bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic and Mixed Organic–Inorganic Fertilization of Plastic-Lined Ponds for Fingerling Walleye Culture
Authors: Rogge Matthew L , Moore Alan A , Morris Joseph E
Published: June 2004

Treatment with organic fertilizer was compared with treatment involving a mix of organic and inorganic fertilizers for culture of walleye Stizostedion vitreum fingerlings in 0.04-ha plastic-lined ponds. Organic fertilization consisted of weekly additions of alfalfa and cottonseed pellets. Each type of organic fertilizer was applied to each pond at 2.3 kg/week. Nitrogen (36–0–0 as N–P–K) and phosphorus (12–49–6) fertilizers were used weekly to adjust the ratio of nitrate-nitrogen to total phosphorus ratios in the mixed-fertilizer treatment to 7:1. Nutrient values in ponds treated with organic fertilizer were similar to those in ponds treated with the organic–inorganic mix. However, the water used to fill the ponds was initially high in both nitrogen and phosphorus, which may have reduced the nutrient differences between treatments. There were also no differences in food base densities (zooplankton and benthos) or fingerling production between treatments. Concentrations of dissolved oxygen at pond bottoms were sometimes less than 1 mg/L in the morning in both treatments; however, this had no apparent effect on fingerling survival in either treatment. Daphnia spp. and copepod populations sharply declined in both treatments after fish were stocked, suggesting that larval walleyes immediately fed on these crustaceans. Zooplankton populations remained low until near the end of the season. Benthic invertebrate densities were high throughout the season in both treatments and showed no differences between treatments. Stomach content analyses revealed walleye fingerlings consumed Daphnia spp. and copepods throughout the experiment, whereas dipteran larvae became increasingly important once walleyes reached 20 mm, about 2 weeks into the experiment. Both fertilization treatments produced relatively large fish (0.57 g) with good survival rates (>50%). The results from this study suggest that dipteran management is important for providing food items for larval walleyes and that high initial nutrient levels from water sources may reduce the requirements for inorganic enrichment in plastic-lined ponds for walleye culture.
Successful Sex Reversal of Brook Trout with 17α-Methyldihydrotestosterone Treatments
Authors: Galbreath Peter F , Adams Nathan D , Sherrill Lee W.
Published: June 2004

Monosex female stocks are widely used in the commercial production of rainbow trout Oncorhynchus mykiss. The potential for commercial production of brook trout Salvelinus fontinalis, however, is constrained by the lack of published protocols for producing the sex-reversed males required to create monosex female stocks. Immersion and immersion plus feeding treatments with 17α-methyltestosterone (MT) and 17α-methyldihydrotestosterone (MDHT) were applied to genotypically female gynogenetic brook trout to induce phenotypic sex reversal. The fry were exposed to a 6-h immersion in a solution of MT or MDHT on day 10 following completion of hatch and/or to a steroid-treated diet for 60 d beginning at first feeding. Immersion dosages were 0.5 or 1.0 mg/L, and feeding dosages were 1.0 or 2.0 mg/kg of feed for MT and 0.5 or 1.0 mg/kg for MDHT. Phenotypic sex of the fish was determined 19 or 22 months after first feeding. Control gynogenetic fish were 100% phenotypic females. Treatments with MT had minimal effect: most fish remained female, with only a low incidence of phenotypic males (1–3% in four of the treatments), intersex fish, or sterile fish. In contrast, a substantial number of phenotypic males were observed in several of the MDHT treatments, with the highest proportion (45%) occurring in the 0.5 mg/L immersion plus 0.5 mg/kg feeding treatment. Sperm was obtained from 29 males from five MDHT treatment groups and one MT treatment group examined at maturity (22 months) and was used in progeny tests of these males. The progeny were 100% female, confirming the male parents to be genotypically female. These protocols may be used to create sex-reversed brook trout males for the production of monosex female progeny, although additional trials are ongoing to test similar MDHT immersion dosages applied once or multiple times, with or without feeding treatments, to identify protocols with increased efficacy.
Use of Size for Early Detection of Juvenile Hatchery Steelhead Destined to Be Precocious Males
Authors: Tipping Jack M , Gannam Ann L , Hillson Todd D , Poole Jeff B
Published: June 2004

At two Washington State hatcheries in August 1999–2002, juvenile steelhead Oncorhynchus mykiss were size-graded and the largest fish (4.8–9.2% of the population) were coded-wire-tagged and mixed with small fish to determine whether the large fish were those that became precocious males. The results showed that the large fish in August at Merwin Hatchery tended to become precocious, although the mean lengths of the precocious and nonprecocious fish were similar at their time of release in April. At Abernathy Fish Technology Center (FTC), the large fish in August did not disproportionately become precocious, and the nonprecocious fish were significantly larger than the precocious fish at release. We suggest that precocious fish at Abernathy FTC may have committed to precocity before August whereas fish at Merwin Hatchery committed to precocity in August. Because only 0.82% of the large fish became precocious, removing the 5–10% largest fish in August at the Merwin Hatchery would be marginally successful in reducing the number of precocious males.
Lack of Effect of Iodophor on Survival of Westslope Cutthroat Trout Eggs during Water Hardening
Authors: Pravecek Jay , Barnes Michael E
Published: June 2004

Eggs of westslope cutthroat trout Oncorhynchus clarki lewisi were subjected to iodophor (active iodine) concentrations of 0, 25, 50, 75, 100, or 125 mg/L for 30 min during water hardening. Embryo survival to the eyed egg stage was not significantly different among the treatments. Disinfection of westslope cutthroat trout eggs with iodophor during water hardening is recommended.
Time Required for Yolk Coagulation in Pink Salmon and Steelhead Eggs Exposed to Mechanical Shock
Authors: Jensen Nathan R , Collins Keya C
Published: June 2004

Incubation success in management studies and environmental assessments is often applied as a measure of natural spawning productivity as based on the live: dead ratios of excavated eggs. If sampling occurs too early in the development of the embryo, eggs will die from the sampling procedure and could be mistaken for incubation mortality if the yolk coagulates rapidly after experiencing lethal shock. In this study we examined how long it takes for the yolk of fertilized eggs of pink salmon Oncorhynchus gorbuscha and steelhead O. mykiss to coagulate after experiencing lethal mechanical shock, as it applies to that question. Tests were conducted at 12°C from 24 and 48 h (12–24 degree-days) postfertilization to the eyed stage of developing embryos (156 degree-days for steelhead and 223 degree-days for pink salmon). Results demonstrated that yolk coagulation was visible within seconds after shocking, involving as much as 50% of the yolk material within 5 min of shocking. We conclude, therefore, that mortality of eggs can be readily detected within 5 min of experiencing significant shock, regardless of the shock intensity. Yolk coagulation in eggs shocked during excavation of recently prepared pink salmon or steelhead redds occurs rapidly enough to be mistaken for natural incubation mortality. To avoid such potential bias in redd surveys of salmonid incubation success, sampling should be delayed until embryo development from the eggs of the latest spawners has progressed to the eyed stage. This should take approximately 30 d for pink salmon in fall temperatures and 23 d for steelhead in spring temperatures.
Efficacy of Hydrogen Peroxide in Controlling Mortality Associated with Saprolegniasis on Walleye, White Sucker, and Paddlefish Eggs
Authors: Gaikowski Mark P , Rach Jeffrey J , Drobish Mark , Hamilton Jerry , Harder Tom , Lee Lynn A , Moen Clark , Moore Alan
Published: June 2004

The efficacy of hydrogen peroxide in controlling saprolegniasis on eggs of walleye Stizostedion vitreum, white sucker Catostomus commersoni, and paddlefish Polyodon spathula was evaluated at four private, state, and federal production hatcheries participating in an Investigational New Animal Drug efficacy study (experiment 1; walleyes) and in a laboratory-based miniature egg jar incubation system (experiment 2; walleyes, white suckers, and paddlefish). Naturally occurring fungal infestations (saprolegniasis) were observed on eggs in both experiments. Confirmatory diagnosis of infested eggs from one hatchery in experiment 1 identified the pathogen as Saprolegnia parasitica. During experiment 1, eggs were treated daily for 15 min with either 0, 500, or 750 mg/L of hydrogen peroxide, and one trial compared a 500-mg/L hydrogen peroxide treatment with a formalin treatment at 1,667 mg/L. Saprolegniasis infestation was observed in control egg jars, whereas treatment with either formalin or hydrogen peroxide virtually eliminated the infestation. Hydrogen peroxide treatments of 500 mg/L either increased egg hatch or were as effective as physical removal of infested eggs in controlling mortality. Although treatment with formalin at 1,667 mg/L significantly increased the percent eye-up of walleye eggs compared with that of those treated with hydrogen peroxide at 500 mg/L, the difference was only 1.9–2.6%. In experiment 2, noneyed eggs were treated for 15 min every other day with 0, 283, 565, or 1,130 mg/L of hydrogen peroxide until the viable eggs hatched. Saprolegniasis infestation engulfed most control eggs, whereas infestation of treated eggs was either reduced or not visible. Hydrogen peroxide significantly increased egg hatch for all three species tested in experiment 2. Although hydrogen peroxide treatments as low as 283 mg/L significantly increased walleye and white sucker hatch, treatments between 500 and 1,000 mg/L are more likely to be effective in production egg incubation systems.
Determining Annual Production Capabilities for Sequential Rearing Programs through the Use of Routine Fish Culture Data
Authors: Westers Harry , Weeks Christopher T
Published: June 2004

Routine fish culture data, such as growth rates, feed conversion, length−weight relationships, and mortality rates from empirical studies of rainbow trout Oncorhynchus mykiss, are used to model sequential rearing strategies in order to demonstrate their impact on production. Increasing the frequency of cohort introductions into the rearing cycle improves output but at a diminishing rate. Moving from a single-cohort, batch culture strategy to one that involves two cohorts per rearing cycle increases production by as much as 60%. For the same number of cohort introductions per rearing cycle and similar feed conversions, slow-growing fish realize the same annual output as fast-growing fish, but a greater number of fish (i.e., greater biomass) must be maintained with the former. Five different rearing strategies are presented, namely, those involving 1, 2, 4, 6, and 12 cohorts. Two to six cohorts per rearing cycle appear to be optimal for nonmixed production programs.
Trauma to Juvenile Pinfish and Spot Inflicted by Submarine Detonations
Authors: Govoni John Jeffrey , Settle Lawrence R. , West Melissa A.
Published: June 2004

Juvenile pinfish Lagodon rhomboides and spot Leiostomus xanthurus exposed to pressure waves emanating from experimental submarine detonations exhibited both sublethal and probable antemortem trauma. Hyperemia within the swim bladder and liver, hematuria, coagulative liver necrosis, and rupture of the pancreas were the most recurrent and significant traumas evident from histopathological examination and were directly attributed to exposure to pressure waves. These traumas were probably caused by the rapid compression and expansion of the swim bladder as the impulse passed. Of these traumas, hyperemia within visceral organs and hematuria are probably sublethal. Rupture of the pancreas and coagulative liver necrosis are typically irreversible and hence probably antemortem.
Molecular and Phenotypic Characterization of Strains of Photobacterium damselae subsp. piscicida Isolated from Hybrid Striped Bass Cultured in Louisiana, USA
Authors: Hawke John P. , Thune Ronald L. , Cooper Richard K. , Judice Erika , Kelly-Smith Maria
Published: June 2004

Photobacteriosis, which is caused by the bacterium Photobacterium damselae subsp. piscicida (formerly Pasteurella piscicida) was found to be a primary cause of mortality in hybrid striped bass (striped bass Morone saxatilis × white bass M. chrysops) cultured in brackish water in southern Louisiana. The disease was diagnosed on 50 occasions from 1990 through 2000 by the Louisiana Aquatic Diagnostic Laboratory, and mortality ranged from 5% to 90% in individual culture units. Strains of the bacterium from the Louisiana coast of the Gulf of Mexico were identified by means of biochemical tests, guanine–cytosine ratio, and Aquarapid Pp kit. Strains were characterized according to their biochemical phenotype, enzyme activities, plasmid profile, genotypic profile as determined by randomly amplified polymorphic DNA (RAPD) analysis, and antimicrobial susceptibility. When compared with representative isolates from the Chesapeake Bay, Greece, Japan, and Israel, Louisiana Gulf Coast isolates of P. damselae subsp. piscicida were found to be almost identical in biochemical phenotype and enzyme activity. The isolates differed in their plasmid profiles and antimicrobic susceptibilities. Louisiana isolates were found to possess a unique plasmid banding profile relative to strains from other geographic locations. The Louisiana isolates typically produced two large plasmid bands greater than 30 kilo–base pairs (kb) and two smaller bands 8.0 kb and 5.0 kb in size. Isolates from Israel and Greece exhibited similar banding patterns but were different from Louisiana and Japanese isolates. Resistance to Romet and Terramycin by some Louisiana strains was the result of acquisition of an R plasmid. When analyzed by RAPD, the Louisiana Gulf Coast strains were found to belong to clonal lineage group 2, which displays a fingerprint similar to that of the Japanese strains.
Distribution of Myxobolus cerebralis within a Free-Flowing River System during the Migration Period for Juvenile Anadromous Salmonids in Idaho
Authors: Cavender Wade P. , Johnson Keith A. , Cain Kenneth D.
Published: June 2004

To gain a better understanding of the pathogen-associated risk to resident and anadromous salmonid populations, the distribution, prevalence, and intensity of Myxobolus cerebralis infections were assessed during the smolt migration period in the Salmon, Snake, and Clearwater rivers of Idaho. Sentinel exposures of rainbow trout Oncorhynchus mykiss fry (0.6 g) occurred at 10 locations beginning at the headwaters of the Salmon River and extending downstream to the Snake and Clearwater rivers from April 18–28 and May 15–25, 2001. Following exposure, fish were examined for the prevalence and severity of infection by means of histological, pepsin−trypsin digest, and nested polymerase chain reaction analyses. Infections did not occur in the portions of the Snake or Clearwater rivers included in this study but were found in the Salmon River at five locations during April and seven locations during May. The results during April demonstrated moderate to high prevalence of infection (65% and 75% at 900 and 1,800 Celsius temperature units (CTUs), respectively) at the most upstream headwater site (river kilometer (rkm) 619, measuring from the mouth of the Salmon River), but intensity decreased 28 km downstream (rkm 591) to 10% and 0% at 900 and 1,800 CTUs, respectively. Fish exposed at two sites further downstream (rkm 454 and 416) showed 100% prevalence in both April and May. The most downriver sites at which infections were detected in April and May were sites 5 (rkm 308) and 7 (rkm 86). Significant correlations were not found between M. cerebralis infection and the environmental conditions examined in this study. However, the findings from this study show a temporal (April−May) increase in distribution and prevalence and a trend toward decreasing prevalence downstream of rkm 416. Therefore, resident and anadromous salmonids emerging or migrating through the Salmon River during April and May are probably exposed to the infectious stage of M. cerebralis.
Effects of Sublethal Dissolved Oxygen Stress on Blood Glucose and Susceptibility to Streptococcus agalactiae in Nile Tilapia Oreochromis niloticus
Authors: Evans Joyce J. , Shoemaker Craig A. , Klesius Phillip H.
Published: June 2004

The stress effects of sublethal dissolved oxygen (DO) exposures on blood glucose levels and susceptibility to Streptococcus agalactiae infection in Nile tilapia Oreochromis niloticus were determined with the One Touch Ultra blood glucose monitoring system. Fish were monitored for temporal changes in blood glucose concentration before, during, and after exposure to up to 1 mg DO per liter for 24 h. Blood glucose was found to increase significantly (P < 0.001) in response to sublethal DO exposure. In additional experiments, fish were exposed to acceptable or sublethal DO. After exposure, fish were administered 9.5 × 101 or 7.5 × 102 colony-forming units (CFU) of S. agalactiae (infected) or tryptic soy broth (uninfected) by intraperitoneal injection. Significantly higher mean blood glucose levels were found in both infected and uninfected fish following sublethal DO exposure. None of the fish exposed to acceptable DO died due to streptococcal infection after challenge with either dose. Fish exposed to sublethal DO had significantly higher mortality rates (27% and 80%) after infection with S. agalactiae at 9.5 × 101 or 7.5 × 102 CFU than fish exposed to acceptable DO (0%). Increases in the susceptibility of Nile tilapia to S. agalactiae may be the result of the stress response to the sublethal DO exposure.
Shortnose Sturgeon in the Santee–Cooper Reservoir System, South Carolina
Authors: Collins Mark R. , Cooke Doug , Post Bill , Crane John , Bulak James , Smith Theodore J. I. , Greig Thomas W. , Quattro Joseph M.
Published: June 2004

The Santee–Cooper system in South Carolina, USA, is a complex of reservoirs, rivers, and canals. The endangered shortnose sturgeon Acipenser brevirostrum inhabits the rivers below the reservoirs and has also occasionally been reported anecdotally in the reservoirs themselves. During 1998–1999, we conducted a study to determine whether shortnose sturgeon were reproducing in the reservoirs, and if so, to evaluate habitat use and degree of separation from the riverine groups. Fourteen shortnose sturgeon were captured from the reservoirs, and all (even gravid females) appeared qualitatively less robust than riverine fish previously captured below one of the dams. Ten of the fish were implanted with transmitters and tracked at least once per week. Fish tracked in the upper reservoir, Lake Marion, stayed in the upper portion of that lake or in tributary streams flowing into it. We documented seasonal movements among four primary areas of upper Lake Marion and its tributaries. A spawning site on one of the tributaries, the Congaree River, was verified by collection of viable eggs. Genetic analysis demonstrated significant differences between samples from the Santee–Cooper reservoirs and three nearby coastal rivers. Cooper River samples, however, were not significantly different from reservoir samples, although appreciable differences in haplotype frequencies were observed. The need for a larger sample size was apparent. Although telemetry, spawning, genetic, and observational evidence suggests that the shortnose sturgeon in the reservoirs form a separate population segment, the results are not conclusive because possible downstream movement, especially of juveniles, through the dams has not been investigated.
Cardiovascular Responses of Largemouth Bass to Exhaustive Exercise and Brief Air Exposure over a Range of Water Temperatures
Authors: Cooke Steven J. , Ostrand Kenneth G. , Bunt Christopher M. , Schreer Jason F. , Wahl David H. , Philipp David P.
Published: June 2004

In this study we examined the effects of exhaustive exercise and brief air exposure on the cardiovascular function of largemouth bass Micropterus salmoides at four water temperatures (13, 17, 21, and 25°C). We used Doppler flow probes to monitor cardiac output and its components (i.e., stroke volume and heart rate) while we manually chased fish to exhaustion to simulate angling, exposed them to air for 30 s, and then recorded patterns of recovery. Resting cardiac variables generally increased with increasing water temperature except for stroke volume, which was temperature independent. Fish heart rate became erratic during exercise, and during air exposure fish exhibited severe bradycardia before becoming tachycardic when returned to the water. Maximal change occurred most rapidly for cardiac output (about 5 min). Several minutes later, changes in heart rate (increase) and stroke volume (decrease) simultaneously reached maximal deviations from resting values. Cardiac output and heart rate increased 150–200% relative to resting values despite 50% reductions in stroke volume, suggesting that largemouth bass are primarily frequency modulators. Maximal changes generally increased with water temperature for cardiac output and heart rate but not for stroke volume, resulting in heightened scope for cardiac output and heart rate with increasing water temperature. Recovery patterns were not influenced by water temperature. Cardiac output and heart rate generally returned to predisturbance levels in approximately 135 min, whereas stroke volume recovered more rapidly (about 110 min). Based on these findings, we suggest that largemouth bass exposed to exhaustive exercise and brief air exposure are capable of recovering from handling disturbances in several hours across the range of water temperatures that we examined (13–25°C).
Do Endangered Razorback Suckers Have Poor Larval Escape Performance Relative to Introduced Rainbow Trout?
Authors: Wesp Heather M. , Gibb Alice C.
Published: June 2004

Poor recruitment has generated the hypothesis that the endangered razorback sucker Xyrauchen texanus is particularly vulnerable to predation early in its life history. We compared the escape responses of razorback suckers, which are adapted to the historically warm waters of the Colorado River, with those of rainbow trout Oncorhynchus mykiss, an introduced coldwater species, throughout early development at water temperatures of 12°C and 18°C. We quantified escape performance using maximum velocity, acceleration, and time to maximum velocity and acceleration. Both species showed complete temperature compensation for escape performance; individuals reared at 12°C performed as well as those reared at 18°C. Performance was also similar between species, although two variables exhibited a species × size interaction. Small razorback suckers were faster (greater maximum velocity and acceleration) than small rainbow trout, while large larvae performed similarly. We also determined that razorback sucker larval escape performance falls within the range reported for other fishes. Therefore, we conclude that razorback suckers do not have “poor” escape performance and that temperature does not directly cause decreased performance. However, a cold temperature reduces growth rates and delays razorback suckers' attainment of a “predator‐proof” size. Small larvae are also more likely to perform uncoordinated, ineffective escape responses. Hence, razorback sucker performance is indirectly diminished by temperature.
Acute Sensitivity of Juvenile Shortnose Sturgeon to Low Dissolved Oxygen Concentrations
Authors: Campbell Jed G. , Goodman Larry R.
Published: June 2004

There is considerable concern that factors such as eutrophication, industrial pollution, and dredging are adversely affecting the habitats of the endangered shortnose sturgeon Acipenser brevirostrum. Specific knowledge of the environmental requirements of this species is required if environmental managers are to adequately protect it. We conducted experiments to obtain information on the acute sensitivity of young‐of‐year shortnose sturgeon to a low dissolved oxygen (DO) concentration. Flow‐through tests were conducted with hatchery‐produced fish exposed to the ranges of DO, salinity, and temperature expected in the southeastern United States coastal river–estuary interfaces during spring and summer. The estimated concentration lethal to 50% of the test organisms (the LC50 value) after 24 h that we derived for approximately 77‐d‐old fish tested at 2‰ salinity and a nominal temperature of 25°C was 2.7 mg/L (32% saturation). An estimated LC50 of 2.2 mg/L (26% saturation) was obtained for approximately 104‐d‐old fish tested at 4‰ and 22°C. The 24‐h, 48‐h, and 72‐h LC50 values for approximately 134‐d‐old fish tested at 4.5‰ and 26°C were also 2.2 mg/L (28% saturation). However, the test with approximately 100‐d‐old fish at 2‰ and a nominal temperature of 30°C yielded a 24‐h LC50 of 3.1 mg/L (42% saturation). These data should be of value in derivating DO‐protective values for shortnose sturgeon inhabiting estuaries along the Atlantic coast.
Test of a Power Transfer Model for Standardized Electrofishing
Authors: Miranda L. E. , Dolan C. R.
Published: June 2004

Standardization of electrofishing in waters with differing conductivities is critical when monitoring temporal and spatial differences in fish assemblages. We tested a model that can help improve the consistency of electrofishing by allowing control over the amount of power that is transferred to the fish. The primary objective was to verify, under controlled laboratory conditions, whether the model adequately described fish immobilization responses elicited with various electrical settings over a range of water conductivities. We found that the model accurately described empirical observations over conductivities ranging from 12 to 1,030 μS/cm for DC and various pulsed‐DC settings. Because the model requires knowledge of a fish's effective conductivity, an attribute that is likely to vary according to species, size, temperature, and other variables, a second objective was to gather available estimates of the effective conductivity of fish to examine the magnitude of variation and to assess whether in practical applications a standard effective conductivity value for fish may be assumed. We found that applying a standard fish effective conductivity of 115 μS/cm introduced relatively little error into the estimation of the peak power density required to immobilize fish with electrofishing. However, this standard was derived from few estimates of fish effective conductivity and a limited number of species; more estimates are needed to validate our working standard.
Use of Existing and Reconnected Backwater Habitats by Hatchery‐Reared Adult Razorback Suckers: A Predictive Model for the Imperial Division, Lower Colorado River
Authors: Gurtin Scott D. , Slaughter Joe E. , Sampson Schuyler J. , Bradford Richard H.
Published: June 2004

Information regarding the life history and biological requirements and preferences for the razorback sucker Xyrauchen texanus is limited. Current recovery efforts involve rearing fish to juvenile or adult stages in hatcheries before they are released into areas of critical habitat that increase their survival. Our objectives were to develop a model based on habitat use by hatchery‐reared razorback suckers in the lower Colorado River of Arizona and California for predicting preferred habitat and to determine whether fish would use reconnected off‐channel habitats. To this end, we monitored the use of existing and reconnected habitats by hatchery‐reared razorback suckers implanted with sonic transmitters. Off‐channel (backwater) habitats were preferred over main‐channel or side‐channel habitats. We constructed a model using logistic regression to predict which types of backwaters (based on morphology and water quality) were most suitable for use by razorback suckers. The model works well for predicting sites that are less suited for use and can be used to prioritize habitats for reconnection purposes because razorback suckers were found to utilize reconnected habitats.
Winter Ecology of Kokanee: Implications for Salmon Management
Authors: Steinhart Geoffrey B. , Wurtsbaugh Wayne A.
Published: June 2004

We sampled various limnological parameters and measured growth and diet of age‐0 kokanee Oncorhynchus nerka (lacustrine sockeye salmon) during two winters in a high‐mountain lake of the Sawtooth Valley, Idaho. Although winter has been recognized as an important period for many warmwater fishes and for stream‐dwelling salmonids, winter limitations have only recently been studied for coolwater and coldwater species. Ice and snow cover in winter limited light penetration. As a result, chlorophyll‐a and zooplankton density were lower in ice‐covered periods than during ice‐free periods. The weight of stomach contents was often below a maintenance ration, yet the incidence of empty stomachs was extremely low (1 of 63) and the weight of stomach contents increased as energy reserves declined, indicating that kokanee were actively foraging during winter. Kokanee length and weight remained constant during the winter of 1993–1994 but increased from November through May in 1994–1995. Condition factors, however, declined significantly over the winter in both years, and lipid content approached levels associated with mortality. Differences in growth patterns may have been caused by a combination of changes in zooplankton density and kokanee abundance and in kokanee behavior to defend energy reserves or avoid predation. Results demonstrated the ambiguity of some growth measurements and the importance of choosing the correct metric for measuring growth in fishes. Because juvenile kokanee and sockeye salmon are ecologically similar, management efforts to restore the endangered Snake River sockeye salmon to the Sawtooth Valley lakes should recognize that winter conditions might be a bottleneck for this species.
Respiratory and Circulatory Responses to Hypoxia in Largemouth Bass and Smallmouth Bass: Implications for “Live‐Release” Angling Tournaments
Authors: Furimsky Marosh , Cooke Steven J. , Suski Cory D. , Wang Yuxiang , Tufts Bruce L.
Published: June 2004

Arterial blood respiratory variables, ventilation rate, and cardiac output were examined in largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu to compare their physiological responses to graded levels of hypoxia. Reduction in water Po2 (Pwo2) from 150 to 45 torr (1 torr ≈ 133.3 Pa) caused similar decreases in arterial Po2 (Pao2) in both species, although total blood O2 content was markedly higher in largemouth bass at the lower oxygen tensions. Curves for in vitro O2 dissociation in normoxic fish indicated that largemouth bass blood had a higher affinity for O2 than smallmouth bass blood. Severe hypoxia caused a significant increase in blood concentrations of catecholamines in smallmouth bass but not in largemouth bass. Increases in ventilation rate (54%) and decreases in cardiac output (27%) during hypoxia were also more pronounced in smallmouth bass than in largemouth bass. Arterial blood pH did not change during hypoxia exposure in largemouth bass but decreased significantly during severe hypoxia in smallmouth bass. The results of this study indicate that smallmouth bass are more sensitive to hypoxia than largemouth bass are. These results have important implications for situations in which these two bass species may be exposed to periods of hypoxia, such as during live‐release angling events.
Atlantic Sturgeon Marine Distribution and Habitat Use along the Northeastern Coast of the United States
Authors: Stein Andrew B. , Friedland Kevin D. , Sutherland Michael
Published: June 2004

Though the distribution of Atlantic sturgeon Acipenser oxyrinchus is relatively well known in freshwater and estuarine habitats in the northern portion of their range, their distribution in marine habitats is poorly understood. Sturgeon migrate into marine waters to forage between spawning events and probably maintain gene flow between river populations by entering nonnatal river systems to spawn. While at sea, they are captured in commercial fishing gears. We investigated data collected by onboard fishery observers to determine the occurrence and habitat preference of Atlantic sturgeon off the northeastern coast of the United States. Sturgeon distributions were based on monitored fishing trips over the period 1989–2000 and referenced to local bathymetry and sediment data. The results show that peak sturgeon captures along the coast were approximately bracketed by isobaths ranging from 10 to 50 m. Sturgeon were present more frequently on gravel and sand sediment types and were associated with specific coastal features. The factors that may concentrate Atlantic sturgeon in particular coastal areas are discussed.
Evaluation of Nonlethal Methods for the Analysis of Mercury in Fish Tissue
Authors: Baker R. F. , Blanchfield P. J. , Paterson M. J. , Flett R. J. , Wesson L.
Published: June 2004

Thousands of fish are sacrificed each year to determine potential human exposure to mercury (Hg) from fish consumption. In this paper, we use lake whitefish Coregonus clupeaformis and northern pike Esox lucius to demonstrate that accurate and reliable measures of fish muscle Hg concentrations can be determined from small samples (<100 mg) harvested with biopsy tools. Reliability of results primarily depends upon analytical methodology and tissue sample weight. Mercury concentrations estimated by use of cold‐vapor atomic absorption spectrophotometry (CVAAS) on small composite tissue samples harvested with a Tru‐Cut (TC) biopsy needle (mean sample wet weight = 47 mg) were less precise than estimates from tissue samples harvested with a dermal punch (DP; mean sample wet weight = 126 mg). Precision differences presumably occurred because TC samples weighed less than the prescribed minimum weight (>100 mg) for CVAAS. There was no difference in precision of Hg concentrations among tissue extraction methods when biopsy samples were analyzed via cold‐vapor atomic fluorescence spectrophotometry (CVAFS). Mean tissue Hg concentrations obtained with the biopsy techniques and CVAAS or CVAFS were similar to benchmark concentrations in fillet samples (within 6%), even for TC– CVAAS. A field study of the effects of the DP biopsy method on survival of northern pike showed that tissue harvesting did not reduce survival. Our results clearly demonstrate that analysis of Hg content in muscle harvested with biopsy tools provides Hg measures comparable in accuracy to traditional, whole‐fish methods but without causing mortality.
Effects of Lowhead Dams on Riffle‐Dwelling Fishes and Macroinvertebrates in a Midwestern River
Authors: Tiemann Jeremy S. , Gillette David P. , Wildhaber Mark L. , Edds David R.
Published: June 2004

Many studies have assessed the effects of large dams on fishes and macroinvertebrates, but few have examined the effects of lowhead dams. We sampled fishes, macroinvertebrates, habitat, and physicochemistry monthly from November 2000 to October 2001 at eight gravel bar sites centered around two lowhead dams on the Neosho River, Kansas. Sites included a reference site and a treatment site both upstream and downstream from each dam. Multivariate analysis of variance indicated that habitat, but not physicochemistry, varied immediately upstream and downstream from the dams, with resultant effects on macroinvertebrate and fish assemblages. Compared with reference sites, upstream treatment sites were deeper and had lower velocities and downstream treatment sites were shallower and had higher velocities; both upstream and downstream treatment sites had greater substrate compaction than reference sites. Macroinvertebrate richness did not differ among site types, but abundance was lowest at downstream treatment sites and evenness was lowest at upstream treatment sites. Fish species richness did not differ among site types, but abundance was highest at downstream reference sites and evenness was highest at upstream sites. The abundance of some benthic fishes was influenced by the dams, including that of the Neosho madtom Noturus placidus, which was lowest immediately upstream and downstream from dams, and those of the suckermouth minnow Phenacobius mirabilis, orangethroat darter Etheostoma spectabile, and slenderhead darter Percina phoxocephala, which were highest in downstream treatment sites. Although limited to one system during a 1‐year period, this study suggests that the effects of lowhead dams on fishes, macroinvertebrates, and habitat are similar to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.
Spatial and Temporal Variation in the Grilse Proportion of Atlantic Salmon in Norwegian Rivers
Authors: L'Abée‐Lund J. H. , Vøllestad L. A. , Beldring S.
Published: June 2004

Variation in the sea age at maturity of Atlantic salmonSalmo salarwas studied in 158 Norwegian rivers over large spatial (58–71°N; 5–30°E) and temporal (1983–2000) scales. Age at sexual maturity was expressed as the proportion of grilse (fish with one sea winter) in the nominal salmon catch. No general temporal trend was found in the proportion of grilse in the catches. However, grilse proportion declined significantly in 10 rivers and increased significantly in 11 rivers out of the 55 rivers with data for all 18 years. There were no short‐term cycles in grilse proportion within rivers. We found coherence and similarity in the temporal variation in grilse proportion for rivers draining into large fjord systems. Reasons for the temporal variation in grilse proportions must be sought at a river‐specific or regional scale. River‐specific factors (water discharge, river steepness, and presence of lakes) explained a large percentage of the spatial variation in grilse proportion. Grilse proportion increased with decreasing river size (measured as mean annual water discharge) and with increasing proportion of water discharge occurring during summer (i.e., the migration season). Grilse proportion was higher in rivers located nearer to the open ocean, probably indicating an effect of early feeding on growth and maturation. Even after accounting for environmental variation at the local scale, we found large regional differences in grilse proportion. Region captured this variation more efficiently than latitude, but grilse proportion was higher in the northern part of Norway than in the more southerly part. This variability may indicate large‐scale differences in, for example, oceanic migration routes for fish originating from different regions.
Relations among Habitat Characteristics, Exotic Species, and Turbid‐River Cyprinids in the Missouri River Drainage of Wyoming
Authors: Quist Michael C. , Hubert Wayne A. , Rahel Frank J.
Published: June 2004

We used data from 91 stream reaches in the Missouri River drainage of Wyoming to determine whether abiotic and biotic factors were related to the abundance of four cyprinid species associated with turbid‐river environments: flathead chub Platygobio gracilis, sturgeon chub Macrhybopsis gelida, plains minnow Hybognathus placitus, and western silvery minnow H. argyritis. The abundance of these cyprinids was positively related to the percentage of fine substrate in a reach and inversely related to the percentage of gravel substrate, the percentage of large rocky substrate, and the abundance of exotic piscivores. Differences in substrate composition and abundance of exotic piscivores were largely explained by the presence and location of large, main‐stem impoundments. Reaches without any large impoundments in their watershed had a high percentage of fine substrate, high catch rates of turbid‐river cyprinids, few exotic piscivores, and little gravel or large rocky substrate. Reaches with a downstream impoundment (i.e., within 200 km) had habitat characteristics similar to those without impoundments but had few turbid‐river cyprinids and many exotic piscivores. Reaches with an upstream impoundment (i.e., within 200 km) had little fine substrate, a high percentage of large rocky substrate, few turbid‐river cyprinids, and many exotic piscivores. Our results suggest that impoundments have had a substantial influence on the distribution and abundance of cyprinid species adapted to hydrologically dynamic, turbid prairie streams and that conserving these species is dependent on maintaining natural flow and sediment transport regimes and on reducing habitat suitability for exotic piscivores.
Impact of Age and Gender on the Pharmacokinetics of Gemtuzumab Ozogamicin
Authors: Korth‐Bradley Joan M. , Dowell James A. , King S. Peter , Liu H. , Berger Mark S. ,   Mylotarg Study Group
Published: June 2004

Study Objective. To determine the pharmacokinetic parameters of the components of gemtuzumab ozogamicin and to assess the possible influence of age and gender on the values.

Design. Phase II, multicenter, open‐label, nonrandomized, parallel study.

Setting. Hospitals and outpatient oncology clinics.

Patients. Fifty‐eight patients with acute myeloid leukemia in first relapse participated. Demographic data included 29 men and 29 women; 34 were younger than 60 years of age (mean age 53 ± 16 yrs).

Intervention. Patients received gemtuzumab ozogamicin as a single 2‐hour infusion of 9 mg/m2. Serial plasma samples were collected over 10 days after the beginning of the infusion.

Measurements and Main Results. Plasma concentrations of components of gemtuzumab ozogamicin (hP67.6 antibody, total and unconjugated calicheamicin derivatives) were measured by validated enzyme‐linked immunosorbent assays. Pharmacokinetic parameters were determined by noncompartmental methods and comparisons between groups were made by analysis of variance. No significant differences were seen between men and women or between those over 60 and those less than 60 years of age in maximum concentration, time to maximum concentration, area under the curve, clearance, or volume of distribution for components of gemtuzumab ozogamicin.

Conclusion. No differences occur in the pharmacokinetics of the components of gemtuzumab ozogamicin (hP67.6 or calicheamicin) based on gender or age.
Mechanism of Action of and Resistance to Quinolones
Authors: Bearden David T. , Danziger Larry H.
Published: June 2004

A topoisomerase was identified as the bacterial target site for quinolone action in the late 1970s. Since that time, further study identified two bacterial topoisomerases, DNA gyrase and topoisomerase IV, as sites of antibacterial activity. DNA gyrase appears to be the primary quinolone target for gram‐negative bacteria. Topoisomerase IV appears to be the preferential target in gram‐positive organisms, but this varies with the drug. Three mechanisms of resistance against quinolones are mutations of topoisomerases, decreased membrane permeability, and active drug efflux. Although these mechanisms occur singly, several resistance factors are often required to produce clinically applicable increases in minimum inhibitory concentrations. Appropriate drug selection and dosage and prudent human and veterinary interventions are important factors in controlling the emergence of resistance.
Pharmacokinetics and Pharmacodynamics of Fluoroquinolones
Authors: Rodvold Keith A. , Neuhauser Melinda
Published: June 2004

The pharmacokinetic characteristics of levofloxacin, moxifloxacin, and gatifloxacin include excellent oral bioavailability (90–99%), extensive penetration into tissues and body fluids, and an elimination half‐life (6–12 hrs) that allows for once‐daily dosing in patients with normal renal function. Levofloxacin and gatifloxacin primarily are excreted unchanged in the urine, whereas moxifloxacin undergoes hepatic metabolism. The pharmacodynamic values that correlate with successful clinical and microbiologic outcomes, as well as prevent emergence of bacterial resistance, are ratios of maximum or peak unbound drug concentration (Cmax) to minimum inhibitory concentration (MIC), and 24‐hour unbound area under the concentration curve (AUC0‐24hr) to MIC. For gram‐negative infections, a Cmax:MIC greater than or equal to 10 and AUC0‐24hr:MIC greater than or equal to 125 are associated with increased probability of a successful outcome. For infections caused by Streptococcus pneumoniae, an AUC0‐24hr:MIC of 30 or more is suggested for favorable clinical outcomes. Pharmacokinetic and pharmacodynamic values influence rational therapeutic decisions in the selection and dosages of these drugs.
What Do We Really Know About Antibiotic Pharmacodynamics?
Authors: Gunderson Brent W. , Ross Gigi H. , Ibrahim Khalid H. , Rotschafer John C.
Published: June 2004

Antibiotic pharmacodynamics is an evolving science that focuses on the relationship between drug concentration and pharmacologic effect, which is an antibiotic‐induced bacterial death that also can manifest as an adverse drug reaction. The pharmacologic action of antibiotics usually can be described as concentration dependent or independent, although such classifications are highly reliant on the specific antibiotic and bacterial pathogen being studied. Quantitative pharmacodynamic parameters, such as ratio of the area under the concentration‐time curve during a 24‐hour dosing period to minimum inhibitory concentration (AUC0–24:MIC), ratio of maximum serum antibiotic concentration to MIC (Cmax:MIC), and duration of time that antibiotic concentrations exceed MIC (T>MIC), have been proposed as likely predictors of clinical and microbiologic success or failure for different pairings of antibiotic and bacteria. Thus far, most pharmacodynamic data reported have focused on fluoroquinolones, but work has been conducted on vancomycin, β‐lactams, macrolides, aminoglycosides, and other antibiotics. Despite the development of a number of different pharmacodynamic modeling systems, remarkable agreement exists between in vitro, animal, and limited human data. Although still somewhat premature and requiring additional clinical validation, antibiotic pharmacodynamics will likely advance on four fronts: the science should prove to be extremely useful and represent a cost‐effective and efficient method to help develop new antibiotics; formulary committees will likely use pharmacodynamic parameters to assist in differentiating antibiotics of the same chemical class in making antibiotic formulary selections; pharmacodynamic principles will likely be used to design optimal antibiotic strategies for patients with severe infections; and limited data to date suggest that the application of pharmacodynamic concepts may limit or prevent the development of antibiotic resistance. The study of antibiotic pharmacodynamics appears to hold great promise and will likely become a routine part of our daily clinical practices.