Julia A. Clark

A Temperature-Dependent Index of Mitotic Interval (τ0) for Chromosome Manipulation in Paddlefish and Shovelnose Sturgeon

Abstract A temperature-dependent measure of the mitotic interval (τ0) can help standardize chromosome manipulation in fish eggs. A tau unit (τ0) is the duration in minutes of one mitotic cycle during synchronous embryonic cleavage. It is measured over a range of temperatures, and the resulting relationship of τ0 to temperature can be used to anticipiate developmental events that are affected by temperature. Optimum induction of chromosome manipulation requires development of a specific treatment of egg shocking for each species, Timing of shock is a critical variable, but pretreatment incubation temperature affects the rate of development and thus the optimum absolute time for shocking. Mitotic intervals (τ0) are reliable indicators of developmental rates over normal temperatures for egg incubation, and thus can be used to estimate optimal times for chromosome manipulation, Mitotic intervals for paddlefish Polyodon spathula and shovelnose sturgeon Scaphirhynchus platorynchus were estimated by averaging th...

Growth, Feed Conversion, and Protein Utilization of Female Green Sunfish × Male Bluegill Hybrids Fed Isocaloric Diets with Different Protein Levels

Abstract A 10-week feeding trial was conducted in aquaria to evaluate protein requirements of juvenile (4.7-g) hybrids of female green sunfish (Lepomis cyanellus) and male bluegills (Lepomis macrochirus). Three Isocaloric diets containing 26, 31, or 37% protein were evaluated for effects on fish growth, feed conversion, protein utilization, and body composition. Fish fed the 37% protein diet had significantly higher (P 0.05) among diets in protein efficiency ratio (fish weight gained/protein weight fed). Fish fed the 26% protein diet had a significantly higher (P < 0.05) feed conversion (feed weight fed/fish weight gained) than fish fed the 37% protein diet. These results suggest that the use of higher-protein feeds (35% or greater), rather than the 32% protein catfish feed that is often fed to bluegill hybrids, may improve growth performance and production potenti...

Effects of feeding, starvation, and refeeding on the fatty acid composition of channel catfish, ICtalurus punctatus, tissues

1. 1. The effects of feeding, food deprivation (14 and 28 days) and refeeding (starved 14 then fed 14 days) on the fatty acid composition of white muscle, liver and brain of pond-raised channel catfish (Ictalurus punctatus) were investigated. 2. 2. Levels of n-3 fatty acids were significantly higher (P < 0.05) in white muscle of fish starved 28 days (10.7%) than in fish fed throughout the study (8.0%), due primarily to an increase in 22:6(n-3) docosahexaenoic acid or DHA. 3. 3. Significantly higher levels of 20:5(n-3) (eicosapentaenoic acid or EPA) were found in livers offish starved 28 days (P < 0.05) compared to fish fed throughout the study. 4. 4. Results suggest that the fatty acid compositions of channel catfish white muscle and liver are subject to only limited perturbation during periods of starvation and refeeding and that the brain is extremely well protected.

Pond culture of female green sunfish (Lepomis cyanellus) × male bluegill (L. macrochirus) hybrids stocked at two sizes and densities

Abstract The hybrid produced by crossing the female green sunfish ( Lepomis cyanellus ) and male bluegill ( L. macrochirus ) was evaluated under production conditions for 1 year. Juveniles were stocked at two initial sizes (38 and 66 g) and two densities (6175 and 12350/ha) into twelve 0.04-ha ponds and fed a diet containing 36% protein for 371 days. Fish stocked at 6175/ha had significantly higher ( P P P P P > 0.05) in percent protein, fat, and moisture of whole bodies of fish stocked in the different treatments. Stocking of large juveniles at high density produced more harvestable-size fish (> 110 g) per ha. Effects of higher stocking densities on feed utilization and improved feeding regimes should be investigated.

Effects of Yucca shidigera Extract on Water Quality and Fish Growth in Recirculating-Water Aquaculture Systems

Abstract In livestock industries such as poultry and swine, an extract of the Yucca shidigera plant has shown promise in controlling ammonia buildup in production facilities. In three trials, effects of Y. shidigera extract on ammonia levels and fish growth in recirculating-water aquaculture systems were evaluated. When added to in vitro ammonia solutions, extract concentrations of 0.043% and 0.43% caused a significant (P 0.05) in ammonia, nitrite, and dissolved oxygen levels. These result...

Evaluation of three organic fertilizers for paddlefish,Polyodon spathula, production in nursery ponds

Abstract Organic fertilization of paddlefish ( Polyodon spathula ) nursery ponds with rice bran (RB), distillers dry grain (DG) or cottonseed meal (CSM) was evaluated in nine 0.02-ha ponds over a 40-d period. Net yields (kg/ha) and growth rate of fish in ponds fertilized with RB were significantly higher (P ≤ 0.05) than with CSM, but not significantly different (P > 0.05) in ponds fertilized with DG. There was no significant difference (P > 0.05) in fish survival (RB 77%, DG 79%, and CSM 65%) for ponds receiving any of the three fertilizers. Secchi disk visibility and dissolved oxygen were significantly lower (P ≤ 0.05) in ponds fertilized with RB than in ponds fertilized with CSM and DG. Ammonia and nitrite levels differed only during week 3 and were significantly higher (P ≤ 0.05) in ponds fertilized with CSM and DG than in ponds fertilized with RB. Large cladocerans ( Daphnia, Simocephalas, Scaphaleberis ) were the dominant food items found in stomachs of fish in all treatments. RB proved to be superior to CS and DG as an organic fertilizer for paddlefish nursery ponds when evaluated in terms of fingerling growth, water quality, and zooplankton production.