimating ratios of species passing through a counter using length data. Chapter 4 reviews the operational costs and validation (Obj. 3). This chapter provides a general review of operational considerations common to all counters, and then reviews typical counter setups for a range of technologies. The second part of this chapter focuses on exploring validation effort to determine how much validation is necessary to achieve management objectives.

Chapter 5 (Obj. 4) presents a decision and cost model that incorporates all of the information from Chapters 2-4 to determine the feasibility and cost of over 180 counter setups given the characteristics of a potential counter site. The decision model is the main deliverable of the project and is a priority for MSS. Case studies of Scottish rivers are presented to illustrate how the model would prioritize different counter options. Chapters 6 and 7 focus on additional considerations for a counter network. Chapter 6 discusses examples and ideas about combining other technologies such as telemetry and genetics with fish counters to increase the value and diversity of data. Chapter 7 presents a novel approach to evaluating the spatial coverage of a counter network that will provide an additional metric for comparing different counter network designs (Chapter 6).

Chapter 2 - Technical Considerations and Capital Costs

The aim of Chapter 2 is to provide information on the basic function of each counter technology and discuss the performance of counters across various operational sites. A literature review and the experience of InStream Fisheries Research Inc. ( IFR) staff has determined that counter performance varies across sites and is primarily due to differences in their technical limitations and benefits. This chapter reviews all technical considerations, capital costs and the various manufacturers of the major types of counter technology:

• Hydroacoustic counters
• Resistivity counters
• Optical beam counters
• Video

Hydroacoustic Counters

Hydroacoustic counters use sound wave technology to emit pulses of sound into the water and listen for the returning echo. The counter then converts the returning echo to image data. Here we provide an overview of the two major types of hydroacoustic counters: multibeam and splitbeam.

Multibeam Counters

Multibeam counters function by emitting numerous small acoustic beams at a fixed frequency and convert the returning echoes into a high quality video-like image. The videos can be analyzed using proprietary or third-party software. Several different manufacturers produce multibeam counters (Teledyne BlueView and Sound Metrics), with Sound Metric's DIDSON being considered the industry standard, although other manufactures are producing new cost-effective models such as the Teledyne BlueView M900 Series.

Advantages of multibeam counters include:

1. Ease of use (plug and play)
2. High quality data
3. Flexibility in software used for analysis (proprietary and third-party)
4. Low engineering or structural requirements for deployment
5. Low maintenance
6. Operability in high turbidity and low conductivity environments

Limitations of multibeam counters include:

1. High initial cost of equipment
2. Requires operation of personal computer to log and store data
3. High power requirements
4. Post-processing of data is time intensive
5. Validation of counter is not possible under high turbidity conditions
6. Requires personnel on site to manage data daily
7. Specific river profile and bed material required

Splitbeam Counters

Splitbeam echosounders transmit a short sound pulse and listen for the returning echo. The echosounder then magnifies and filters the returning echoes to produce an image echogram; this is the main difference from multibeam counters. The image echogram are then analyzed for further information. Several manufacturers produce splitbeam counters: Simrad, HTI, and BioSonics. We focus on BioSonics DT-X echosounder in our review.

Advantages of splitbeam counters include:

1. Ease of use (plug and play)
2. Automatic counting and data storage capabilities
3. Potential for remote operation
4. Low engineering and structural requirements for deployment
5. Low maintenance
6. Can operate in high turbidity and low conductivity environments

Limitations of splitbeam counters include:

1. High initial cost of equipment
2. Requires operation of personal computer to log and store data
3. High power requirements
4. Post-processing of data is time intensive
5. Validation of counter is not possible under high turbidity conditions
6. Requires personnel on site to manage data daily or purchase of costly remote operating equipment
7. Specific river profile and bed material necessary

Resistivity Counters

Resistivity counters function with the aid of an electrode sensor unit to measures the bulk resistance of the water between pairs of electrodes. When a fish (more conductive than the water displaced) passes over a pair of electrodes, the counter records the momentary reduction in resistance. As the fish moves to another pair of electrodes, the counter assigns a direction to the movement. Currently there are two manufacturers of resistivity counters: Aquantic (Logie 2100C), and EA Technologies and Scottish Southern Energy (Mark 12).

Advantages of resistivity counters include:

1. Moderate cost for counter unit
2. Automatic counting and data storage
3. Potential for real-time backup of data
4. Potential for remote downloading
5. Small file size and large storage capacity
6. Proprietary software reduces amount of time required for validation
   (for Mark 12)
7. Low power requirements
8. Low counter maintenance
9. Adaptive through the use of various types of sensor configurations to suit river conditions

Limitations of resistivity counters include:

1. Can only operate in water with conductivity > 20μS
2. Need a computer or other recording device for data backup
3. Software has limited functionality (no analysis capabilities; for Logie)
4. Operating validation equipment requires higher power demands
5. Third-party fabrication of sensor units (potential for high costs)
6. Deployable in fish pass structures only (for Mark 12)
7. High engineering costs for some sensor unit structures
8. Most practicable in small- and medium-sized rivers (bankfull width
   < 40 m)

Optical Beam Counters

Optical beam counters use vertical optical infrared beams to count fish as they pass through the counter. Vaki is the only commercial supplier of optical beam counters, and they manufacture the Riverwatcher specifically for enumerating migratory fish.

Advantages of optical beam counters include:

1. Moderate cost of counter unit (includes sensor and validation camera)
2. Automatic counting and data storage
3. Potential for data backup
4. Capable of remote downloading
5. Proprietary software is excellent (analysis capabilities)
6. Small file size and large storage capacity
7. Low power requirements
8. Low counter maintenance
9. Sensors are well designed and prefabricated by the manufacturer to fit specific site
10. Validation equipment can be added to sensor unit

Limitations of optical beam counters include:

1. Can only function in waters with low turbidity < 90 NTU
2. Sensor units are small (< 1 m) and always require additional structure in rivers
3. Most practical in small- to medium-sized rivers (bankfull width < 40 m) and fish passes
4. May require multiple units if migration rates are high

Video

Video counters function by placing cameras in fish passes or other areas. Video are then manually counted or analyzed by third-party software.

Advantages of video counters include:

1. Equipment is readily available
2. Low cost
3. Simple to operate

Limitations of video counters include:

1. Can only function in waters with low turbidity < 30 NTU
2. Images require manual processing or third party software
3. Post-processing is time consuming

Structures

Electronic counters cannot function as standalone units. Each technology requires specific structures to allow counter units to operate at their full potential. In this section, we examine structures commonly used with fish counters and discuss general capital costs. In particular, the report focused on:

• Fences
• Resistivity counter sensor structures

Fences

Fences generally include a full-span barrier across a river or fish pass, along with a trap box or passageway into which fish are directed and counted using a fish counter. Our review of counter structures showed that two types of temporary fences are commonly used: picket fences and Alaskan floating fences.

Picket Fences

Picket fences are structures of vertical pickets held together by aluminum rails, connected horizontally between metal tripods.

Advantages of picket fences include:

1. Low cost of fabrication and installation
2. Portability
3. Versatility - can be used in a variety of configurations to fit specific river needs

Limitations of picket fences include:

1. Risk of fence breach due to debris loading
2. Daily maintenance for debris removal
3. Risk of fence loss during high flow events
4. High cost of materials

Floating Fences

Alaskan floating fences use a combination of air-filled pipes held together by a metal frame to form panels. Panels, along with planar boards, are held in place on the riverbed by a wire (fixed to a mooring point on riverbed) running through cleats on the panels' upstream end. Panels float at an angle to provide a barrier for any fish moving upstream or downstream.

Advantages of floating fences include:

1. Low maintenance and installation costs
2. Semi-portable
3. Low risk of fence loss during high flow events

Limitations of floating fences include:

1. Risk of fence sinking from debris build up
2. Require mounting structure on riverbed
3. Risk of damage to PVC pickets in debris-laden events

Fence costs are integrated into the decision and cost model through functions that scale costs according to bankfull width.

Resistivity Counter Sensor Structures

Resistivity counters do not come with sensors and require an electrode sensor unit to function. Sensor units are built by third-party fabricators and are purpose-built for specific sites, thus resistivity counters are versatile in their mode of application and can adapt to a variety of structures. Four common types of structures are commonly used to mount electrode sensors: Crump weirs, flat pads, boxes and tubes. Our review outlines the advantages and disadvantages of each sensor type.

Crump Weirs

Crump weirs are full-river structures that originally measure open flow channels to predict discharge and change flow characteristics in rivers. Design of the structure modifies the behaviour of fish as they swim over the structure, forcing the fish to swim at a constant height, which is ideal for resistivity counters.

Advantages of Crump weirs include:

1. Modifies fish behaviour to swim at a constant height, reducing variation in counter measurement height
2. Typically high counter accuracy (> 90% accurate)
3. Consistent counter accuracy

Limitations of Crump weirs include:

1. High cost of installation
2. High impact to the river
3. Most practicable in small- to medium-sized rivers (bankfull width
   < 40 m)

Flat pads

Flat pads are rectangular frames placed on the riverbed. Frames are constructed out of non-conductive materials (e.g., fiberglass, plastic) and provide a mounting location for the electrodes. Pads can be used in series to provide multiple channels covering the desired wetted width of the site.

Advantages of flat pads include:

1. Low cost of fabrication and installation
2. Low impact to the river
3. Very adaptive to site-specific requirements

Limitations of flat pads include:

1. Counter accuracy decreases with depth
2. Counter accuracy can change with discharge
3. Useful for shallow sites only
4. Susceptible to loss during high flow events
5. Most practicable in small- to medium-sized rivers (bankfull width
   < 40 m)

Box and Tube Sensors

Box and tube sensors have been developed for specific applications in fish passes, and provide consistent accurate counts due to the constant conditions under which they occur.

Chapter 3 - Software: Automating Counts and Quality Control

DIDSON Software

We provide a review of the proprietary software included with the DIDSON multibeam sonar system ( DIDSON Display and Control Software [ DCS]). Literature review and personal communication with DIDSON operators identified the DCS to be both the hardware controller and data collection interface.

Limitations of DIDSON Display and Control Software include:

1. Cannot count migrating fish automatically, and as such, a large time investment is required for users to review the video data footage to enumerate fish
2. Bias may occur due to human subjectivity

Echoview Software

The Echoview third-party hydroacoustic analysis software is reviewed. Echoview's functionality, time estimation of a typical analysis, training time, software cost, and advantages and disadvantages are described. Our evaluation of Echoview was accomplished through a literature review and an analysis of DIDSON data using the software.

Our analysis found two main disadvantages of DIDSON DCS (manual analysis) in comparison to Echoview (semi-automated analysis).

1. When performing manual analysis in DCS, budgetary and time constraints often force users to increase the viewing speed of the hydroacoustic data to complete the analysis on time. This results in a reduction in the effectiveness of fish counts due to missed or misidentified fish (see Case Study 1).
2. To improve the effectiveness of fish counts when using DCS, the viewing speed of videos need to be reduced. This results in additional time and costs (see Case Study 2).

Advantages of using Echoview include:

1. Ability to semi-automate counting of fish in hydroacoustic data files
2. Integrating an objective method into analyses
3. Ability to interpret fish tracks that are impossible to detect with the naked eye (see Case Study 1)

Disadvantages of using Echoview include:

1. Initial cost is high
2. Separating fish tracks is time consuming when migration densities are high (see Case Study 2)
3. Results are dependent on the quality of the raw data used

Based on our findings, we recommend the use of Echoview when possible in the analysis of multibeam data as we show that it dramatically reduces operational costs, which far outweigh the high initial cost of the software.

Case Study 1 - Kitwanga River Steelhead Enumeration Using Low Resolution (0.7 MHz) DIDSON Data

This case study provides an in depth comparison on the effectiveness and time efficiency of analyzing low resolution DIDSON raw data (0.7 MHz) using Echoview, compared to the traditional method of manually counting fish by watching raw DIDSON video data. We compare fish length in relation to distance from the sonar head and signal strengths, as determined by both analysis methods.

Our analysis found that the fish length data from the two methods differ, resulting in misidentification of fish species using target lengths. Echoview's ability to detect fish is much greater than the human eye. Low signal strengths (due to low resolution data) translate to an inaccurate length measurement using both methods.

The most important finding was that Echoview reduces the effort and subjectivity in generating fish data compared to manual enumeration. For example, Echoview's semi-automated process for counting fish was up to 50% faster than manual counting fish. For periods of low or single-file fish migration, the software was able to identify fish with ease. Accurate counts for clusters of fish were difficult for both Echoview and manual enumeration. One limitation of Case Study 1 is that accurate fish target sizing is not present. Fish length data generated by both methods needs to be validated to determine accuracy.

Case Study 2 - Mitchell River Sockeye Enumeration Using High Resolution (1.8 MHz) DIDSON Data

Case Study 2 provides a comparison on the accuracy and efficiency of analyzing high resolution DIDSON raw data (1.8 MHz) using Echoview compared to the traditional method of manually counting fish by watching raw DIDSON video data. We compared the fish counts generated by both analysis methods.

Our analysis found no significant difference in the total number of fish counted between the two methods but did find substantial time savings when counting fish using Echoview compared to manual counting. Echoview provided similar counts compared to manual enumeration methods. High-resolution DIDSON data enabled us to readily verify each fish compared to the low-resolution DIDSON data used in Case Study 1. For periods of low or single-file fish migration, the software was able to accurately identify fish. Accurate counts for clusters of fish were difficult for both Echoview and manual enumeration methods. A limitation of Case Study 2 is a comparison of fish lengths between the two methods could not be made, as fish were not measured during the manual analysis.

BlueView

We provide a review of the proprietary software included with the BlueView multibeam sonar system (ProViewer 4.2). ProViewer functions as both the hardware controller and data collection interface. We found the data analysis tools cannot count migrating fish automatically, and as such, should only be used as a viewing and operating software.

We noted two key limitations of this software. Firstly, users have to review the video data footage to count the number of migrating fish, requiring a large time investment for manual analysis. Finally, bias may occur due to human subjectivity.

We found the functionality of ProViewer to be substandard compared to the third-party software Echoview. We recommend the use of Echoview as it substantially reduces analysis time and subjectivity of fish counts compared to manual counts using ProViewer.

Vaki

We provide a review of the proprietary software (Winari) included with the Riverwatcher fish counter. Literature review and personal communication with the manufacturer identified Winari to be both a hardware controller and data collection, analysis, and export interface. Unlike the hydroacoustic multibeam sonars, fish data is only collected when an object breaks the optical beam in the counter. Fish length, size, timestamp, visibility, temperature, and image data are collected when the counter is triggered. Data can be exported separately or synchronized, allowing the user to verify each fish with ease and accuracy. We found the functionality of Winari to be superb, as it provides the user with a multitude of verification options to optimize data quality control.

Mark 12

We provide a description of the counter controlling interface and proprietary software for the Mark 12 counter. Mark counters operate through a text-based menu system and can be accessed from any text-based terminal application. Setup and control of the counter is described in detail.

Through personal communication with the Mark 12 manufacturer we identified that a separate proprietary analysis software exists. We have not had the chance to view or review Mark's proprietary analysis software, but through personal communication with the manufacturer, it is suggested the software will become invaluable. Mark's software should allow users to link all the corresponding fish events or partial events data from each of the files, thereby facilitating the validation process, which is similar to Vaki's Winari functionality.

Logie Software

We provide a review of the three proprietary software included with the Logie fish counter: 2100C PC Control Program, 2100C Graphics Programme, and the 2100B/C Windows Graph Programme with Video Capture. Through extensive experience, we found the 2100C PC Control Program to function as both a hardware controller and data collection and export interface. 2100C Graphics Programme and 2100B/C Windows Graph Programme with Video Capture are designed to collect and view Logie counters graphical output files used to verify fish counts generated by the counter.

Our assessment found the functionality of the proprietary software to be adequate for fish enumeration but lacks some of the more advanced capabilities and stability of other software (e.g., Vaki's Winari software).

SalmonSoft: FishTick Software

We provide a review of the video analysis software FishTick, a motion detection software developed by SalmonSoft. Through a literature review and personal communication with the manufacturer, we found the software functions as a video-capture program (FishCap) and a video-review program (FishRev). Program setup, functionality and cost are described in depth. A UK Environment Agency report determined that FishTick can analyze large amounts of video data quickly, with a detection rate of 90%. Our evaluation found the functionality of FishTick to be promising. If the program performs as intended, it can save valuable time by providing the user with features that can aid in the analysis of digital video recordings.

New Methods

Some counter technologies lack software for managing and visually displaying counter data such as the Logie counter by Aquantic. To fill this software gap, IFR developed an open source software package for the statistical program R called FishCounter that can be used to manage datasets and generate data visualizations. Specific functions of the FishCounter software package are to:

• Remove erroneous data - These are errors in the dataset that are generated during the download process and while testing the counter. FishCounter provides functions for removing erroneous data and can report the errors that are removed.
• Assemble master datasets - A new file is created every time the counter is downloaded. Files may also contain duplicate data depending on the download protocol being used. Duplicate data need to be removed and the individual files compiled into a master dataset for organizational purposes and for further analysis. FishCounter provides user-friendly functions for creating master datasets from individual download files.
• Diagnostic plots - Plotting raw counter data can be used to evaluate how well the counter is operating. FishCounter provides a series of functions that automate the visualization of data for diagnostic purposes.
• Summary plots - Summary plots of counter data in-season can provide immediate and valuable information about fish abundance and migration behaviour to fisheries managers. FishCounter provides a series of functions that automates the visualization of data for summary purposes.

Species Identification Models

Identifying the species of individual fish passing over an electronic fish counter is difficult and can prevent species-specific estimates of abundance. While video validation can provide information about species identification, most rivers in Scotland have turbid water during some periods of salmon migrations that prevents some species of fish from being identified. IFR created species identification models that estimate the species proportions using length-species relationships whereby some species are smaller on average than another species (e.g., sea trout are typically smaller than salmon). Proportions from these models can be used to estimate the abundance of two species. Two models were developed:

• Historic model uses all data on length-species relationships, which is most applicable to predicting the probability of a fish being one species or another when there is inadequate information on the length-species relationship for the current year.
• Current model only uses data on length-species relationships from the current year, which is most applicable to predicting the probability of fish being one species or another when there is adequate information on the length-species relationship for the current year.

Length and migration timing data collected from a Vaki optical beam counter from River Tweed in 2014 were used to compare abundance estimates of salmon and trout generated from the two models. Main findings from this study were:

• Length and migration timing was related to species identification. The probability of being a salmon or trout depended on an individuals' length and migration date through the counter.
• Estimates of salmon abundance were similar for both models. The probability of being a salmon was summed across all individuals to estimate the total number of salmon. Estimates of salmon abundance were similar between both models, with 95% confidence intervals overlapping.
• Estimates of trout abundance were similar for both models. The probability of being a trout was summed across all individuals to estimate the total number of trout. Estimates of trout abundance were similar between both models, with 95% confidence intervals overlapping.

Chapter 4 - Operational Costs and Validation

Operational Costs

In this section, cost considerations for operating and maintaining all major types of counter technologies are reviewed and discussed. The costs considered represent typical budgets, but site-specific considerations are also discussed. Chapter 4 highlights the main cost considerations for operating fish counters, including:

• Counter structure - Structure type is one of the largest determinants of cost and varies greatly among counter setups.
• Debris load - The amount of debris (i.e., wood, bedload) that is transported downstream will affect the number and duration of site visits required to ensure proper counter operation.
• Fish abundance - High fish abundance (i.e., high number of fish events) can rapidly fill data storage for some counters (e.g., resistivity), requiring frequent downloads and higher costs.
• Equipment malfunction - Equipment malfunctions will increase in-season maintenance costs and can jepordize data quality. It is recommended to purchase backup equipment (high capital cost).
• Power supply - Power consumption and availability of mains power varies among counter equipment. Alternative power sources are more expensive but can also be more reliable.
• Site access - Remote sites are more costly than local sites due to increased travel costs and the need for alternative power supplies.

All operational costs reviewed are considerated in the decision and cost model.

Validation

Validation is critical for producing accurate population estimates; increased validation results in more certain abundance estimates. However, validation can be expensive and determining the appropriate amount of validation can be difficult. Our analysis evaluates the trade-off between validation effort (i.e., number of fish validated) and uncertainty in population estimates (i.e., accuracy, precision, and bias) to provide guidelines for how much to validate.

As validation effort increased, the value of additional fish counts being validated decreased. In other words, validating more fish when few counts had been validated was more important than when many counts had been validated. Our analysis also highlighted the different parameters that required a greater number of fish counts to be validated to achieve a given level of uncertainty:

• Mean counter accuracy - Lower counter accuracy required greater validation effort.
• Counter accuracy variability - More variable counter accuracy required greater validation effort.
• Number of species - More species required greater validation effort.

We found that the more complex the system the more validation was required, and that this depends on both counter and population characteristics.

Methods for incorporating validation data into uncertainty in population estimates are presented. Methods include using validation data and a beta binomial distribution to:

• Estimate up and down counter accuracy
• Estimate species ratios of up and down counts

Recommendations are made as to the minimum number of fish that need to be validated to produce abundance estimates within 5 and 10% relative error of the true abundance for three measures of uncertainty:

• Accuracy - A measure of how close an estimate is to the true abundance (a combination of precision and bias).
• Precision - A measure of how repeatable an estimate is.
• Bias - A measure of whether or not estimates are consistently higher or lower than the true abundance.

Methods for converting validation effort into validation time using migration duration and the mean abundance of a population are presented. Such a conversion is necessary because validation time is a more relevant metric for calculating the cost of validation than the number of fish to be validated. Validation cost estimates are included in the decision and cost model and based on the length of a migration, population size, number of species, counter accuracy, and consistency.

Chapter 5 - Counter Decision and Cost Model: Integrating Technological and Economic Considerations to Determine Choice of Counter Technology and Structure

In this section, the main deliverable of the report is presented as a decision model that incorporates information on technical limitations, and costs of installation and operation based on the characteristics of a potential site. This model is intended to aid MSS in determining the most cost-appropriate counter setup for a given site.

Based on an extensive literature review and IFR's professional experience, 10 site variables were determined to be important for the decision model and would be used as input variables:

• River bankfull width is the width of the river just before a river floods its banks. This variable is used to determine the cost of structures that scale with river width.
• Conductivity is a measure of the conductance of water. Resistivity counters are not suitable for rivers with conductivities < 20 µS during salmon migrations.
• Turbidity is a measure of the amount of light that can pass through water. Optical beam counters are not suitable for rivers with a turbidity > 90 NTU during salmon migrations. Video counters are not suitable for rivers with a turbidity > 30 NTU during salmon migrations.
• Maximum water depth can influence fish migration behavior and the performance of specific counters. Resistivity flat pad sensors are not suitable in locations with a water depth > 1.5 m during salmon migrations.
• Minimum water depth at the deepest point in a river's cross-section can influence the performance of specific counters. Hydroacoustic counters require water depths to be > 0.9 m to operate effectively.
• Channel type determines the type of structure needed, and is designated as either a fish pass or a river.
• Power type provides information about the type of existing power at the potential site and the preferred power if none exists.
• Number of species is the number of species that will be counted by the counter during salmon migrations.
• Migration duration is the number of days between the start and end of the salmon migration. This influences a number of cost functions that are based on time.
• Mean population size is the mean abundance for the population (use the previous 10 years). This influences the time required to validate a given number of fish.
• Wadeability refers to whether or not a moderately experienced person can safely wade across a river during the salmon migration.

Using these input variables, a decision model was developed to determine the technical feasibility of technologies and the costs of construction and operations of the equipment. The model evaluates 184 counter scenarios that vary in the technology, counter settings, sensors, structure, power options, and software. The model structure is shown in the flow diagram below.

Schematic of the counter decision and cost model.

We apply the decision and cost model to a range of sites located throughout Scotland. The model produces summaries of costs for all feasible counter scenarios and ranks each scenario in order of cost, from least to most expensive. These case studies illustrate how to use and interpret the model output of capital, 10-year operational and 10-year total costs. We discuss the output with regards to limitations in both capital and operational budgets.

Each case study outlines:

• General watershed and site characteristics
• Population characteristics - life history information, co-migrating species
• Site visits by IFR
• Qualitative evaluation of sites - General assessment of the site's benefits and limitations by IFR staff
• Model evaluation of sites and counter options - Ranked summary of counter options for each site

The collective finding from many case studies suggests there is no one clear counter setup but that many counter setups have potential. There were some potential counter sites, however, where only one counter setup was identified as feasible. Furthermore, for most counter setups the 10-year operational costs were much greater than the initial capital costs indicating that considering operational costs might be a priority.

Chapter 6 - Opportunities for Combining Technologies

Electronic counters can be paired with other technologies to improve counter estimates and provide additional biological information relevant to management. Examples of how to combine technologies with electronic counters are reviewed and discussed. Main topics discussed include:

• Species identification - Identifying species using fish counters can be challenging, but the use of other technologies can provide such information. For example, electronic telemetry tags can be used to determine the proportion of species migrating past counters.
• Generating estimates for large watersheds - Of course it can be difficult to deploy counters on the mainstem of a large watershed. Alternative approaches include combining high accuracy counters on smaller tributaries with telemetry tags to determine the proportion of fish in different reaches or tributaries of a large river. Collectively this information can be used to calculate a total abundance for the watershed.
• Estimating population level survival - Estimating survival of fish at the population level from individual-based telemetry studies is difficult. Pairing counters with telemetry can provide population level estimates of survival, which is rarely done.
• Estimating age structure - Age structure is important for fisheries management as it relates to population productivity and dynamics. This requires sampling of fish for ageing structures to determine ages.
  This information can be combined with counter data to determine the
  age-composition of populations.

Chapter 7 - Spatial Considerations for a Counter Network

While the technical and economic considerations are important for determining the suitability of sites, the development of a counter network requires the spatial coverage of counters to be considered. Spatial coverage refers to the percent of Scottish salmon populations for which a counter-based estimate of abundance is available. Because populations covary, a counter on one river could provide information (i.e., coverage) about the abundance of salmon on another, whereby the amount of information or coverage is equal to the covariance between the populations. A coverage index is described using Pearson's correlation coefficients between rivers. Application of the coverage index is discussed in relation to:

• No count data - When no counter data are available, rod catch data can be used to estimate covariation between streams.
• Comparing counter networks - The counter coverage index can be used with costs and life history characteristics to compare different counter network designs.
• Challenges using the coverage index - Some of the main limitations of the counter coverage index is data quality and rivers with multiple populations.

Chapter 8 - Future Research and Recommendations

Future Research

• Investigate potential renewable power sources such as solar, wind, and hydropower generators for powering counters in remote areas.
• Further investigate Mark 12's hardware availability and software functionality. Mark 12 technology is currently not commercially available and information on the counter is extremely limited. Furthermore, its use has been limited to fish passes and small sensor units and has not been tested in free-flowing river channels.
• Further investigate SalmonSoft's FishTick software. Limited information on its time savings and effectiveness exists as a video counting software.
• Further investigation into the accuracy of length data generated by multibeam hydroacoustic counters operating at low resolution.
• Further investigation of how to acquire the raw data that make up Aquantic's graphical trace plots. Such data could be useful for manipulating the Logie 2100C's counting algorithm.

• Further investigate integrating remote sensing technologies (e.g., telemetry) with fish counters.

• Further develop the concept of a spatial coverage index for evaluating counter networks.
• Develop expertise throughout Scotland through training and knowledge exchanges with experienced personnel.

Recommendations

• Findings of this report emphasize the need for the validation of counter data. Validation should be completed for all counter technologies, including those that are not typically considered (e.g., hydroacoustic counters).
• Our decision and cost model provides real options for counter scenarios, but does not take into account the importance of site visits. We recommend a minimum of one year of monitoring at potential counter sites to collect the information needed to make an informed decision. Site-specific evaluations are needed to ensure the proper application of counter technology.