Search

Coastal rivers and estuaries provide habitat and migratory corridors for freshwater estuarine-opportunists. We evaluated movement patterns of 61 blue catfish (Ictalurus furcatus) in the tidal York and Rappahannock rivers in Virginia, USA with acoustic telemetry from July 2015 to June 2016. To evaluate river-specific movements, we utilized a multistate Cormack–Jolly–Seber (CJS) model within a Bayesian framework to estimate probabilities of detection and transition (movement) among established salinity zones (i.e., tidal-fresh (0‰–0.5‰), oligohaline (>0.5‰–5‰), mesohaline (>5‰–18‰)). We considered flow as an environmental covariate. Despite high site fidelity in tidal-fresh zones, some individuals displayed movements into oligohaline and mesohaline habitats indicative of partial migration. Once downstream movement occurred, the probability of staying in the new salinity zone was higher than the probability of movements to other salinity zones. In the Rappahannock River only, movement upstream from mesohaline habitats was associated with below average flow. As flow increased, the probability of remaining in oligohaline and mesohaline zones increased. Our study shows blue catfish can move into downstream areas of tidal rivers with elevated salinities and that increased freshwater flow may allow them to remain in these habitats for extended durations. more...

We provide the first evidence for chronic effects of disturbance by commercial vessels on the spatial distribution and abundance of fishes in the channels of a large river. Most of the world's large rivers are intensively managed to satisfy increasing demands for commercial shipping, but little research has been conducted to identify and alleviate any adverse consequences of commercial navigation. We used a combination of a gradient sampling design incorporating quasicontrol areas with Akaike's information criterion (AIC)-weighted model averaging to estimate effects of disturbances by commercial vessels on fishes in the upper Mississippi River. Species density, which mainly measured species evenness, decreased with increasing disturbance frequency. The most abundant species — gizzard shad (Dorosoma cepedianum) and freshwater drum (Aplodinotus grunniens) — and the less abundant shovelnose sturgeon (Scaphirhynchus platorhynchus) and flathead catfish (Pylodictis olivaris) were seemingly unaffected by traffic disturbance. In contrast, the relative abundance of the toothed herrings (Hiodon spp.), redhorses (Moxostoma spp.), buffaloes (Ictiobus spp.), channel catfish (Ictalurus punctatus), sauger (Sander canadensis), and white bass (Morone chrysops) decreased with increasing traffic in the navigation channel. We hypothesized that the combination of alteration of hydraulic features within navigation channels and rehabilitation of secondary channels might benefit channel-dependent species. more...

In the tidal freshwaters of Virginia, U.S.A., the blue catfish (Ictalurus furcatus), an introduced piscivore, derives a significant proportion of its nutrition from spawning anadromous fish (genus Alosa, including blueback herring (A. aestivalis), American shad (A. sapidissima), and alewife (A. pseudoharengus)). Because the Alosa are not continually available to I. furcatus, there is an isotopic turnover, defined as change in isotope composition due to growth and metabolic tissue replacement, in I. furcatus tissues associated with the diet switch from freshwater to anadromous fishes. However, isotopic turnover rates for ictalurid fish are unknown. This study determined the maximum isotopic turnover rate of channel catfish (Ictalurus punctatus) tissues and compared this maximum rate with that of I. furcatus captured in the field over the 3-month Alosa spawning run. Maximum turnover rates for δ13C were 0.014 and 0.017‰ per day in muscle and blood. For δ34S, rates were 0.017 and 0.020‰ per day in muscle and blood, respectively. Isotopic turnover of muscle carbon reflected growth rate, but sulfur did not match growth as well. Ictalurus furcatus captured in the field showed no enrichment during the Alosa spawning run owing to slow turnover and variable diet. In aquatic ecosystems that have migrating prey, exploitation by predators may be underestimated using isotopes because of slow tissue turnover. more...

The disposition of malachite green was determined in channel catfish (Ictalurus punctatus) after intravascular dosing (0.8 mg·kg n1 ) or waterborne exposure (0.8 mg·L n1 for 1 h). After intravascular dosing, mean plasma concentrations of the parent compound exhibited a triphasic decline with a terminal elimination half-life of 6.2 h. Malachite green was rapidly absorbed and concentrated in the tissues during waterborne exposure. The rate of accumulation was directly related to pH of the exposure water. After waterborne exposure, elimination of the parent compound from plasma also was triphasic with a terminal half-life of 4.7 h. In muscle, the half-life of the parent compound was approximately 67 h. Malachite green and its metabolites were widely distributed in all tissues. In fish exposed to 14 C-labeled malachite green, total drug equivalent more...

In humans, glycine enters the red cell via four distinct plasma membrane carrier systems. The purpose of the present experiments was to measure the mode of transport of glycine by channel catfish (Ictalurus punctatus) red cells. About 54% of the glycine was transported by system L, while 16.1% of the glycine was transported by system Gly. A further 15.6% of transport was via system ASC and system asc together. An unidentified Na+-independent system was responsible for the transport of 7.2% of the glycine. No solute appeared to be carried into the cell by band 3. The remainder of the glycine entered the cell by diffusion. The Na+-independent system exhibited a Ktvalue of 57 ± 12 (mean ± standard deviation) μM and Vmaxof 142 ± 27 nmol∙g hemoglobin−1∙min−1(this compares with system L, which exhibited a Ktvalue of 65 ± 21 μM and Vmaxof 516 ± 117 nmol∙g hemoglobin−1∙min−1). These results demonstrate that channel catfish red cells are capable of transporting glycine by three of the four transporters involved in human red cells, although the relative contributions differ markedly, and by an additional unidentified transport system not requiring Na+. The differences in glycine transport between human and catfish red cell membranes can be attributed to evolutionary influences. more...

Cytochrome P4501A induction was used to evaluate exposure of fish to bleached kraft mill effluent in experimental stream channels. Immunodetectable P4501A and associated ethoxyresorufin-O-deethylase (EROD) activity were elevated in largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus) throughout 263 days of exposure to 8% and 4% effluent from a mill that used 70% chlorine dioxide substitution for chlorine in the pulp bleaching process. In largemouth bass, P4501A was elevated as high as 55-fold over control fish. Large temporal and species variations were observed in enzyme levels and activity. Levels of chlorinated organic compounds present in effluent also varied throughout exposures. However, there was no apparent relationship between P4501A and any of those compounds measured. P4501A and EROD in channel catfish declined to control levels within seven days after transfer of fish to clean water or after terminating introduction of effluent into the channels. In another exposure, induction was observed in largemouth bass at 4 and 12% effluent after the mill began using oxygen in the delignification process and 100% substitution of chlorine dioxide for chlorine. more...

The pharmacokinetics, bioavailability, and disposition of oxolinic acid (OA), a quinolone antibacterial drug, were examined in a warmwater (channel catfish (Ictalurus punctatus)) and coldwater fish species (rainbow trout (Oncorhynchus mykiss)). Studies were performed at 24 and 14 °C for catfish and at 14 °C for trout to compare temperature- and species-related differences. Analysis of OA pharmacokinetics when determined by HPLC provided elimination half-life [Formula: see text], volume of distribution (Vss), and clearance (Clb) estimates for 24 °C catfish, 14 °C catfish, and 14 °C trout of 40.9, 69.3, and 81.3 h, 939, 880, and 1817 mL/kg, and 16.3, 8.9, and 16.9 mL∙kg∙h−1, respectively. Following oral administration, OA plasma concentrations peaked between 8 and 24 h for all treatments; however, 14 °C trout and 14 °C catfish sustained peak concentrations for a longer duration than 24 °C catfish. Oral OA bioavailabilities were 56.0, 91.8, and 90.7% for 24 °C catfish, 14 °C catfish, and 14 °C trout, respectively. OA distribution data for muscle of 14 °C catfish demonstrated an inordinately high peak concentration and delayed time to peak relative to other treatments. Elimination half-lives of OA in muscle were 33.1, 54.3, and 141 h for 24 °C catfish, 14 °C catfish, and 14 °C trout, respectively. more...

Models of potential brood predators placed near the nest were used to elicit defence behaviour in male smallmouth bass (Micropterus dolomieui) in the field. The three predator models represented a conspecific, a species found in the lake (yellow perch, Perca flavescens), and a species not present in the lake (brown bullhead, Ictalurus nebulosus). Aggressive behaviour increased with brood age and with decreasing distance between model and nest. Brood-guarding smallmouth bass exhibited a generalized response to the three predator models and did not discriminate between them by altering levels of aggression. more...

Channel catfish (Ictalurus punctatus) of different tissue fat contents (0.5–11.0%) were held in water containing approximately 0.5 μg/L of the off-flavor compound 2-methylisoborneol (MIB) for various times. A new analytical method was developed to quantify tissue burdens of MIB. Fish showed significant bioconcentration of MIB after 2 h and equilibrium by 24 h. The fatter fish (> 2.5% muscle fat) accumulated nearly three times more MIB than lean fish ( more...

Diel feeding chronology and daily ration were determined from stomach or foregut contents of common carp (Cyprinus carpio), golden redhorse (Moxostoma erythrurum), channel catfish (Ictalurus punctatus), smallmouth bass (Micropterus dolomieu), and longear sunfish (Lepomis megalotis) in the Vermilion River, Illinois. Feeding was highly variable among individuals, hours, and months for each species. Discontinuous feeding was detected in common carp, golden redhorse, and channel catfish. Common carp and the two centrarchid species fed with greatest intensity near sunrise and sunset; golden redhorse and channel catfish feeding was highest at night. Daily ration estimates were higher for fishes with stomachs than those for stomachless species. Microhabitats occupied by fish over the diel period were identified using nondisruptive techniques: direct observation, prepositioned electrofishing, and radiotelemetry. Microhabitat use during high-feeding periods was significantly different [Formula: see text] than that during low feeding for at least one habitat variable in each species examined. Association with cover also varied between feeding regimes. Our findings suggest that realism of instream flow assessments may be improved if habitat suitability criteria are stratified by feeding regime. more...

To better characterize neoplasm epizootics in the Great Lakes basin and their association with families of contaminants, we sampled five locations: the Fox and Menominee rivers, Lake Michigan; Munuscong Lake, St. Mary's River; and the Black and Cuyahoga rivers, Lake Erie. Frequencies of external and liver tumors were determined for brown bullhead (Ictalurus nebulosus) from all locations except the Black River and for walleye (Stizostedion vitreum) from the Lake Michigan and St. Mary's River sites. Sediment samples were analyzed for metals, polychlorinated aromatics, and polynuclear aromatic hydrocarbons (PAH). Liver neoplasms occurred in brown bullhead from the Cuyahoga River and Munuscong Lake; brown bullhead captured from Munuscong Lake were older than those collected from the other locations. Brown bullhead from these same two rivers had elevated hepatosomatic indexes. No liver neoplasms were found in brown bullhead from the Fox and Menominee rivers, although polychlorinated aromatics were highest in both Fox River sediment and Fox and Menominee brown bullhead, and arsenic was highest in Menominee River sediment and fish. Liver neoplasms in brown bullhead from the Cuyahoga River fit the prevailing hypothesis that elevated PAH in sediment can induce cancer in wild fish. The cause of the liver neoplasms in Munuscong Lake brown bullhead is undetermined. more...

Two pools of liver cells, enriched either in periportal or in perivenous hepatocytes, were obtained from the catfish Ictalurus melas by the selective destruction of the liver by digitonin infusion. Following digitonin pulses directed either orthograde via the portal vein or retrograde via the hepatic vein, hepatocytes from undamaged perivenous and periportal zones, respectively, were isolated by the conventional collagenase perfusion procedure. Eluates from either periportal or perivenous zones were collected for a total of 9 min before, during, and immediately following the digitonin pulse. The eluates were assayed for protein, glycogen, glucose, and activities of lactate dehydrogenase and alanine aminotransferase, and their yield ("recovery") was estimated as a percentage of the total hepatic content. The aforementioned metabolic compounds and enzyme activities were measured also in periportal and perivenous liver cells. No significant differences were obtained between these cells. Both pools of hepatocytes were more than 90% viable and remained hormone responsive. Epinephrine (3 × 10−8 M) or salmon glucagon (3 × 10−8 M) elevated cAMP content, and stimulated glycogen phosphorylase a activity, glycogen depletion, and glucose release in periportal and perivenous liver cells. No differences were observed between periportal and perivenous cells in their metabolic responsiveness to either hormone. more...

Vitellogenin (VG) was localized in the cytoplasm of hepatocytes in freeze-dried, plastic-embedded and Bouin's-fixed, paraffin-embedded sections of channel catfish liver. The location of VG was demonstrated by using a peroxidase–antiperoxidase immunohistochemical method. Positive immunostaining was obtained only in naturally vitellogenic females and in fish that had been injected with 2 mg/100 g body weight 17β-estradiol. Vitellogenin reaction product was observed in most but not all of the hepatocytes from estradiol-induced and naturally vitellogenic fish. Glycogen content was reduced in hepatocytes that showed positive VG immunostaining. Nuclear size was larger in hepatocytes from vitellogenic fish compared with nonvitellogenic fish. more...

Ormetoprim is used to potentiate sulfadimethoxine in treating certain bacterial diseases of aquatic species. The tissue disposition and renal excretion of ormetoprim and metabolites were examined after intravascular and oral administration (4 mg∙kg−1) in channel catfish (Ictalurus punctatus). Peak plasma level (0.66 μg∙mL−1) of14C-ormetoprim occurred at 6 h after oral dosing. The oral bioavailability was estimated at 52%. Ormetoprim and metabolites were widely distributed in the tissues. The tissue concentrations were highest in the liver, trunk kidney, head kidney, and spleen. Clearance of the radiolabel from tissues was rapid. The muscle contained 49.3% of the intravascularly administered dose at 2 h; however, at 72 h, less than 1% of the dose remained in this tissue.14C-Ormetoprim was more persistent in the skin than in the muscle. Ormetoprim was extensively metabolized in catfish. After intravascular administration, 21.1% of the dose of14C-ormetoprim was eliminated in the urine in 48 h, predominantly as polar metabolites; less than 4% of the dose was eliminated as the parent compound. Biliary excretion was a minor route of elimination (5–6% of the dose). The data suggest branchial excretion of ormetoprim and/or metabolites. more...

The tissue disposition of the off-flavor compound 2-methylisoborneol (MIB) was examined in market-sized channel catfish (Ictalurus punctatus). Purified MIB was intravascular administered to channel catfish at a dosage of 1 mg∙kg−1 body weight. Body tissues and fluids were collected at intervals following administration and were analyzed for MIB by microwave distillation and capillary gas chromatography. Plasma clearance of MIB was characterized by a two-compartment open model with half-lives of 0.14 and 3.62 h or distribution and elimination phases, respectively. MIB was more concentrated in peritoneal fat and subepidermal adipose tissue than in other tissues. The concentration in the edible flesh decreased from 0.107 μg∙g−1 at 2 h to 0.025 μg∙g−1 at 96 h. There was no evidence of biotransformation of MIB to the related compounds 2-rnethylenebornane and 2-methyl-2-bornene over the 96-h sampling period. The low recoveries of the administered dose in body fluids and tissues and the rapid clearance suggested significant gill excretion of this compound. more...

The lesions observed in channel catfish (Ictalurus punctatus) as a consequence of exposure to Edwardsiella ictaluri via gut and water were studied. Channel catfish fingerlings were exposed to 1010 bacterial cells via the gut and placed in tanks with unexposed fish. Both groups of fish were sampled periodically over a 35-day period. The gut-exposed fish exhibited gross signs of a systemic infection within 2 wk. Enteritis, hepatitis, interstitial nephritis, and myositis, all of which began as acute reactions and developed into chronic lesions, were observed histologically. Some of the contact fish developed systemic infections beginning in the intestine, thus demonstrating horizontal transmission. However, only contact fish developed the characteristic "hole in the head" lesion, which began in the olfactory sac and progressed to a granulomatous meningioencephalitis. These results indicate that both gut and nares are sites of primary infection in natural outbreaks of E. ictaluri. more...

The implications of chemosensory feeding and associated ictalurid morphology were investigated through a seasonal study of the diets of the brown bullhead (Ictalurus nebulosus) and yellow bullhead (I. natalis) relative to food availability. Based on the attributes of chemosensory feeding (little discrimination between prey types) and bullhead morphology (poor sight, broad mouth), it was predicted that bullheads would be food generalists and opportunists, and that age-class diets would overlap. These predictions were generally supported for the brown bullhead. Some food types (amphipods) were harvested when most abundant; however, others (chironomid larvae) were consistently taken, and a few potential prey types were underutilized. The yellow bullhead, by contrast, was a food generalist only when young. Adults were specialized piscivores and crayfish feeders. The brown bullhead showed greater weight and length increases than co-occurring visually feeding centrarchids with diets of similar calorific values. Because of the similarity in calorific intake among species, a greater metabolic efficiency in brown bullheads was indicated. Other workers have shown that brown bullheads have lower standard and active metabolisms than some fish species. more...

The 96-h median lethal concentrations of nitrite to channel catfish (Ictalurus punctatus), tilapia (Tilapia aurea), and largemouth bass (Micropterus salmoides) under similar water quality conditions were 7.1 ± 1.9, 16.2 ± 2.3, and 140.2 ± 8.1 mg NO2-N/L (mean ± SE), respectively (pH 7.7–8.2; temperature 23 °C). During 24-h sublethal exposures to nitrite, methemoglobin concentrations in the blood of all three species generally increased with increasing nitrite concentrations. Channel catfish and tilapia concentrated nitrite in their blood above environmental levels and generated higher methemoglobin concentrations than largemouth bass at all nitrite concentrations tested. Largemouth bass did not develop elevated methemoglobin concentrations until NO2-N concentrations reached 48.7 mg/L, and plasma nitrite concentrations in largemouth bass were never observed higher than environmental concentrations. These data indicate that differences in resistance to nitrite among species may be partially due to a differential ability of some species to prevent the concentration of nitrite in the plasma. more...

A virus (strain F82-34) was isolated from channel catfish (Ictalurus punctatus) that was clearly distinct from channel catfish virus (CCV). The virus induced extensive syncytia in channel catfish ovary (CCO) cells incubated at 26 °C. The BB and CHSE-214 cell lines supported virus replication but the FHM line was refractory. Virus replication was optimal at 25 °C where, after 96 h, approximately 50% of the virus was found to be released from CCO cells. Virus infectivity was stable for 1 mo at4, 16, and 23 °C and for 5 mo at −20 and −8Q °C but was lost after 7 d at45 °C. Partially purified virions are double-shelled hexagonal capsids characteristic of reoviruses and have an average diameter of 75 nm. F82-34 was related to but distinct from two other reoviruses from fish in neutralization studies; these three viruses, and possibly a fourth from American oysters (Crassostrea virginica), appear to represent a new taxonomic group within the family Reoviridae. We therefore propose that this new virus be tentatively designated catfish reovirus (CRV). more...

Specimens of the kinetophragminophorid ciliates Chilodonella cyprini (Moroff, 1902) from goldfish (Carassius auratus) in Nova Scotia and Chilodonella hexasticha (Kiernik, 1909) from channel catfish (Ictalurus punctatus) in Arkansas were examined by scanning electron microscopy. They are round to foliate, ventrally flattened protozoa well suited for adherence to, and movement over, a flat host surface. Organelles including ventral ciliary rows, dorsal cilia, excretory pores, and a prominent cytopharynx are described. Dorsal surfaces of both species have a distinct reticulate pattern which represents a modification of the pellicle. Ventrolateral margins of C. cyprini contain rows of short cuticular proturberances not seen in C. hexasticha. Our specimens of the two species were distinguished by their total ventral ciliary row number (12–14 in C. hexasticha, 21 in C. cyprini). General morphology as revealed by scanning electron microscopy is compared with previous light microscopical observations. The taxonomic separation of the two species, C. cyprini and C. hexasticha, is confirmed. more...

Channel catfish (Ictalurus punctatus) fingerlings fed a diet containing 20 ppm Aroclor® 1242 for 20 wk responded with a reduced weight gain and liver hypertrophy when compared to controls. When treated fish were fed the control diet for 8 subsequent wk followed by 8 additional wk of Aroclor® feed, they approached control values for liver weight and surpassed the rate of gain for control fish. No histopathological lesions were observed in the fish fed PCB. The total PCB in fish declined slightly during an 8-wk PCB-free period beginning at week 12, but the PCB burden remained constant when the PCB-free period was begun at week 20. During PCB-free periods, there was a shift in residues from the edible carcass to the offal. Residues are discussed as components as well as total PCB. We found that a tetrachlorobiphenyl is more persistent than some higher chlorinated components and that various tissues accumulated different profiles of components. more...

Cell lines from apparently normal gill, gonad, and kidney tissue of adult walking catfish (Clarias batrachus) were established and have been subcultured 75, 80, and 95 times, respectively. The cells were propagated in a modified Ham's F-12 medium at 25 °C but are capable of growth at 37 °C. The gill and kidney cells are the first to have been established from these tissues in fish. The kidney cell line is fibroblastic, the gonad is a mixed epithelioid–fibroblastic type, and the gill is pleomorphic. All three cell lines are susceptible to channel catfish virus (CCV), exhibiting cell fusion and other marked cytopathic effects. A live attenuated vaccine strain of CCV was produced by repeated passage of a virulent strain of CCV in kidney cell cultures. The vaccine strain is less virulent than the wild-type CCV and protects fingerling catfish against challenge with wild-type virus.Key words: channel catfish virus, Clarias batrachus, fish cell cultures, vaccine more...

Locomotor and feeding activity was investigated under(1) 12 h light(L): 12 h dark(D)and 16 h L: 8 h D, (2) 24 h D and 24 h L, and (3) dark pulses (0.75 h L: 0.25 h D), in the brown bullhead (Ictalurus nebulosus). In addition to locomotor and feeding activity, reaction time (latency time on lights-off and lights-on) was also measured.Fish subjected to a light–dark regime showed nocturnal behaviour, in many cases with a positive phase angle difference (i.e., the animals ceased their activity several hours before lights-on). Further, the actograms showed, as expected, a distinct 24 h rhythm. Only 2 brown bullheads out of 15, subjected to constant conditions, showed a circadian component in the locomotor activity, which could only be detected by frequency analysis.Nine out of 12 animals subjected to dark pulses (0.75 h L: 0.25 h D) showed a free-running circadian rhythm (approximately 23 h) in locomotor activity and 2 out of 3 showed such a rhythm in feeding activity. Observations and measurements of reaction time on leaving and re-entering the shelter after lights-off and lights-on (0.75 h L: 0.25 h D) showed also that this parameter has a circadian course. Measurements performed a fortnight later showed a similar, but less pronounced, pattern of behaviour.Dark pulses are thought to prevent rapid dissociation of a flexible multioscillatory circadian system in the brown bullhead. more...

Two groups of fingerling channel catfish (Ictalurus punctatus), one experimentally infected with channel catfish virus disease by transmission through water, and the other collected during an active epizootic, were examined histologically. Previously unreported pathology of pancreatic and brain tissue is described. The virus elicits a histopathological response similar to that reported for the salmonid viruses. more...

Radioactive antimycin was readily taken up in bile and tissues of brown bullheads (Ictalurus nebulosus) exposed to 0.045 μg/ml of 14C-antimycin for as long as 48 h. Bile contained the most and blood the least radioactivity at all sampling periods. The highest concentration of 14C-antimycin in muscle was 0.12 μg/g, after 12 h of exposure. The average amount of 14C-antimycin per fish was 0.94 μg/g. The 14C-antimycin concentration decreased with the elapse of time in the muscle and in samples of combined head, skin, and viscera. The concentration of l4C-antimycin in the exposure solution decreased from 0.045 μg/ml to 0.015 μg/ml after 12 h and 0.010 μg/ml after 48 h. The initial half-life of 14C-antimycin in the exposure solution was about 6.5 h. A second group of fish was exposed to 0.045 μg/ml of l4C-antimycin for 48 h and then transferred to antimycin-free, flowing water for up to 96 h. The 14C-activity decreased in muscle tissue from 0.11 μg/g to 0.05 μg/g in 96 h. Half-life of 14C-antimycin was about 75 h in muscle and 61 h in the combined head, skin, and viscera. more...

Channel catfish (Ictalurus punctatus) fingerlings were fed semipurified diets containing 0–150 mg/kg of vitamin C for 14 wk and subsequently at two temperature regimes infected with the pathogenic bacterium Edwardsiella tarda. Mortality rates were determined 96 h after infection. A supplemental vitamin C level of 30 mg/kg of diet was sufficient for normal growth and for prevention of deficiency signs such as lordosis, scoliosis, and a reduction in bone collagen formation. However, increased resistance against infection was provided when the level of supplemental vitamin C was increased to the highest dietary level, 150 mg/kg, at a water temperature of 23 °C. At 33 °C, increasing the supplemental level of vitamin C had significantly less effect on resistance against infection. The difference in response at the two temperatures indicates that the vitamin C requirement for resistance to infection is possibly higher when channel catfish are infected at lower temperatures, where the natural resistance is reduced, than when infected at a temperature near optimum for the natural resistance mechanisms of the fish.Key words: vitamin C, channel catfish, disease resistance, Edwardsiella tarda, infection more...

Tadopole madtom (Noturus gyrinus) and black bullhead (Ictalurus melas) adjusted buoyancy by altering swimbladder volume becoming less buoyant in current than in still. Extent of adjustment was dependent on size. Tadpole madtom adjusted buoyancy within 96–192 h but partial adjustment occurred within 12–48 h. Year 0 fish made a more rapid decrease in buoyancy than did year 1 or 2. As buoyancy was decreased year 0 and 1 tadpole madtom showed significant changes in internal pressure of swimbladder gases. Black bullhead secreted gases into the swimbladder to increase buoyancy while tadpole madtom showed no such ability. more...

Livers of 50 channel catfish (25–15 cm long) obtained by seining from the Ross Barnett Reservoir near Jackson, Mississippi were subjected to light, electron microscopic, and enzyme histochemical examination to describe the hepatic parenchyma and exocrine pancreas as well as localize acid phosphatase. Similar to that of other fish species, catfish liver parenchyma consisted of laminae of dual-plated muralium and, unlike that of many species, dispersed exocrine pancreatic tissue was observed circumscribing the portal vein, its tributaries, hepatic artery, and its branches. Acid phosphatase activity was histochemically localized to reaction product in lysosomal-like bodies arranged in peribiliary canalicular patterns. Electron microscopic observations were consistent with the above observations and biliary canaliculi were noted with long microvillar processes occupying their lumens. The exocrine pancreatic cells contained granular endoplasmic reticulum, free ribosomes, Golgi bodies, and numerous membrane-bound zymogen granules. more...

Although anitmicrobial drugs are frequently added to water to treat bacterial diseases of fish, their absorption is largely unquantified. Channel catfish weighing 3–5 g each were exposed to varying concentrations (4 mg/L to 32 mg/L) of chloramphenicol, erythromycin, furpyrinol, and oxytetracycline, respectively. Antibiotic levels measured after 5 h utilizing Bacillus subtilus spore germination inhibition showed that furpyrinol and oxytetracycline were absorbed by the fish in proportion to the antimicrobial concentration in the water. Minimum inhibitory concentrations can be attained in the fish with practical concentrations of these drugs in the water. Erythromycin (carrier-free) was poorly absorbed and chloramphenicol was not absorbed. Significant antibiotic degradation in water occurred in all drugs except furpyrinol.Key words: fish, antimicrobic, chloramphenicol, erythromycin, furance, oxytetracycline more...

Fingerling channel catfish (Ictalurus punctatus) 12–15 cm long were fed semipurified diets containing 0, 5, 10, 20, 40, and 80 mg of dl-α-tocopherol acetate per 100 g dry diet, and slaughtered after 97 d. Storage stability of fillets for the different treatments was determined by 2-thiobarbituric acid analysis after 3 mo frozen storage and after 3 mo freezing followed by refrigeration for 3 d. Fillets from fish fed the two lowest α-tocopherol levels exhibited significant oxidative rancidity after frozen storage. All higher levels showed similar but negligible oxidation. The 3 d of additional refrigerated storage significantly increased the amount of fat oxidation in all fillets from fish fed less than 40 mg/100 g. These results strongly indicate that increased dietary levels of α-tocopherol are effective in increasing the storage stability of catfish fillets. Key words: storage stability, channel catfish, antioxidants, dl-α-tocopherol, 2-thiobarbituric acid more...

Plasma sodium and chloride levels of channel catfish (Ictalurus punctatus) increased after a 5-day exposure to 10 and 12 g/liter sodium chloride. Exposure of fish to 4 and 8 g/liter for 5 days resulted in plasma electrolyte levels higher than those of fish kept in aged tap water, but were not different from values usually found in freshwater fish. These observed differences may have been due to handling. Tests were performed during several months and no effect due to season was observed.When fish in July (27 C) were exposed to 10 g/liter sodium chloride, the plasma electrolyte concentration increased for 48 h and then stabilized. Exposure to the same concentration in March (9 C) resulted in a slow increase of plasma electrolytes throughout the 13 days of the experiment. Injection of 100 μg/kg cortisol had no effect on plasma electrolyte increase during 48 h after transfer to 12 g/liter sodium chloride. more...

Fingerling channel catfish (Ictalurus punctatus) were given diets containing 0, 0.4, 0.8, or 4.0 μg dieldrin/g of food (dry weight) for 210 days, followed by a dieldrin-free diet for 56 days. Catfish receiving 4.0 μg dieldrin/g of food gained about 17% less weight than the control fish in 210 days and about 35% less weight during the last 126 days of the 210-day period. No growth differences were attributable to the ingestion of 0.4 or 0.8 μg dieldrin/g of feed. Mortality during the experiment was random and not appreciable.Dieldrin accumulations were characterized by an immediate rapid rise of residue levels in the tissues, followed by a period during which concentrations were relatively stable. Residues in tissues decreased rapidly after dieldrin was withdrawn from the diet. Dieldrin half-life was 9.6 days (mean for the three groups).Theoretical residue concentrations calculated from the growth, feeding, and half-life data were similar to the empirical concentrations, although the theoretical values were consistently the higher. The recoverable concentration accounted for 25.7% (mean of the three treatments) of the theoretical concentration. more...

Rainbow trout (Salmo gairdneri), bluegill (Lepomis macrochirus), and brown bullhead (Ictalurus nebulosus) were exposed to a gradual (over several hours) reduction in dissolved oxygen. Muscle and liver lactic and pyruvic acid concentrations were measured at seven environmental [Formula: see text]. The response was an increase in anaerobic metabolism of the resting fish at a threshold [Formula: see text] that varied with the species and acclimation temperature. A lower anaerobic threshold occurred after acclimation to cold in rainbow trout and possibly bluegill; cold acclimated brown bullhead did not metabolize anaerobically when held in water for 20 min with an oxygen tension near zero. The anaerobic thresholds correspond reasonably well to the relative positions of the blood oxygen dissociation curves for the three species. Only in the trout, however, does the anaerobic threshold found in this study compare to the critical oxygen tension (PC; [Formula: see text] below which aerobic metabolism becomes dependent on [Formula: see text] in the water). PC is far higher in both the bluegill and brown bullhead than the anaerobic threshold which suggests a reduction in overall energy expenditure in these species at rest when in water of low dissolved oxygen.Key words: anaerobic metabolism, lactate/pyruvate ratios, muscle, liver, rainbow trout, Salmo gairdneri; bluegill, Lepomis macrochirus; brown bullhead, Ictalurus nebulosus more...

We describe a new method for the isolation of 2-methylisoborneol (MIB) from channel catfish (Ictalurus punctatus) that have been declared "off-flavor" organoleptically. The method involves microwave cooking fish under a nitrogen stream and trapping the condensate at −80 °C. The fish condensate was extracted with hexane which was reduced to 100 μL and analyzed by gas chromatography. Concentrations as low as 5 ng MIB∙g fish−1 were routine detected. A bioconcentration value for MIB in off-flavored fish flesh was 28.1 ± 14.0 (±SD) concentration water/concentration fish. Analysis of off-flavored fish collected at the processing plant consistently showed elevated concentrations of MIB. Geosmin, another compound known to cause flavor and odor problems in fish flesh, was not detected. more...

Yearling rainbow trout, Salmo gairdneri, and channel catfish, Ictalurus punctatus, were subjected to 0.5- and 3-h periods of narcosis using continuous direct current. Galvanonarcosis treatments decreased the immediate individual and group activity in both species of fish. Twenty-four hours after treatment, all fish except trout narcotized for 3 h recovered to levels of individual and group activity equivalent to those of untreated fish. Photonegative response was strong in both fish species and was not influenced by galvanonarcosis treatments. Trout narcotized with direct current were more vulnerable to predation than untreated fish; susceptability increased with increasing treatment periods. The potential of extended galvanonarcosis as a fish immobilization technique is strong. Key words: galvanonarcosis, behavior, extended narcosis, direct current, rainbow trout, channel catfish, photonegative, activity, prey vulnerability, immobilization more...

The effects of relative body size (larger or smaller fish), absolute body size differences, food level, and social interactions on the growth rates of juvenile brown bullhead (Ictalurus nebulosus) catfish were determined for pairs of fish. Overall growth rate of the larger fish was higher than for the smaller fish, although this difference did not depend on absolute body size difference within pairs. The reduced growth rates of both larger and smaller fish at limited food level was independent of both relative size difference and absolute body size difference within pairs. Both larger and smaller fish had highly variable growth rates. Size dominance and aggression were common within many pairs, yet this behavior was unrelated to food level and absolute body size difference. Aggression within pairs was not diminished by adding structural complexity to simple environments. It is suggested that the high variability in growth rates was due to differences in individuals within pairs with respect to the intensity of behavioral interactions. Social interactions within pairs offish were apparently unrelated to food level and were strong enough to mask both exploitative and interference mechanisms which may have been functional in competition for limited food.Key words: body size, dominance hierarchies, exploitation competition, food level, Ictalurus nebulosus, interference competition, behavioral interactions more...

Seine and dip net samples taken on the spawning grounds in Rivière aux Pins were used to describe the growth of young-of-the-year brown bullhead (Ictalurus nebulosus Le Sueur). One-year-old and older bullheads were aged by counts of annual growth marks on sections of their pectoral fin bony ray. Several aspects of the growth of these fish were determined: a faster growth in length and weight in ma les than in females; the presence in Rivière aux Pins of two groups of bullhead, one more slowly growing and one more rapidly growing; the effects of tagging on growth; the isometric length–weight relationship; and variations of condition during the few months when spawners occupy Rivière aux Pins. more...

Immunoenzyme techniques were developed for detecting subclinical infections of Yersinia ruckeri and differentiating acute yersiniosis from motile aeromonas septicemia in channel catfish (Ictalurus punctatus). Immunoenzyme techniques were comparable to immunofluorescence and cultural procedures for detecting and differentiating Y. ruckeri and Aeromonas hydrophilia infections in catfish. The availability of immunoenzyme microscopic techniques extends immunostaining microscopy to laboratories possessing only conventional microscopes.Key words: Aeromonas hydrophila, EIA, ELISA, enteric redmouth disease, enzyme labeled antibody, fluorescent antibody, HRM, ictalurid, motile aeromonas septicemia, Yersinia ruckeri more...

A new bacterial disease affecting primarily pond reared fingerling channel catfish, Ictalurus punctatus, is described from 17 instances reported from June 1976 through December 1978. Terramycin medicated feed controlled the disease when early diagnosis was possible. Terramycin resistant strains were not detected. The causitive organism was confirmed as a previously unidentified species of Edwardsiella by the Center for Disease Control Atlanta Georgia. The disease is referred to as Enteric Septicemia of Catfish (ESC). Optimum growth temperature is between 25 and 30 °C; this correlated with pond water temperatures during instances of mortality on fish farms. Koch's postulates were fulfilled using channel catfish fingerlings in 40-L aquaria. Key words: Fish disease, bacterial fish pathogen, enteric bacteria, channel catfish diseases more...

Studies of food habits of the brown bullhead (Ictalurus nebulosus) in the Ottawa River have often shown a high proportion of filamentous algae in the stomach. This study was designed to determine whether the algae were utilized as food. Isotopic and caloric techniques showed that about 23% of the carbon from Spirogyra and 67% of the carbon from Anaebena flos-aquae was assimilated by the fish within 24 h of ingestion. more...

Exposure of channel catfish (Ictalurus punctatus) fingerlings for 24 h to 1.0, 2.5, and 5.0 mg/L nitrite (pH = 7; hardness = 40 mg/L; temperature = 22–25 °C) produced methemoglobin levels of 20.7 ± 1.9%, 59.8 ± 1.9%, and 77.4 ± 1.4% (SE), respectively. However, methemoglobin levels were not elevated when fish were simultaneously exposed to 1.0, 2.5, and 5.0 mg/L nitrite and 25, 50, and 100 mg/L sodium chloride, respectively. Acclimation to sodium chloride for 24 h before exposure to nitrite did not enhance the inhibitory action of sodium chloride. Fish exposed to 5 mg/L nitrite for 5 h developed 42.5 ± 3.8% methemoglobin. When transferred to water containing 5 mg/L nitrite and 250 mg/L sodium chloride, methemoglobin levels returned to normal within 24 h. Environmental chloride probably inhibits methemoglobin formation by competing with nitrite for entrance into the gills of the fish. An ionic ratio of 16 Cl− to 1 NO2− is capable of complete suppression of nitrite-induced methemoglobin formation. Bicarbonate ion present in the test water (1 meq/L) may also have contributed to the inhibitive action of chloride. Key words: nitrite, methemoglobin, chloride, channel catfish more...

Adult channel catfish (Ictalurus punctatus) were fed diets containing menhaden oil (MHO), soybean oil (SBO), or beef tallow (BFT) as lipid sources for 116 d. The effects of these diets on two important hepatic xenobiotic-metabolizing enzyme systems, cytochrome P-450-dependent monooxygenases (MOs) and glutathione S-transferases (GSTs), were evaluated. Microsomal MO and cytosolic GST activities were consistently greater in fish fed MHO than in those receiving SBO or BFT. Generally, enzyme activities in fish fed SBO and BFT were similar. The different diets also markedly influenced the fatty acid composition of the liver, particularly with respect to the relative abundance of specific fatty acid families. These data demonstrate that dietary lipid does affect the activities of xenobiotic-metabolizing enzymes in fishes, and thereby could influence the sensitivity of fishes to certain organic toxicants. more...

During June and July 1970, an estimated 5.3 million eggs (4.1/103m3) and 56.6 million young fish (43.8/103m3), 3–62 mm FL, were pumped by the Muddy Run Pumped Storage Generating Station from Conowingo Reservoir (lower Susquehanna River, Pennsylvania) into Muddy Run Pumped Storage Reservoir. A maximum of only 2% of the eggs and 39% of the young were returned to the lower reservoir during generation. The eggs were predominately Carpiodes cyprinus. Of the young, 73% entrained during pumping and 83% entrained during generating were Ictalurus punctatus, Cyprinus carpio, and Carpiodes cyprinus. Similar results are reported for 1969. The species and numbers of specimens entrained reflect the utilization of the area near and above the lower reservoir intake discharge structure as spawning and nursery grounds, the extent and peaks of spawning seasons, and the phases of development and behavior of the young. Sufficient numbers of specimens pumped into and retained by the upper reservoir, in which natural reproduction is nearly precluded by the extensive fluctuation of water level, survive to maintain many of the reservoir’s fish populations. more...

Plasma corticosteroid concentrations in channel catfish (Ictalurus punctatus) increased in response to increasing concentrations of both ammonia and nitrite. Corticosteroid levels in fish exposed to nitrite increased continuously during a 24-h exposure whereas corticosteroid concentrations of fish exposed to ammonia peaked after 8 h and then decreased for the remainder of the 24-h experiment. Low environmental pH and elevated environmental chloride were effective in preventing elevated corticosteroid levels in fish exposed to ammonia and nitrite, respectively. Based on plasma corticosteroid concentrations, no additive or synergistic toxic interaction was evident in fish simultaneously exposed to environmental ammonia and nitrite. These data indicate that (1) corticosteroids are released into circulation probably in response to a physiological dysfunction brought about by the toxins and not simply their presence in the environment, and (2) the absence of a toxic interaction between ammonia and nitrite as measured by plasma corticosteroid concentrations may be due to the temporal separation of their toxic effects coupled with the apparently rapid ability of channel catfish to acclimate to ammonia.Key words: Ictalurus punctatus, corticosteroids, toxicology, environmental contaminants more...

The seasonal changes in the cytology of the anterior spermatogenic testis permitted the reproductive cycle of Ictalurus nebulosus Lesueur to be divided into four periods: (i) a prespawning period (mid-April to June), associated with an increased gonadosomatic index (GSI), when the overwintering secondary spermatocytes matured into biflagellate spermatids and spermatozoa, and there was an increased vacuolation of Leydig and Sertoli cells; (ii) a spawning period (June to mid-July), associated with a fall in GSI, when Leydig cell vacuolation was maintained, Sertoli cell size and vacuolation became maximal, and spermatozoa were released; (iii) a postspawning period (mid-July to mid-August) characterized by an increase in spermatogenic activity and ending when the seminiferous tubules were filled with secondary spermatocytes; and (iv) a resting (overwintering) period (mid-August to mid-April) when the seminiferous tubules were filled with secondary spermatocytes; quiescent spermatogonia were evident in decreasing numbers and Sertoli and Leydig cells were small and apparently inactive until late in the period. The posterior glandular testis similarly exhibited seasonal changes in size and vacuolation with peak activity associated with the spawning period. more...

In stomachs of 550 sauger (Stizostedion canadense) collected by gillnetting in the Ohio River during June 1980 through August 1981, Dorosoma cepedianum were the most abundant prey (42% of all identified prey), followed by Notropis atherinoides (28%), Aplodinotus grunniens (16%), and Ictalurus punctatus (12%). Annual food consumption of sauger averaged 1.1% of the body weight per day. Growth and daily ration followed similar patterns, being high from September to January (maximum in October) and low from March to August. Rapid growth and high food consumption throughout fall and early winter were related to an extended period of high temperatures and increased availability of Dorosoma cepedianum. The annual period of growth and food consumption was longer and peaked later in the year in the river than those previously observed in other types of aquatic systems. more...

Effects of nutrition on xenobiotic-metabolizing enzymes in fishes are not well known. We fed three groups of channel catfish (Ictalurus punctatus) either a synthetic, laboratory-prepared diet or one of two commercial catfish rations. After 3 mo on each diet, fish were treated with the enzyme inducer Aroclor 1254. Hepatic microsomal monooxygenase (MO) activity was lower in untreated fish fed a commercial diet than in those fed the laboratory diet. Aroclor 1254 increased MO activity to a lesser degree in fish fed that same commercial diet compared with those receiving the laboratory or other commercial diet. Hepatic microsomal UDP-glucuronosyltransferase (UDPGT) activity was similar in all control fish; however, Aroclor 1254 increased UDPGT activity to differing degrees in the three diet groups. Hepatic cytosolic glutathione S-transferase (GST) activity was increased by Aroclor 1254 to a similar extent in all diet groups; however, levels of GST activity generally were higher in fish fed the commercial diets than in those fed the laboratory ration. These data indicate that diet can affect the toxicity of xenobiotics to fishes through alterations in hepatic enzyme systems, and thus should be considered a potential source of variation in toxicological studies with fishes. more...