Brad J. Argue

Selective breeding of Pacific white shrimp (Litopenaeus vannamei) for growth and resistance to Taura Syndrome Virus

Abstract From 1995 to 1998, the Oceanic Institute operated a breeding program for Pacific white shrimp, Litopenaeus vannamei, based on a selection index weighted equally for growth and resistance to Taura Syndrome Virus (TSV). In 1998, two separate breeding lines were established. One line was selected 100% for growth (Growth line) and a second line was selected on an index weighted 70% for TSV resistance and 30% for growth (TSV line). After one generation of selection, select shrimp from the Growth line were 21% larger than unselected control shrimp (24.2 vs. 20.0 g). The half-sib heritability (h2) estimate for growth was 0.84±0.43(s.e.) and realized h2 was 1.0±0.12. Females were 12.7% larger than males. Shrimp tails accounted for 65.1% of total body weight and males had a significantly higher percent tail than females (65.7% vs. 64.5%; P

Enhanced Bacterial Disease Resistance of Transgenic Channel Catfish Ictalurus punctatus Possessing Cecropin Genes

The cecropin B gene from the moth Hyalophora cecropia, driven by the cytomegalovirus promoter, was transferred to the channel catfish Ictalurus punctatus. Transgenic individuals (P1) were mated to produce individuals (F1) that exhibited enhanced disease resistance and survival when challenged with pathogenic bacteria. During the epizootic of Flavobacterium columnare in an earthen pond, the percentage of transgenic individuals containing preprocecropin B construct that survived (100%) was significantly greater (P <0.005) THAN THAT OF NONTRANSGENIC CONTROLS (27.3%). ALSO, WHEN CHALLENGED IN TANKS WITH EDWARDSIELLA ICTALURI, THE CAUSATIVE AGENT OF ENTERIC SEPTICEMIA OF CATFISH, THE PERCENTAGE OF TRANSGENIC INDIVIDUALS CONTAINING CATFISH IG LEADER CECROPIN B CONSTRUCT THAT SURVIVED (40.7%) WAS SIGNIFICANTLY GREATER (P <0.01) THAN THAT OF NONTRANSGENIC CONTROLS (14.8%). THERE WERE NO PLEIOTROPIC EFFECTS OF THE TRANSGENES, AND GROWTH RATES OF THE TRANSGENIC AND NONTRANSGENIC SIBLINGS WERE NOT DIFFERENT (P > 0.05). Inheritance of the transgene by the F1 generation, 20.2% to 30.7% was typical of that in studies with transgenic channel catfish.

Random amplified polymorphic DNA markers : usefulness for gene mapping and analysis of genetic variation of catfish

Abstract Catfish are the most important aquacultural species in the United States. A genetic linkage map is needed to improve efficiency of breeding by marker-assisted selection (MAS), and for identification, isolation and eventual cloning of commercially important genes. To identify DNA-based genetic polymorphism for constructing a genetic linkage map of catfish, we tested 100 random amplification of polymorphic DNA (RAPD) primers for their utility in identifying genetic polymorphism in catfish. The overall polymorphism was low among strains within a species for both channel catfish ( Ictalurus punctatus) and blue catfish ( Ictalurus furcatus) . However, considerably higher levels of polymorphism were detected between channel catfish and blue catfish. Among the 100 primers tested, 42 produced highly clean and reproducible RAPD profiles; 33 produced medium quality RAPD profiles; and 25 produced poorly reproducible RAPD profiles or non-polymorphic RAPD profiles. The 75 high and medium quality primers generated 462 polymorphic bands, an average of 6.1 bands per primer. The RAPD markers were highly reproducible in a size range from 200 to 1500 base pairs (bp). They were transmitted to F 1 hybrids as dominant markers. There was no difference in RAPD profiles between channel catfish×blue catfish F 1 hybrids or their reciprocal hybrids. The markers segregated in F 2 or backcross progeny with ratios as expected from Mendelian inheritance.

Dress-out and fillet yields of channel catfish, Ictalurus punctatus, blue catfish, Ictalurus furcatus, and their F1, F2 and backcross hybrids

Abstract The channel catfish, Ictalurus punctatus, ♀×blue catfish, Ictalurus furcatus, ♂ F1 hybrid showed increased processing yields over the most commonly cultured catfish, channel catfish, in the US. The F1 hybrid had higher dress-out and fillet percentage (61.1% and 45.7%, respectively) than channel catfish (57.5%, 42.5%), blue catfish (58.9%, 44.4%), F2 hybrid catfish (57.3%, 42.5%), F1×channel catfish (57.3%, 42.7%), F1×blue catfish (58.3%, 42.4%), blue catfish×F1 (58.2%, 43.2%), and channel catfish×F1 (56.8%, 42.1%). Individual heterosis had a strong positive effect on dress-out and fillet percentage. Channel catfish additive genetic effects had a strong negative effect on dress-out and fillet percentage. Females had greater dress-out (58.4% to 57.9%) and fillet percentage (43.6% to 43.0%) than males (P

Seinability of Channel Catfish, Blue Catfish, and Their F1, F2, F3, and Backcross Hybrids in Earthen Ponds

Abstract Blue catfish Ictalurus furcatus were significantly easier to harvest by seining than channel catfish I. punctatus female channel catfish × male blue catfish F1 and F2 hybrids, channel catfish backcrosses, and blue catfish backcrosses (P < 0.05). The F1 hybrid was significantly easier to catch than channel catfish (P < 0.05). The F3 hybrid was significantly easier to catch than the F2 hybrid, channel catfish, and channel catfish backcrosses (P < 0.05). Individual epistatic recombination loss had a positive effect on percent fish caught in the first seine haul. Channel catfish additive genetic effects had a negative effect on ease of capture by seining. The more channel catfish genes present, the harder the fish was to catch.

Predator Avoidance of Transgenic Channel Catfish Containing Salmonid Growth Hormone Genes

Abstract: Transgenic channel catfish (Ictalurus punctatus) containing salmonid growth hormone genes can grow 33% faster than normal channel catfish under aquaculture conditions. However, before transgenic catfish are released and utilized by the private sector, their genetic impact on the natural environment must be examined. Predator avoidance is one of the major fitness traits determining potential environmental risk. To determine the predator avoidance ability and growth performance of transgenic catfish in a natural habitat, various densities of transgenic and nontransgenic channel catfish were communally stocked in 0.04-ha earthen ponds without supplemental feeding. Largemouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus) were stocked as predators. Nontransgenic fry had better predator avoidance than transgenic channel catfish when data were pooled (p < .01). When data were not pooled, nontransgenic catfish had better predator avoidance in six trials and transgenic individuals had better predator avoidance in four trials. There was no difference in predator avoidance in three trials. Overall predator avoidance was also better for nontransgenic individuals (p < .01) when the fish were evaluated as 3.5-g fingerlings, more clearly than as fry, as transgenic individuals were more vulnerable in 3 of 4 trials at this life stage. There was no significant difference in growth performance between transgenic and nontransgenic channel catfish in ponds without supplemental feeding. These findings indicate that transgenic channel catfish could be used for commercial aquaculture without affecting the natural environment. Although transgenic channel catfish may be released to nature by accident, any ecological effect would be unlikely because the increased susceptibility of transgenic channel catfish to predators would most likely decrease or eliminate the transgenic genotype.

Comparison of manual stripping and pen spawning for production of channel catfish × blue catfish hybrids and aquarium spawning of channel catfish.

Abstract We compare manual stripping to pen spawning for production of hybrids of female channel catfish Ictalurus punctatus × male blue catfish I. furcatus, as well as to aquarium spawning of channel catfish. The ovulation rate for manually stripped females (91%) was not significantly different from that of females spawned in aquaria with channel catfish males (67%; P > 0.05); however, ovulation rate of manually stripped females during week 10 (80%) was superior to that of females spawned in pens (15%; P < 0.05) with blue catfish males. Female channel catfish spawned in aquaria with male channel catfish produced more (P < 0.05) eggs per kilogram body weight (6,607) than manually stripped females (4,587). Pen spawning of female channel catfish and male blue catfish also produced significantly more (P < 0.05) eggs per kilogram (7,950) than hand-stripping females (3,448) during week 10. Hatching rate (21%) and fry per kilogram (1,065) of female body weight were higher (P < 0.05) for channel catfish spawned ...

Development of Amplified Fragment Length Polymorphism (AFLP) Markers Suitable for Genetic Linkage Mapping of Catfish

Abstract Genomic research requires many molecular markers for construction of the genetic linkage map and for marker-assisted selection (MAS). Amplified fragment length polymorphism (AFLP) markers are inherited with Mendelian expectations in catfish and, thus, are suitable for use in gene mapping and MAS. To identify large numbers of AFLP markers, 64 primer combinations were tested to generate AFLP patterns between channel catfish Ictalurus punctatus and blue catfish I. furcatus. The 64 primer combinations amplified 7,871 bands, of which 3,081 were polymorphic between the two mating parents of channel catfish and blue catfish used to produce the reference families for mapping analysis. The primer combinations that produced fewer bands showed higher rates of polymorphism. Of the 64 primers, 53 primer combinations produced clean and reproducible AFLP profiles. Nine primer combinations produced fair AFLP profiles. The remaining two primers produced poor AFLP profiles with intensive background bands. The 53 e...

Reproduction among Channel Catfish, Blue Catfish, and Their F1 and F2 Hybrids

Abstract Reproductive traits of the channel catfish Ictalurus punctatus, the blue catfish I. furcatus, their F1 hybrid—channel catfish female × blue catfish male—and their F2 hybrid were examined. The absence of reproductive isolating mechanisms in F1 and F2 generations is important in terms of allowing for breeding programs for the development of a synthetic breed that has the best culture traits from the two species. Conversely, if reproductive fitness is high in F1 and F2 generations, the possibility of introgression with the parent species in the natural environment increases, thereby increasing the potential for risk from F1 generation (and higher) hybrids. F2 hybrid females had a lower frequency of ovulation (P < 0.05; 12.2%) than did channel catfish, blue catfish, and F1 hybrid catfish (83.5, 58.4, and 56.5%, respectively) when these females were induced to spawn with carp pituitary extract and were then hand-stripped. F2 hybrids that ovulated produced fewer eggs per kilogram of body weight (P < 0....

Hybrid Fertility, Introgression, and Backcrossing in Fish

ABSTRACT The literature was reviewed to determine the number of fertile, interspecific fish hybrids produced naturally and artificially. A total of 130 interspecific, natural crosses resulted in fertile F1 hybrids, and 150 artificially produced interspecific crosses produced fertile F1 hybrids. The validity of species concepts with reproductive isolation in their definition is questioned. The presence of fertile hybrids in 45 intergeneric crosses makes their current classification questionable.