Family and genetic group effects for resistance to proliferative gill disease in channel catfish, blue catfish and channel catfish×blue catfish backcross hybrids

The severity of gill damage (percentage of gill lamellae with lytic lesions) was determined in juveniles from 10 USDA 103 line channel catfish Ictalurus punctatus full‐sib families, 10 channel catfish×blue catfish I. furcatus backcross hybrid (7/8 channel catfish, 1/8 blue catfish) full‐sib families and a mixed‐family group of blue catfish placed in a commercial catfish pond experiencing proliferative gill disease (PGD)‐related fish mortalities. An initial challenge was conducted with all families, and a second challenge was conducted using the two most susceptible (most gill damage) channel catfish and backcross hybrid families and the two most resistant (least gill damage) channel catfish and backcross hybrid families. In the initial challenge, percentage gill damage was not different between channel catfish (12.3%) and backcross hybrids (11.6%), but was lower in blue catfish (0.2%). Mean percentage gill damage in the second challenge was not different among resistant backcross hybrid families (6.9%), resistant channel catfish families (7.6%) and blue catfish (4.8%), but was higher in susceptible backcross hybrid and channel catfish families (19.0% and 11.9% respectively). The correlation among family means for gill damage from challenge 1 and challenge 2 was r=0.87. Consistent differences between channel catfish and blue catfish and between resistant and susceptible families within genetic groups for gill damage after PGD challenge suggest that there is a genetic component for resistance to PGD and that improving PGD resistance through selection may be possible.     

沿海滩涂低盐水体条件下大型池塘斑点叉尾鱼回高效养殖技术

为进一步优化沿海滩涂低盐水体条件下大型池塘斑点叉尾鱼回养殖技术模式,在江苏盐城东台、大丰、射阳、连云港等地分别设置4个试验点,每个试验点选取2口池塘开展了养殖试验.采取低密度(9000～15000尾/hm2)放养大规格(0.25～0.30 kg)斑点叉尾鱼回鱼种的方式,加强饲养管理,投喂优质膨化颗粒饲料,并做好养殖病害...     

Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds

Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04‐ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6–12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing.     

Dose-Confirmation of Copper Sulfate for Treating Fungus on Channel Catfish,Ictalurus punctatus,Eggs at a Commercial Hatchery

This study at a commercial hatchery was required by the U.S. Food and Drug Administration to provide independent substantiation of the results of previous laboratory dose-confirmation studies on the use of copper sulfate (CuSO₄) to control fungus (Saprolegnia spp.) on the eggs of channel catfish, Ictalurus punctatus. The study compared an untreated control group of eggs to eggs treated with 10 mg/L CuSO₄ in a flow-through system; mean water temperature was 23.5°C. Eggs were treated once daily until the embryos reached the eyed stage (5 treatments). Hatching was complete by day 11, and fry were counted to determine the percentage of survival in each treatment. Fungus was identified by polymerase chain reaction (PCR) as Saprolegnia spp. The mean survival in the control treatments was 4% and 40% in the CuSO₄ treatments; the latter survival was significantly higher, but still lower than normal. This study confirms that 10 mg/L CuSO₄ is an effective treatment to control fungus on catfish eggs when used daily until the eggs are eyed. However, continued treatment of eggs until hatching occurs may be warranted based on fungal growth rates observed after treatments were discontinued.     

Effects of Environmental Sodium Chloride on Percent Hatch, Yolk Utilization, and Survival of Channel Catfish Fry

Abstract.— Only limited research has addressed the effect of salinity on hatching of channel catfish Ictalurus punctatus eggs, and no studies have evaluated the effect of salinity on fry development and survival. This study was undertaken to determine the effect of environmental sodium chloride (0, 1, 2, and 4 g/L. NaCl) on percent hatch, yolk utilization, and survival of channel catfish fry. Experiments were conducted in recirculating systems using seven egg masses (1–2 d old). Each egg mass was divided into smaller portions which remained undissociated or were dissociated with sodium sulfite (NaSO₃). Eggs were incubated until hatching. Wet and dry weights were obtained for sacfry at 1 and 5 d post-hatch to determine wet weight gain and dry weight loss, and fry were sampled 7 d after initiation of exogenous feeding to determine survival. Percent hatch, yolk utilization, and survival of fry hatched from undissociated eggs were greatest at 1 g/L NaCl. In addition, treatment of eggs with NaSO₃ significantly reduced percent hatch at all NaCl levels. Although our results indicate that addition of NaCI to hatchery water supplies can increase production of channel catfish fry, additional research is needed before this practice can be recommended on a commercial basis.     

Effect of Low-Temperature Incubation of Channel Catfish Ictalurus punctatus Eggs on Development, Survival, and Growth

To determine whether the embryonic period of channel catfish lctalurus punctatus could be extended at low temperatures, fertilized channel catfish eggs were incubated at five constant water temperatures: 4, 11. 16. 21, and 26 C. Low-temperature incubation of catfish eggs extended the embryonic period at 16 (244%) and 21 C (56%) when compared to the control hatchery incubation temperature of 26 C. All eggs incubated at 4 and 11 C died within 24–48 h. Developmental stage had a significant ( P > 0.05) effect on percent hatch at 16, 21, and 26 C. Eggs held at 16 C prior to embryonic axis formation died within 48 h. Larvae from eggs hatched at 16 C were incompletely developed and died upon acclimation to 26 C for growth tests. Growth of fry reared at 26 C, following egg incubation at 21 C. paralleled that of fry from eggs incubated at 26 C. The underdevelopment of fry at 16 C combined with the significant effect of egg stage on survival at this temperature suggests that 16 C is below the lower thermal tolerance limit for normal development in this species. The period prior to the formation of the embryonic axis may be considered a vulnerable stage in channel catfish development. Increasing the embryonic period through low temperature incubation would increase the duration of juvenile availability for researchers and commercial operations.     

Effects of Calcium and Magnesium Hardness of Incubation Waters on the Hatching Success of Hybrid Eggs of ♀ Channel Catfish,Ictalurus punctatus × ♂ Blue Catfish,Ictalurus furcatus

Hatching efficiency is generally lower in channel catfish, Ictalurus punctatus × blue catfish, Ictalurus furcatus, hybrid catfish hatcheries compared to hatcheries hatching pond‐spawned channel catfish eggs. Egg quality and hatching water hardness are known variables influencing the efficiency of hybrid catfish fry production in hatcheries. Previous research recommended that at least 60 mg/L hardness had to be contributed only by calcium to optimize the hatching success of hybrid catfish eggs. However, whether the effect of waterborne magnesium in hatching waters facilitates or impedes the hatching success of hybrid catfish is not known. Two trials were conducted to determine the effects of calcium alone or magnesium hardness, in combination with the hatching success of hybrid catfish eggs. Trial 1 showed that if the previously identified minimum hardness criterion of 60 mg/L was met by calcium in the hatching waters, added magnesium had no effect on the hatching success of hybrid catfish eggs. Trial 2 showed that the previously identified minimum hardness of 60 mg/L can be met by either calcium alone or magnesium replacing up to 50% of the total hardness in the hatchery waters for optimal hatching success of hybrid catfish eggs. Calcium provides a specific requirement during embryonic development of catfish. The results from this study can be used to design treatment processes for hatchery water supplies to improve efficiency of hybrid catfish fry production in hatcheries.     

Suspending Mammalian LHRHa‐injected Channel Catfish,Ictalurus punctatus,in Individual Soft Mesh Bags Reduces Stress and Improves Reproductive Performance

Hormone‐induced spawning of channel catfish held communally in tanks is a reliable method to produce channel catfish, Ictalurus punctatus ♀ × blue catfish, Ictalurus furcatus ♂, F₁ hybrid catfish fry. However, mature catfish are crowded, and repeatedly handled during the process of induced ovulation. Repeated handling of gravid females is stressful and may impair ovulation, egg quality, and reproductive performance. Three trials were conducted to evaluate the effects of two methods of confining post‐hormone‐injected female channel catfish on stress response (cortisol concentrations) and reproductive performance: fish were either held individually while suspended in soft, nylon‐mesh bags or communally in a concrete tank. Percent of females ovulated to hormone treatment, relative fecundity, percent egg viability, and latency of channel catfish did not differ for fish in the two treatments. However, percent hatch and fry/kg of females was higher (P < 0.05) for fish held in bags that for fish held communally in tanks. Mean plasma cortisol response immediately prior to the first hormone injection (0 h) did not differ among fish groups in the two treatments. However, mean plasma cortisol concentrations were significantly lower (P < 0.05) for fish in the bag treatment at 16 and 36 h compared to fish held communally in tanks. Plasma estradiol levels (measure of oocyte maturation) were assessed at 0, 16, and 36 h after hormone injection; concentrations were (P < 0.05) higher at 16 h compared to 0 and 36 h; however, estradiol concentrations did not differ for fish held in the two treatments (P > 0.05). Suspending hormone‐injected broodfish individually in soft bags reduced stress response, improved egg hatching rate, and increased hybrid fry produced per kg weight of female broodfish. Using this simple technology, farmers can improve the efficiency of hatcheries producing hybrid catfish fry.     

Wildlife-Caused Losses for Producers of Channel Catfish Ictalurus punctatus in 1996

The National Agricultural Statistics Service surveyed by telephone and mail in January and February 1997 all known producers of channel catfish letalurus punctatus to acquire current information about wildlife-caused losses in calendar year 1996. Many producers tried to prevent wildlife-caused losses of their catfish by shooting (57%), vehicle patrol (55%), or frightening (36%), at an estimated cost of >$5 million. Yet, 69% of catfish producers cited some wildlife-caused losses. Birds were most frequently cited as a cause of losses, and double-crested cormorants Phalacrocorax auritus was the species cited most frequently (53%). The next most frequently cited birds were herons Ardea spp. (48%), egrets Egretta spp . (16%), and pelicans Pelecanus spp. (8%). Muskrats Ondatra zibethicus were cited by 10% of producers, primarily for damaging dikes and roads. The main problems caused by wildlife were feeding on catfish (67%), injuring catfish (40%) or disturbing feeding patterns of the catfish (23%). The total estimated cost of losses was $12 million. Overall, wildlife damage and damage prevention may have cost catfish producers > $17 million, about 4% of the total $425 million of catfish sales in 1996. Of the 44% of all catfish producers who were familiar with Wildlife Services (WS), 51% had ever contacted WS for assistance, 55% used methods suggested by WS to reduce their losses, and 40% received direct assistance from WS in 1996. Mississippi producers, who most frequently received direct assistance from WS, had proportionately lower wildlife-caused losses.     

Evaluation of Three Feeds for Hatchery Rearing Channel Catfish Fry

Two 7 day feeding trials were conducted with channel catfish swim-up fry to evaluate growth, feed conversion ratio, and body composition of fish fed one of the following feeds: salmon starter, catfish starter, or trout starter. Fish fed the salmon or trout starter feeds gained 50–75% more weight, converted feed more efficiently, and had higher body fat stores than fish fed the catfish starter feed. This may be related to the higher protein and energy content of these two feeds. It may be advantageous to feed salmonid starter feeds to hatchery reared catfish fry; however, it is not known whether or not the improved performance observed in the hatchery continues once the fish are stocked into nursery and grow out ponds.     

Studies on the manganese requirement of fingerling channel catfish

Fingerling channel catfish (Ictalurus punctatus) were fed purified diets containing varying levels of manganese for 13 weeks in two experiments. Weight gain and feed efficiency data of catfish fed the basal diet (2.4 mg Mn/kg diet) were not significantly different from those of catfish fed manganese-supplemented diets in both experiments. Liver manganese superoxide dismutase activity, liver manganese concentration, serum alkaline phosphatase activity and hexosamine content of gill filament cartilage did not differ in catfish fed basal and manganese-supplemented diets. Bone manganese concentration increased almost linearly with increasing dietary manganese levels. The 2.4 mg Mn/kg supplied by the basal diet was apparently sufficient to meet the manganese requirement of fingerling channel catfish during these experiments.     

The relationship between channel catfish female body weight and relative fecundity and fry production when induced to ovulate with carp pituitary extract and fertilized with blue catfish sperm

ABSTRACT

Little is known regarding the correlation between channel catfish female body weight and relative fecundity and fry production when the females are induced to ovulate with carp pituitary extract and fertilized with blue catfish sperm. A total of 145 female channel catfish were used in the early, middle, and late spawning season. Female body weight of channel catfish had negative correlations with relative fecundity (r = ?0.33 and ?0.25, P < .05; r = ?0.23, P > .05) and before the late spawning season with fry/kg (r = ?0.21, P > .05; r = ?0.30, P < .05). Eggs/kg female body weight and fry/kg female body weight followed a parallel pattern throughout the season, illustrating the logical relationship between relative fecundity and fry output. The size of females used is a consideration to maximize hybrid catfish embryo production during the early and middle spawning season but not late in the spawning season. However, these correlations are relatively small even though significant; thus a dramatic change in fry production would not be predicted. Since reproductive relationships can change during the spawning season, conclusions and recommendations could be flawed if data are not collected periodically during an entire spawning season.     

Folate-Degrading Bacteria in Channel Catfish Feeds

Two "Pseudomonas" spp., designated as PF1 and PF2, were isolated from 147 of 148 channel catfish feed samples and 10 different orgns from anemic and healthy channel catfish, "Ictalurus punctatus." Both PF1 and PF2 are capable of using folic acid as the sole source of carbon and nitrogen, and they hydrolized folic acid to pteroic acid. They did not utilize common carbohydrates. In vitro, the bacteria destroyed over 93% of folic acid in media containing only folic acid and inorganic salts. The morphological and biochemical properties of the bacteria indicate that they are "Pseudomonas" spp. and similar to some other "Pseudomonas" spp. and similar to some other "Pseudomonas" species that utilize folic acid. It is suspected that these folate degrading bacteria are involved in a nutritionally related anemia of cultured channel catfish.     

Forced-Air Incubation of Catfish Eggs

A low pressure, high volume, forced-air method of incubation was evaluated for eggs of channel catfish, "Ictarlurus punctatus," and channel catfish ♀ X blue catfish, "I. furcatus," ♂ hybrids and was compared to the traditional paddle-type incubation method. No significant difference was observed in hatching percentage, survival, or weight of sac-fry and swim-up fry or in total weight after 21 days of feeding for 10 egg masses that were divided equally and incubated with paddles or forced air. The forced-air method was inexpensive, safe, quiet, and as effective as paddle-type aeration.     

Masculinization of Channel Catfish Ictalurus punctatus by Oral Administration of Trenbolone Acetate

All-male populations of channel catfish, Ictalurus punelatus , were produced by feeding a diet containing trenbolone acetate to swim-up fry for 60 d. This hormone was effective in producing 100% males at doses of 50 to 150 mg/kg of diet. Fish that received 0 or 1 mg/kg of diet did not differ from the expected 1:1 sex ratio. Survival of control fish and fish fed diets containing trenbolone acetate were similar ( P > 0.05) at the end of the treatment period and after a 60-d grow-out period. Our results represent the first report of successful masculinization of channel catfish with a synthetic anabolic androgenic steroid.     

Validation of a whole-body cortisol extraction procedure for channel catfish (<Emphasis Type="Italic">Ictalurus punctatus</Emphasis>) fry

We validated a whole-body cortisol extraction technique for channel catfish, Ictalurus punctatus, fry. Three volume enhancement methods were tested: CAL method (zero calibrator A diluent added to lipid extract), PBS method (phosphate buffered saline added to lipid extract), and VO method (food grade vegetable oil added to lipid extract). The volume enhancement extracts were evaluated using a commercial radioimmunoassay kit. Sensitivity, accuracy, precision, reproducibility, and parallelism could not be determined for the PBS method as cortisol levels were not detected in any of the extracted samples. Intra-assay coefficient of variation (CV) for the CAL and VO methods were 7.3 and 8.3%, respectively, while inter-assay CV were 9.6 and 10.6%, respectively. Based on the sensitivity, accuracy, precision, reproducibility, and parallelism results, we conclude that the CAL method is the most appropriate method for volume enhancement of catfish fry lipid extract. Using the CAL method to detect cortisol in catfish fry, fish were stressed daily for 2 weeks. Fry weights were similar throughout the study while whole-body cortisol levels were higher (P < 0.01) in stressed fish after 1 day of stress. These data show the CAL method can effectively measure whole-body cortisol in catfish fry.     

Effects of Stocking Sac-Fry and Hatchery-Fed Fry on Production of Fingerling Channel Catfish Ictalurus punctatus

Abstract.— Channel catfish Ictalurus punctatus fry are typically held under hatchery conditions for 7 to 14 d after hatching to allow feeding and growth before they are stocked into nursery ponds to produce fingerling catfish. In an attempt to reduce hatchery operating costs, several catfish fingerling producers in Louisiana presently stock fry within 2 d after hatching before yolk absorption is complete. Fry at this stage of development are commonly referred to as "sac-fry." Although research has shown that fry can be stocked at the onset of yolk absorption with no detrimental effects on subsequent fingerling production, stocking sac-fry has been reported to result in reduced fingerling survival. To further investigate this topic, production trials were conducted in experimental outdoor pools over the course of two growing seasons to evaluate the effect of stocking fry of three different ages (2-, 7-, and 14-d post-hatch, DPH) on survival, growth (weight and length), condition factor (K), yield, feed consumption, and feed conversion ratio (FCR) of fingerling catfish. Results from both trials indicated that the age at which fry were stocked had no effect on production characteristics with the exception of growth. Specifically, fingerlings reared from fry stocked at 2 and 7 DPH were significantly larger than fingerlings reared from fry stocked at an age of 14 DPH. These findings suggest that the practice of stocking sac-fry may be a suitable alternative to the traditional procedure of holding and feeding fry under hatchery conditions prior to stocking. However, in order to fully evaluate the effects of early-age stocking of catfish fry on fingerling production, additional studies must be conducted under pond conditions. Furthermore, these studies must be coupled with a rigorous economic analysis before the practice of stocking sac-fry can be recommended to the catfish industry.     

Effects of Seasonal Variations, Thyroid and Steroid Hormones, and Carp Pituitary Extract on the Artificial Production of Channel Catfish Ictalurus punctatus× Blue Catfish I. furcatus Hybrids

The primary objective was to compare thyroid hormones and levels of carp pituitary extract for the artificial production of female Ictalurus punctatus × male I. furcatus hybrid catfish. The effects of different carp pituitary extract dosage rates (5, 6, 9, and 10 mg/kg), carp pituitary extract (6 and 10 mg/kg) supplemented with the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃), or pregnenolone (DHP) were determined for inducing ovulation of female channel catfish, fertilization of channel catfish eggs with male blue catfish sperm, and hatching rate of these embryos. Hormone treatments thyroxine and tri-iodothyronine with carp pituitary extract, carp pituitary extract alone, and pregnenolone with carp pituitary extract used to artificially produce hybrid catfish were not different in terms of ovulation rates, eggs/kg, fry/kg body weight of female channel catfish, fertilization rates, or hatching rates (P > 0.05). These findings suggest that lower amounts of carp pituitary extract may be used to induce spawn of female channel catfish for production of channel-blue catfish hybrids and the addition of thyroid and steroid hormones is ineffective at the rates used in this study.     

Studies on Vaccination of Channel Catfish,Ictalurus punctatus,Against Edwardsiella ictaluri

Enteric septicemia of cattish (ESC), caused by the bacterium Edwardsiella ictaluri, has become the most significant disease problem affecting the commercial channel catfish, Ictalurus punctatus, industry in the United States. Although antibiotics are used extensively for the control of ESC, there are inherent problems associated with their use. Consequently, experiments were initiated to evaluate the effectiveness of vaccination program that used immersion and oral delivery methods to administer a killed E. ictaluri vaccine to fry and fingerling channel cafish. In a preliminary pond study with laboratory challenge, mortality in a group vaccinated with a combination of immersion and oral procedures was only 5.0% in both high- and low-dose challenges. This was significantly different (P c 0.01) from non-vaccinated controls, which had 46.7%mortality in the lowdose challenge and the 6 1.7% mortality in the highdose challenge. This corresponds to relative percent survival (RPS) values of 89.3 and 91.9 respectively. Subsequent field trials further indicated the efficacy of a vaccination program for the prevention of ESC in channel catfish. In 1987-1988, a field study was conducted using 12 commercial ponds, with three replicates of four treatments. The four treatments included vaccination by immersion only, oral only, a combination of both immersion and oral procedures, and non-vaccinated conwols. Relative percent survival was 57.4 for the immersion only treatment, 50.3 for the oral only treatment, and 53.5 for the combination immersion and oral treatment. In 1989-1990, no significant difference was found between vaccinated and non-vaccinated fish. However, in 1989-1990, a vaccine-oil emulsion was topcoated on a floating feed, rather than incorporating vaccine in a sinking pellet. In 1990-1991, overall mortality in vaccinated fish was significantly less (P < 0.05) than non-vaccinated fish, with 41.2% mortality in vaccinates compared to 63.5% in non-vaccinated fish, for an RPS of 35.1. In examining RPS values for individual farms, two farms had excellent results, with RPS values of 81.3 and 76.9; two farms had only moderate success, with RPS values of 26.6 and 15.4; and one location had greater mortality in the vaccinated fish than in the non-vaccinated fish. However, that farm had only two ponds in the study and experienced significant losses to proliferative gill disease in the pond with vaccinated fish.     

Nutritional effects of protein source in starter diets for channel catfish (Ictalurus punctatus Rafinesque) in suboptimal water temperature

Intensive tank rearing of channel catfish (Ictalurus punctatus Rafinesque) fry can be successfully accomplished with commonly available ‘salmonid’ starter diets. Ingredient substitution in starter diets is less important from the cost perspective but growth, survival and health of fish are major concerns. Several combinations of fish meals and animal protein substitutes were evaluated in diet formulations for hatchery rearing of catfish fry. Sub‐optimal thermal conditions were used which are characteristic for the north‐central USA where catfish culture is important for stocking purposes and live‐fish markets. A diet formulated on the basis of menhaden fish meal (29.1%), herring fish meal (25.1%) and animal by‐product mixture (16.38%) gave numerically the highest growth rate after 13 weeks of feeding, although growth reductions in fish fed diets exclusively with mehaden meal (77.6%) as protein or substituted with 50% animal by‐product protein were not significant. Instantaneous mortality rates were the highest between weeks 2 and 4 of rearing and increased almost proportionally with the increased fish meal protein substitution. A diet based on menhaden fish meal had the highest concentration of phosphorus and several other essential minerals, but these were not reflected in the mineral composition of the fish body at the termination of feeding. Among activities of digestive enzymes, trypsin was depressed in fish offered diets with 75–100% fish meal protein replacement. A diet superior in terms of fish performance was defined in the present study and it was concluded that the initial feeding can greatly affect physiological status of juvenile channel catfish.