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At least 649 records · Page 36Linked to original sources
USGS2001

Proposed standard-weight equations for brook trout

Weight and length data were obtained for 113 populations of brook trout Salvelinus fontinalis across the species' geographic range in North America to estimate a standard-weight (Ws) equation for this species. Estimation was done by applying the regression-line-percentile technique to fish of 120-620 mm total length (TL). The proposed metric-unit (g and mm) equation is log10Ws = -5.186 + 3.103 log10TL; the English-unit (lb and in) equivalent is log10Ws = -3.483 + 3.103 log10TL. No systematic length bias was evident in the relative-weight values calculated from these equations.

North American Journal of Fisheries Management↗
USGS2001

Short-duration electrical immobilization of lake trout

Chemical anesthetics induce stress responses, and most leave residues in fish tissues that require a certain withdrawal time before the animal can be released into the environment. Therefore, alternatives are needed in cases when fish must be released immediately, for example, during egg-collecting operations or after implanting elastomer tags. To evaluate pulsed direct current as an alternative method of immobilization, individual lake trout Salvelinus namaycush were electrically immobilized using various pulsed-DC voltage gradients and shock durations. Duration of opercular recovery and narcosis were measured for individual fish. Fish were euthanized 24 h after electrical immobilization and processed for lateral radiograph analysis and assessment of perivertebral hemorrhaging by dissection. Survival of lake trout after electrical immobilization at 0.6 V/cm for 30 or 40 s or 0.8 V/cm for 5 or 15 s was monitored for 81 or 84 d after immobilization. Mean narcosis duration increased with voltage gradient and shock duration. Larger fish had longer periods of narcosis at the same combination of voltage gradient and shock duration. Radiological evaluation indicated that 9 of 28 fish in the oldest age-class tested had detectable injuries of the vertebral column, but all but one were in the lowest injury category. Although vertebral column injuries were observed in most small fish, the majority of vertebral column injuries were minor compressions involving two to seven vertebrae. Of the 82 lake trout electrically immobilized to assess long-term survival, only 5 died (6%). Our data suggest that lake trout could be electrically immobilized for a sufficient period to allow field workers to collect length and weight data and implant visible implant tags or colored elastomer tags. The technique we used, however, is probably not appropriate for procedures that require immobilization for more than 2–3 min.

North American Journal of Fisheries Management↗
USGS2001

Residence times and diel passage distributions of radio-tagged juvenile spring chinook salmon and steelhead in a gatewell and fish collection channel of a Columbia River Dam

The amount of time radio-tagged juvenile spring chinook salmon Oncorhynchus tshawytscha and juvenile steelhead O. mykiss spent within a gatewell and the juvenile collection channel at McNary Dam, Columbia River, USA, was measured to determine the diel passage behavior and residence times within these portions of the juvenile bypass system. The median gatewell residence times were 8.9 h for juvenile chinook salmon and 3.2 h for steelhead. Juvenile spring chinook salmon spent 83% of their time in the 18-m-deep gatewell at depths of 9 m or less, and juvenile steelhead spent 96% of their time in the upper 11 m. Fish released during midday and those released in the evening generally exited the gatewell in the evening, indicating that fish entering the gatewell during daylight will have prolonged residence times. Median collection-channel residence times of juvenile chinook salmon were much shorter (2.3 min) than those of steelhead (28.0 min), most likely because of the greater size of the steelhead and the high water velocities within the channel (2.1 m/s). This and other studies indicate most juvenile salmonids enter gatewells of several Columbia and Snake river dams in the evening and pass into the collection channels quickly. However, this is not consistent with the natural in-river migration patterns of these species and represents a delay in dam passage.

Washington; Oregon↗
USGS2001

Guidance of yearling shortnose and pallid sturgeon using vertical bar rack and louver arrays

Some populations of shortnose sturgeon Acipenser brevirostrum and pallid sturgeon Scaphirhynchus albus have been divided by hydroelectric dams, and migration downstream past the dams likely continues. No protection for downstream migrants is presently available, and the behavior of sturgeon to guidance structures has not been studied. We conducted experiments in a 5.4-m-long × 1.5-m-wide flume with a water depth of 37 cm to determine the guidance efficiency and behavior of yearling shortnose and pallid sturgeon to two guidance structures, a bar rack and a louver array. We tested one vertical bar rack configuration with slats spaced 3.9 cm apart (clear spacing). The bar rack slats were oriented directly into the approach flow, and the row of slats was oriented at a 45° angle to the flow. We tested two louver array configurations, one with slats spaced 3.9 cm apart and one with slats spaced 9.0 cm apart (clear spacing). Louver slats were oriented at a 90° angle to the flow, and the row of slats was oriented at a 20° angle to the approach flow. Mean approach velocity to both structures was 31–34 cm/s. Eighteen shortnose sturgeon tagged with passive integrated transponders were tested once in each configuration; 24–38 pallid sturgeon were tested in each configuration. Shortnose sturgeon showed some behavioral differences due to experience with the bar rack, but experience did not affect the percent guided. Both sturgeon species were guided efficiently by the louver array (96–100%) but less efficiently by the bar rack (58–80%). Shortnose sturgeon were more likely to contact the bar rack at night than during the day ( P = 0.01) and at night were more likely to contact the bar rack than the louver array ( P = 0.006). Bar racks guided fewer individuals at night than during the day. For pallid sturgeon, the percentages guided by day and night were 80 and 58, respectively; for shortnose sturgeon, the percentages were 80 and 67. Both species used vision to avoid structures because both increased contact with structures at night. Shortnose sturgeon were superior to pallid sturgeon at swimming off the bottom and avoiding structures.

Massachusetts↗
USGS2001

Effects of an agricultural drainwater bypass on fishes inhabiting the Grassland Water District and the lower San Joaquin River, California

The Grassland Bypass Project, which began operation in September 1996, was conceived as a means of diverting brackish selenium-contaminated agricultural drainwater away from canals and sloughs needed for transporting irrigation water to wetlands within the Grassland Water District (the Grasslands), Merced County, California. The seleniferous drainwater is now routed into the San Luis Drain for conveyance to North Mud Slough and eventual disposal in the San Joaquin River. The purpose of this study was to determine the extent to which the Grassland Bypass Project has affected fishes in sloughs and other surface waters within and downstream from the Grasslands. During September-October 1997, 9,795 fish representing 25 species were captured at 13 sampling sites. Although several species exhibited restricted spatial distributions, association analysis and cluster analysis failed to identify more than one fish species assemblage inhabiting the various sites. However, seleniferous drainwater from the San Luis Drain has influenced selenium concentrations in whole fish within North Mud Slough and the San Joaquin River. The highest concentrations of selenium (12-23 ??g/g, dry weight basis) were measured in green sunfish Lepomis cyanellus from the San Luis Drain where seleniferous drainwater is most concentrated, whereas the second highest concentrations occurred in green sunfish (7.6-17 ??g/g) and bluegills Lepomis macrochirus (14-18 ??g/g) from North Mud Slough immediately downstream from the drain. Although there was some variation, fish in the San Joaquin River generally contained higher body burdens of selenium when captured immediately below the mouth of North Mud Slough (3.1-4.8 ??g/g for green sunfish, 3.7-5.0 ??g/g for bluegills) than when captured upstream from the mouth (0.67-3.3 ??g/g for green sunfish, 0.59-3.7 ??g/g for bluegills). Waterborne selenium was the single most important predictor of selenium concentrations in green sunfish and bluegills, as judged by results from multiple-regression analyses. Among bluegills, water temperature also contributed to the prediction of selenium body burdens.

California↗
USGS2001

Precision and bias of largemouth, smallmouth, and spotted bass ages estimated from scales, whole otoliths, and sectioned otoliths

We compared the precision and bias of age estimates derived from scales, whole otoliths, and sectioned otoliths and by readers of varying experience level for largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, and spotted bass M. punctulatus from Skiatook Lake, Oklahoma. Precision was assessed with the coefficient of variation of age estimates for each fish. Bias was determined among readers and structures from age bias graphs derived from least squares regression. Precision was similar among species for all three structures and among structures for any species, except for smallmouth bass; its age estimates were more precise with whole otoliths. Bias between pairs of readers was found for scales and whole otoliths among all three species but never for sectioned otoliths. The experience level of the reader influenced the bias between readers for scales but not for otoliths. Bias between structures was found between scales and whole otoliths for all three species and between scales and sectioned otoliths for smallmouth bass and spotted bass. Age estimates were unbiased between whole and sectioned otoliths for all three species. Although sectioned otoliths required more preparation time, they provided the best age estimates for the three populations in Skiatook Lake.

Oklahoma↗
USGS2001

Retention of internal anchor tags by juvenile striped bass

We marked hatchery-reared striped bass Morone saxatilis (145-265 mm total length) with internal anchor tags and monitored retention for 28 months after stocking in the Savannah River, Georgia and South Carolina. Anchor tags (with an 18-mm, T-shaped anchor and 42-mm streamer) were surgically implanted ventrally, and coded wire tags (1 mm long and 0.25 mm in diameter) were placed into the cheek muscle to help identify subsequent recaptures. The estimated probability of retention (SD) of anchor tags was 0.94 (0.05) at 4 months, 0.64 (0.13) at 16 months, and 0.33 (0.19) at 28 months. Of 10 fish recaptured with only coded wire tags, 5 showed an externally visible wound or scar near the point of anchor tag insertion. The incidence of wounds or scars, which we interpreted as evidence of tag shedding, increased to 50% in recaptures taken at 28 months (three of six fish). Our estimates for retention of anchor tags were generally lower than those in other studies of striped bass, possibly because of differences in the style of anchor or sizes of fish used. Because of its low rate of retention, the type of anchor tag we used may not be suitable for long-term assessments of stock enhancement programs that use striped bass of the sizes we evaluated.

North American Journal of Fisheries Management↗
USGS2001

Sample-size requirements for evaluating population size structure

A method with an accompanying computer program is described to estimate the number of individuals needed to construct a sample length-frequency with a given accuracy and precision. First, a reference length-frequency assumed to be accurate for a particular sampling gear and collection strategy was constructed. Bootstrap procedures created length-frequencies with increasing sample size that were randomly chosen from the reference data and then were compared with the reference length-frequency by calculating the mean squared difference. Outputs from two species collected with different gears and an artificial even length-frequency are used to describe the characteristics of the method. The relations between the number of individuals used to construct a length-frequency and the similarity to the reference length-frequency followed a negative exponential distribution and showed the importance of using 300-400 individuals whenever possible.

North American Journal of Fisheries Management↗
USGS2001

Statistical properties of relative weight distributions of four salmonid species and their sampling implications

We assessed relative weight (Wr) distributions among 291 samples of stock-to-quality-length brook trout Salvelinus fontinalis, brown trout Salmo trutta, rainbow trout Oncorhynchus mykiss, and cutthroat trout O. clarki from lentic and lotic habitats. Statistics describing Wr sample distributions varied slightly among species and habitat types. The average sample was leptokurtotic and slightly skewed to the right with a standard deviation of about 10, but the shapes of Wr distributions varied widely among samples. Twenty-two percent of the samples had nonnormal distributions, suggesting the need to evaluate sample distributions before applying statistical tests to determine whether assumptions are met. In general, our findings indicate that samples of about 100 stock-to-quality-length fish are needed to obtain confidence interval widths of four Wr units around the mean. Power analysis revealed that samples of about 50 stock-to-quality-length fish are needed to detect a 2% change in mean Wr at a relatively high level of power (beta = 0.01, alpha = 0.05).

North American Journal of Fisheries Management↗
USGS2001

Body conditions and stomach contents of subadult trout during fall and winter in three Wyoming tailwaters

We studied three tailwaters in Wyoming from October 1997 through February 1998 to determine whether body conditions of stocked, subadult rainbow trout Oncorhynchus mykiss or cutthroat trout O. clarki declined from fall through winter and to assess whether lack of food in stomachs might be related to any declines. Body conditions of rainbow trout in two tailwaters remained high through the winter. Body conditions of cutthroat trout in a third tailwater declined between October and February but not to levels anticipated to affect the overwinter survival of the fish. Trout with substantial amounts of food in their stomachs were found throughout the fall and winter in all three tailwaters. In no subadult trout in any of the three tailwaters did we observe rapid declines in body conditions during fall or continuous declines in body conditions to very low levels by the end of winter in association with low biomass of food in stomachs.

North American Journal of Fisheries Management↗
USGS2002

Tag retention and survival of Age-0 Atlantic salmon following surgical implantation with passive integrated transponder tags

We evaluated an alternative to using hypodermic needles to implant passive integrated transponder (PIT) tags in the body cavities of juvenile salmonids. We used surgical techniques to place PIT tags into the body cavities of 3,037 age-0 Atlantic salmon Salmo salar and then held fish under hatchery conditions for 9 months. Tag retention was 99.8% (six fish lost tags), and survival was 94.3% (174 fish died) after controlling for initial mortality (0.7%). A single tagger was able to tag 80–100 fish per hour. Surgically implanting PIT tags into the body cavities of age-0 Atlantic salmon proved to be a viable alternative to using hypodermic needles.

North American Journal of Fisheries Management↗
USGS2002

A night seining technique for sampling juvenile Atlantic salmon in streams

For many studies of the population dynamics, growth, and movement of juvenile Atlantic salmon Salmo salar , it is necessary to resample tagged individuals multiple times. However, common sampling techniques such as electrofishing can have negative effects on fish survival and growth, especially when individuals are repeatedly sampled. We describe an alternative to electrofishing that involves sampling at night with small, one-person seines. Juvenile Atlantic salmon in a small brook were tagged with passive integrated transponder tags and sampled 15 times by means of night seining, day electrofishing, and day seining techniques. Capturing juvenile Atlantic salmon by day seining was inefficient, resulting in a capture probability estimate of 0.18. The mean capture probability estimate was 0.45 during night seining samples and 0.78 during electrofishing samples. The total number of age-0 Atlantic salmon captured via night seining increased 4.5 times after fish attained a mean fork length of just over 60 mm. A much greater number of brook trout Salvelinus fontinalis and brown trout Salmo trutta were captured in electrofishing samples than in night seining samples. Night seining may prove useful when electrofishing is impractical, when threatened or endangered species exist, or when multiple recaptures of individuals are desired.

Massachusetts↗
USGS2002

Effects of triploid grass carp on aquatic plants, water quality, and public satisfaction in Washington State

We investigated effects of triploid grass carp Ctenopharyngodon idella on aquatic macrophyte communities, water quality, and public satisfaction for 98 lakes and ponds in Washington State stocked with grass carp between 1990 and 1995. Grass carp had few noticeable effects on macrophyte communities until 19 months following stocking. After 19 months, submersed macrophytes were either completely eradicated (39% of the lakes) or not controlled (42% of the lakes) in most lakes. Intermediate control of submersed macrophytes occurred in 18% of lakes at a median stocking rate of 24 fish per vegetated surface acre. Most of the landowners interviewed (83%) were satisfied with the results of introducing grass carp. For sites where all submersed macrophytes were eradicated, average turbidity was higher (11 nephelometric turbidity units, NTU) than at sites where macrophytes were controlled to intermediate levels (4 NTU) or unaffected by grass carp grazing (5 NTU). Chlorophyll a was not significantly different between levels of macrophyte control; therefore, we concluded that most of this turbidity was abiotic and not algal. Triploid grass carp were a popular control option and effectively grazed most submersed macrophytes in Washington State. However, calculating stocking rates based on landowner estimates of aquatic plant coverage rarely resulted in intermediate levels of aquatic plant control. Additionally, the effects of particular stocking rates varied considerably. We recommend against using grass carp in Washington lakes where eradication of submersed vegetation cannot be tolerated.

North American Journal of Fisheries Management↗
USGS2002

Effects of antenna placement and antibiotic treatment on loss of simulated transmitters and mortality in hybrid striped bass

We compared the effects of two antenna placements (trailing and nontrailing) and antibiotic treatments (treated and nontreated) on mortality and transmitter loss in hybrid striped bass Morone saxatilis ?? M. chrysops (364 ?? 28 mm total length, 645 ?? 129 g [mean ?? SD]) implanted with simulated transmitters and held in the laboratory for 90 d. Although antibiotic treatment significantly increased the time to first mortality in fish surgically implanted with simulated transmitters (by an average of 14 d), we did not detect an effect on cumulative mortality. We also did not detect an effect of antenna type on the time to first mortality, but cumulative mortality was higher in the trailing antenna groups (50%) than in the nontrailing antenna groups (12%). Three transmitters were expelled during the study, all from trailing-antenna treatment groups, indicating a significant effect of antenna placement on the level of transmitter expulsion. Antibiotic treatment appears to be effective in preventing initial postsurgical infection; however, the antenna may serve as a continuous source of irritation and route of infection into the body cavity. The potential for infection and mortality in experimental animals must be weighed against the improved performance of transmitters with trailing antennas.

North American Journal of Fisheries Management↗
USGS2002

Performance of barbed and barbless hooks in a marine recreational fishery

We used an angling study to examine catch per unit effort (CPUE), bait loss, and total landings by anglers fishing with natural bait on barbed and barbless hooks in a nearshore marine sport fishery located in the Gulf of Mexico near St. Petersburg, Florida. Anglers fished half the day with a barbed hook and half the day with a barbless hook. We also recorded anatomical hook placement, severity of injury or bleeding, and hook extraction times for each landed fish. Bait loss, CPUE, and mean length of catch did not differ between gears, but anglers landed 22% more fish with barbed hooks. Loss of hooked fish was significantly higher with barbless hooks, and efficiency appeared to vary among species. Mean unhooking times were significantly shorter with barbless hooks. Anatomical hook placement did not differ between gears and most fish were hooked in the jaws. Bleeding did not differ between gears because bleeding was influenced strongly by hook placement, but barbless hooks reduced unhooking injuries. In this fishery, barbless hooks probably did not reduce hooking mortality and conferred only slight benefits at the expense of reduced catches.

North American Journal of Fisheries Management↗
USGS2002

Quantifying flow-dependent changes in subyearling fall chinook salmon rearing habitat using two-dimensional spatially explicit modeling

We used an analysis based on a geographic information system (GIS) to determine the amount of rearing habitat and stranding area for subyearling fall chinook salmon Oncorhynchus tshawytscha in the Hanford Reach of the Columbia River at steady-state flows ranging from 1,416 to 11,328 m3/s. High-resolution river channel bathymetry was used in conjunction with a two-dimensional hydrodynamic model to estimate water velocities, depths, and lateral slopes throughout our 33-km study area. To relate the probability of fish presence in nearshore habitats to measures of physical habitat, we developed a logistic regression model from point electrofishing data. We only considered variables that were compatible with a GIS and therefore excluded other variables known to be important to juvenile salmonids. Water velocity and lateral slope were the only two variables included in our final model. The amount of available rearing habitat generally decreased as flow increased, with the greatest decreases occurring between 1,416 and 4,814 m3/s. When river discharges were between 3,682 and 7,080 m3/s, flow fluctuations of 566 m3/s produced the smallest change in available rearing area (from -6.3% to +6.8% of the total). Stranding pool area was greatly reduced at steady-state flows exceeding 4,531 m3/s, but the highest net gain in stranding area was produced by 850 m3/s decreases in flow when river discharges were between 5,381 and 5,664 m3/s. Current measures to protect rearing fall chinook salmon include limiting flow fluctuations at Priest Rapids Dam to 850 m3/s when the dam is spilling water and when the weekly flows average less than 4,814 m3/s. We believe that limiting flow fluctuations at all discharges would further protect subyearling fall chinook salmon.

Washington↗
USGS2002

Effect and acceptance of bluegill length limits in Nebraska natural lakes

Bluegill Lepomis macrochirus populations in 18 Nebraska Sandhill lakes were evaluated to determine if a 200-mm minimum length limit would increase population size structure. Bluegills were trap-netted in May and June 1998 and 1999, and a creel survey was conducted during winter 1998-2001 on one or two lakes where bluegills had been tagged to determine angler exploitation. Thirty-three percent of anglers on one creeled lake were trophy anglers (i.e., fishing for large [???250 mm] bluegills), whereas 67% were there to harvest fish to eat. Exploitation was always less than 10% and the total annual mortality averaged 40% across all 18 lakes. The time to reach 200 mm ranged from 4.3 to 8.3 years. The relative stock density of preferred-length fish increased an average of 2.2 units in all 18 lakes with a 10% exploitation rate. However, yield declined 39% and the number harvested declined 62%. Bluegills would need to reach 200 mm in 4.2 years to ensure no reduction in yield at 10% exploitation. Both yield and size structure were higher with a 200-mm minimum length limit (relative to having no length limit) only in populations with the lowest natural mortality and at exploitation of 30% or more. Although 100% (N = 39) of anglers surveyed said they would favor a 200-mm minimum length limit to improve bluegill size structure, anglers would have to sacrifice harvest to achieve this goal. While a 200-mm minimum length limit did minimally increase size structure at current levels of exploitation across all 18 bluegill populations, the populations with the lowest natural mortality and fastest growth provided the highest increase in size structure with the lowest reduction in yield and number harvested.

North American Journal of Fisheries Management↗
USGS2002

Spawning characteristics of redband trout in a headwater stream in Montana

I investigated the spawning characteristics of redband trout Oncorhynchus mykiss gairdneri (a rainbow trout subspecies) during the spring of 1998 in Basin Creek, a third-order headwater stream located in the Kootenai River drainage in northwestern Montana. I examined the timing of spawning as related to discharge and water temperature and analyzed microhabitat selection of 30 completed redds in a low-gradient (0.5–1.5%) reach. Redband trout spawned as flow declined after peak runoff and as mean daily water temperature exceeded 6.0C and maximum daily temperature exceeded 7.0C. Redband trout began spawning on 6 June (mean daily discharge = 2.1 m3/s), 10 d after the peak discharge (8.7 m3/s) occurred. The last redd was completed on 24 June, when discharge was 1.5 m3/s. The mean total redd length was 53 cm (SD = 14; range = 31–91 cm), and the mean total area was 51 cm2 (SD = 8; range= 46– 76 cm2). Eighty percent of the redds were located in pool tailouts, 13% in runs, and 7% in riffles. Spawning redband trout selected redd sites based on substrate size and water depth but not water velocity. Fish selected substrate sizes of 2–6 mm, water depths of 20–30 cm, and water velocities of 40–70 cm/s. My results suggest that redband trout in a low-gradient, third-order mountain stream found suitable spawning habitat in pool tail-outs that contained abundant gravels.

Montana↗