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USGS2007

Effect of relative volume on radio transmitter expulsion in subadult common carp

Expulsion of surgically implanted radio transmitters is a problem in some fish telemetry studies. We conducted a 109-d experiment to test the hypothesis that variation in relative volume of transmitters surgically implanted in subadult common carp Cyprinus carpio would affect transmitter expulsion. We also necropsied fish at the end of the experiment to evaluate histological evidence for the mechanism of expulsion. Survival rate was high during our experiment; all control fish and 88% of the fish subjected to the implantation surgery survived. Expulsion rate was low; of the 23 fish that received transmitters and survived the experiment, only two (9%) expelled the transmitters. One of these expulsions occurred through a rupture of the incision and the other occurred via the intestine. Retained transmitters were all encapsulated by tissue, and most exhibited multiple adhesions to the intestine, gonads, and body wall. Adhesions were more numerous in fish that received larger transmitters. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗

USGS2007

A comparison of shoreline seines with fyke nets for sampling littoral fish communities in floodplain lakes

We compared shoreline seines with fyke nets in terms of their ability to sample fish species in the littoral zone of 22 floodplain lakes of the White River, Arkansas. Lakes ranged in size from less than 0.5 to 51.0 ha. Most contained large amounts of coarse woody debris within the littoral zone, thus making seining in shallow areas difficult. We sampled large lakes (>2 ha) using three fyke nets; small lakes (<2 ha) were sampled using two fyke nets. Fyke nets were set for 24 h. Large lakes were sampled with an average of 11 seine hauls/ lake and small lakes were sampled with an average of 3 seine hauls/lake, but exact shoreline seining effort varied among lakes depending on the amount of open shoreline. Fyke nets collected more fish and produced greater species richness and diversity measures than did seining. Species evenness was similar for the two gear types. Two species were unique to seine samples, whereas 13 species and 3 families were unique to fyke-net samples. Although fyke nets collected more fish and more species than did shoreline seines, neither gear collected all the species present in the littoral zone of floodplain lakes. These results confirm the need for a multiple-gear approach to fully characterize the littoral fish assemblages in floodplain lakes. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗

USGS2008

Response of fish populations to natural channel design restoration in streams of the Catskill Mountains, New York

Many streams and rivers throughout North America have been extensively straightened, widened, and hardened since the middle 1800s, but related effects on aquatic ecosystems have seldom been monitored, described, or published. Beginning in the early 1990s, reach-level restoration efforts began to base projects on natural channel design (NCD) techniques and Rosgen's (1994b, 1996) river classification system in an effort to duplicate or mimic stable reference reach geomorphology. Four reaches in three streams of the Catskill Mountains, New York, were restored from 2000 to 2002 using NCD techniques to decrease bed and bank erosion rates, decrease sediment loads, and improve water quality. The effects of restoration on the health of fish assemblages were assessed through a before-after, control-impact (BACI) study design to quantify the net changes in population and community indices at treatment reaches relative to index changes at unaltered reference reaches from 1999 to 2004. After restoration, community richness and biomass at treatment reaches increased by more than one-third. Changes in fish communities were caused mainly by shifts in dominant species populations; fish community biomass and total fish abundance were generally dominated by daces or daces and sculpins before restoration and by one or more salmonid species after restoration. Density and biomass of eastern blacknose dace Rhinichthys atratulus, longnose dace R. cataractae, and slimy sculpin Cottus cognatus did not change appreciably, whereas net salmonid density and biomass increased substantially after restoration. These changes were driven primarily by large increases in populations of brown trout Salmo trutta. The findings demonstrate that the structure, function, and ultimately the health of resident fish populations and communities can be improved, at least over the short term, through NCD restoration in perturbed streams of the Catskill Mountains. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2007

Assessment of gaseous CO2 and AQUI-S as anesthetics when surgically implanting radio transmitters into cutthroat trout

Tricaine methanesulfonate (MS-222) and CO2 are anesthetics that can be legally used in fisheries work in the United States, but they are limited in their field applications. A mandatory 21-d withdrawal period is required for fish exposed to MS-222. Carbon dioxide is not approved by the U.S. Food and Drug Administration, but it is a "low regulatory priority drug" that can be used legally for fish anesthesia. However, stressful induction and lengthy recovery times have been associated with CO2. AQUI-S is a clove oil derivative that has the potential to become an approved anesthetic without the limitations of MS-222 or CO2. We compared the efficacy of CO2 with that of AQUI-S when surgically implanting radio transmitters into cutthroat trout Oncorhynchus clarkii. A 20% survival rate was observed when CO2 was used in combination with silk sutures, but a 100% survival rate was observed when CO2 was used in combination with surgical staples to shorten the duration of the surgical procedure. A 100% survival rate was observed when AQUI-S was used in combination with either silk sutures or surgical staples. Carbon dioxide in combination with surgical staples seemed to provide a reasonable option when surgically implanting radio transmitters into cutthroat trout, but AQUI-S may be the preferred anesthesia because high pH and dissolved oxygen levels and low free-CO2 concentrations are maintained during surgical procedures.

North American Journal of Fisheries Management↗

USGS2008

Zero-inflated modeling of fish catch per unit area resulting from multiple gears: Application to channel catfish and shovelnose sturgeon in the Missouri River

Fisheries studies often employ multiple gears that result in large percentages of zero values. We considered a zero-inflated Poisson (ZIP) model with random effects to address these excessive zeros. By employing a Bayesian ZIP model that simultaneously incorporates data from multiple gears to analyze data from the Missouri River, we were able to compare gears and make more year, segment, and macrohabitat comparisons than did the original data analysis. For channel catfish Ictalurus punctatus, our results rank (highest to lowest) the mean catch per unit area (CPUA) for gears (beach seine, benthic trawl, electrofishing, and drifting trammel net); years (1998 and 1997); macrohabitats (tributary mouth, connected secondary channel, nonconnected secondary channel, and bend); and river segment zones (channelized, inter-reservoir, and least-altered). For shovelnose sturgeon Scaphirhynchus platorynchus, the mean CPUA was significantly higher for benthic trawls and drifting trammel nets; 1998 and 1997; tributary mouths, bends, and connected secondary channels; and some channelized or least-altered inter-reservoir segments. One important advantage of our approach is the ability to reliably infer patterns of relative abundance by means of multiple gears without using gear efficiencies. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2008

Physical, biotic, and sampling influences on diel habitat use by stream-dwelling bull trout

We used daytime and nighttime underwater observation to assess microhabitat use by bull trout Salvelinus confluentus (N = 213) in streams of the intermountain western USA during the summers of 2001 and 2002. We recorded fish focal points and measured a set of habitat characteristics as well as habitat availability via line transects. Bull trout were benthic and solitary; most (88%) were observed at night. We developed a conditional logistic regression model to account for the effect of fish movement in response to snorkeling, and we fitted 18 candidate models to evaluate the relative influences of biotic and abiotic factors on habitat use. The candidate models were also fitted with a naive logistic regression (i.e., no movement) to evaluate the effects of movement on inferences of microhabitat use. The most plausible model describing bull trout habitat use was the same for the conditional and nai??ve regressions and included depth, velocity, percent rubble substratum, and the day X depth, body size X depth, and body size X day X depth interactions. The presence of brook trout S. fontinalis and the abundance of conspecifics did not strongly influence microhabitat use by bull trout. The relative rankings of the remaining models differed substantially between the conditional and nai??ve models. Relative to the conditional models, the naive models overestimated the importance of diurnal differences in habitat use and overestimated the use of deepwater habitats, particularly during the day. Both model types suggested that all sizes of bull trout were generally found in deeper, low-velocity habitat at night, whereas small bull trout (70-90 mm total length) were found in shallower habitats during the day. We recommend lhat biologists account for fish movement in response to sampling to avoid biasing modeled habitat use patterns by bull trout. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2008

Factors affecting bottom trawl catches: Implications for monitoring the fishes of Lake Superior

An annual daytime bottom trawl survey of the Lake Superior fish community designed in 1978 does not adequately assess the entire community. Whereas recent studies have recommended that pelagic species be surveyed with a combination of acoustic and midwater trawling methods (AC-MT), we used bottom trawling to study the effects of depth, diel period, and season on biomass estimates and the sizes of bottom-oriented species. Day and night bottom trawl samples were collected within 48 h at three depths (30, 60, and 120 m) at a Lake Superior site during eight sampling periods that included two seasons each year (early summer and late summer to early fall) for 2 years (2004 and 2005). Depth significantly affected the biomass of seven of the eight species analyzed, while diel period affected the biomass of six species. For most species, average biomass levels were higher at night. The effect of season on biomass was comparatively low (three species were significantly affected). Depth significantly affected the sizes of six bottom-oriented species, as the average length of most species increased with depth. The effects of diel period (three species) and season (one species) on average length were comparatively small. By adding night bottom trawl samples to night AC-MT collections, the entire fish community of Lake Superior can be monitored with a single lakewide survey employing multiple gears. The establishment of offshore sampling (i.e., where depths exceed 80 m) will provide estimates of deepwater species that have been largely undersampled by the 1978-designed survey. We recommend that the present fish community survey be maintained, albeit at a reduced level, until a nighttime survey time series is well established (in 3-5 years).

North American Journal of Fisheries Management↗

USGS2008

Measuring the performance of two stationary interrogation systems for detecting downstream and upstream movement of PIT-tagged salmonids

We tested the performance of two stationary interrogation systems designed for detecting the movement of fish with passive integrated transponder (PIT) tags. These systems allowed us to determine the direction of fish movement with high detection efficiency and high precision in a dynamic stream environment. We describe an indirect method for deriving an estimate for detection efficiency and the associated variance that does not rely on a known number of fish passing the system. By using six antennas arranged in a longitudinal series of three arrays, we attained detection efficiencies for downstream- and upstream-moving fish exceeding 96% during high-flow periods and approached 100% during low-flow periods for the two interrogation systems we tested. Because these systems did not rely on structural components, such as bridges or culverts, they were readily adaptable to remote, natural stream sites. Because of built-in redundancy, these systems were able to perform even with a loss of one or more antennas owing to dislodgement or electrical failure. However, the reduction in redundancy resulted in decreased efficiency and precision and the potential loss of ability to determine the direction of fish movement. What we learned about these systems should be applicable to a wide variety of other antenna configurations and to other types of PIT tags and transceivers.

North American Journal of Fisheries Management↗

USGS2008

Effect of artificial sunlight on the retention of external calcein marks on lake trout

When choosing a fish marking technique to address fishery related questions, it is important to consider factors that affect mark retention. Calcein, a chemical marking agent, is under investigation for potential use on fish. Two laboratory trials were conducted with calcein-marked lake trout Salvelinus namaycush to determine the effect of artificial sunlight on calcein mark intensity. In trial 1, fish exposed to 18,000 lx for 7 d lost 90% or more of the calcein mark intensity (relative to the colorimetric key, mg/L) on the head, body, ventral region, and pectoral fins relative to mark intensity in fish that were maintained in darkness. In trial 2, light intensity was reduced 2.5-3.0-fold. After 7 d of light exposure, calcein mark intensity on the head was reduced by 40-45% relative to mark intensity in fish that were held in darkness; by day 14, calcein mark intensity on the head was reduced by 55-60% relative to that of dark-treated fish. No further decline was observed in light-exposed fish, and head mark intensity values did not differ among days 14, 21, and 28 for this treatment group. Of the four areas evaluated, the head and pectoral fin were more easily read using a colorimetric key than the lateral or ventral regions of the fish. The concentration of calcein spotted on filter paper to devise the colorimetric key ranged from 1 to 100 mg/L. A difference of approximately 7 mg/L in apparent calcein mark intensity means for the head region could be detected using the colorimetric key. These trials showed that calcein mark intensity on lake trout declined when fish were exposed to artificial sunlight, and the use of a colorimetric key improved the objectivity of calcein mark intensity assessment.

North American Journal of Fisheries Management↗

USGS2008

Length variation in age-0 westslope cutthroat trout at multiple spatial scales

Phenotypic diversity provides ecological and evolutionary functions, stabilizing populations in variable environments. Although benefits of larger body size in juvenile fishes are well documented, size variation may have value as well. We explored the distribution of length and length variation in age-0 westslope cutthroat trout Oncorhynchus clarkii lewisi at three spatial scales: area (102 km2), stream (101 km2), and site (100 km2). In addition, we examined relationships between length variables (mean length and interquartile range of length) and instream (temperature and conductivity) and landscape (aspect, elevation, headwater distance, and valley width) variables that were expected to be associated with fish size. Conductivity was included as a surrogate for productivity. Most variation in mean length and interquartile range of fish length was found among areas (62.2% and 62.6%, respectively). Mean length also varied among streams and sites (21.9% and 15.8%, respectively). Similarly, interquartile range of fish length varied among streams and sites (19.1% and 18.3%, respectively). Both length variables were associated with temperature and elevation. Mean fish length was also associated with conductivity, but the association between interquartile length range and conductivity was weak. We conclude that the conservation of variation in phenotypic attributes, such as length, in westslope cutthroat trout may require conservation of viable populations across broad areas and across environmental gradients that are associated with growth. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2008

Population size and relative abundance of adult Alabama shad reaching jim woodruff lock and dam, Apalachicola River, Florida

We estimated the population size of migrating Alabama shad Alosa alabamae below Jim Woodruff Lock and Dam in the Apalachicola River (located in the central panhandle of northwestern Florida) using mark-recapture and relative abundance techniques. After adjustment for tag loss, emigration, and mortality, the population size was estimated as 25,935 (95% confidence interval, 17,715-39,535) in 2005, 2,767 (838-5,031) in 2006, and 8,511 (5,211-14,674) in 2007. The cumulative catch rate from boat electrofishing averaged 20.47 Alabama shad per hour in 2005, 6.10 per hour in 2006, and 13.17 per hour in 2007. The relationship between population size (N) and electrofishing catch per unit effort (CPUE) was modeled by the equation N = -9008.2 + (electrofishing CPUE X 1616.4). Additionally, in 2007 the hook-and-line catch rate averaged 1.94 Alabama shad per rod hour. A predictive model relating the population size and hook-and-line CPUE of spawning American shad A. sapidissima was applied to Alabama shad hook-and-line CPUE and produced satisfactory results. Recent spawning populations of Alabama shad in the Apalachicola River are low relative to American shad populations in other southeastern U.S. rivers. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2008

Survival of the faucet snail after chemical disinfection, pH extremes, and heated water bath treatments

The faucet snail Bithynia tentaculata, a nonindigenous aquatic snail from Eurasia, was introduced into Lake Michigan in 1871 and has spread to the mid-Atlantic states, the Great Lakes region, Montana, and most recently, the Mississippi River. The faucet snail serves as intermediate host for several trematodes that have caused large-scale mortality among water birds, primarily in the Great Lakes region and Montana. It is important to limit the spread of the faucet snail; small fisheries equipment can serve as a method of snail distribution. Treatments with chemical disinfection, pH extremes, and heated water baths were tested to determine their effectiveness as a disinfectant for small fisheries equipment. Two treatments eliminated all test snails: (1) a 24-h exposure to Hydrothol 191 at a concentration of at least 20 mg/L and (2) a treatment with 50°C heated water for 1 min or longer. Faucet snails were highly resistant to ethanol, NaCl, formalin, Lysol, potassium permanganate, copper sulfate, Baquacil, Virkon, household bleach, and pH extremes (as low as 1 and as high as 13).

Wisconsin↗

USGS2008

Adherence of Myxobolus cerebralis myxospores to waders: Implications for disease dissemination

The vectors involved in the spread of whirling disease, which is caused by Myxobolus cerebralis, are only partly understood. However, the parasite has rapidly become established in many regions, suggesting that it is easily disseminated. We gained insight into transport vectors by examining the surface porosity of common wading equipment materials and the adherence of M. cerebralis myxospores to them. Interstitial spaces within rubber, felt, lightweight nylon, and neoprene were measured on scanning electron microscope images. Myxospores were applied to each material, the material was rinsed, and the myxospores recovered to assess adherence. The mean interstitial space size of rubber was the smallest (2.0 ??m), whereas that of felt was the largest (31.3 ??m). The highest recovery rates were from rubber and the glass control. Percent myxospore recovery varied by material, the recovery from felt being lower than that from all other materials. The potential for felt to carry even small numbers of myxospores suggests that the introduction of M. cerebralis by felt-soled wading boots is possible. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗

USGS2009

Evaluation of a gastric radio tag insertion technique for anadromous river herring

Anadromous river herring (alewives Alosa pseudoharengus and blueback herring A. aestivalis ), which constitute a historically and ecologically important component of coastal rivers, have declined precipitously throughout the Atlantic seaboard. Suggested causes of river herring decline include commercial fishing and predation by striped bass Morone saxatilis . Although the causes of this recent trend are poorly understood, river herring are especially vulnerable to adverse impacts during their spring spawning migration. Radiotelemetry is an especially useful method for addressing potential problems encountered during the movement of these fish from the ocean to freshwater. In spite of frequent calls for evaluation of telemetry methods, controlled tests of posttagging effects are rare for alosids and virtually nonexistent for anadromous river herring. We developed a protocol for gastric tagging of anadromous river herring, and we used hatchery and field studies to evaluate behavior, tag placement, stress response, and posttagging mortality. We also compared tagger effects and quantified posttagging upstream movements of fish in the field. In controlled hatchery trials, no fish died at 10 min, 1 h, or 14 d posttagging. No tags were rejected, and only 1 of 35 tags ruptured the gut. In field cages, mortality, plasma cortisol, glucose, and chloride measured at 24 h were similar between tagged and untagged fish. In the field, 12 of 14 fish moved upriver after tagging and spent 114 h on average at upriver sites. Using a variety of approaches, we found no evidence that our tagging protocol adversely affected river herring in comparison with untagged fish that were subjected only to handling and holding. Our protocol, evaluated by comparing responses of tagged and untagged fish under controlled conditions, may be useful in future studies that seek to understand causes of decline for anadromous river herring.

Massachuetts↗

USGS2009

Hatch Timing Variations Among Reservoir Gizzard Shad Populations: Implications for Stocked Sander spp. Fingerlings

Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in relation to the peak in density of larval gizzard shad Dorosoma cepedianum. However, coordinating stockings to coincide with peaks in gizzard shad density is difficult due to temporal variation in spawn timing among reservoirs. We used weekly estimates of larval gizzard shad density and length distributions to identify dates of peak hatching and peak total density in Ohio reservoirs and to explore the influence of spring water temperature regimes on timing of peak larval density. Gizzard shad density peaked over 21–32 d among reservoirs but generally varied by 12 d or less among years for any given population. Density peaks were driven by hatching, as larvae smaller than 10 mm accounted for a majority of the gizzard shad collected on the peak date. Peaks in gizzard shad density corresponded to water temperatures of 17–22°C and occurred most frequently when water temperatures had been stable or rising. Reservoirs in the southern portion of the state were 2–5°C warmer than northern reservoirs throughout the spring; thus, gizzard shad spawning and date of peak larval density were earliest in southern reservoirs and became progressively later for populations in more northerly reservoirs. Historical stocking dates for fingerling walleyes S. vitreus and saugeyes (sauger S. canadensis × walleye) in Ohio reservoirs indicated that southern reservoirs were often stocked after the expected peak in gizzard shad density and northern reservoirs were stocked before the peak. A statewide approach to stocking that incorporates latitudinal variations in gizzard shad hatch timing whereby southern reservoirs are stocked earliest would better align stockings with peak gizzard shad density, potentially improving survival of fingerling walleyes and saugeyes.

North American Journal of Fisheries Management↗

USGS2009

Physiological development and vulnerability to Ceratomyxa shasta of fall-run Chinook Salmon in the Upper Klamath River Watershed

We evaluated a stock for restoring runs of fall Chinook salmon Oncorhynchus tshawytscha in the Upper Klamath River basin by monitoring its development in Iron Gate Hatchery and in net-pens in the Williamson River and Upper Klamath Lake in Oregon. We transferred age-1 hatchery fall Chinook salmon to net-pens in October 2005 and age-0 fall Chinook salmon in May 2006. Indices of smolt development were assessed in the hatchery and after 3 and 14 d in net-pens. Based on gill Na + , K + -ATPase activity and plasma thyroxine (T4) concentration, age-1 Chinook salmon were not developing smolt characteristics in the hatchery during October. Fish transferred to the river or lake had increased plasma cortisol in response to stress and increased T4 accompanying the change in water, but they did not have altered development. Variables in the age-0 Chinook salmon indicated that the fish in the hatchery were smolting. The fish in the river net-pens lost mass and had gill ATPase activity similar to that of the fish in the hatchery, whereas the fish transferred to the lake gained mass and length, had reduced condition factor, and had higher gill ATPase than the fish in the river. These results, along with environmental variables, suggest that the conditions in the lake were more conducive to smoltification than those in the river and thus accelerated the development of Chinook salmon. No Chinook salmon in the hatchery or either net-pen became infected with the myxosporean parasite Ceratomyxa shasta (the presence of which in the river and lake was confirmed) during either trial or when held for 90 d after a 10-d exposure in net-pens (2006 group). We concluded that that there is little evidence of physiological impairment or significant upriver vulnerability to C. shasta among this stock of fall Chinook salmon that would preclude them from being reintroduced into the Upper Klamath River basin.

North American Journal of Fisheries Management↗

USGS2010

Factors associated with mortality of walleyes and saugers caught in live-release tournaments

We measured the initial mortality (fish judged nonreleasable at weigh-in), prerelease mortality (fish judged nonreleasable 1–2 h after weigh-in [which includes initial mortality]), and postrelease mortality (fish that died during a 5-d retention in net-pens) in 14 live-release tournaments for walleye Sander vitreus conducted in April–October 2006 and April–July 2007 in lakes and rivers in Michigan, Minnesota, North Dakota, South Dakota, and Wisconsin. Among the 14 events, initial mortality was 0–28%, prerelease mortality was 3–54%, and postrelease mortality was 0–100%; the mortality of reference fish (walleyes ≥31 cm long that were captured by electrofishing and held in net-pens with tournament-caught walleyes to measure postrelease mortality) was 0–97%. Mortality was generally low in events conducted when water temperatures were below 14°C but substantially higher in events when water temperatures were above 18°C. The mortality of reference fish suggests that capture by electrofishing and minimal handling when the water temperature exceeds 19°C results in high mortality of walleyes that is largely the result of the thermal conditions immediately after capture. Mortality was not related to the size of the tournaments (number of boats), the total number or weight of walleyes weighed in, or the mean number or weight of walleyes weighed in per boat. Mortality was positively related to the depth at which walleyes were caught and the live-well temperature and negatively related to the live-well dissolved oxygen concentration. Surface water temperature was the best predictor of mortality, and models were developed to predict the probability of prerelease and postrelease mortality of 10, 20, and 30% or less of tournament-caught walleyes due to water temperature.

Michigan, Minnesota, North Dakota, South Dakota, W↗

USGS2010

Use of portable antennas to estimate abundance of PIT-tagged fish in small streams: Factors affecting detection probability

Portable passive integrated transponder (PIT) tag antenna systems can be valuable in providing reliable estimates of the abundance of tagged Atlantic salmon Salmo salar in small streams under a wide range of conditions. We developed and employed PIT tag antenna wand techniques in two controlled experiments and an additional case study to examine the factors that influenced our ability to estimate population size. We used Pollock's robust‐design capture–mark–recapture model to obtain estimates of the probability of first detection ( p ), the probability of redetection ( c ), and abundance ( N ) in the two controlled experiments. First, we conducted an experiment in which tags were hidden in fixed locations. Although p and c varied among the three observers and among the three passes that each observer conducted, the estimates of N were identical to the true values and did not vary among observers. In the second experiment using free‐swimming tagged fish, p and c varied among passes and time of day. Additionally, estimates of N varied between day and night and among age‐classes but were within 10% of the true population size. In the case study, we used the Cormack–Jolly–Seber model to examine the variation in p , and we compared counts of tagged fish found with the antenna wand with counts collected via electrofishing. In that study, we found that although p varied for age‐classes, sample dates, and time of day, antenna and electrofishing estimates of N were similar, indicating that population size can be reliably estimated via PIT tag antenna wands. However, factors such as the observer, time of day, age of fish, and stream discharge can influence the initial and subsequent detection probabilities.

North American Journal of Fisheries Management↗