“…MANAGEMENT BRIEF designs evaluated in this study were from fish counts at a dam, the results also likely apply to other fish sampling gears such as DIDSON sonar (Lilja et al 2008) or fish-counting towers (Reynolds et al 2007). FIGURE 6.…”
Fifteen years of video census data from a fishway at Winchester Dam on the North Umpqua River, Oregon, were used to evaluate sampling designs to estimate abundance of spring‐ and fall‐run Chinook Salmon Oncorhynchus tshawytscha, summer‐ and winter‐run steelhead O. mykiss, Coho Salmon O. kisutch, and Pacific Lamprey Entosphenus tridentatus. Five probabilistic sampling designs were evaluated via simulation, with variation in the number of days and the number of hours within a day that were sampled over a 1‐year period. For most species, stratified one‐stage and two‐stage cluster designs were more accurate at estimating abundance than simple random sampling designs. There was very little gain in accuracy beyond sampling 8 h per day for all species. The stratified two‐stage cluster nonuniform probability design was more accurate than the stratified two‐stage cluster uniform probability design at estimating the abundance of steelhead, spring Chinook Salmon, and Coho Salmon, whereas using uniform probabilities resulted in more accurate estimates of abundance for Pacific Lamprey and fall Chinook Salmon. Additionally, the stratified and nonuniform probability designs can be adjusted for high‐priority species through allocation of the sample and assigning selection probabilities of secondary sampling units that optimize efficiency for those species. The consistency in patterns observed among species suggests that the results of this study can be applied to other systems where the abundance of multiple species is of interest.
Received December 5, 2014; accepted March 28, 2015
“…MANAGEMENT BRIEF designs evaluated in this study were from fish counts at a dam, the results also likely apply to other fish sampling gears such as DIDSON sonar (Lilja et al 2008) or fish-counting towers (Reynolds et al 2007). FIGURE 6.…”
Fifteen years of video census data from a fishway at Winchester Dam on the North Umpqua River, Oregon, were used to evaluate sampling designs to estimate abundance of spring‐ and fall‐run Chinook Salmon Oncorhynchus tshawytscha, summer‐ and winter‐run steelhead O. mykiss, Coho Salmon O. kisutch, and Pacific Lamprey Entosphenus tridentatus. Five probabilistic sampling designs were evaluated via simulation, with variation in the number of days and the number of hours within a day that were sampled over a 1‐year period. For most species, stratified one‐stage and two‐stage cluster designs were more accurate at estimating abundance than simple random sampling designs. There was very little gain in accuracy beyond sampling 8 h per day for all species. The stratified two‐stage cluster nonuniform probability design was more accurate than the stratified two‐stage cluster uniform probability design at estimating the abundance of steelhead, spring Chinook Salmon, and Coho Salmon, whereas using uniform probabilities resulted in more accurate estimates of abundance for Pacific Lamprey and fall Chinook Salmon. Additionally, the stratified and nonuniform probability designs can be adjusted for high‐priority species through allocation of the sample and assigning selection probabilities of secondary sampling units that optimize efficiency for those species. The consistency in patterns observed among species suggests that the results of this study can be applied to other systems where the abundance of multiple species is of interest.
Received December 5, 2014; accepted March 28, 2015
“…For example, when the escapement of Pacific salmon Oncorhynchus spp. stocks is expected to exceed 75 000 fishes, then mark-recapture programmes are better replaced by cost-effective hydroacoustic methods (Lilja et al ., 2008) like split-beam techniques or digital identification sonar (DIDSON) (Belcher et al ., 2001). The main disadvantages of the present mark-recapture programme were high personnel demand in the field, statistical prerequisites and substantial disturbance at a sensitive stage of the life cycle, e.g.…”
Hydroacoustic counting and a three-year mark-recapture study with passive integrated transponders (PIT tags) were used to estimate the size of a spawning population of nase Chondrostoma nasus, a threatened potamodromous cyprinid that undertakes annual spawning migrations into a tributary of the Danube River. In 2005, the estimates of the size of the spawning population from the hydroacoustic counts (N = 2234, 95% CL 1929-2538) and from the Jolly-Seber model (N = 1198, 95% CL 461-5842) corresponded well. Estimates from the jackknife-estimator based on the hydroacoustic counts yielded slightly higher values (N = 2783, 95% CL 2529-3037), but were still in the same order of magnitude as those from the hydroacoustic and mark-recapture approach. At low run-size, hydroacoustic counting was more time consuming and technically demanding than mark-recapture studies. At the same time, it was non-invasive, provided real-time data on a fine temporal scale, and estimates showed less variability than the Jolly-Seber model. Mark-recapture of fish in spawning streams involved substantial disturbance at a sensitive stage of the life cycle. Hence, hydroacoustics is highly suited for population estimates of threatened potamodromous fishes, where interference needs to be minimized.
“…Echogram visualization (1) and DIDSON screen view (2) of DIDSON data, with (B) and without (A) background subtraction (Hughes ).Timer data entry: files are large, around 14–18 MB.min −1 (Maxwell and Gove ; Lilja et al . ; Pipal et al . ).…”
Section: Description Of Didson Technologymentioning
confidence: 97%
“…Thresholds for minimum and maximum cluster sizes can be set (in cm²) to distinguish small and big fish or to filter out macrophytes, debris and other parasitic echoes. Cluster sizes can be adapted to target species, for example, minimum cluster sizes of 250 cm 2 to distinguish sea trout (Salmo trutta, Salmonidae) and 300 cm 2 to distinguish Atlantic salmon (Salmo salar, Salmonidae) (Davies 2009 Lilja et al 2008). Nevertheless, estimation of population abundance is more relevant when migration rate is constant, and fish densities are high .…”
Section: Recording and Processing Of Didson Datamentioning
confidence: 99%
“…Timer data entry: files are large, around 14-18 MB.min À1(Maxwell and Gove 2004;Lilja et al 2008;Pipal et al 2010b). Consequently, long-term monitoring requires high-capacity hard drives, and sampling strategies adapted to reduce data size.…”
European Union legislation, through the Water Framework Directive (2000/60/ EC), as well as national legislation, such as the 'Grenelle Environnement ' (2007) in France, requires restoration of ecological connectivity in streams to improve free circulation of migratory fish. Different methods (e.g. capture by trap or net, telemetry, hydroacoustics) are used to evaluate the efficiency of fish passes to estimate the migratory species abundance and analyse changes in their within-river distributions. Among these methods, hydroacoustics is non-intrusive, allowing long-term observation and description of fish populations based on physical properties of sound in water. However, the main limit to hydroacoustic tools is their difficulty in identifying species. Initially designed for military purposes, dual-frequency identification sonar (DIDSON) has been used in environmental management for a decade. This acoustic camera uses higher frequencies and more sub-beams than common hydroacoustic tools, which improves image resolution and then enables observation of fish morphology and swimming behaviour. The ability to subtract static echoes from echograms and directly measure fish length improve the species-identification process. However, some limits have been identified, such as automatic dataset recording and the low range of the detection beam, which decreases accuracy, but efficient tools are now being developed to improve the accuracy of data recording (morphology, species identification, direction and speed). The new technological properties of acoustic cameras, such as the video-like visualization of the data, have greatly improved monitoring of diadromous fish populations (abundance, distribution and behaviour), helping river and fisheries managers and researchers in making decisions.
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