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N. C. Parker

Publications and source records attributed to N. C. Parker.

At least 19 recordsLinked to original sources
USGS2009

Plasma corticosteroid and electrolyte dynamics of hybrid striped bass (white bass x striped bass) during netting and hauling

Striped bass hybrids ( Morone chrysops female x Morone saxatilis male) confined in a net for 10 minutes had significantly elevated corticosteroid levels (24.2 † 5.4 μg/100 ml) and significant hyperchloremia (150.02 † 2.7 meq/liter), in comparison with baseline levels of 0.8 † 0.1 μg/100 ml and 132.6 † 1.5 meq/liter, respectively. Hauling hybrids for 2 hours in freshwater significantly elevated corticosteroid levels (12.2 † 1.2 μg/100 ml) and reduced chloride levels (119.8 † 1.4 meq/liter). Corticosteroid levels remained high and hypochloremia developed within 24 hours after both netting and hauling. Although netting and hauling in 25 mg/liter MS-222 3 or 10 g/liter NaCl prevented chloride depletion during the stress, hypochloremia developed within 72 hours after the fish were transferred to freshwater. The development of hypochloremia several hours after handling indicates that hybrid bass that survive the initial stress do not necessarily recover, but may die in the days following handling. Fish anesthetized in 50 mg/liter MS-222 for 15 minutes prior to handling followed by hauling in water containing a combination of 25 mg/liter MS-222 and 10 g/liter NaCl did not develop hypochloremia within 72 hours after hauling; plasma corticosteroids were elevated during transport, but returned to nearly normal levels within 24 hours. This combination of 25 mg/liter MS-222 and 10 g/liter salt was the most successful handling medium tested.

Conference Paper↗
USGS2006

Plasma corticosteroid dynamics in channel catfish, Ictalurus punctatus (Rafinesque), during and after oxygen depletion

Plasma corticosteroid concentrations in channel catfish, Ictalurus punctatus, (normally 1.0 &plusmn; 0.3 &mu;g/100 ml) increased significantly (to 5.9 &plusmn; 1.2&mu;g/100 ml) in response to acute oxygen depletion and then returned to control levels within 30 min after the dissolved oxygen concentration was increased; however, a secondary increase in plasma corticosteroid levels was observed 6 h after exposure. Corticosteroid levels also increased in fish exposed to dissolved oxygen concentration of <0.2 mg/1 for three days. Methylene blue was not effective in preventing interrenal response to low dissolved oxygen. No diurnal plasma corticosteroid rhythm was observed in fish exposed to diurnal chemical rhythms of culture ponds.

Journal of Fish Biology↗
USGS2006

Growth, body composition and hepatic tyrosine aminotransferase activity in cortisol-fed channel catfish, Ictalurus punctatus Rafinesque

Metabolic consequences of chronic elevation of cortisol in the diet of yearling channel catfish, Ictalurus punctatus , were studied. Cortisol was incorporated into the diet in concentrations of 1, 10, 50 and 100 μg/g of food. This diet was offered at 3% of the body weight per day for 10 weeks. Fish were individually weighed and measured at 2-week intervals and feeding rates were adjusted. Body weight, liposomatic index and condition factor were significantly lower and food conversion was significantly higher in fish fed 50 or 100 μng cortisol/g of food when compared with controls. The hepatosomatic index of fish fed cortisol at the rate of 100 μg/g of food decreased significantly. Specific activity of hepatic tyrosine aminotransferase was significantly higher at the two highest cortisol doses. Long-term cortisol administration can reduce growth and condition factor by activating gluconeogenic mechanisms in which lipids and amino acids, rather than carbohydrates, are used for energy production. The metabolic effects of exogenous cortisol in this study offer an explanation for the decreased growth of fish under conditions that activate the secretion of endogenous cortisol.

Journal of Fish Biology↗
USGS2002

Effects of sludge filtrate on the survival and reproduction of Ceriodaphnia dubia

The objective of this study was to determine if the runoff from croplands fertilized with municipal sludge was toxic to aquatic biota and, therefore, a potential threat to either public health or the environment. Seven-day bioassays with Ceriodaphnia dubia showed that the No-Observed-Effect-Concentration (NOEC) was 24 g/L and the Lowest-Observed-Effect-Concentration (LOEC) for survival was 30 g/L for soil samples treated with 35.2 metric tonnes (MT)/ha of municipal sludge. For soil samples treated with 0 and 17.6 MT/ha of sludge, the survival rates of C. dubia were not significantly affected at concentrations of 6-30 g/L of soil. Reproduction was suppressed by 25% when daphnids were exposed to 3.3 g/L concentration of soil treated with sludge at 35.2 MT/ha. A 50% suppression of reproduction occurred when daphnids were exposed to 15 g/L concentration of soil treated with sludge at 17.6MT/ha. A sludge application rate of 17.6MT/ha suppressed reproduction at a treatment concentration of 18g/L. These data indicate that the runoff from agricultural lands treated with municipal sludge has the potential to affect reproduction in daphnids and, therefore, the environment through the aquatic food chain.

Ecotoxicology↗
USGS1987

Design of airlift pumps for water circulation and aeration in aquaculture

Water flow rates were measured in airlift pumps 3·75-30 cm in diameter to develop performance data that might be useful to aquaculturists. Flows were determined when submergence of airlifts was 100% and when the center-line of the discharge was between 12·5 cm above and 5 cm below the water surface. Air was injected at 15-cm intervals from 15 cm to 120 cm below the discharge of the airlift and air flow was varied from 28 to 1416 liters min −1 . An increase in the vertical lift reduced flow rates greatly in large-diameter pipes, but only slightly affected flow rates in small-diameter pipes. Water flow increased linearly as air flow increased logarithmically.

Aquacultural Engineering↗
USGS1987

Feed conversion indices: Controversy or convention?

Various methods of calculating and reporting the efficiency of food use in fish husbandry are examined. The effects of moisture content of feed and fish flesh, supplemental feeds augmented with natural feed items, differences in energy content due to feed formulations, and the usefulness of the various feed efficiency indices to aquaculturists and fish husbandry researchers are discussed.

Progressive Fish-Culturist↗
USGS1986

Tissue distribution and elimination of radiolabelled methyltestosterone fed to sexually undifferentiated blue tilapia

Populations of monosex male Oreochromis aureus can result when the synthetic androgen 17α-methyltestosterone (MT) is fed to sexually undifferentiated fish; however, concerns exist over residues of the androgen remaining in fish destined for human consumption. Radioactivity in the carcass and viscera was evaluated in juvenile fish fed steroid-incorporated diet (tritium and carbon-14 labelled MT and 30 μg unlabelled MT/g feed) for 21 days, and depletion was monitored for 21 days after return to an untreated diet. Radioactivity was detected in the carcass within 1 h after initial feeding and reached highest levels by 6 h. Most of the radioactivity (> 90%) was in the viscera during the 21 days the radio-labelled diet was being fed. Radioactivity was eliminated exponentially, decreasing by 90% within 24 h after the last feeding. After 21 days of feeding untreated diet, < 1% of the original radioactivity remained (representing about 5 ng MT/g of tissue), and was evenly distributed between carcass and viscera. The observed low levels of residual radioactivity at conclusion of the sex reversal period, as well as anticipated dilution through growth during the culture of fish to marketable size, support the conclusion that no potential health hazard exists for people who eat fish that have been fed MT as juveniles.

Aquaculture↗
USGS1986

Tissue distribution and elimination of radiolabelled methyltestosterone fed to adult blue tilapia

Radioactivity levels in 10 tissues were monitored for 21 days after adult (1-year-old) blue tilapia, Oreochromis aureus , were fed a single meal of a diet containing 30 μg unlabelled methyltestosterone (MT) per gram of feed and radiolabelled MT ( 3 H-labelled steroid nucleus and 14 C-labelled 17α-methyl group). Radioactivity was highest in all tissues 6–12 h after the feeding; about 90% of the radioactivity was in the digestive tract, liver, gall bladder, and kidney. Radioactivity declined nearly 90% by 4 days and only 0.5% of original radioactivity (67 ng/g of fish) remained after 21 days. Half of the remaining exogenous hormone was in digestive and excretory tissues; concentrations in muscle were less than 1 ng/g of tissue. Ratios of 3 H: 14 C in tissues were similar to those incorporated in the diet and suggested that the 17α-methyl group was not removed during metabolism.

Aquaculture↗
USGS1986

Environmental regulation and influence of the eyes and pineal gland on the gonadal cycle and spawning in channel catfish (Ictalurus punctatus)

Blinded, pinealectomized, or blinded and pinealectomized female channel catfish ( Ictalurus punctatus ) were placed with normal (unoperated on) control fish in outdoor tanks at constant temperature (21 ± 2 C) or earthen ponds (ambient conditions) in February or August, when they were 21 or 27 mo old. Fish were sampled through the following reproductive season. The gonadosomatic index (GSI) and plasma estrogen concentration changed seasonally in 3-yr-old fish, but the changes were less marked or lacking in 2-yr-olds. The GSI levels of sexually mature (≥3 years old) fish peaked about a month earlier in the tanks than in the ponds; the estrogen peak for fish in the tanks was lower than that for pond fish. All experimental fish (both ages) in ponds delayed ovarian resorption for about 1 mo, compared with normal control fish. Exposure to constant 21 C water allowed earlier gonadal recrudescence. All groups of sexually mature fish that were surgically altered in August spawned during the following spring. Fish with eyes spawned earlier and had higher spawning percentages (control 68%, pinealectomized 75%) than did fish without eyes (blinded 50%, blinded and pinealectomized 56%). Neither the eyes nor the pineal is essential for spring gonadal maturation or for spawning in channel catfish, but one or both may have a role in timing these events. An annual internal oscillator that may be modified by environmental temperature is suggested as the primary control of reproductive cycling in the species. Light information obtained through the pineal, eyes, or both appears to affect the time of gonadal resorption.

Ecological and Evolutionary Physiology↗
USGS1986

Plasma corticosteroid stress response of fourteen species of warmwater fish to transportation

Plasma corticosteroid concentrations were measured in 14 species of fish immediately after they were electrofished from reservoirs on the Alabama River and after they had been transported for 2 h. There was no corticosteroid response in spotted gars Lepisosteus oculatus. Bowfins Amia calva, longnose gars Lepisosteus osseus, and freshwater drums Aplodinotus grunniens had only small corticosteroid increases (14–39 ng/mL) during transportation. Corticosteroids increased by intermediate amounts (59–184 ng/mL) during transportation in blue catfish Ictalurus furcatus, paddlefish Polyodon spathula, largemouth bass Micropterus salmoides, channel catfish Ictalurus punctatus, river carpsuckers Carpiodes carpio, white bass Morone chrysops, striped bass Morone saxatilis, and crappies Pomoxis sp. The greatest increases were 223 ng/mL in gizzard shad Dorosoma cepedianum and 286 ng/mL in common carp Cyprinus carpio. Spotted and longnose gars, largemouth bass, and common carp also were held in tanks for about 2 months at 21°C and then stressed by confinement in a dip net for 30 min. The confinement caused significant increases (P < 0.01) of plasma corticosteroid concentration in all four species. Dip‐net confinement appears to be a useful method for comparing corticosteroid responses among species of warmwater fish.

Transactions of the American Fisheries Society↗
USGS1986

Marking fingerling striped bass and blue tilapia with coded wire tags and microtaggants

Fingerling striped bass ( Morone saxatilis ) of two year classes were tagged in four body locations with coded wire tags and on two locations with Microtaggants (laminated plastic particles containing layers of fluorescent and magnetic material). Retention of coded wire tags ranged from 33% for tags in the nose to 100% for tags in the cephalic portion of the adductor mandibularis (a small muscle located below the eye). Twenty percent of the fish tagged with Microtaggants in 1982 retained tags after 471 d; 98% of the ones tagged in 1983 retained Microtaggants after 270 d. Fingerling blue tilapias ( Tilapia aurea ) were tagged on the body with Microtaggant particles and in the nose and epaxial muscle with coded wire tags. After 328 d, retention was 11% for Microtaggants. Coded wire tag retention was 93% for tags in the nose, 94% for tags in the epaxial muscle anterior to the dorsal fin, and 88% for tags in the muscle posterior to the dorsal fin. For striped bass, implantation of coded wire tags in the adductor mandibularis is recommended for long-term tag retention. Implantation of coded wire tags in the nose is recommended for blue tilapia for long-term retention. Microtaggants are not recommended for long-term tagging of either species, but are appropriate for short-term studies of 1 year or less.

North American Journal of Fisheries Management↗
USGS1984

Technological innovations in aquaculture

Technology in aquaculture has expanded at a phenomenal rate during the last 50 to 100 years. Based on both this past progress and the present technological advances being made in our society, it is reasonable to expect aquaculturists to profit from the rapid technological advances being made in both hardware and biological systems. These advances will result as spinoffs from medicine, from analytical chemistry, and most importantly, from the evolution of new consumer products such as auto-focus cameras, electronic watches, and microprocessor-monitored automobiles. We can expect to use economical, reliable instrumentation capable of environmental monitoring for predictive purposes and instrumentation that will contain alarm and control circuits. Genetic engineering will result in biological organisms that produce hormones, drugs, and other biological materials as well as detoxify pollutants on demand. When we as aquaculturists identify the need for a product, that product will be developed.

Fisheries↗
USGS1984

Biotic and abiotic influences on corticosteroid hormone rhythms in channel catfish

Plasma‐corticosteroid concentrations in resting channel catfish Ictalurus punctatus held at 21 C varied only slightly during a 24‐hour period; further, increases in hormone concentrations induced by confinement stress were independent of time of day and photoperiod. Temperature strongly affected both resting corticosteroid concentrations and the dynamics of hormone secretion when fish were stressed. Resting concentrations were greatest in fish acclimated to 5 and 10 C (25–29 ng/ml), sharply lower in fish held at 15, 20, or 21 C (5–9 ng/ml), and intermediate in fish maintained at 25, 30, or 35 C (12–13 ng/ml). Hormone concentrations increased when fish were stressed by confinement. Corticosteroid concentrations hardly changed in fish held at 5 or 10 C, but increased markedly in fish at higher temperatures; in addition the response was more delayed at the lower temperatures.

Transactions of the American Fisheries Society↗