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

This report provides an extensive review of electronic counter technologies and their potential for implementation in Scotland’s rivers. We consider all major types of proven counter technologies and software implemented by companies and government agenci

Appendix 1. Counter Literature Review

Counter Type Reference Summary
Didson Baumgartner, L.J., Reynoldson, N., Cameron, L., and Stanger, J. 2006. Assessment of a Dual-frequency Identification Sonar ( DIDSON) for application in fish migration studies. NSW Department of Primary Industries -Fisheries Final Report Series No. 84 ISSN 1449-9967 Movements of salmon were recorded using a passive integrated transponder ( PIT) tag and detector system as they migrated through Tongland fish pass. Salmon were captured in 2007 and 2008 in a box trap about 900m below the entrance to the fish pass. A total of 11 of 29 fish tagged were recorded to have found the pass. Overall rate of passage decreased as time of year advanced. Most fish traversed to the upper chambers of the pass within a day. There was variation in time taken to traverse the sections of the pass, primarily due to delay at the exit sections. Some of the increased delay in upper sections may have been due to higher likelihood of impending nightfall by the time fish had traversed the pass. However, several of the few fish detected leaving the pass were delayed over one or more days. The cause of low detection in the exits is unclear.
Didson Belcher, E.O. 2004. Case study: Alaska Department of Fish and Game uses DIDSON to count salmon swimming up-river to spawn. Available at Fish communities of the Murray-Darling Basin are highly migratory, exhibiting movements in both upstream and downstream directions. Until recently, fish migration studies within the Murray-Darling Basin focused primarily on species of recreational or commercial importance. However, recent studies have also demonstrated that larval native fish also undertake substantial passive downstream movements and that many small-bodied species are also migratory. The ecology of migrations vary greatly between species but are usually in response to increases in water temperature or river flow. Fish movements are also highly seasonal, sometimes peaking during summer and autumn and, in some cases, individuals have traversed over 2,300km during flood conditions. Although migrations over such large scales are infrequent, many fish species are frequently observed to either negotiate fishways or accumulate downstream of obstructions. Across the Murray-Darling Basin thousands of weirs obstruct the passage of fish and contribute to significant declines in many fish species. As part of a plan to rehabilitate native fish populations, the Murray-Darling Basin Authority ( MDBA) is restoring fish passage along the Murray River from the sea upstream to the Hume Dam - a distance of 2,225 km. To monitor and assess the outcomes of the construction program, a team of freshwater scientists from the states of New South Wales, Victoria and South Australia were established. This tri-state research team is conducting a comprehensive research program that is monitoring fish as they approach, pass through, and leave the fishways. Four techniques are providing data on the effectiveness of the newly installed fishways: electrofishing accumulations; passive integrated transponder tagging to detect long distance movements, direct sampling of the fishways and developing long-term electronic monitoring tools. Many fish within the Murray-Darling Basin are long-lived (> 10 years). This means that the benefits of a fishway construction program may not be immediate, and increases in fish numbers may take time. It is impossible to continuously trap fishways to gather information on migratory behaviour. The long-term deployment of an electronic monitoring unit to continuously monitor fish migrations is therefore an attractive alternative to manual trapping. If a system can be found which determines count and length information accurately, it could be used to determine long-term trends in fish passage and document increases in fish migration rates over time. This study aimed to perform a field study on the effectiveness of an infrared fish counter, the Vaki Riverwatcher in anticipation of wider application throughout the Murray-Darling Basin. The limitations and advantages of the system were fully explored in both controlled and field environments
Didson Boswell, K.M., Wilson, M.P., and Cowan Jr., J.H. 2008. A Semi automated Approach to Estimating Fish Size, Abundance, and Behavior from Dual-Frequency Identification Sonar ( DIDSON) Data, North American Journal of Fisheries Management 28 (3):799-807, DOI: 10.1577/M07-116.1 This study aimed to ascertain the influence of turbidity and migration rate on the count accuracy and size determination of an automatic infrared fish counter. The effect of turbidity on enumerating silver perch (Bidyanus bidyanus) migration rates was insignificant when compared to the inability of the infrared counter to deal with large numbers of migrating fish. The infrared counter underestimated counts by 56-84% at moderate migration rates (12 fish h)1) and by 62-82% at the highest migration rate (120 fish h)1). When multiple fish were simultaneously passed through the counter, the software detected them as a single fish and overestimated fish length. Fish passed through the unit ranged from 340 to 520 mm but the infrared counter estimated the range to be 140-780 mm, with the lengths of a high proportion of individuals being underestimated. Most issues of inaccuracy appeared to be software-related and could be overcome with further software development. Further assessment of the applicability of the unit to enumerate fish migration, at high migration rates, should then be considered.
Didson Burwen, D.L., Fleischman, S.J., Miller, J.D. 2007. Evaluation of Dual-Frequency Imaging Sonar for Detecting and Estimating the size of migrating salmon. Alaskan Department of Fish and Game, Fishery Data Series No. 07-44: 1-34. Anchorage. Freshwater fish need to move within and among different habitats. Objects that obstruct migrations, such as dams and weirs, have led to worldwide declines in fish populations. Although the adoption of various management strategies (such as weir removal and fishway construction), has improved fish populations in many areas the success of any rehabilitation project relies heavily on a fundamental understanding of the biological requirements of fish. Such biological information is needed to ensure that any effects of human disturbance can be adequately ameliorated. The ability to observe fish in their natural environment is often difficult to achieve, especially in turbid or low visibility conditions. Although many recent advances in technology have been developed, traditional methods generally require catching the fish in some way to obtain biological information. Whilst in some cases this is the only practical method to obtain data, it is largely unknown whether handling fish can alter their 'natural' behaviour. Recently developed sonar systems are currently being assessed in North America and their non-invasive application to fish migration studies is very promising. One such device, the Dual-Frequency Identification Sonar ( DIDSON), uses sound-distorting lenses to create high quality video images (Figure 1). When operating in high frequency mode, these features can define the outline, shape and even fins of target fish. In addition, DIDSON software can count and measure fish automatically. With such features, this technology can potentially allow the observation of fish behaviour such as spawning, feeding and migration. To date, no assessment of this technology for fisheries-based applications has ever been undertaken in Australia. Subsequently, this study was undertaken to provide the first assessment of a DIDSON unit in Australian systems. The results indicated that the DIDSON is a powerful tool for observing freshwater fish populations. When used in conjunction with conventional trapping equipment, the DIDSON consistently provided additional data on fish behaviour that could not be otherwise determined. For example, at fishways on the Murray River, the DIDSON demonstrated that many more fish were approaching and entering the fishways than were trapped as they passed through. In many cases, these fish were actively avoiding traps or displayed a behavioural impediment to entering the fishway. In addition, several fish actively migrated downstream through the fishway when no traps were in place. The DIDSON also provided useful observations of non-migratory activity and non-finfish fauna. In particular, predatory birds and fish were observed to use fishways to actively hunt prey. Such observations are not possible through conventional sampling, especially in turbid conditions. A ground-truthing trial was also performed to determine the accuracy of the automatic counting and measuring interfaces of the operating software. In general, total fish numbers were frequently underestimated and estimated fish lengths were quite variable. Further development of the operating software could alleviate these problems. Despite some limitations with its automated features, when operated manually, the DIDSON was a powerful tool that provided a viable alternative to traditional fish sampling techniques. Possible research applications of the technology to Australian systems include habitat mapping, fish-habitat associations, migration studies, bottom mapping, underwater survey and determination of sampling gear efficiency. The results of this study show that further use of a DIDSON unit would add substantial value to data collected from a number of research projects in Australia
Didson Burwen, D.L., Nealson, P.A., Fleischman, S.J., Mulligan, T.J., and Home, J.K., 2007. The complexity of narrowband echo envelopes as a function of fish side-aspect angle. ICES Journal of Marine Science 64.5: 1066-1074 Advantages and disadvanges of DIDSON sonar counter in the Wood, Anchor, and Kenai rivers of Alaska
Didson Burwen, D.L., Fleischman, S.J., and Miller, J.D., 2010. Accuracy and Precision of Salmon Length Estimates Taken from DIDSON Sonar Images. Transactions of the American Fisheries Society 139(5): 1306-1314. We present a semiautomated analytical approach incorporating both image and acoustic processing techniques to apply to dual-frequency identification sonar ( DIDSON) data. Our objectives were (1) to develop a standardized analysis pathway in order to reduce the effort associated with counting, measuring, and tracking fish targets; and (2) to empirically obtain estimates of basic target information (e.g., size, abundance, speed, and direction of travel). Analyses were conducted on DIDSON data collected at three different locations (the Kenai River, Alaska; Mobile River, Alabama; and Port Fourchon, Louisiana) with different equipment and deployment configurations. We developed an efficient postprocessing approach that can be applied to a variety of data sets, independent of user and deployment method. For two of the three data sets analyzed, the estimates of fish abundance derived from DIDSON analyses were not significantly different from the manual counts of DIDSON files. The analyses produced estimates of mean fish length, direction and speed of travel, and target surface area for all targets within each data set. A consistent analysis platform increases the acceptance and reliability of the DIDSON as a tool for fisheries surveys and further demonstrates the usefulness of DIDSON technology in fisheries applications
Didson Cronkite, G.M.W., Enzenhofer, H.J., Ridley, T., Holmes, J., Lilja, J., and Benner, K. 2006. Use of High-Frequency Imaging Sonar to Estimate Adult Sockeye Salmon Escapement in the Horsefly River, British Columbia, iv+47 pp. Large river systems can be challenging in relation to stock assessment and catchment management, especially those large rivers with numerous or important tributaries that may contain sub-populations or stocks. Initial testing of existing counter technology (resistivity, infrared and split-beam hydroacoustics) in such a system - the River Moy, Co. Mayo - highlighted the difficulties in their use and operation. In this study, an alternative hydroacoustic system, DIDSON (Dual-frequency Identification Sonar), was deployed and assessed for the first time in Ireland. The DIDSON's near video quality imagery allowed for observations of fish migrations and it was easy to install and operate. Methodologies for the operation and data processing using DIDSON in Irish rivers for counting Atlantic salmon have been established, including software development of DIDSON SMC Software (SoundMetrics) (e.g. CSOT Analysis), allowing for the acquisition of real time data and quality fish length measurements. As an alternative to adult counts, mark-recapture estimates were successfully carried out on Atlantic salmon smolts on the River Deel (a tributary of the River Moy) using a screw trap. Both classic and Bayesian models were successfully applied. These stock assessment data were also used to determine the main environmental influences on Atlantic salmon migration in the River Deel. While air and water temperature were shown to be significant to adult migration, no direct correlations were determined with smolt migration. The combined use of DIDSON and Genetic Stock Identification was developed for salmon stock assessment. The genetically determined proportion of River Deel fish were used, along with the DIDSON count, to provide the first estimate of a large river system, the River Moy, using this unique methodology. This advance in stock assessment methodology allowed for a stock assessment of all discrete populations within a large river system.
Didson Cronkite, G.M.W., Enzenhofer, H.J., and Holmes, J.A. 2008. Evaluation of the BlueView ProViewer 900 Imaging Sonar as a tool for counting adult sockeye salmon in the Adams River, British Columbia. Canadian technical report of fisheries and aquatic sciences 2798: iv + 21 p. Experiments were conducted with a multibeam dual-frequency identification sonar ( DIDSON) to evaluate the accuracy and precision of estimating lengths from images of tethered fish insonified at side aspect in an Alaskan river. Live tethered Chinook salmon Oncorhynchus tshawytscha and sockeye salmon O.nerka were suspended in front of a long-range DIDSON (1.2 MHz, 48 beams) equipped with an ultra-highresolution lens. Lengths measured manually from DIDSON images were highly correlated with the actual lengths (R2 ¼ 0.90, RMSE ¼ 5.76 cm). No range dependency in the accuracy of the range estimates was documented. We conclude that relatively accurate and precise estimates of fish length are now possible with certain DIDSON system configurations at up to 21 m.
Didson Enzenhofer, H.J. and Cronkite, G. 2005. A simple adjustable pole mount for deploying DIDSON and split-beam transducers. Canadian technical report of fisheries and aquatic sciences 2570: iv + 14 p. Experiments were conducted using a DIDSON acoustic system to evaluate the potential for estimate fish size from images of tethered and free swimming fish in two alaskan rivers. DIDSON is a recently developed imaging sonar that incorporates a sophisticated lensing system to improve image quality. In the firhst experiment, DIDSON images were collected from six Chinook salmon and four sockeye salmon tethered in the center of the DIDSON's multibeam array. in the second experiment, 130 pacific salmon and Dolly Varden were allowed to swim freely through the DIDSON multibeam array ater being released from a weir live box. length estimates from DIDSON images of tethered fish were subject to a positive bias that incereased with range of the fish from the transducer (approximately 1.3cm/m of range). Mreasurements from the free swimming fish did not demonstrate the same size bias with range. possible cases for the differing results are discussed, as well as the performance of the DIDSON with respect to detecting fish, determining direction of travel, and tarcking fish at high densities.
Didson Galbreath, P.F., and Barber, P.E. 2005. Validation of a Long-Range Dual Frequency Identification Sonar ( DIDSON-LR) for Fish Passage Enumeration in the Methow River. Final Report - PSC Southern Fund 2004/2005 Project 24 pages. High-frequency, narrowband acoustic signals may contain more information on fish size and orientation than previously thought. Our observations of dual frequency identification sonar ( DIDSON) images of fish orientation paired with split-beam echo envelopes helped clarify why metrics such as echo duration have performed better than target strength measurements when predicting salmon lengths at side aspect. Fish orientation has a pronounced effect on the duration and shape of split-beam echo envelopes from large (80-130 cm) salmon insonified at side aspect. At near-normal aspect angles, echo envelopes are unimodal, symmetrical, and resemble echo envelopes from calibration spheres. With increasing oblique-aspect angle, echo shapes become less symmetrical as the number of peaks increases, and echo duration and amplitude become more variable. Using angle and range coordinates, peaks in an echo envelope can be traced to their origin on a DIDSON image. At oblique-aspect angles, discrete peaks develop that are reflected from regions close to the head and tail. In addition, the distance between peaks increases with increasing aspect angle and is larger than can be explained by swimbladder length.
Didson Gray, D., Bachman, R., Kowalske, T., Forbes, S., Meredith, B., and Coonradt, E. 2014. 2014 Southeast Alaska drift gillnet Fishery Management Plan. Alaska Department of Fish and Game, Division of Commercial Fisheries, Regional Information Report 1J14 -03, Douglas. We evaluated the BlueView ProViewer 900 imaging acoustic system as a tool for counting migrating adult sockeye salmon (Oncorhynchus nerka) in clear-water riverine spawning environments in British Columbia, Canada. Hourly fish passage rates during our testing on the Adams River did not exceed approximately 252 fish/hour because spawning returns were much lower than the predicted returns available when we chose this stock for our testing. We applied standard techniques to perform tests on the accuracy and precision of the resulting ProViewer counts compared with concurrent visual counts. The results showed that the salmon count data produced using the Blueview ProViewer 900 were systematically biased relative to visual counts, except if we assumed that all the variability in these data was associated with the visual counts. Variability between observers counting the net upstream passage from the ProViewer data files was high at 25.7%, and with repeated independent counts of the ProViewer files expecting to achieve the same count 80.7% of the time. These results were believed to be due to the level of image resolution and idiosyncrasies of the ProViewer software. Improvements to the software could increase the usefulness of the ProViewer for counting migrating salmon in rivers.
Didson Gurney, W.S.C., Brennan, L.O., Bacon, P.J., Whelan, K.F., O'Grady, M., Dillane, E., and McGinnity, P. 2014. Objectively Assigning Species and Ages to Salmonid Length Data from Dual-Frequency Identification Sonar. Transactions of the American Fisheries Society 143(3): 573-585. We estimated adult sockeye salmon (Oncorhynchus nerka) escapement in the Horsefly River between August 06 and October 09, 2005, using a dual-frequency identification sonar ( DIDSON) imaging system. This project was the first attempt to integrate the DIDSON system operationally into sockeye salmon assessment programmes in British Columbia. Our primary objectives were 1. To assess the ability of a high-frequency imaging sonar system deployed in a fixed position immediately upstream of a fish deflection weir to produce escapement estimates of migrating adult salmon returning to the Horsefly River.2. Determine an effective method for data handling and processing to produce updated estimates of fish passage in a timely manner. 3. Determine if increases in passage rate impact the ability to produce estimates of fish passage within the ensonified region.4. Implement use of in-river accessory equipment to optimise our ability to detect and enumerate fish passage. 5. Test the effectiveness of solar panels and high amperage batteries to power the acoustic system for extended periods.6. Train field staff to setup and operate a fixed-location hydroacoustic facility so they can manage future deployments of the DIDSON. -- Sockeye salmon returning to the Horsefly River were directed through an 11 m wide opening in a weir installed across the river to allow DIDSON enumeration at high-frequency using manual counting techniques. Maximum sockeye salmon passage observed was approximately 8000 fish per hour during the season. We estimated total sockeye salmon escapement into the Horsefly River from 06 Aug to 09 Oct. Based on analysis of visual counts and DIDSON based counts, we found that the DIDSON data were not biased by undetected fish and we conclude that the DIDSON counts of escapement on the Horsefly River are as accurate as counts of migrating fish through an enumeration fence. We compared the distribution of the on-screen DIDSON length measurements (N = 2874) with length measurements from the tagging site of the mark and recapture project located 100 m downstream of the DIDSON site (N = 6260), and found that both measurements were normally distributed with a single mode and that the mean DIDSON length was significantly larger than the mean length of tagged fish (P < 0.05). Based on these findings, we conclude that the DIDSON and mark-recapture programme provided estimates of escapement for the same population of sockeye salmon, i.e., neither method was biased relative to the other by selective sampling. We expected that the mean length of fish measured with the DIDSON system would be larger than the mark-recapture programme due to biases in length measurements associated with beam spreading and the downrange resolution of the system as deployed. Empirical corrections for these biases, which are range- and window-length dependent, respectively, can be derived on-site in future applications of the DIDSON technology. We found that overall the DIDSON counts were statistically indistinguishable from comparative visual counts made from the weir, yielding an error of 0% from this source. We made measurements of precision by comparing the manually counted data sets between observers and found the error from this source was ± 6%. The 95% confidence limits ( CIs) from temporal sub-sampling ranged from 4 to 10% depending on the number of minutes of data used from each hour. Combining the errors from these three known sources gave a total confidence limit of ± 14% to give a total population estimate of 645 310 ± 90 599. The use of a DIDSON system will allow accurate and cost effective enumeration of sockeye salmon on the Horsefly River for fisheries management purposes.
Didson Hateley, J. and Gregory, J. 2006. Evaluation of a multi-beam imaging sonar system ( DIDSON) as Fisheries Monitoring Tool: Exploiting the Acoustic Advantage. Technical Report. Closed-circuit television was used to provide a visual record of the events associated with the counts recorded by a resistivity fish counter. The fish seen were classified as ' large ' fish 250 cm length and ' small ' fish of < 50 cm. Some of the ' large ' fish escaped detection by the counter, some ' small ' fish were counted and some counts were registered when nothing was seen. The sensitivity of the counter varied inversely with water conductivity which varied inversely with discharge. Evidence was obtained suggesting that fish ascending a weir tend to swim closer to the bottom than do those descending. It was found that fish tended to move upstream just after sunset and downstream just before sunrise except when the water was turbid and when the fish were very close to spawning. The numbers of fish movements recorded increased during those periods when discharge was decreasing after a spate but when spawning activity was at its peak, increased activity occurred in the complete absence of any change in discharge. Instances of the same fish re-crossing the counting zone several times were recorded and the simultaneous passage of more than one fish through the counting zone was observed.
Didson Holmes, J.A., Cronkite, G.M.W., and Enzenhofer, H.J. 2005. Feasibility of deploying a dual frequency identification sonar ( DIDSON) system to estimate salmon spawning ground escapement in major tributary systems of the Fraser River, British Columbia. Canadian technical report of fisheries and aquatic sciences 2592: xii + 51 p. We have designed an adjustable pole mount that attaches to a boat or other stationary platform. The mount allows the precise aim of an acoustic transducer. The mount allows manual control of the deployment depth, bearing, roll angle and tilt angle of an attached split-beam transducer or DIDSON dual imaging sonar transducer. It can be attached to boat gunnels up to 27 cm thick, or to a stationary platform such as a modified stepladder for riverine applications. We describe the construction, assembly and deployment of the stainless steel and powder-coated aluminium pole mount. We also describe the add-on attachments that allow: 1) the extension of the mount by 1 m; 2) the addition of a second transducer and; 3) the 90° rotation of a DIDSON transducer for bottom profiling.
Didson Holmes, J.A., Cronkite, G.M.W., Enzenhofer, H.J., and Mulligan, T.J. 2006. Accuracy and precision of fish-count data from a ''dual-frequency identification sonar'' ( DIDSON) imaging system. ICES Journal of Marine Science 63(3): 543-555. A long range model of a Dual Frequency Identification Sonar ( DIDSON-LR) was operated in parallel with visual observations to validate reliability of the instrument to enumerate fish passage at distances up to 40 m. Two testing designs were used. The first involved manually passing a tethered salmon to and from across the field of a DIDSON-LR installed in a pond at the Washougal Salmon Hatchery (Washington Department of Fish and Wildlife, Washougal). The second involved making visual counts of naturally migrating salmon in the Methow River (Okanogan County, Washington). In both tests, data recorded for the visual observations was compared to that noted on concurrently recorded DIDSON-LR files. The visual and DIDSON data for the hatchery pond trials were 100% concordant. Of 55 visual observations of migrating salmon in the Methow River, 48 concordant observations were noted on the DIDSON-LR recordings. In seven instances, no observation was made on the DIDSON-LR recording. These discrepancies are more likely explained by improper installation of the DIDSON or observer error rather than technical inadequacy of the instrument. When operated at low frequency (0.7 MHz), the DIDSON-LR provided images of fish at distances to 42 m (the limit of our tests). For fish passing at the farther end of this range, the recordings were easier to read when a 20m window length was used in combination with a 20m Start Length, as opposed to a 40m Window Length and a 1 m Start Length. When operated at its higher frequency (1.2 MHz) the DIDSON-LR provided images of improved resolution, although the maximum distance at which it could be operated was 33 m - a 20 m Window Length and a Start Length up to 13 m. In either case ( LF or HF), however, the level of resolution of the images was only sufficient to provide a qualitative measure of size and pattern of movement. The level of resolution did not to permit distinguishing between species of similarly sized fish, e.g., between Chinook salmon Oncorhynchus tshawytscha and steelhead Oncorhynchus mykiss, which were both migrating in the Methow River during our trials and had overlapping size ranges (total range 60 to 100 cm). Additional DIDSON-LR files recorded over extended periods without visual observation confirmed that salmon/steelhead passage at the Methow River site occurred primarily during the hours from 9 pm to 2 am. Use of a DIDSON-LR in a planned series of recordings should provide data of sufficient reliability to calculate an accurate estimate of net escapement of salmon/steelhead to an open system such as the Methow River. Photos and video clips illustrating operation of the DIDSON-LR and the effects of the different settings on resolution of the resulting images are provided at:
Didson Langkau, M.C., Balk, H., Schmidt, M.B., and Borcherding, J. 2012. Can acoustic shadows identify fish species? A novel application of imaging sonar data. Fisheries Management and Ecology, 19(4): 313-322. This management plan provides an overview of the expected salmon run sizes, regulations, management issues, and harvest strategies for the Southeast Alaska drift gillnet fisheries in 2014. Drift gillnet fisheries are planned at Tree Point and Portland Canal (District 1), Price of Wales and Stikine (Districts 6 and 8), Taku River / Snettisham (District 11), Lyn Canal (District 15), and In the following terminal hatchery areas: Neets Bay (District 1), Nakat Inlet (District 1), Anita Bay (District 7), Speel Arm (District 11), Deep Inlet (District 13), and Boat Harbor (District 15)
Didson Lilja, J., Ridley, T., Cronkite, G.M.W., Enzenhofer, H.J., Holmes, J.A. 2008. Optimizing sampling effort within a systematic design for estimating abundant escapement of sockeye salmon ( Oncorhynchus nerka) in their natal river. Fisheries Research (Amsterdam) 90.1-3: 118-127 Fishery managers need robust ways of objectively estimating the quantitative composition of fish stocks, by species and age-class, from representative samples of populations. Dual-frequency identification sonar data were used to first visually identify fish to a broad taxon (Salmonidae). Subsequently, kernel-density estimations, based on calibrated size-at-age data for the possible component species, were used to assign sonar observations both to species (Atlantic Salmon Salmo salar or Brown Trout Salmo trutta) and age-classes within species. The calculations are illustrated for alternative sets of calibration data. To obtain close and relevant fits, the approach fundamentally relies on having accurate and fully representative subcomponent distributions. Firmer inferences can be made if the component data sets correspond closely to the target information in both time and space. Given carefully chosen suites of component data, robust population composition estimates with narrow confidence intervals were obtained. General principles are stated, which indicate when such methods might work well or poorly.
Didson Lilja, J., Romakkaniemi, A., Stridsman, S. and Karlsson, L. 2010. "Monitoring of the 2009 salmon spawning run in River Tornionjoki/Torneälven using Dual-frequency IDentification SONar ( DIDSON). A Finnish-Swedish collaborative research report. March 2010. 43p. In March 2005, the Environment Agency began a full evaluation of a standard DIDSON unit and it's associated data-processing software, applied to a range of fisheries applications across England and Wales. These applications included: 1. Monitoring salmon smolt in small shallow streams- River Frome. 2. Counting fish at high passage rates - River Tywi sea trout and River Wye twaite shad. 3. Counting fish at low passage rates with high debris loads - Silver eels, River Dee smolt. 4. Behavioural studies: Using DIDSON as a surrogate for video - River Tyne Fish Deflection System; River Tyne fish counter; Benacre, Soham and Bourne Eau fish deflector systems. 5. Mobile applications One: As an aid to interpretation of split-beam data. 6. Mobile applications Two: Resolution of small targets in shoals. 7. Fish stock assessment - Biomass estimates of Rochdale Canal.
DIDSON was found to be very simple to use. Its live output is in the form of images that can be easy to interpret and its 96 acoustic beams (in high frequency mode) combine to give it a wide overall beam angle without the disadvantages a split-beam system would incur in shallow water. It is very deployment friendly. The data gathered can be played back as if it were video which allows fish targets to be examined and behaviour studied by anyone with basic computer skills. However, there were applications where it was more difficult for an observer to identify fish targets.The software to automate this process is relatively easy to implement. Its effectiveness comparing output to fish identified from a full image playback mode was found to vary considerably between applications and for many the associated lower target detection rate may not warrant the time saved by automation. This will have resource implications for potential medium to long term monitoring applications.
Didson Maxwell, S.L. and Gove, N.E. 2004. The feasibility of estimating migrating salmon passage rates in turbid rivers using a Dual Frequency Identification Sonar ( DIDSON) 2002. Regional Information Report 1 No. 2A04-05, Alaska Department of Fish and Game Division of Commercial Fisheries, Anchorage, AK. The dual-frequency identification sonar ( DIDSON) system was identified during strategic planning as a new acoustic technology with the potential to deliver a cost-effective means of producing salmon escapement estimates with similar or better levels of precision and accuracy as mark-recapture programs ( MRP). The objectives of our 2004 field work were to determine where the DIDSON acoustic imaging system could be used to estimate sockeye salmon (Oncorhynchus nerka) and Chinook salmon (O. tshawytscha) escapement in the Fraser River watershed and to determine the additional equipment needed (e.g., weirs, mounting system and platform) for effective operation of a DIDSON imaging system. We developed a preliminary list of 22 sites on 10 rivers for investigation through consultation with stock assessment staff in Kamloops and knowledge of the requirements of fisheries managers and general criteria for hydroacoustic sites. Based on a combination of in-stream testing and site visits, we conclude that the DIDSON system could be used effectively to estimate escapement of sockeye salmon in Scotch Creek, Chilko, Horsefly, Mitchell and Seymour Rivers, and probably the Lower Adams River as well. Additional equipment needed to effectively enumerate populations in these systems is minimal but includes a transducer mounting pole and bracket, a modified step-ladder from which the transducer is deployed and that can be used as a viewing platform for species composition estimates, a secure shed for topside equipment (computer and battery bank), solar panels to provide power, and 5- 10 m of weir, depending on the site. Although additional work is needed on some systems to choose the most appropriate site for deployment (Mitchell River) or to confirm that fish do not exhibit unusual behaviours (e.g., milling, holding) that would degrade the performance of the DIDSON system (Mitchell River, Scotch Creek, Seymour River), we do not believe that the additional time commitment required to address these issues is large. The Lower Shuswap, Lower Stuart, and Tachie Rivers were not suitable for deployment of the DIDSON system in our judgement. We suspect that acoustic counting of migrating fish in the Lower Stuart River, particularly Chinook salmon, could be accomplished with shore-based side-looking split-beam systems, but at least one season of testing would be required to confirm this hypothesis. Neither the Lower Shuswap nor the Tachie were amenable to acoustic counting because of the high probability of unusual fish behaviour and poor site characteristics, respectively. The list of deployment sites and operational requirements (e.g., accessory equipment and sampling strategy) documented in this report can be cross-referenced to existing management priorities in order to determine deployment opportunities that best exploit the capabilities of the DIDSON technology within existing programs.
Didson Maxwell, S.L., Faulkner, A.V., Fair, L. and Zhang, X. 2011. A comparison of estimates from 2 hydroacoustic systems used to assess sockeye salmon escapement in 5 Alaska Rivers. Alaska Department of Fish and Game, Fishery Manuscript Series No. 11-02, Anchorage. The reliability of sockeye-salmon (Oncorhynchus nerka) count data collected by a dual-frequency, identification sonar ( DIDSON) system is evaluated on the basis of comparisons with visual counts of unconstrained migrating salmon and visual counts of salmon constrained to passing through an enumeration fence. Regressions fitted to the DIDSON count data and the visual count data from the enumeration fence were statistically indistinguishable from a line with slope¼ 1.0 passing through the origin, which we interpret as agreement in both counts. In contrast, the regressions fitted to the DIDSON count data and the unconstrained visual count data had slopes that were significantly <1.0 ( p< 0.001) and are consistent with an interpretation of systematic bias in these data. When counts of both unconstrained and constrained fish from the DIDSON system were _50 fish event_1, repeated counts of the DIDSON files were observed to produce the same counts 98e99% of the time, respectively, and based on the coefficient of variation, counts of individual passage events varied <3% on average. Therefore, the DIDSON count data exhibit high precision among different observers. As an enumeration fence provides a complete census of all fish passing through it, we conclude that fish-count data produced by the DIDSON imaging system are as accurate as visual counts of fish passing through an enumeration fence when counts range up to 932 fish event_1, the maximum count recorded during our study, regardless of the observer conducting the count. These conclusions should be applicable to typical riverine applications of the DIDSON system in which the bottom and surface boundaries are suitable for acoustic imaging, the migrating fish are adult salmon, and the transducer is carefully aimed so that the beams ensonify the area through which the salmon are migrating.
Didson Mercer, B. and Associates Ltd. 2012. 2011 Teslin River DIDSON Sonar Feasibility Study. 31 pages This study addresses a fish species discrimination method based on normalised elliptic Fourier descriptors applied to acoustic shadows derived by Dual-frequency Identification Sonar ( DIDSON). Acoustic shadows of templates (20, 30, 40 and 50 cm) and live fish of four species [bream, Abramis brama (L.); barbel, Barbus barbus (L.); chub, Leuciscus cephalus (L.); and trout, Salmo trutta (L.)] were projected on a plate in an experimental set-up and tested on suitability for species discrimination. Twenty-centimetre templates were correctly classified in 97.5% of the cases, indicating a size threshold. The larger templates reached values of 100% correct classification based on cross-validated discriminant function analysis. It was also possible to classify moving fish based on screenshots of their acoustic shadows with a certainty of 83.9%. Extended field tests are required to evaluate the method for use in practical monitoring applications in multispecies river environments
Didson Metheny, M.D. 2012. Use of dual frequency identification sonar to estimate salmonid escapement to Redwood creek, Humboldt county California. A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Natural Resources: Fisheries Biology, 90 pages. Atlantic salmon spawning run into the River Tornionjoki/Torneälven was monitored by Dualfrequency Identification Sonar ( DIDSON) in 2009. In the beginning of the spawning run, one DIDSON unit was deployed at the river mouth (Tornio site), and two DIDSON units were deployed about 100 km upstream from the sea (Kattilakoski site). The plan was to collect run timing index data from the Tornio site by monitoring only a part of the river transect, and to enumerate all upstream migrants at the Kattilakoski site by monitoring the whole river transect. Monitoring at the Tornio site was started in late May and but it was interrupted after one month, when the unit was moved to the Kattilakoski site due to a system breakdown at that site. The results from the Torno site from the early part of spawning migration indicate that the site selection was not successful, as a too small fraction of the total upstream passage was detected in order to provide a reliable run timing index. At the Kattilakoski site monitoring supposedly covered the whole migration period, i.e. from the end of May until the late August. Acoustic data were collected for 78% and 65% of the available sample time on the Swedish and the Finnish shore, respectively. The near-bottom area at the 15-20 meter wide deepest mid-cannel was in constant shadow. In spite of the monitoring problems due to the mid-channel shadow area and the equipment breakdowns due to voltage peaks during thunderstorms, the Kattilakoski site was found to be fairly suitable for permanent monitoring of the salmon spawning run. Counts at Kattilakoski were expanded across the unsampled periods, but it was assumed that no salmon passed the monitoring site through the mid-channel shadow area. Records and catch samples from angling, and fish ladder data from the nearby River Kalixälven were used to infer the species composition and the separation between grilse ( 1SW) and multi-sea-winter ( MSW) salmon in the counts. It was concluded that length measurements from the DIDSON data underestimated the true length of the observed fish. After a preliminary correction of length measurements and species identification it was concluded that 31 780 salmon and 2130 fish of other species (mainly sea trout) passed the site. Salmon counts were further divided between grilse (5420 ind.) and MSW salmon (26 360 ind.). The median date of salmon migration (grilse and MSW salmon combined) was on 1 July. The preliminary calculations taking into account salmon that ascended the river but did not pass the Kattilakoski site (either being caught or spawned below the site) indicated that totally about 33 000 - 35 000 salmon ascended the river in 2009. Future monitoring with auxiliary investigations may bring new information based on which the 2009 data have to be reassessed. The auxiliary investigations should include estimation of precision (detection rate may vary between persons post-processing the data) of counts, improving and verification of length measurements, data collection from the mid-channel shadow area, and special studies to quantify the amount of salmon that do not pass the counting site. A more permanent mounting system of the DIDSON units and fish deflection weirs could be planned and built up. Electronic equipment must also be better protected against breakdowns due to thunderstorms. Finally, obtaining direct information concerning the timing and dynamics of river entry of fish would require more test runs with one or several DIDSON units at various sites near the river mouth (Tornio).
Didson Moursund, R.A., Carlson, T.J. and Peters, R.D. 2003. A fisheries application of a dual-frequency identification sonar acoustic camera. ICES Journal of Marine Science 60: 678-683. The upstream migration of adult sockeye salmon (Oncorhynchus nerka) in the Horsefly River was monitored by a DIDSON imaging sonar during the dominant stock-cycle year 2005 using a systematic 20-min h−1 sampling scheme. We used a subset of these data collected between 16 and 29 September to investigate whether this sampling protocol was justified based on temporal variation in the salmon migration data. During post-processing, the 20-min sequence was split into two 10-min periods and the number of migrating salmon was counted separately. Cross- and autocorrelation analysis showed that estimates from the first and second 10-min samples were similar (r = 0.65) and variation between them (i.e. within the hour) was random, supporting the conclusion that systematic-hourly sampling is a defensible sampling design for acoustic enumeration when temporal variation in fish migration is unknown a priori. Using a simple benefit-cost model (statistical reliability of point estimates of salmon escapement-sampling effort), we recommend a minimum sampling effort of 10-min h−1 and a maximum effort of 20-min h−1 for projects using a systematic sampling scheme in which the goal is to estimate total upstream salmon escapement. An alternative sampling approach targets high-passage events such as diurnal peaks or periods when total daily upstream escapement exceeds 25 000 fish d−1, for increased sampling effort while reducing sampling effort during low-passage periods. This design will improve the statistical reliability of the resulting point estimates of upstream escapement relative to that achievable with a systematic effort with no overall change in total sampling effort over the course of the migration period.
Didson Mueller, A.M., Burwen, D.L., Boswell, K.M. and Mulligan, T. 2010. Tail-Beat Patterns in Dual-Frequency Identification Sonar Echograms and their Potential Use for Species Identification and Bioenergetics Studies. Transactions of the American Fisheries Society 139.3: 900-910. We tested the feasibility of using a dual frequency identification sonar ( DIDSON) to count migrating adult salmon in turbid Alaskan rivers as a potential replacement for Bendix echo counting sonars. Our evaluation was divided into five main components: 1) a comparison of sockeye salmon (Oncorhynchus nerka) counts from DIDSON, Bendix sonar, and split beam sonar against visual tower and video counts; 2) a range test in a turbid river to test the DIDSON's detection limits; 3) a comparison of two sonars ( DIDSON and split beam) at the Miles Lake sonar site; 4) a comparison of two sonars ( DIDSON and Bendix) at the Kenai River; and 5) a test of the performance of the DIDSON on rocky river bottoms and artificial substrates. The sonar, video, and tower methods produced similar sockeye salmon counts in the clear Wood River, although the split beam sonar was only tested at relatively low fish passage rates. We detected an artificial target 17-18 m from the transducer in the turbid Copper River. More total fish were counted from DIDSON images compared to counts obtained from split beam sonar echograms with the largest difference occurring in the first 5 m at the Miles Lake sonar site on the Copper River. The discrepancy was greater if downstream-moving fish were subtracted from upstream-moving fish. In the turbid Kenai River, a DIDSON (high frequency) and Bendix sonar comparison of fish counts produced mixed results with one dataset producing regression slopes close to one while a second dataset was more dissimilar. From DIDSON images, we observed a variety of fish behaviors that could impact counts made by more traditional sonars. We successfully deployed DIDSON and observed fish over rocky river bottoms and artificial substrates. Advantages of the DIDSON include easy-to-detect images of fish; a wider viewing angle, better coverage of the water column, simpler aiming and operation, accurate upstream-downstream target resolution, background subtraction feature, less multipathing, and reasonable measures of fish length out to 12 m. Disadvantages include limited range capabilities, high electronic data loads, and manual target counting. In addition, the majority of the DIDSON's electronics are deployed in the river making the unit vulnerable to damage from debris. Better data storage methods and automated fish counting software are being investigated. The DIDSON exceeded our expectations for counting salmon in turbid rivers and is our choice for a Bendix sonar replacement.
Didson Osborne, B.M. and Melegari, J.F. 2008. Site Selection and Feasibility of Enumerating Dolly Varden using Dual Frequency Identification Sonar in the Hulahula River, Arctic National Wildlife Refuge, Alaska, 2006. Fisheries Information Services, Annual Report FIS 04-103, U.S. Fish and Wildlife Service. We tested the feasibility of using a dual frequency identification sonar ( DIDSON) to count migrating adult salmon in turbid Alaskan rivers as a potential replacement for Bendix echo counting sonars. Our evaluation was divided into five main components: 1) a comparison of sockeye salmon (Oncorhynchus nerka) counts from DIDSON, Bendix sonar, and split beam sonar against visual tower and video counts; 2) a range test in a turbid river to test the DIDSON's detection limits; 3) a comparison of two sonars ( DIDSON and split beam) at the Miles Lake sonar site; 4) a comparison of two sonars ( DIDSON and Bendix) at the Kenai River; and 5) a test of the performance of the DIDSON on rocky river bottoms and artificial substrates. The sonar, video, and tower methods produced similar sockeye salmon counts in the clear Wood River, although the split beam sonar was only tested at relatively low fish passage rates. We detected an artificial target 17-18 m from the transducer in the turbid Copper River. More total fish were counted from DIDSON images compared to counts obtained from split beam sonar echograms with the largest difference occurring in the first 5 m at the Miles Lake sonar site on the Copper River. The discrepancy was greater if downstream-moving fish were subtracted from upstream-moving fish. In the turbid Kenai River, a DIDSON (high frequency) and Bendix sonar comparison of fish counts produced mixed results with one dataset producing regression slopes close to one while a second dataset was more dissimilar. From DIDSON images, we observed a variety of fish behaviors that could impact counts made by more traditional sonars. We successfully deployed DIDSON and observed fish over rocky river bottoms and artificial substrates. Advantages of the DIDSON include easy-to-detect images of fish; a wider viewing angle, better coverage of the water column, simpler aiming and operation, accurate upstream-downstream target resolution, background subtraction feature, less multipathing, and reasonable measures of fish length out to 12 m. Disadvantages include limited range capabilities, high electronic data loads, and manual target counting. In addition, the majority of the DIDSON's electronics are deployed in the river making the unit vulnerable to damage from debris. Better data storage methods and automated fish counting software are being investigated. The DIDSON exceeded our expectations for counting salmon in turbid rivers and is our choice for a Bendix sonar replacement.
Didson Petreman, I.C., Jones, N.E. and Milne, S.W. 2014. Observer bias and subsampling efficiencies for estimating the number of migrating fish in rivers using Dual-frequency IDentification SONar ( DIDSON) Fisheries Research 155: 160-167. A Logie 2100C resistivity fish counter was installed in the Keogh River in the summer of 1997. Data were collected on fish numbers, sizes, and time of migration and compared to alternative methods of enumeration (area-under-the-curve and mark-recapture estimates). Counter escapement estimates of 8246 coho adults, 8505 pink salmon and 92 steelhead adults were calculated based on observed counter efficiency, through video validation techniques. Area-under-the-curve ( AUC) estimates for pink salmon were high (15,631 adults) in part due to some escapement into the river occurring before counter operation began. Coho AUC estimates varied and very dependant on the values used for residence time in the stream count areas. AUC estimates ranged from 5411 to 13,060 adults, with no confidence limits available due to low tag re-sightings. Mark-recapture data for steelhead predicted a similar value for escapement to counter data, with an estimate of 98 fish.
Didson Pipal K., Jessop, M., Boughton, D. and Adams, P. 2010. Using dual-frequency identification sonar ( DIDSON) to estimate adult steelhead escapement in the San Lorenzo River, California. California Fish and Game 96 (1): 90-95. Multiple beam high resolution sonars were used to enumerate the 2012 Chinook salmon (Onchorynchus tshawytscha) escapement to the Teslin River system. This was the first year of a full sonar project at this site following a feasibility study in 2011. The sonar was operated on the mainstem Teslin River at the site identified during the 2011 feasibility study; approximately 12 km upstream of the confluence of the Teslin and Yukon Rivers at Hootalinqua. The camp and sonar station set-up was initiated on July 3. Sonar operation began on July 17 and operated continuously through to September 3. A total of 3,396 targets identified as Chinook salmon was counted during the period of operation. An additional 58 Chinook were estimated to have passed during the 20.5 hours the sonars were inoperative over the course of the project. The total escapement was estimated to be 3,454. The first Chinook salmon was observed on July 27, ten days later than anticipated. A peak daily count of 186 fish occurred on August 21, at which time 76% of the run had passed the sonar station; 90% of the run had passed the station on August 25. A carcass pitch was conducted over approximately 120 km of the mainstem Teslin River, yielding 147 sampled Chinook. Of these, 95 (66%) were female and 52 (34%) were male. The mean fork length of females and males sampled was 853 mm and 773 mm, respectively. The DFO scale lab determined ages from 118 Chinook sampled. Age-5 (68%) was the dominant age class, followed by age-4 fish (28%) and age-3 fish (4%). A total of 106 tissue samples was collected for GSI analysis.
Didson Tiffan K.E., Rondorf D.W. and Skalicky J.J. 2004. Imaging fall Chinook salmon redds in the Columbia River with dual frequency identification sonar. North American Journal of Fisheries Management 24: 1421-1426. I used dual frequency identification SONAR ( DIDSON) to estimate escapement of adult coho salmon, Chinook salmon, steelhead and coastal cutthroat trout entering Redwood Creek to spawn. Effective estimates of salmonid escapement include a quantifiable error associated with the number of fish. The errors associated with DIDSON estimates were described and computed to assess whether or not the technology is appropriate for monitoring salmonid escapement in Redwood Creek. DIDSON counts of unidentified fish were assigned a species using models developed from spawning survey observations in the Redwood Creek watershed. The DIDSON deployment on Redwood Creek worked well during flows below 3000 cubic feet per second. Multiple regression of environmental variables showed no clear relationships with daily fish passage rates. Between 17 November 2009 and 18 March 2010, I estimated that 2,435 Chinook salmon, 375 coho salmon, 775 steelhead and 400 coastal cutthroat trout entered Redwood Creek to spawn. Calculation of sampling variance and a census of 88 hours suggested that a sample of 10 minutes to represent the hour resulted in a 9-13% confidence interval around the point estimate.
Didson Tiffan, K., Haskell, C. and Kock, T. 2010. Quantifying the behavioral response of spawning chum salmon to elevated discharges from Bonneville Dam, Columbia River, USA. River Research Applications 26: 87-101. Kenai river Chinook salmon passage was estimated in 2010 using split beam sonar and experimental DIDSON counter/ the splitbeam sonar operated continuously from 16 may to 4 august, when operations were curtailed due to milling salmon that prevented accurate counting. the DIDSON was successfully deployed on both banks of the river and operated successfully on 48 days between 11 june and 10 august. based on split beam sonar target strength and range thresholds, total upstream passage of chinook salmon was estimated to be 13248 ( SE 235) fish during the early run (16 may - 30 june) and 18401 ( SE 698) fish for the late run (1 july - 10 august) Detailed comparison of split beam and DIDSON data indicated taht the assumption underpinning split beam traget strength based estimates are not valid. it is recommended taht target based strength based split beam sonar estimate be discontinued in favor of DIDSON based estimate 2011.
Didson Upper Fraser Fisheries Conservation Alliance and Department of Fisheries and Oceans (2010) System-wide DIDSON Estimation of Sockeye Salmon Escapement in the Quesnel River System. Project # 07350-35/ FSWP 09 D SIFM 93. 65 pages. The uses of an acoustic camera in fish-passage research at hydropower facilities are being explored by the U.S. Army Corps of Engineers. The ''Dual-Frequency Identification Sonar'' ( DIDSON) is a high-definition imaging sonar that obtains near-video quality images for the identification of objects underwater. Developed originally for the U.S. Navy by the University of Washington's Applied Physics Laboratory, it bridges the gap between existing fisheries-assessment sonar and optical systems. The images within 12m of this acoustic camera are sufficiently clear such that fish can be observed undulating as they swim and their orientation ascertained in otherwise zero-visibility water. In the 1.8 MHz high-frequency mode, this system comprises 96 beams over a 29_ field-of-view. The high resolution and fast frame rate provide target visualization in real time. The DIDSON can be used where conventional underwater cameras would be limited by low light levels and high turbidity.
Didson Xie, Y., Gray, A.P., Martens, F.J., Boffey, J.L. and Cave, J.D. 2005. Use of Dual-Frequency Identification Sonar to Verify Salmon Flux and to Examine Fish Behaviour in the Fraser River. Pacific Salmon Comm. Tech. Rep. No. 16: 58 p. We observed patterns in echograms of data collected with a dual-frequency identification sonar ( DIDSON) that were related to the tail beats of fish. These patterns reflect the size, shape, and swimming motion of the fish and also depend on the fish's angle relative to the axis of the beam. When the tail is large enough to reflect sound of sufficient intensity and the body is angled such that the tail beat produces periodic changes in the range extent covered by the fish image, then the tail beat becomes clearly visible on echograms that plot the intensity maximum of all beams. The analysis of DIDSON echograms of a mix of upstreammigrating Chinook salmon Oncorhynchus tshawytscha and sockeye salmon O. nerka resulted in the separation of two groups: (1) fish of sockeye salmon size that swam with a tail-beat frequency ( TBF) between 2.0 and 3.5 beats/s and (2) fish of Chinook salmon size with a TBF between 1.0 and 2.0 beats/s. There was no correlation between TBF and fish size within each group, which suggests that the observed difference in TBF between the two groups was species-specific rather than an indirect effect of the groups' difference in size. The technique of extracting TBF from DIDSON echograms may also be useful for bioenergetics studies. Compared with electromyogram telemetry, it offers the advantages of being nonintrusive and faster to set up and analyze and therefore is suitable for analyzing larger sample sizes. The disadvantages are that the technique's potential is limited to relatively large fish, it can cover only relatively small areas, it cannot be used to follow individual fish over long distances, and some environments are too noisy to produce DIDSON images of sufficient quality.
Didson Xie, Y., Michielsens, C.G.J., Gray, A.P., Martens, F.J. and Boffey, J.L. 2008. Observations of avoidance reactions of migrating salmon to a mobile survey vessel in a riverine environment. Canadian journal of fisheries and aquatic sciences/Journal canadien des sciences halieutiques et aquatiques 65 (10): 2178-2190. A study using a fixed-location, Dual Frequency Identification Sonar ( DIDSON) was initiated in 2004 to assess the population status of Dolly Varden Salvelinus malma in the Hulahula River, Alaska. An abundance estimate from the DIDSON data was generated to describe the variability in run size and timing of Dolly Varden. During 2006 data collection began August 1 and continued through September 20. A total of 1,157 hours of data was collected, providing an estimate of 7,471 Dolly Varden migrating upriver. Species identification was accomplished with hook and line sampling, beach seining, and an underwater camera. A total of 127 fish was captured, identified as Dolly Varden, sexed, and measured. Based on observed swimming pattern, estimated size, and lack of other species observed or captured, all fish enumerated were assumed to be Dolly Varden. Visual observations using an underwater video camera positioned in the ensonified zone detected 125 fish and of these, 68 were identified as Dolly Varden. The remaining 57 fish were too small to identify. No fish were observed during two aerial surveys conducted using helicopter (September 17 and 20) flown from the DIDSON site to the river mouth. Positional data indicated that most fish were detected by the DIDSON with few fish observed near the outer range limits of acoustic detection. Most fish traveled on the river bottom. The peak daily count of 535 fish occurred on September 1. The hourly passage rates of upriver fish showed a slight diel pattern (highest during nighttime hours). The estimate of Dolly Varden migration upriver is conservative because it only included fish that passed while DIDSON was in operation.
Resistivity Dunkley, D. and Shearer, W. 1982. An assessment of the performance of a resistivity fish counter. J. Fish Biol. (1982) 20, 717-737 Monitoring trends in abundance of Endangered Species Act ( ESA) listed adult steelhead (Oncorhynchus mykiss) is essential to assessing their viability. However, in central and southern California (the southern extent of their range), monitoring is difficult due to the low abundance and patchy distribution of adults. The only successful method has been counting stations at barriers (e.g., dams, weirs, etc.) that involve a certain amount of ESA "take" in handling listed fish. As a new alternative that avoids "take," we have successfully used dual-frequency identification sonar ( DIDSON) for monitoring adult steelhead abundance (Pipal et al. In press). The operational aspects of using DIDSON to monitor small fish populations in a more urbanized setting are different than for its more common use to enumerate large runs of salmon in more remote regions. We have deployed DIDSON in three different locations in central California to monitor steelhead and have gained significant insight into the necessary operational considerations. These are described here in detail and include the following:1) site selection, 2) DIDSON unit configuration, 3) deployment and system security, 4) data management (recording, processing and storage), 5) species identification, 6) and data analyses, which include a Decision Support Tool used to standardize fish counts. We also identify areas needing further research, particularly species identification, and offer suggestions for possible solutions.
Resistivity McCubbing, D., Ward, B. and Burroughs, L. 1999. Salmonid escapement enumeration on the Keogh River: a demonstration of a resistivity counter in British Columbia. Fisheries Technical Circular No 104 In order to assess the accuracy and reliability of automated fish counters for counting adult Atlantic salmon, Salmo salar L., a "Logie' resistivity counter was installed in late June 1989 in the control dam above the fishway in Northeast River, Placentia, Newfoundland, Canada. The counter was in operation for 26 days (1-26 July). The accuracy of daily counts recorded by the counter was verified by visual counts of Atlantic salmon released from a trap located downstream of the counter and immediately above the fishway. All the fish released from the trap had to pass over the counter. A total of 517 salmon (mainly grilse) was released from the trap and the net number of upstream migrants recorded by the counter was also 517. This is the first test and use of an open-channel counter in eastern Canada. The results suggest that some counting fences and fishways may be easily adapted for installation of automated counters and that counters offer a cost-effective means of counting adult Atlantic salmon.
Resistivity Reddin, D., O'Connell, M. and Dunkley, D. 1992. Assessment of an automated fish counter in a Canadian river. Aquaculture and Fisheries Management 1992, 23, 113-121 An application of a new automated fish counting device - the Riverwatcher System ( RW) - was used to monitor upstream fish movements in a pool-and-weir fish pass in the River Zeˆ zere, Portugal, for 141 days from June 2002 to May 2003. Fish populations were also collected downstream using multimesh gillnets (5 different mesh sizes ranging from 30 mm to 85 mm knot to knot; ratio between mesh sizes of about 1.30) and electrofishing for comparison with fish records produced by the RW. More than 3000 individual Iberian nase Chondrostoma polylepis ascended the fish pass and moved through the RW during the study period. However, only 18% of the records produced by the RW contained silhouettes similar to fish; no individual smaller than 15 cm TL was recorded by the counter. Most seasonal movements (73.9%) occurred in spring and were associated with reproduction. Displacements seemed to occur independently of time of day. Water temperature (range: 12-22_C) was the only significant environmental variable (P < 0.01) influencing upstream movements of this species. Further development of hardware and software will be necessary to improve performance of the counter, particularly in Mediterranean rivers, where more turbid waters and a greater proportion of small-size species are present.
Resistivity Smith, I., Johnstone, A., and Dunkley, D. 1996. Evaluation of a portable electrode array for a resistivity fish counter. Fisheries Management and Ecology, 1996, 3, 129-141 Vaki, Ltd., of Iceland has designed a system for counting the in-river migration of salmonids via infrared sensors. The Vaki fish counter is used in Iceland, the United Kingdom, and Europe but is much less used in North America partly because of the system's unknown ability to count large populations accurately. In tests in the Big Qualicum River of Vancouver Island, British Columbia, we found the accuracy of the counter to be inversely correlated with migration rate of chum salmon Oncorhynchus keta. The fish counter was very accurate (.95%) for migration rates less than 500 fish/h but accuracy declined to 76% at a rates exceeding 1,500 fish/h. The principal cause for the decline in accuracy was the inability of the infrared sensors to count the passage of more than one fish simultaneously.
Vaki Armstrong, J.D., Armstrong, R.M., Graham, J.L., Middlemas, S.J., Ribbens, J.C.H., Rycroft, P. and Stewart, D.C. 2012. Movements of Returning Atlantic Salmon Through Tongland Fish Pass. Marine Scotland Science Report 05/12 We tested the efficacy of a dual-frequency identification sonar ( DIDSON) for imaging and enumeration of fall Chinook salmon Oncorhynchus tshawytscha redds in a spawning area below Bonneville Dam on the Columbia River. The DIDSON uses sound to form near-video-quality images and has the advantages of imaging in zero-visibility water and possessing a greater detection range and field of view than underwater video cameras. We suspected that the large size and distinct morphology of a fall Chinook salmon redd would facilitate acoustic imaging if the DIDSON was towed near the river bottom so as to cast an acoustic shadow from the tailspill over the redd pocket. We tested this idea by observing 22 different redds with an underwater video camera, spatially referencing their locations, and then navigating to them while imaging them with the DIDSON. All 22 redds were successfully imaged with the DIDSON. We subsequently conducted redd searches along transects to compare the number of redds imaged by the DIDSON with the number observed using an underwater video camera. We counted 117 redds with the DIDSON and 81 redds with the underwater video camera. Only one of the redds observed with the underwater video camera was not also documented by the DIDSON. In spite of the DIDSON's high cost, it may serve as a useful tool for enumerating fall Chinook salmon redds in conditions that are not conducive to underwater videography.
Vaki Baumgartner, L., Bettanin, M., McPherson, J., Jones, M., Zampattin B. and Beyer, K. 2012. Influence of turbidity and passage rate on the efficiency of an infrared counter to enumerate and measure riverine fish. J. Appl. Ichthyol. 28 (2012), 531-536 Chum salmon Oncorhynchus keta that spawn in main-stem habitats below Bonneville Dam on the Columbia River, USA, are periodically subjected to elevated discharges that may alter spawning behaviour. We investigated behavioural responses of spawning chum salmon to increased water velocities associated with experimental increases in tailwater elevation using acoustic telemetry and a dual-frequency identification sonar. Chum salmon primarily remained near their redds at base tailwater elevations (3.5m above mean sea level), but displayed different movement and behavioural responses as elevations were increased to either 4.1 or 4.7m for 8-h periods. When velocities remained suitable (<0.8m s_1) during elevated-tailwater tests, female chum salmon remained near their redds but exhibited reduced digging activity as water velocities increased. However, when velocities exceeded 0.8ms_1, the females that remained on their redds exhibited increased swimming activity and digging virtually ceased. Female and male chum salmon that left their redds when velocities became unsuitable moved mean distances ranging from 32 to 58m to occupy suitable velocities, but returned to their redds after tailwaters returned to base levels. Spawning events (i.e. egg deposition) were observed for five of nine pairs of chum salmon following tests indicating any disruptions to normal behaviour caused by elevated tailwaters were likely temporary. We believe a chum salmon's decision to either remain on, or leave, its redd during periods of unsuitably high water velocities reflects time invested in the redd and the associated energetic costs it is willing to incur. Published in 2009 by John Wiley & Sons, Ltd.
Vaki Santos, J.M., Pinheiro, P.J., Ferreira, M.T. and Bochechas, J. 2008. Monitoring fish passes using infrared beaming: a case study in an Iberian river. Journal of Applied Ichthyology 24: 26-30. System-wide DIDSON estimation of sockeye salmon escapement in the Quesnel river system. Project Objectives as outlined in the proposal, and used to guide the completion of the project were as follows: 1) DIDSON site selection: Identification and utilization of the best possible DIDSON field site for producing a total Quesnel Lake system sockeye salmon escapement estimate in 2009. 2) Installation and operation of 2 DIDSON systems (one on each river bank, directly opposite) for the entire sockeye salmon migration period, including on-site visual counts. 3) Generation of a total 2009 Quesnel Lake system (Quesnel Lake sockeye Conservation Unit) sockeye salmon escapement estimate, and comparison to the upstream estimates of spawning escapement. 4) Establishment of a capacity-sharing relationship between the UFFCA, NSTC and DFO for providing experience to First Nations fisheries technicians on all aspects of a DIDSON project - from concept to completion phases.
Vaki Shardlow, T.F. and Hyatt, K.D. 2004. Assessment of the Counting Accuracy of the Vaki Infrared Counter on Chum Salmon. North American Journal of Fisheries Management, 24(1): 249-252 Beginning in 2004 the Pacific Salmon Commission implemented a split-beam sonar system to provide real-time estimates of salmon abundance returning to the Fraser River at Mission B.C., replacing less robust single-beam technology which had been in operation since 1977. Dualfrequency identification sonar ( DIDSON) provides more detailed information on underwater objects and provides an opportunity to verify some important assumptions in the split-beam methodology. Analysis of DIDSON information confirmed that the left-bank split-beam system produces valid estimations for upstream fish-flux in the "commonly insonified zones" for the two comparable technologies. Analysis of a limited amount of DIDSON information indicated that the "nearest-neighbour" extrapolation method used in the split-beam fish flux model produces reasonable estimates of fish flux at high passage rates in the blind zone. DIDSON studies indicated that the direction of travel and swimming speed of fish migrating in the middle of the channel were not significantly different from similar statistics routinely collected from the leftbank split-beam system. Unknown "fish-like" targets previously observed near the right bank and other indiscernible targets were clearly identified as debris. Also, in the area of the right bank, salmon were clearly identified as migrating towards the shore, but still oriented upstream. DIDSON studies confirmed that fish react to the transecting vessel by changing their normal upstream swimming direction. This avoidance behaviour was found to be more sensitive to the vertical separation between fish and the vessel than the horizontal separation. Trials were also conducted using the DIDSON technology at an upstream site near Boston Bar B.C. and the technology was found to be applicable for the riverine conditions in that area.
Comparison of Vaki and DIDSON Baumgartner, L., Bettanin, M., McPerson, J., Jones, M., Zampatti, B. and Beyer, K. 2010. Assessment of an infrared fish counter (Vaki River watcher) to quantify fish migrations in the Murray-Darling Basin. Industry & Investment NSW - Fisheries Final Report Series No. 116. ISSN 1837-2112. Detailed avoidance reactions of adult migrating salmon to a mobile survey vessel were successfully observed with side-looking dual frequency indentification sonar ( DIDSON) in the lower Frasner River ( BC, Canada). Both adult sockeye (Oncorhynchus nerka) and pink salmon (Oncorhynchus gorbuscha) returning to the river were found to avoide the approaching vessel by initiating lateral movements away from the vessel, making the fish unlinkely to be insonified by the downward looking transducer towed by the vessel. The vessel was found to have an estimated mean interference range of 4m from its propeller. Analyses of the data concluded that once the vessel and fish were separated by more than 7 m, the vessel no longer affected the normal migration behaviour of the fish.
Comparison of Didson Vaki Resistivity Brennan, L.O. 2013. A Stock Assessment of Atlantic salmon in Large Riverine Catchments. Vol. I and II. A thesis submitted to The National University of Ireland in fulfilment of the requirements for the Degree of Doctor of Philosophy. Head of Department: Prof. Martin Feely. Supervisors: Prof. Ken Whelan and Tiernan Henry. Earth & Ocean Sciences, School of Natural Sciences, National University of Ireland, Galway. 368 (Vol I) + 116 (Vol II) Pages. Available at <> Fixed-location, side-looking, multibeam, sonar techniques offer a practical approach to estimate thenumbers of migrating fish in rivers that are too large or occluded for traditional sampling methods,such as weir trapping, visual observation techniques, and netting. While this technology has been usedto enumerate salmonid escapement in coastal river systems of western North America, little use andevaluation has occurred in inland waters such as the Great Lakes, where rivers and runs of fish areconsiderably smaller than those along the Pacific coast. We use a "Dual-frequency IDentification SONar"(" DIDSON") imaging sonar system to investigate the error and variability among nine people performingfish counts. There was no significant difference found among observers' estimates of fish abundanceper DIDSON file; however, the total count of all fish differed from the benchmark value by as muchas 26%. Post-processing simple fish counts from DIDSON raw data is labour-intensive and costly. Three subsampling methods of fish passage estimations were developed and evaluated for their accuracy and precision for daily and seasonal time frames. The random and systematic subsampling methods had similar seasonal and daily accuracy and precision with few exceptions. Automation-assisted counting was much more accurate and efficient for seasonal estimates. A ratio of approximately 2:1 was found for the automated to manual fish counts and this varied little among years. The DIDSON multibeam sonar unit is useful in estimating potamodromous fish migrations for large tributaries of the Great Lakes. DIDSONimage processing costs can be minimized through suitable subsampling approaches. The automation-assisted method is the most cost-effective means of estimating moderate levels of fish passage overlonger study periods. Multiple individuals can be used interchangeably for the manual post-processing of DIDSON data.
Comparison of Didson and Splitbeam Miller, J.D., D.L. Burwen, and S.J. Fleischman. 2013. Estimates of Chinook salmon passage in the Kenai River using split-beam and dual-frequency identification sonars, 2010. Alaska Department of Fish and Game, Fishery Data Series No. 13-58, Anchorage. This study aimed to develop and test an electrode array for a resistivity fish counter that could be easily installed in a small river without a weir. An electrode array consisting of three steel cables laid in parallel across the stream channel and connected to a microprocessor-based counter was tested in an Atlantic salmon, Salmo salar L., spawning tributary. The accuracy of the counter was assessed by observing fish movements with closed-circuit television. Most salmon moving upstream were registered correctly (90% overall). Detection of downstream movement was less reliable (60% overall), as a consequence of downstream swimming behaviour. The accuracy of the downstream count was improved by tensioning the cable electrodes, but remained lower than that of the upstream count. Since salmon swam repeatedly up- and downstream, this discrepancy resulted in an overestimate of the net upstream count. The accuracy of the downstream count needs to be improved before a bed-mounted electrode array could be used for routine salmon counting.


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