摘要:

AbstractThe efficacies of formalin, potassium permanganate, sodium chloride, and copper sulfate as prophylactic treatments for saprolegniosis (“winter kill”) in channel caffishIcralums puncratuswere evaluated. Formalin and copper sulfate were also evaluated as postinfective treatments for the disease. Each of the five experiments was conducted with 5–to 7‐g channel catfish placed in static water aquaria maintained in refrigerated tanks. Water temperature was reduced from 25 to 10 C within 36 h and maintained at 10 ± 0.5 C for 28 d. Fish were exposed to culturedSaprolegniasp. at 20 C, and morbidity and mortality data were recorded for 28 d.Saprolegniasp.‐associated mortalities occurred 7–10 d after exposure. Formalin (25 mg/L) was effective as both a prophylactic and postinfective treatment for saprolegniosis. Copper sulfate was effective in preventing saprolegniosis at a concentration of 0.1 mg/L, but was ineffective as a postinfective treatment. Sodium chloride at 5,000 mg/L was effective in preventing saprolegniosis, but was not practical for use in the commercial catfish industry. Potassium permanganate (up to 0.5 mg/L) was not effective in preventing or treating saprolegniosis in channel caffish. Based on the results of this study, it may be possible to prevent saprolegniosis in channel catfish using formalin or copper sulfate during winter when fish are immunosuppressed by rapid decreases in water temperature or to treat infected fish with formalin. However, the routine use of chemicals to control this disease should not be recommended until studies on their efficacy under typical caffish culture conditions and the effect of long‐term use of chemicals on fish and on the environment

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00587.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe aerobiological (aerosol) pathway ofAeromonas salmonicidasubspeciessalmonicida(ATCC 33658) was investigated. Results indicate that viableA. salmonicidacan travel as an aerosol/droplet spray at least 104.1 cm (limits of the test chamber used) when carried by air currents. Additionally, viableA. salmonicidawas recovered from water exposed to an experimentally generated aerosol/droplet spray ofA. salmonicidadownwind from the contaminant source. It is possible that viable bacterial aquatic animal pathogens can be spread via the airborne route. This possible route of pathogen introduction could effect current management or system designs, especially when aquaculture systems consist of tanks in close proximity.

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00588.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe microbial metabolite 2‐methylisoborneol (MIB) imparts a muddy off‐flavor to channel catfishIctalurus punctatus. Uptake and depuration of MIB from fish are important considerations in the design and implementation of systems to remove off‐flavors from fish prior to processing. The kinetics of MIB uptake by channel catfish were determined by placing fish in 6.5, 14.0, 25.0, and 34.0 C water containing approximately 1.0 μg/L chemically‐synthesized MIB. Fish were sacrificed following 0, 2, 4, 8, and 24 h exposure to MIB. Fillet tissue samples were subjected to gas chromatographic and fat content analysis. The model for MIB uptake was:MIB in fillet tissue (μg/kg) =−0.61 ± 4.2 [log(h± 1)] ± 0.0076(T) (h) ± 0.089(T),where h is the duration of exposure to MIB in hours and T is the water temperature in degrees C. The model accounted for 74% of the total variation observed in the tissue MIB concentrations and indicated that the fillet fat content was not strongly correlated with MIB uptake. To investigate the depuration of off‐flavors, exposure to MIB was halted. Tissue samples were obtained 4, 8, 24, 48, and 72 h from fish held at 6.5, 14.0, 25.0, and 34.0 C. These data yielded the model:MIB in fillet tissue (μg/kg) = 3.6 ± 0.176(T) – 2.06 [log(h± 1)] – 0.00296(T) (h) ± 0.197 (% fat),wherehis the duration of exposure to MIB in hours, T is the water temperature in degrees C, and % fat is the % fat in the fillet tissue. The model accounted for 67% of the total observed variation in tissue MIB concentrations. Reducing the fat content of fish and optimizing water temperatures may augment MIB removal from fish ti

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00589.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA data set describing annual variation of water quality in ten commercial channel catfishIctalurus punctatusponds was subjected to exploratory statistical analysis to infer ecological processes affecting pond water quality. Two factors explained 67% of the variation in concentrations of water quality variables. The first factor (Factor 1) explained 49% of the variance and was associated with a large negative loading by total ammonia‐nitrogen and large positive loadings by total nitrogen, total phosphorus, chemical oxygen demand, and chlorophylla. Factor 1 was interpreted with respect to factor loadings to represent the effect of phytoplankton biomass. The second factor (Factor 2) explained an additional 18% of the variance and was associated with a large negative loading by soluble reactive phosphorus and large positive loadings by nitrite‐nitrogen and, to a lesser extent, nitrate‐nitrogen. Factor 2 was interpreted to be related to variation in pond sediment oxygenation. Although factor analysis indicated the overwhelming effect of phytoplankton biomass on water quality, opportunities for management of phytoplankton communities in large commercial aqua‐culture ponds are limited. However, maintenance of an oxidized sediment‐water interface may improve water quality by limiting the diffusion of reductant‐soluble phosphorus from sediment to water and increasing sediment nitrific

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00590.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWinter flounderPleuronectes americanusis being developed for aquaculture in Atlantic Canada. Weaning, the switch from a live diet to formulated feed, is a critical stage in the culture of any fish species. In this study, we used wild young‐of‐the‐year stock to determine whether juvenile winter flounder can be weaned from live, culturedArtemiaonto dry feed. The dry feed used was originally formulated for turbotScophthalmus maximusand codGadus morhuaby BP Nutrition, Stavanger, Norway. The performance of live feed and dry pellets was compared in terms of survival, growth and feed efficiency over three months. We were able to wean wild juvenile winter flounder onto dry feed after one week. Increased specific growth rates and feed efficiency ratios in weaned juveniles indicated that prepared diet was a better food source thanAnemia. Survival was not influenced by food

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00591.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThyroid hormones, 3,5,3′,5′‐ tetraiodothyronine (T4) and 3,5,3′‐ triiodothyronine (T3) have been found in the eggs of several teleost species and are potential regulators of larval development, growth, and survival. The purpose of the present study was to determine whether natural variation of T3and T4in the eggs of six stocks of walleye, five wild stocks from Kansas, Iowa, Wisconsin, Minnesota, and North Dakota, and a semi‐domesticated stock from an Ohio fish hatchery, have an effect on larval performance in mass culture. Immersion studies were conducted with samples of larvae from four of the same stocks at exposure concentrations of 0.01, 0.05, and 0.1 ppm of T3and T4. Natural egg concentrations of T3(range from 0.70 to 1.5 ng/g wet weight of egg) were not significantly different among stocks. Although means of T4concentration among stocks were significantly different (range 0.53–9.27 ng/g), the difference was caused by the exceptionally high concentration for the Wisconsin stock (9.27 ng/g ± 2.20). Performance measures of the Wisconsin stock (Mississippi River), were not related to T4concentration in that stock. In spite of similarity in concentrations of T4and T3in the eggs, there were significant performance differences among the stocks (survival to 21 d, gas bladder inflation, viability, cannibalism, and growth). The immersion studies, however, revealed a significant difference in incidence of cannibalism and temperature units (TU) to 50% mortality (i.e., survival) between the control groups and treatment groups exposed to 0.01 to 0.1 ppm T3and T4. Survival was extended more than 2‐fold longer in larvae immersed in T3compared with T4. The immersion study indicated that thyroid hormones are potentially regulators of walleye development, but further investigations are needed to determine reasons for differences in larval performance based on natural concentrations in the egg and artificial expo

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00592.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractGrowth, survival and feed conversion ratio of juvenile snakeheadChanna striatuswere evaluated when fed a dry, formulated feed (50% crude protein) at 24 ± 1 C. Six daily feed application rates were used (0%, 5%, 10%, 15%, 20%, and 30%), as a percentage of fish body weight, with three replicates per treatment. After 29 d, final weights were all significantly greater (P0.05). Feed conversion ratio was 0.99 at 5% feed application, and 6.3 at 30% feed application. Fish survival was increased by providing formulated diet, but no further improvement was found when feed applications exceeded 5%. Cannibalism was reduced by providing formulated feed, but it was unavoidable when substantial differences in fish size existed, even when feedingad libitum. Our results indicate that the optimal feed application rate is close to 5% body weight/d for juvenile snakehead

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00593.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThree oilseed protein concentrates (soybean, canola, and sunflower) were evaluated to determine their potential, when supplemented with deficient essential amino acids, to partially or completely replace fish meal in diets fed to rainbow troutOncorhynchus mykiss. Triplicate aquaria of juvenile trout (average weight of 12 g) were fed the experimental diets for 10 wk, at which time the average weight of the fish was approximately sixfold higher than the initial weight. Average fish weight gains on diets in which the protein component was 100% fish meal; 75% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soybean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different (P<0.05). The average weight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different from fish fed the three other formulations mentioned above. Fish fed diets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly lower average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain. Fish survival exceeded 95% on all diets. Apparent protein digestibility coefficients ranged from 79.5% (75% soybean protein concentrate, 25% canola protein concentrate) to 90.6% (100% soybean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein sources in rainbow trout feeds when properly supplemented with essential amino acids.

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00594.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAlthough the common snapping turtleChelydra serpentinais cultured commercially in the United States, little information is available on nutritional and culture requirements. This study was conducted to evaluate the effects of dietary energy: protein ratio and stocking density on survival, growth, feed consumption, feed conversion, liposomatic index, dress‐out percentage, and productive protein value of cultured, common snapping turtles. Hatchling turtles were stocked at 29 and 58 animals/m2and fed one of seven prepared diets. Six diets contained 30, 35, or 40% protein at two digestible energy (DE) levels (7 or 9 kcal DE/g protein); the seventh was a reference diet (66% protein and 5 kcal DE/g protein) formulated to equal or exceed the whole‐body essential amino acid composition of wild, common snapping turtles. Turtles stocked at 58/m2exhibited greater mortality, lower weight gain, higher feed consumption, less‐efficient feed conversion, lower liposomatic index, and lower productive protein value than turtles stocked at 29/m2(P<0.05). The reference diet produced the greatest weight gain (P<0.001). The superior performance of turtles fed the reference diet suggests that: 1) the protein (amino acid) content and/or energy: protein ratio of the reference diet was superior to that of the other diets tested; 2) improvements in growth parameters can be made with dietary manipulation; and 3) high levels of plant protein can be used in prepared, snapping turtle

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00595.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractHigh oleic corn is a genetic variant that contains more protein, lipid, and oleic acid and less linoleic acid than regular corn. A study was conducted to compare weight gain and feed conversion of year‐1 and year‐3 channel catfishIetalurus punctatus, and processing yield, body composition and frozen storage stability of year‐3 channel catfish fed high oleic corn and number 2 yellow (regular) corn in extruded production diets. A commercial‐type diet formulated to contain 30% protein and made with regular corn served as a control. A second diet contained high oleic corn in place of regular corn on an equal (air‐dry) weight basis. A third diet contained high oleic corn in substitution for regular corn and part of the soybean meal to limit protein content to 28%, which was equal to that of the control diet. The experimental diets were fed to year‐1 channel catfish (average initial weight 5.1 g) in aquaria for 10 wk and to year‐3 channel catfish (average initial weight 1.07 kg) in 0.04–ha ponds for 14 wk. Substitution of high oleic corn for regular corn on an equal (air‐dry) weight basis provided significant gain (P<0.01) of year‐1 channel catfish but not of year‐3 fish. Use of high oleic corn diets designed to be equal in protein content did not affect weight gain of either group of fish. Replacement of regular corn with high oleic corn caused a significant (P0.20) increase in oleic acid in the flesh of fish. Proximate body composition, dressing yield, fillet yield, visceral fat, and liver weight were not significantly different among treatments. Sensory scores of fillets frozen for 3 and 6 mo were not significantly different among treatments. Peroxide value, thiobarbituric acid number and free fatty acids increased with frozen storage time but were not diffe

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00596.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY