bluuebunny/crossref_metadata_2025 huggingface dataset:
Selected Methods for Dusky Darter Captive Propagation
Authors: Labay A A , Standage R W , Brandt T M
Published: June 2004

Past disturbance of eggs or larvae of dusky darters Percina sciera has resulted in almost 100% mortality of the larvae within 9 d of hatch. Photoperiod and water temperature were manipulated to induce dusky darters collected from the wild to spawn in the laboratory. Eggs spawned in gravel spawning trays were transferred while in the trays to specially designed egg incubators. Dusky darter larvae were collected after they emerged from the gravel and swam out of the incubator. Groups of larvae were offered ground TetraMin (≤0.3 mm), zooplankton (≤0.3 mm), or a combination of both foods in aquariums that had circulated or noncirculated water. The highest mean survival per treatment was for zooplankton and no circulation (71%); the lowest mean survival was for TetraMin with no circulation (3%). A dusky darter growth curve from egg to first spawn, approximately 1 year, was developed. Dusky darters reared in the laboratory from eggs were successfully spawned.
Gut Content of First-Feeding Wild Darters and Captive-Reared Dusky Darters
Authors: Labay A A , Collins K , Standage R W , Brandt T M
Published: June 2004

Five of 18 blackside darter Percina maculata larvae and 3 of 18 leopard darter P. pantherina larvae collected in light traps from the Glover River, McCurtain County, Oklahoma, contained ingested items. The maximum diameter of prey ingested was between 0.27 and 0.37 mm and was 70–90% of their gape widths. None of the larvae that contained prey items possessed a visible yolk sac. Forty-three of 48 laboratory-reared larval dusky darters P. sciera offered zooplankton (≤0.30 mm in diameter; harvested from hatchery ponds) contained ingested items. The dominant prey was Ceriodaphnia spp. adults and neonates. The maximum number of Ceriodaphnia consumed by an individual larva was 20. Calanoid copepods were abundant in the zooplankton offered but were not found in any but the 18-d-old larvae. Rotifers in low densities also were offered, but none were observed in any of the alimentary canals. We conclude that small (≤0.30-mm), pond- reared cladocerans such as Ceriodaphnia and Bosmina are suitable food for the first-feeding Percina species examined during this study.
Toxicological Evaluation of Two Anthraquinone-Based Cyanobactericides to Channel Catfish
Authors: Schrader Kevin K , Foran Christy M , Holmes Brad D , Schlenk Daniel K , Nanayakkara N P Dhammika , Schaneberg Brian T
Published: June 2004

The use of biocides to control blooms of cyanobacteria (blue-green algae) is important for the aquaculture industry because cyanobacteria produce chemicals that cause off-flavors in fish. However, the consequences of exposure to biocides for fish health will determine the effective use of a biocide treatment. Two novel cyanobactericides, anthraquinone-19 and anthraquinone-59, were evaluated for acute toxicity to fingerlings of channel catfish Ictalurus punctatus. Acute toxicity was determined through measurement of 50% mortality following 96 h of aqueous exposure (96- h LC50). In addition, the no-observed-effect concentration (NOEC) was determined for each compound. Following a 1-week acclimation, groups of catfish fingerlings were exposed at each of six different concentrations ranging from 0.01 mg/L to 20 mg/L for each compound. Two groups of unexposed fingerlings served as the controls. The 96-h LC50 value for anthraquinone-19 was 2.51 ± 0.51 mg/L (mean ± SD) and that for anthraquinone-59 was 2.06 ± 0.31 mg/L. Among catfish exposed to the sublethal doses, no differences were detected in body size (weight and length) and gill and liver weight. The NOEC was determined to be 1 mg/L for both test compounds. Compared with anthraquinone-19, anthraquinone-59 has a greater margin between concentrations that are toxic to channel catfish and concentrations that reduce undesirable cyanobacteria in catfish ponds.
Lack of Correlation between Chinook Salmon Spawn Survival and the Number of Overripe Eggs as Determined by Digital Imagery
Authors: Barnes Michael E , Durben Dan J
Published: June 2004

The number of overripe eggs in spawn of landlocked fall Chinook salmon Oncorhynchus tshawytscha was determined quantitatively from digital images recorded prior to fertilization. The percentage of overripe eggs recorded from the digital images was not significantly correlated with survival at egg eye-up, fry hatch, or swim-up but was significantly correlated with the visually estimated number of overripe eggs (r  2 = 0.914, P < 0.001). There was also no significant difference between the percentages of overripe eggs determined by the two methods. Neither the digital image nor visual-estimation techniques for assessing overripe eggs are reliable predictors of egg survival, but the digital imagery validated the use of visual estimates.
Utilization of Glucose and Cornstarch by Juvenile Grass Carp
Authors: Tian Li-Xia , Liu Yong-Jian , Hung Silas S O
Published: June 2004

An experiment was conducted in a recirculation system to study the carbohydrate utilization of juvenile grass carp Ctenopharyngodon idella (11.3 ± 0.1 g) fed a 30% glucose or cornstarch diet for 70 d and maintained at 28.9 ± 0.5°C. While weight gain, feed efficiency, protein efficiency ratio, carcass-to-body weight ratio, and whole-body moisture were significantly higher (P < 0.05), the viscera-to-body weight ratio, mesenteric fat index, and whole-body and tissue lipid levels were lower in the glucose than in the cornstarch group. These results showed that carbohydrate utilization by juvenile grass carp was affected by the complexity of the carbohydrates, which, in turn, resulted in different degrees of enlarged hepatopancreas and viscera as well as increased body and tissue lipid depositions.
An Improved Method for Determining the Fineness Value of Agricultural Limestone for Aquaculture
Authors: Silapajarn Kom , Boyd Claude E , Silapajarn Orawan
Published: June 2004

The original method for determining the fineness of agricultural limestone was modified for the greater contribution of particles less than 0.25 mm in diameter that is found in the modern agricultural limestone used in aquaculture. Crusher-run limestone was screened to give nine particle size separates. Systems containing 3.0 kg of soil (pH = 5.21) and 23.5 L of water (total alkalinity = 0.39 mg/L) were treated with 8.0 g of each separate, and total alkalinity and pH were monitored. After 70 d, total alkalinity equilibrated at 55 mg/L in systems treated with particles less than 0.106 mm. The total alkalinity in systems treated with other particle size separates were as follows: control, 0.52 mg/L; greater than 2.0 mm, 2.28 mg/L; 2.0–0.85 mm, 5.75 mg/L; 0.85–0.42 mm, 12.25 mg/L; 0.42–0.25 mm, 26.8 mg/L; 0.25–0.15 mm, 45.62 mg/L; and 0.15–0.106 mm, 49.30 mg/L. Water pH exceeded 7.36 after 2 weeks for systems treated with particles less than 0.25 mm. Wet soil samples (2.5 kg) of pH 5.04 were placed in trays and treated with 6.7 g of limestone of different particle size separates. After 1 week, pH was 6.9–7.1 in soil treated with particles less than 0.106 mm. By 10 weeks, a pH greater than 6.5 was attained in soils treated with particles less than 0.25 mm. The pH of soil treated with particles greater than 0.25 mm was similar to the control pH. Efficiency factors were assigned to particle size-classes as follows: less than 0.106 mm, 100%; 0.25–0.106 mm, 86.7%; 0.42–0.25 mm, 49.06%; 0.85–0.42 mm, 22.4%; and greater than 0.85 mm, 7.3%. The sum of the products of the proportion of each particle size-class and the corresponding efficiency factor gave the fineness value. Fineness values usually were smaller when determined by the new method instead of the old method.
Assessment of Floating Vertical Raceways for the Culture of Phase-II Hybrid Striped Bass
Authors: Volkman Eric T , Kohler Christopher C , Kohler Susan T
Published: June 2004

A floating vertical raceway is a system designed to provide a constant, unidirectional flow of water to fish confined in a flexible raceway that is suspended vertically in the water column. This study evaluated the potential of floating vertical raceways for the culture of phase-II sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) reared at two densities (125 and 188 fish/m3). Fish with a mean starting weight of 0.7 g were fed a diet containing 40% crude protein to satiation for 121 d. Fish in the low-density treatment reached a significantly higher final mean weight (160.0 g) than those in the high-density treatment (136.9 g). Survival was also significantly higher in the low-density treatment (81.1%) than in the high-density treatment (73.8%). No significant differences in water quality were detected for dissolved oxygen, total ammonia, un-ionized ammonia, or temperature between high-density and low-density treatments. Unlike the surrounding reservoir, water temperature inside the raceways remained destratified throughout the growing period. Based on the performance of fish, the high water quality maintained inside the enclosures, and ease of use, the floating vertical raceway system offers considerable promise as an alternative rearing system for deepwater impoundments.
Hatchery Performance Attributes of Juvenile Lake Sturgeon Fed Two Natural Food Types
Authors: Volkman Eric T , Pangle Kevin L , Rajchel Deborah A , Sutton Trent M
Published: June 2004

The use of stocking programs to rehabilitate depressed populations of lake sturgeon Acipenser fulvescens requires the optimization of early life stage growth in hatchery settings. We evaluated the performance of juvenile lake sturgeon fed different proportions of two natural food types—adult brine shrimp Artemia spp. and larval bloodworms Chironomus spp.—over a 10-week laboratory experiment. The following five diet treatments were provided: (1) 100% bloodworms; (2) 75% bloodworms : 25% brine shrimp; (3) 50% bloodworms : 50% brine shrimp; (4) 25% bloodworms : 75% brine shrimp; and (5) 100% brine shrimp. Lake sturgeon growth was positively related to bloodworm content in the diet and was significantly different among treatments. Although the initial sizes of fish were similar, mean fork length and wet weight were greatest for the 100% bloodworm treatment (183.1 mm and 37.5 g, respectively) and lowest for the 100% brine shrimp diet (118.4 mm and 9.5 g) by the end of the study. Mean specific and absolute growth rates in length (0.93% and 1.28 mm/d, respectively) and weight (2.61% and 0.45 g/d) were greatest for the 100% bloodworm diet, followed by the other treatments in order of decreasing amount of bloodworms in the diet. Percent weight gain (525%) and food conversion efficiency (67%) were also greatest for the 100% bloodworm diet, followed by the other treatments in order of decreasing dietary bloodworm content. Whole-body protein (13.9%), lipid (2.5%), and gross-energy (3.77 kJ/g) content were greatest for fish fed 100% bloodworms, with these proximate-composition measures also ranked in order of decreasing dietary bloodworm content for the other treatments. We recommend that juvenile lake sturgeon reared in hatchery environments be fed high proportions of bloodworms to maximize growth, body size, and lipid content for rehabilitation stocking programs.
Accounting for Water Temperature during Hydrogen Peroxide Treatment of Channel Catfish Eggs
Authors: Small Brian C
Published: June 2004

The effect of water temperature on the efficacy of hydrogen peroxide (H2O2) as a disinfectant for channel catfish Ictalurus punctatus eggs was examined at 24°C and 28°C. Eggs at each temperature were treated with H2O2 at 0, 100, 250, 500, or 1,000 mg/L as a daily 15-min bath. Mean hatching success at 24°C was greatest (P > 0.05) for eggs treated with 250 and 500 mg/L H2O2, hatching success tending to increase with increasing treatment concentration between 100 and 500 mg/L. The opposite effect was observed at 28°C: hatching success was greatest (P < 0.05) for eggs treated with 100 and 250 mg/L H2O2, hatching success tending to decrease with increasing H2O2 concentration between 100 and 500 mg/L. The results of this research, together with previously published results, demonstrate that there is a negative correlation between H2O2 concentration and water temperature with respect to the optimal efficiency of H2O2 as an egg disinfectant and suggest that there is an increased toxicity of H2O2 at higher temperatures. Careful consideration of temperature is necessary when disinfecting channel catfish eggs with H2O2.
Plasma Cortisol and Chloride Stress Responses in Juvenile Walleyes during Capture, Transport, and Stocking Procedures
Authors: Barton Bruce A , Haukenes Alf H , Parsons Bradford G , Reed Jeffrey R
Published: June 2004

Extensively reared juvenile walleyes Stizostedion vitreum subjected to capture and transport stressors associated with stocking procedures in South Dakota and Minnesota displayed acute increases in plasma cortisol and extended declines in concentrations of plasma chloride. In four separate South Dakota transport hauls, mean plasma cortisol in walleyes rose from 12–49 ng/mL at the time of trap-net capture to 138–174 ng/mL after 1 h of transport; these concentrations remained increased at 3 h. Plasma chloride decreased by about 19% during this period; by 3 h, mean values had dropped about 30%, to 53–61 meq/L. Similarly, in Minnesota mean plasma cortisol in captured and transported walleyes increased from 13–26 ng/mL during trap-net capture to 154–214 ng/mL by 1 h after transport in three separate trials and remained at the higher values at 3 h posttransport. Mean plasma chloride concentrations dropped about 28%, to 65–72 meq/L, by 3 h after transport and remained significantly decreased at 68–82 meq/L 24 h later, even though plasma cortisol, an acute stress indicator, had returned to near pretransport values. Results from these experimental transport hauls indicate that the juvenile walleyes experienced considerable physiological stress when captured and transported to lakes for stocking. This stress was reflected by an appreciable decrease in plasma chloride that failed to recover to pretransport values after 24 h, which suggests a possible mechanism for poststocking mortality.
An Evaluation of Selective Feeding by Three Age-Groups of the Rainbow Mussel Villosa iris
Authors: Beck Kevin , Neves Richard J
Published: June 2004

A tri-algal diet was fed to three age-groups of the rainbow mussel Villosa iris: ages 2–3 d, 50–53 d, and 3–6 years. Changes in the relative abundance of each algal species were determined in 5-h feeding trials from feeding chambers and by gut content analyses. All age-groups rejected Scenedesmus quadricauda and preferentially selected Nannochloropsis oculata and Selenastrum capricornutum, principally on the basis of size. Changes in the relative abundance of algae in feeding chambers did not differ significantly among age-groups. Observed differences in the ingested quantities of the similar-sized N. oculata and S. capricornutum were attributed to other particle-related characteristics. Results indicate that the rainbow mussel can be fed similar-sized algae at all ages in captive propagation facilities. When developing a suitable algal diet for rearing juvenile mussels, one probably need not investigate different species at each stage of development if the algae used are in the 2.8–8.5-μm size range.
Relative Triacylglycerol and Morphometric Measures of Condition in Sunshine Bass Fry
Authors: Lochmann Steve E , Ludwig Gerald M
Published: June 2004

Condition measures are assessed for wild populations of fish fry to examine production and the implications for recruitment variability. These condition measures might guide management decisions, such as those in fish culture. We developed two condition measures, one based on morphometric measurements and one based on lipid class composition, for sunshine bass (white bass Morone chrysops × striped bass M. saxatilis) fry. Prey concentrations were varied during three tank studies. Fry were sampled periodically and analyzed morphometrically and biochemically. Discriminant function analyses of morphometrics and lipid class composition were used to classify fry into treatment groups. The most successful discriminant function, which was based on morphometrics, correctly classified 75% of the test fry. We developed a condition measure based on relative triacylglycerol (TAG) content. Well-fed fry (15–20 prey/mL) had significantly higher average relative TAG values than poorly fed fry during the third week in two of the studies. Undernourished fry had relative TAG values of approximately 0.5, whereas well-fed fry had values ranging from 1.0 to 5.0. Relative TAG and the morphometric discriminant function are indicators of feeding success and might be used to guide management decisions, such as fertilization or feeding, during phase-I fingerling production of sunshine bass.
The Toxicity of Bayluscide and TFM to Tubifex tubifex: Implications for Chemical Control of the Oligochaete Host of Myxobolus cerebralis, the Causative Agent of Whirling Disease
Authors: Kowalski Dan A , Bergersen Eric P
Published: June 2004

Standard 24-h toxicity tests were performed to determine the acute toxicity of Bayluscide (5,2′-dichloro-4′-nitrosalicylanilide) and 3-trifluoromethyl-4-nitrophenol (TFM) to two strains of the oligochaete worm Tubifex tubifex exposed and unexposed to Myxobolus cerebralis, the causative agent of whirling disease. In addition, microcosm trials were conducted to test the effect of three treatment levels of each chemical on the density of T. tubifex in an earthen hatchery pond. In the toxicity tests, worms that were susceptible to M. cerebralis infection were more sensitive to both chemicals than worms that were resistant to the parasite. The toxicity differences of exposed and unexposed worms within a lineage were not as great as those between lineages. Among worms that were susceptible to M. cerebralis, the concentrations of TFM that were lethal to 50% of the test organisms (LC50s) were 6.3 mg/L for worms that had been exposed to M. cerebralis myxospores and 7.3 mg/L for unexposed worms; for resistant worms, the corresponding LC50s were 8.2 and 7.7 mg/L. Among susceptible worms, the LC50s of Bayluscide were 0.060 mg/L for organisms exposed to M. cerebralis myxospores and 0.062 mg/L for unexposed organisms; resistant worms had LC50s of 0.096 and 0.106 mg/L. In the microcosm trials, Bayluscide treatments reduced worm densities by 73–82%, while the TFM treatments reduced worm densities by 34–88%. Given its rapid degradation, relatively selective toxicity, lower cost, and regulatory status, Bayluscide appears to be the best candidate for further study as a chemical control of the oligochaete host of the parasite that causes whirling disease in salmonid fishes.
Effects of Temperature and Salinity on Growth of Juvenile Black Sea Bass, with Implications for Aquaculture
Authors: Cotton Charles F , Walker Randal L , Recicar Todd C
Published: June 2004

The black sea bass Centropristis striata has recently gained popularity in the live seafood markets of the northeastern United States. Fish farmers need instruction on optimizing environmental parameters for the growth of black sea bass. In this study, optimal temperature and salinity were determined experimentally for the growth of juvenile black sea bass (initial mean weight, ∼9.2 g). The temperature experiment compared growth at temperatures of 15, 20, 25, and 30°C; the salinity experiment compared growth at 10, 20, and 30‰ salinities. Both of these experiments were performed in closed aquaria. At the end of the temperature experiment (6 weeks), Tukey's Studentized range test (α = 0.05) showed that fish reared at 25°C were significantly larger than those reared at 20°C and 30°C. All of these temperatures produced significantly larger fish than did the 15°C treatment. At the end of the salinity experiment (12 weeks), Tukey's Studentized range test (α = 0.05) showed that salinities of 20‰ and 30‰ did not produce significantly different weights in fish. However, both of these salinities produced significantly larger fish than did a salinity of 10‰. Given the results of these experiments, fish farmers can manipulate the environmental parameters of their aquacultural systems to optimize growth of juvenile black sea bass, thereby reducing the time required to produce a marketable product.
Cryopreservation of Sperm from the Endangered Colorado Pikeminnow
Authors: Tiersch Terrence R , Figiel Chester R. , Wayman William R , Williamson J Holt , Gorman Owen T , Carmichael Gary J
Published: June 2004

We developed methods for the cryopreservation of sperm of the endangered Colorado pikeminnow Ptychocheilus lucius. Sperm were collected from a captive broodstock population of Colorado pikeminnow reared and maintained at the Dexter National Fish Hatchery and Technology Center. Our objectives were to (1) evaluate the effects on sperm motility of 24-h storage in Hanks' balanced salt solution (HBSS); (2) characterize sperm motility and duration; (3) examine the relationship between sperm motility and osmotic pressure; (4) examine the effect of four cryoprotectants (dimethyl sulfoxide [DMSO], dimethyl acetamide [DMA], glycerol, and methanol [MeOH] at two concentrations [5% and 10%]) on postthaw motility; and (5) compare the effect of two cooling rates (40°C/min and 4°C/min) on postthaw motility. The sperm samples diluted with HBSS retained higher motility (mean ± SD, 77 ± 22%; n = 9) than did undiluted samples (12 ± 30%; n = 9) after 24 h of storage. When exposed to HBSS at 274 mosmols/kg or more, few sperm became motile (∼1%). Exposure to HBSS at 265 mosmols/kg elicited threshold activation (defined as 10% motility), and maximum motility (>95%) was observed at 93 mosmols/kg. The maximum motility of sperm was observed within 10 s after activation with deionized water, and sperm remained motile for 57 s. The sperm that were cooled at a rate of 40°C/min and cryopreserved with 5% MeOH retained higher postthaw motility (56 ± 13%) than did sperm cryopreserved with DMSO, DMA, or glycerol (at 5% and 10%). When the sperm samples were cooled at a rate of 4°C/min, sperm cryopreserved with MeOH (5% or 10%) or DMSO (5% or 10%) retained the highest postthaw motilities (≤14%). The use of cryopreserved sperm can assist hatchery managers in the production of fish, provide for the long-term conservation of genetic resources, and assist in the recovery of endangered species such as the Colorado pikeminnow.
An Effective Minimum Concentration of Un-ionized Ammonia Nitrogen for Controlling Prymnesium parvum
Authors: Barkoh Aaron , Smith Dennis G , Schlechte J Warren
Published: June 2004

The minimum concentration of un-ionized ammonia nitrogen needed to kill the alga Prymnesium parvum in 24–48 h was determined from ammonium sulfate treatments. Five treatments [0, 3, 5, 10, and 15 mg (NH4)2SO4/L] were tested at pH 8 and pH 9 and temperatures of 15, 20, and 25°C to generate various concentrations of total and un-ionized ammonia nitrogen; their effectiveness in killing the alga was then monitored for 48 h. There was a strong relationship between treatment success and the level of ammonium sulfate or un-ionized ammonia nitrogen. The ammonium sulfate treatments that killed the alga did so within the first 24 h, and their effectiveness at 48 h was not significantly different from that at 24 h. At pH 9, ammonium sulfate concentrations above 5 mg/L eradicated the alga approximately 90% of the time, compared with 33% for the other treatments. In terms of un-ionized ammonia nitrogen, 0.055 mg/L was similar to the control in failing to kill the alga; however, 0.17 mg/L eradicated the alga 80% of the time. We suggest 0.17 mg/L of un-ionized ammonia nitrogen as the minimum concentration for therapeutic control of P. parvum.
Hydrogen Peroxide Treatment during Egg Incubation Improves Channel Catfish Hatching Success
Authors: Small Brian C , Wolters William R
Published: June 2004

Three trials were conducted to evaluate the effect of hydrogen peroxide (H2O2) treatment on the hatching success of channel catfish Ictalurus punctatus when administered during egg incubation as a 15-min bath or as a flow-through treatment. In the first trial, initial treatment with 100 mg povidone iodine/L followed by daily 15-min baths of 250 mg H2O2/L yielded a 26% increase (P < 0.05) in hatching success above controls. In the second trial, daily 15-min baths with H2O2 (250 mg/L) yielded a 30% increase (P < 0.05) in hatching success compared with povidone-iodine-treated controls and significantly improved hatching success compared with formalin-treated (1,600 mg/L) eggs. In the third trial, hydrogen peroxide was administered in flow-through hatching troughs. Egg masses treated with 70 mg H2O2/L had significantly improved (P < 0.05) hatching success compared with untreated controls (68.3% and 24.2%, respectively). The results of this research show that significant improvements in channel catfish hatching success can be obtained through the use of hydrogen peroxide as a cost-effective alternative to formalin.
The Sock-Saver: A Small Trailer for Providing Liquid Oxygen to Remote Sites on Commercial Channel Catfish Farms
Authors: Torrans Eugene L , Hogue Charles D. , Pilkinton Sam
Published: June 2004

A small, single-axle trailer was designed and built to hold three 50-gal liquid oxygen Dewar flask tanks. The unit is small enough to be moved around a commercial channel catfish Ictalurus punctatus farm with a pickup truck or small tractor. It is being used successfully to provide supplemental oxygen at remote on-farm locations to channel catfish that are being held in a sock (net cage or live car) at high density before sale. The total materials cost of the complete sock-saver with trailer, Dewar tanks, pressure/flow regulators, and diffusers was $8,333.16. It is simple to operate, durable, and virtually maintenance free. Because no electrical or mechanical power source is required, it can be set up anywhere. The small “footprint” of the trailer does not interfere with the other equipment normally used when loading fish from a sock. Individual flow regulators allow use of one, several, or all eight diffusers as needed. The diffusers and hoses are self-weighted and tangle-free and do not interfere with the normal process of crowding the fish in the sock and dipping them up in the loading basket. The unit can increase dissolved oxygen in a sock by as much as 0.9 mg/L.
Pond Fertilization Does Not Affect Nutritional Value of Zooplankton in Channel Catfish Nursery Ponds
Authors: Mischke Charles C , Li Menghe H , Zimba Paul V
Published: June 2004

We determined the nutritional value of large zooplankton (500–1,000 μm) from fertilized and nonfertilized channel catfish Ictalurus punctatus nursery ponds. Proximate composition, amino acids, fatty acids, and assimilated algal pigments were statistically compared between pond groups. Analyses of vitamin and mineral composite samples of zooplankton from fertilized and nonfertilized ponds are presented. Treatment and control pond zooplankton were similar in nutritional value. Only two fatty acids (16:0 and 20:4[n-6]) were significantly different (P < 0.05) between fertilized and nonfertilized ponds, but total n-3 and n-6 highly unsaturated fatty acids were not different. The zooplankton in this study met or exceeded all nutritional requirements of channel catfish fry except that zooplankton in nonfertilized ponds appeared to contain less -than the required levels of pantothenic acid and vitamin B6. However, no statistical comparison of vitamins was made between fertilized and nonfertilized ponds. Because of the high nutritional value of zooplankton present in channel catfish nursery ponds, the importance of maintaining high densities of zooplankton is confirmed. If fertilization practices maintain large numbers of zooplankton, all fry nutritional requirements can be met through the natural biota. Supplemental feeding with prepared diets may still be necessary to ensure that sufficient food sources are available to the fry for optimum growth and survival.
Growth Performance and Body Composition of Palmetto Bass Fed Five Levels of Dietary Protein at Two Energy-to-Protein Ratios
Authors: Gummadi Ramesh C , Reigh Robert C
Published: June 2004

A feeding trial was conducted to determine the effects of dietary crude protein (CP) level and digestible energy-to-protein (DE:P) ratio on the growth performance and body composition of palmetto bass (female striped bass Morone saxatilis × male white bass M. chrysops). Ten soybean-meal-based diets were prepared to contain 30, 35, 40, 45, or 50% CP at DE:P ratios of 33.48 or 41.85 kJ/g CP. The diets contained lyophilized palmetto bass muscle as the sole animal protein source to improve dietary amino acid composition. Wheat middlings and corn grain were the major sources of carbohydrates, and the diets were formulated to meet the known nutritional requirements of palmetto bass. Fish fed 35% or 40% CP at 33.48 or 41.85 kJ/g CP had significantly (P ≤ 0.05) greater weight gains and higher feed efficiency ratios than fish fed the other diets. The protein efficiency ratio (g weight gain/g CP consumed) decreased and visceral fat ([g visceral fat × 100]/g body weight) increased as the dietary protein level increased in both DE:P treatments. The hepatosomatic index ([g liver weight × 100]/g body weight) increased with the dietary protein level up to 40–45% CP. Whole-body muscle content and fillet yield did not differ significantly among fish fed any of the diets at either DE:P ratio. The lipid content of fillets was higher among fish fed 45–50% CP than among those fed up to 40% CP. Hematocrit and serum protein concentrations were not affected by the dietary CP level or the DE:P treatment. Overall, the DE:P ratio had little or no effect on most of the parameters of interest. Based on our comparisons of weight gain, diet utilization efficiency, and body composition among treatment groups, a 35% CP diet with 41.85 kJ/g CP was considered optimum for palmetto bass under the conditions of this study.
Effectiveness of the Minimally Invasive Surgical Technique (MIST) for Removal of Ovulated Eggs from First-Time and Second-Time MIST-Spawned Paddlefish
Authors: Mims Steven D , Onders Richard J , Gomelsky Boris , Shelton William L
Published: June 2004

A minimally invasive surgical technique (MIST) for the removal of ovulated eggs from paddlefish Polyodon spathula was tested on broodstock that had been previously spawned using MIST to determine whether repeat spawning affected fecundity or hatching rate compared with broodstock than had not previously been induced to spawn. There were no significant differences in the number of eggs removed or in the hatching rate between first- and second-time MIST spawners. The oviducts from second-time MIST spawners appeared normal and had no scarring or blockage. The MIST approach is efficient, practical, and less stressful to broodstock during artificial propagation than other reported egg collection procedures.
Mariculture of the Oyster Toadfish: Juvenile Growth and Survival
Authors: Mensinger Allen F , Price Nichole N , Richmond Hazel E , Forsythe John W , Hanlon Roger T
Published: June 2004

Nests of oyster toadfish Opsanus tau with guardian males were transported from Waquoit Bay, Massachusetts, to the Marine Biological Laboratory in Woods Hole, Massachusetts. Following larval detachment from the nest, the offspring were separated from the males and placed into culture tanks with flow-through seawater. The juveniles were initially fed adult brine shrimp Artemia spp. supplemented with small pieces of frozen squid Loligo spp. During the second year of the study, the majority of the diet was squid supplemented with locally available food. Fish were maintained at different temperatures (approximately 15°C, 20°C, and ambient) and densities (2–90 fish/m2). Although the culture density did not have an appreciable effect on growth, fish maintained in warmer water grew significantly faster than fish kept at cooler temperatures. After 2 years, the fish reared in warm water averaged 10.0 cm and 40.5 g, while those reared in cold water averaged 6.5 cm and 11.0 g. Growth in weight was shown to be exponential from day 76 to day 200, with rates of 1.4% and 0.38% body weight per day at 20°C and 15°C, respectively, an almost fourfold difference. Beyond day 200, growth in weight at both temperatures was best fitted by a power function; however, there was no significant difference in the slope of the growth curve between the two temperature groups. Thus, temperature did not accelerate growth rates from day 225 onward. Survival rates were greater than 68% in four of the five treatment groups. Despite constant high temperatures and food availability throughout the winter months, oyster toadfish underwent a quiescent period during the second year of life and exhibited minimal growth during this time, indicating that shortened day length may affect growth rates.
Effect of Citric Acid, Copper Sulfate Concentration, and Temperature on a Pond Shoreline Treatment for Control of the Marsh Rams-Horn Snail Planorbella trivolvis and the Potential Toxicity of the Treatment to Channel Catfish
Authors: Mitchell Andrew J , Hobbs Melissa S
Published: June 2004

Tests were run to determine whether any refinements were warranted in an established copper sulfate–citric acid pond shoreline treatment (Environmental Protection Agency registration number 1278–8) for aquatic marsh rams-horn snails Planorbella trivolvis. The treatments applied in these studies consisted of two levels (full and half) of copper sulfate (CuSO4; 589 and 294.5 g) with and without citric acid (CA; 58.9 and 0 g) that were delivered in a 2-m swath 10-m length of shoreline. In research ponds, shoreline treatments without CA were significantly more effective against the snails than the treatments with CA. The full CuSO4 treatment without CA was significantly more effective than the half treatment without CA at all temperatures tested below 35°C. There was a significant reduction in the effectiveness of the full treatment without CA at 17 ± 0.5°C (40% snail survival), while snail survival (average, 3.2%) in the trials run at 21.5, 23, 26, and 35°C was not significantly different from each other. When applied to the perimeter of 0.41-ha research ponds (ponds smaller than recommended for the shoreline treatment), the full CuSO4 treatment with CA was found to be significantly more toxic to channel catfish Ictalurus punctatus over a 120-h period at 31°C (<35% survival) than at 28°C (>95% survival, which was similar to that of the control). It was also more toxic than an application of the same amount of CuSO4 without CA at 31°C. The study indicates that the most effective pond shoreline treatment (589 g of CuSO4 without CA applied in a 2-m swath over a 10-m length of shoreline) should be administered in water with a temperature of at least 21°C.
Effects of Partial Tank Covers on the Growth of Juvenile Feral Rainbow Trout during Hatchery Rearing
Authors: Barnes Michael E , Durben Dan J
Published: June 2004

Partial tank covers were evaluated for their effects on the growth of juvenile feral McConaughy strain rainbow trout Oncorhynchus mykiss during hatchery rearing. Trout were reared in 1999 and 2000 in circular tanks that were either completely open on top or partially (29%) covered. Trout reared in tanks with partial covers were 93 mm long at the end of 55 d of rearing in 1999, which was significantly longer than the 88-mm mean length of trout reared in uncovered tanks. Total lengths were also significantly different after 34 d of rearing in 2000: 81 mm for fish from partially covered tanks and 78 mm for fish from open tanks. The total weight gains of fish per tank were significantly greater (23.9 versus 22.7 kg) and feed conversions were significantly better (0.83 versus 0.87) in partially covered tanks in 1999. In 2000, the total weight gain of fish per tank was 15.4 kg in tanks with partial covers and 13.5 kg in uncovered tanks, and the respective feed conversions were 0.90 and 1.05. However, neither weight gain nor conversion was significantly different in 2000. No significant differences in percent mortality were observed in fish reared with or without partial covers.
Efficacy of Hydrogen Peroxide in Controlling Mortality Associated with External Columnaris on Walleye and Channel Catfish Fingerlings
Authors: Rach Jeff J , Schleis Susan M , Gaikowski Mark , Johnson Alan
Published: June 2004

The efficacy of hydrogen peroxide in controlling mortality associated with external columnaris infections on walleye Sander vitreus (formerly Stizostedion vitreum) and channel catfish Ictalurus punctatus fingerlings was evaluated in two on-site trials. Microscopic examination of skin scrapes before treatment confirmed the presence of bacteria indicative of columnaris disease. In separate trials, walleyes (12 g) and channel catfish (2.3 g) were exposed to a total of three every-other-day hydrogen peroxide treatments of 0, 50, 75, or 100 mg/L for 60 min. Each treatment regimen was tested in triplicate, and each replicate contained 13 walleyes or 26 channel catfish. Hydrogen peroxide exposures of 50 mg/L for 60 min significantly increased walleye survival relative to that at other treatment concentrations, including the controls. Exposures of 50, 75, or 100 mg/L of hydrogen peroxide for 60 min significantly increased channel catfish survival in comparison with that of controls. These trials indicated that hydrogen peroxide treatments effectively reduce mortality in walleyes and channel catfish infected with external columnaris.
Tag Retention and Survivorship of Hatchery Rainbow Trout Marked with Large-Format Visible Implant Alphanumeric Tags
Authors: Isely J Jeffery , Trested Drew G , Grabowski Timothy B
Published: June 2004

Large-format visible implant alphanumeric (VIalpha) tags were implanted into 15,400 rainbow trout Oncorhynchus mykiss. Tag retention after 25 d was 82.6%, and survivorship was 92.8%. The results of this study compare favorably with those of similar studies on other species and suggest that large-format VIalpha tags are an appropriate choice for studies requiring the individual identification of larger rainbow trout.
Age-Dependent Susceptibility of Chinook Salmon to Myxobolus cerebralis and Effects of Sustained Parasite Challenges
Authors: Sollid Sarah A. , Lorz Harriet V. , Stevens Donald G. , Bartholomew Jerri L.
Published: June 2004

Laboratory challenges with triactinomyxons of Myxobolus cerebralis demonstrate that Chinook salmon Oncorhynchus tshawytscha have a lower susceptibility to infection and the development of whirling disease than rainbow trout O. mykiss. In age-dependent challenges, triplicate groups of each species were exposed at 1, 3, 5, 7, and 9 weeks posthatch to 1,000 triactinomyxons per fish and juvenile Chinook salmon were exposed to a high dose of 10,000 triactinomyxons per fish. Assessment of infection at 5 months postchallenge showed that Chinook salmon acquire resistance to clinical disease after 3 weeks posthatch, as compared with 7 weeks posthatch for rainbow trout. Furthermore, all measures of infection severity, including myxospore burden and lesion score, were lower in Chinook salmon. To model natural exposure and evaluate the ability of the fish to retain resistance following repeated challenge, replicate groups of Chinook salmon and rainbow trout were exposed daily to low parasite doses (5–200 triactinomyxons per fish) for 4 weeks. A low prevalence of infection and no clinical disease signs were recorded in the sustained exposure. These challenges indicate an overall lower susceptibility to M. cerebralis for Chinook salmon.
Ulcerative Mycosis Caused by Aphanomyces invadans in Channel Catfish, Black Bullhead, and Bluegill from Southeastern Louisiana
Authors: Hawke John P. , Grooters Amy M. , Camus Alvin C.
Published: June 2004

Eight cases of chronic ulcerative mycosis affecting populations of channel catfish Ictalurus punctatus, black bullhead Ameiurus melas, and bluegill Lepomis macrochirus cultured in recreational fishing ponds were submitted to the Louisiana Aquatic Diagnostic Laboratory between April 2000 and January 2002. Diseased clinical specimens presented with multiple foci of skin ulceration, typically overlying more extensive areas of granulomatous myositis that extended to the vertebral column in advanced cases. Lesions were predominated by fields of plump macrophages and multinucleated giant cells surrounding nonseptate, thick-walled hyphae with nonparallel cell walls suggestive of an oomycete. Because deep ulcerative mycoses in other fish species in the western Atlantic (USA), Australia, and Southeast Asia have been attributed to Aphanomyces spp., diagnostic methods were employed to isolate and identify this oomycete along with other potential pathogens. The organism was isolated from sites deep in the musculature with modified peptone−yeast−glucose medium containing 200 μg/mL streptomycin and 100 μg/mL ampicillin. Morphological features were consistent with A. invadans; the internal transcriber spacer (ITS) and 5.8S subunit regions of the rRNA gene were amplified, sequenced, and found to be identical with the ITS1 sequences from five isolates of A. invadans deposited in the GenBank database, indicating complete homology. Koch's postulates were fulfilled in juvenile (40–50-g) channel catfish. This report of ulcerative mycosis caused by A. invadans represents new host records for channel catfish and black bullheads from freshwater ponds in southeastern Louisiana.
Electroshocking-Induced Injuries in Newly Transformed Juvenile Fish
Authors: Henry Theodore B. , Grizzle John M.
Published: June 2004

Electroshocking-induced injuries in fish have not been described histologically, and little is known about such injuries in fish that have recently completed the transformation from larva to juvenile. We electroshocked newly transformed juvenile channel catfish Ictalurus punctatus, rainbow trout Oncorhynchus mykiss, striped bass Morone saxatilis, largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and Nile tilapia Tilapia nilotica (also known as Oreochromis niloticus). Fish were exposed for 5 s (bluegills only) or 20 s to homogeneous electric fields of 30-Hz to 120-Hz pulsed DC. Only 2.8% of the survivors (N = 800) and 0.7% of the fish that died immediately after electroshocking (N = 600) had gross injuries. Hemorrhage in the posterior trunk or anterior tail was the most common gross lesion, occurring in 17 fish. Nine of these fish were examined histologically, and 8 had an injured vertebra, sometimes associated with a notochord hernia, at the location of hemorrhage. In largemouth bass, bluegills, and channel catfish that survived electroshocking without gross injuries, a vertebral lesion occurred in 17% (N = 12) of the bluegills exposed for 5 s (8 V/cm) and in 40% (N = 15) of the channel catfish (4 V/cm). No vertebral injuries occurred in 16 bluegills exposed for 20 s (4 V/cm) or in 22 largemouth bass (2 V/cm). Necrotic skeletal muscle was the most common histological lesion, occurring in 60% of the channel catfish, 64% of the bluegills, and 18% of the largemouth bass that survived electroshocking without gross injuries. Necrotic muscle was also found in one control largemouth bass (8%) and one control bluegill (20%). The types and frequencies of lesions were similar in fish that survived and in those that died after electroshocking.
Estimating the Relative Contribution of Spring‐ and Summer‐Spawned Cohorts to the Atlantic Coast Bluefish Stock
Authors: Conover David O. , Gilmore Todd , Munch Stephan B.
Published: June 2004

The timing of recruitment for age‐0 bluefishPomatomus saltatrixalong the southern and mid Atlantic coast of the USA is bimodal, consisting of spring‐spawned and summer‐spawned cohorts. We present evidence from surveys of age‐0 fish that the recent precipitous decline in the Atlantic bluefish stock over the past decade has been associated with a switch in the relative production of the two cohorts from predominance by spring‐spawned fish throughout the 1970s and 1980s to predominance by summer‐spawned fish in most years from 1992 to 2002. Given this evidence of a shifting recruitment pattern, we reexamined the contribution of the two cohorts to the adult portion of the population and compared our results with similar earlier assessments. Cohort origin of adults was identified based on back‐calculated length at age 1. In four year‐classes in which age‐0, summer‐spawned bluefish predominated, there was little evidence of summer‐spawned fish among harvested adults from the same year‐classes captured one or more years later. Most adults examined in this study (N= 976) displayed lengths at age 1 greater than 20 cm, as predicted for spring‐spawned bluefish. This contrasts with year‐classes of bluefish from the late 1950s, when back‐calculated size at age 1 was clearly bimodal, consisting of both spring‐spawned and summer‐spawned cohorts. Low numbers of summer‐spawned bluefish in our samples did not appear to be an artifact of inaccuracies in aging or back‐calculation. The recent decline in the abundance of Atlantic coast bluefish appears to result from poor age‐0 recruitment of the spring‐spawned cohort and failure of the summer‐spawned cohort to contribute substantially to the adult population.
Competitive Interactions between Age‐0 Bighead Carp and Paddlefish
Authors: Schrank Sally J. , Guy Christopher S. , Fairchild James F.
Published: June 2004

The effects of bighead carp Hypophthalmichthys nobilis on native planktivores in the USA is unknown. The objectives of this study were to experimentally test for competitive interactions between age‐0 bighead carp and age‐0 paddlefish Polyodon spathula. Differences among water chemistry variables, invertebrate densities, and relative growth of fish were assessed in mesocosms. Water chemistry variables were similar among treatments throughout the experiment and only exhibited a temporal effect. Zooplankton density declined in mesocosms after fish were introduced. In general, zooplankton densities did not differ among treatments but did differ from the control. The relative growth of paddlefish was negative in the paddlefish and paddlefish–bighead carp treatments. The relative growth of bighead carp was negative in the bighead carp treatment but positive in the paddlefish–bighead carp treatment. Age‐0 paddlefish exhibited the greatest decrease in relative growth in mesocosms with bighead carp. Bighead carp exhibited the greatest increase in relative growth in mesocosms with paddlefish. These data suggest that bighead carp have the potential to negatively affect the growth of paddlefish when food resources are limited.
Diel Feeding Patterns of Red Snapper on Artificial Reefs in the North‐Central Gulf of Mexico
Authors: Ouzts Allyson Clair , Szedlmayer Stephen T.
Published: June 2004

Diets of red snapper Lutjanus campechanus were compared among four diel feeding periods (dawn, day, dusk, and night) and among three standard length size‐classes: small (200–299 mm), medium (300–399 mm), and large (400–499 mm). Fish were collected from August through October 2000 in the north‐central Gulf of Mexico. A total of 432 stomachs were examined, of which 164 (37%) contained prey. Size‐class influenced diets; diets of small red snapper were dominated by fish, those of medium red snapper by fish and tunicates, and those of large red snapper by crabs and fish. Red snapper fed on prey from several different habitats. Small red snapper fed mostly on reef and sand prey types; medium red snapper fed on similar portions of reef, sand, and mixed prey types; and large red snapper fed on mixed prey types. Adjusting for fish size, mean gut fullness was significantly lower for the dusk than for the day period. Fish were the most important prey for all periods. The second most important prey group changed with period: stomatopods for dawn, tunicates for day, and crabs for dusk and night periods. Prey habitat type also varied over periods. Sand prey type dominated dawn and dusk periods, whereas reef prey type dominated day and night periods. We used multidimensional scaling analysis to compare the relative influence of diel period to size‐class on red snapper diets. This analysis suggested that fish size‐class had a greater influence on red snapper diet than did period. However, with size effects removed, red snapper still showed significant diet shifts with periods.