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Ludwig G.M.,Harry pree Stuttgart National Aquaculture Research Center | Perschbacher P.,University of Arkansas at Pine Bluff | Edziyie R.,University of North Texas
Journal of the World Aquaculture Society | Year: 2010

Rooted macrophytes make harvesting fingerling fish difficult because they can smother fish or tangle in the seines during harvest. Aquashade®, a dye, is used to reduce macrophyte growth. Fingerling culturists are reluctant to use it because it may reduce phytoplankton concentrations and zooplankton food supplies of larval fish. Aquashade was applied at 4 mg/L (twice the recommended rate) to three ponds when filled and to three ponds when fry were started on prepared feed. Three ponds served as a control. All ponds were stocked with sunshine bass larvae at 15,000/0.04 ha. Water quality and plankton were monitored daily until harvest. Few differences were found among treatment ponds for water quality, chlorophyll a, primary productivity, phytoplankton and zooplankton concentrations, or weight of rooted macrophytes. Unionized ammonia and pH increased to potentially harmful levels in ponds that did not receive the dye. No differences were found in the number, total weight or percent survival of fingerlings harvested. No differences in average individual total length, total weight, or coefficient of condition were found either. At the concentration of dye used, the dye was not effective for rooted macrophyte control but may offer fish some protection from high pH or unionized ammonia concentrations. © Copyright by the World Aquaculture Society 2010.

Faukner J.,University of Arkansas at Pine Bluff | Rawles S.D.,Harry pree Stuttgart National Aquaculture Research Center | Proctor A.,University of Arkansas | Sink T.D.,University of Arkansas at Pine Bluff | And 3 more authors.
North American Journal of Aquaculture | Year: 2013

Fish consumption is a common method of obtaining beneficial n-3 highly unsaturated fatty acids (LC-PUFAs), but increased use of vegetable oils in fish diets to reduce dependence on fish oil dilutes the amounts of LC-PUFAs. Conjugated linoleic acids (CLAs) are also considered beneficial for human health. Therefore, we investigated four different lipid sources in Channel Catfish Ictalurus punctatus diets for their ability to enhance fatty acid profiles of fillets to benefit human health while maintaining or improving fish performance. In a 175-d grow-out trial, Channel Catfish (71.4 ± 0.1 g [mean ± SE]) were fed a commercial 32% protein diet supplemented with 2% lipid from soybean oil (SO), soybean oil enhanced with conjugated linoleic acids, menhaden fish oil (FO), or an algal supplement of Schizochytrium sp. high in 22:6(n-3) (docosahexaenoic acid, DHA). Diet effects were assessed by measuring fish growth performance, muscle proximate and fatty acid composition, sensory characteristics of fillets, consumer taste preferences, and oxidative stability of fillets during cold storage. There were no differences in fish growth performance or proximate composition. Only fish fed the CLA diet contained CLAs in the muscle. Fish fed the FO and algal DHA diets had higher concentrations of 22:6(n-3) in the muscle compared with fish fed the SO and CLA diets. Sensory evaluation and consumer preference testing were more favorable for fillets from fish fed the SO and CLA diets than from fish fed the FO and algal DHA diets. There were no differences in storage characteristics of fish refrigerated at 4°C for 2 weeks or frozen at -18°C for 4 weeks. Fillets from fish fed the FO diet yielded the highest concentration of fatty acids for human health benefits, followed by the fillets from fish fed the algal DHA diets. The CLA diet produced increased fillet concentrations of CLAs. © American Fisheries Society 2013.

Bastola U.,University of Arkansas at Pine Bluff | Engle C.R.,University of Arkansas at Pine Bluff | Haukenes A.,University of Arkansas at Pine Bluff | Freeman D.,Harry pree Stuttgart National Aquaculture Research Center
Journal of Applied Aquaculture | Year: 2012

Previous work suggested that feeding catfish, Ictalurus punctatus, more frequently over the winter might reduce weight loss. Twelve 0.10-ha ponds were stocked with 987 kg/ha market-sized fish and 2,960 kg/ha sub-marketable fish in November 2008 with treatments of: (1) unfed, (2) fed daily (fed 90 d), and (3) temperature-threshold feeding (fed 62 d). Total gross yield was significantly greater for the temperature-threshold feeding treatment than the unfed control, but survival and mean weight of fish at harvest were not. Net yield was negative for all treatments, due primarily to mortality of market-sized fish. Plasma glucose and insulin-like growth factor-1 did not differ significantly, but plasma osmolality was significantly lower in fasted than in fed fish. Mean feed consumption rates in vats provided evidence to support more frequent feeding over the winter. Overwintering costs were $0.11/kg with temperature-threshold feeding. Research on strategies to reduce winter mortality has potential to reduce overwintering costs. © Taylor & Francis Group, LLC.

Davis K.B.,Harry pree Stuttgart National Aquaculture Research Center | Gaylord T.G.,Harry pree Stuttgart National Aquaculture Research Center
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology | Year: 2011

The integrated responses of the hormonal regulation of growth and stress in sunshine bass (Morone chrysops X Morone saxatilis) as regulated by feed deprivation were investigated. Groups of fish were fed 1.5% of the body weight per day or offered no feed for 4. weeks. Another group of fish was not fed for 3. weeks and feed was offered during the fourth week. Fish in each group were sampled immediately before or after a 15-min low water confinement stressor after each week of the experiment. Liver mass and liver glycogen content were decreased after one week of fasting and remained low until the end of the study. However, both recovered after a week of refeeding. Intraperitoneal fat was significantly lower after two weeks of fasting and did not recover after a week of refeeding. None of these components were affected by confinement stress. Plasma glucose in unstressed fish was generally unaffected by fasting or refeeding; however, plasma glucose increased after confinement stress in fed but not in fasted fish. The cortisol stress response was unaltered by fasting and remained robust. Plasma IGF-I generally decreased in fasted fish but was not significantly lower than fed fish until the fourth week. A week of refeeding did not restore plasma IGF-I concentrations. Plasma IGF-I concentrations were higher in confinement stressed fed fish after two and four weeks but were unchanged in the fourth week. There was no change in the plasma IGF-I concentrations in fasted or refed fish due to the stress. Liver weight and liver glycogen were essentially depleted after 2. weeks of fasting. The reduction of liver glycogen greatly reduced the glucose response to stress; however, the cortisol stress response was maintained for at least four weeks of fasting. Intraperitoneal fat was decreased very little after 4 weeks of fasting. Plasma IGF-I concentrations were reduced only after 3 weeks of fasting. © 2010.

Farmer B.D.,Harry pree Stuttgart National Aquaculture Research Center | Mitchell A.J.,Harry pree Stuttgart National Aquaculture Research Center | Straus D.L.,Harry pree Stuttgart National Aquaculture Research Center
Journal of Aquatic Animal Health | Year: 2011

Ammonia concentrations in water can affect the severity of Flavobacterium columnare infections in fish. Two trials lasting 7 d each were conducted to determine the effect of a single immersion flush treatment of total ammonia nitrogen (TAN; 15 mg/L) on the survival of channel catfish Ictalurus punctatus infected with F. columnare; the chemical was added while the water flowed continuously through the tanks. Both trials consisted of four treatments: (1) no ammonia exposure and no bacterial challenge (control), (2) ammonia exposure only, (3) bacterial challenge only, and (4) both ammonia exposure and bacterial challenge. Two hours after exposure to ammonia, the highest un-ionized ammonia level was 0.43 mg/L. The percent un-ionized ammonia is based on TAN, temperature, and pH. Caudal fins from three fish in each treatment were sampled at 24 h posttreatment to be analyzed by quantitative real-time polymerase chain reaction (qPCR). No significant difference in survival (mean ± SE) was noted between the channel catfish in treatment 1 (95.2 ± 1.2%) and those in treatment 2 (95.6 ± 1.0%); however, survival in both treatments 1 and 2 differed significantly from that in treatments 3 (8.5 ± 4.5%) and 4 (41.8 ± 12.7%). Treatment 4 catfish had significantly higher survival than treatment 3 catfish. Quantitative PCR data showed that treatment 4 fish had significantly less F. columnare (7.6 × 105) than did treatment 3 fish (1.2 × 107), and treatment 2 fish (8.5 × 103) had significantly less bacteria than did treatment 1 fish (6.9 × 104), indicating that ammonia limited the F. columnare infection. The highest mean concentration of the bacteria (3.9 × 107) was found on moribund fish. The ammonia concentrations tested did not negatively influence fish survival but interfered with the infection process. An in vitro assay was also conducted to evaluate the direct effects of ammonia on F. columnare. © American Fisheries Society 2011.

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