Location: Warmwater Aquaculture Research Unit2010 Annual Report
1a. Objectives (from AD-416)
1) Identify mechanisms and develop tools and methods to improve growth efficiency of catfish. 2) Determine mechanisms of host-pathogen interactions and sources of variation in catfish immune function to improve catfish health and survival. 3) Improve efficiency of channel and blue catfish reproduction and channel x blue hybrid production. 4) Identify genomic regions affecting variation in traits of economic importance through quantitative trait locus (QTL) discovery and fine mapping strategies. 5) Develop, and transfer to commercial producers, channel catfish and blue catfish germplasm improved for growth, yield, and disease resistance for improved production of channel, blue and hybrid catfish.
1b. Approach (from AD-416)
To attain the first objective, we will correlate mitochondrial functional variation with catfish feed efficiency and identify and determine the role of specific genes and gene products (peptides and proteins) involved in controlling growth in catfish. For the second objective, we will construct a catfish microarray targeted toward immune function, characterize functional genetic variation in resistant vs. susceptible channel catfish, and characterize the effect of prebiotic administration on catfish immune function. For the third objective we will induce early maturation in channel catfish and blue catfish through compressed annual temperature cycles, increase ovulation and fertilization efficiency for production of blue X channel F1 hybrid catfish, and establish a technique for spematogonial transplantation between blue and channel catfish. For the fourth objective we will enhance and integrate genetic and physical maps, and identify quantitative trait loci associated with superior production traits, especially carcass traits and survivability to E. ictaluri infection. For the fifth objective, we will produce a line of select channel catfish based on multi-trait selection within a commercial composite population, produce a line of select blue catfish based on males that produce hybrid offspring with superior growth and carcass yield, and produce male channel and blue catfish which have a YY sex chromosome complement for all male catfish production.
3. Progress Report
Cryopreserved sperm from 20 blue catfish from two strains were used to fertilize eggs from channel catfish to initiate evaluation of the effects of blue catfish germplasm on hybrid performance. Growth and fillet yield of 190 families of channel catfish is being evaluated as part of the Catfish Genetics Research Unit (CGRU) breeding program. Catfish from multiple studies were analyzed for processing yield at the CGRU processing facility for cooperators at Mississippi State University and the University of Arkansas Pine Bluff (an 1890s institution) to determine impact of altering diet composition on processing yield. Fingerling channel x blue hybrid catfish were stocked at five different densities to determine effects of stocking density on growth, feed conversion, fillet yield, and survival because effects of density on production are not well documented for hybrid catfish. Five replicate groups of 10 similarly aged full-sib channel catfish families (a total of 50 families) are being reared in different competitive environments to determine effects of environment of growth rankings of families. The 3-5 year generation interval of blue catfish slows progress in selective breeding. Investigations are underway to use controlled temperature cycling in tanks to shorten the time to sexual maturation. Blue catfish fry were hormonally feminized by feeding estrogens for 3 weeks during neonatal development to produce female blue catfish with an XY sex genotype. These fish will be used to produce YY males which would, in turn, produce all male offspring for use in hybrid catfish production. Intracranial and ovarian lavage methods of hormone delivery methods were evaluated for hybrid catfish production to improve the efficiency of induce spawning in channel catfish females. Improvements were made on hybrid fry production protocols (broodfish selection, egg treatments, harvesting methods) in commercial hatcheries. Maternal transfer of vitamin C was assessed for reproductive performance in channel catfish and subsequent hybrid progeny performance was evaluated for growth, disease resistance and stress response for low dissolved oxygen. Pond trials were conducted to determine the response of five levels of dietary lipids on the reproductive performance of channel catfish in hybrid catfish production. DNA sequence was produced from pooled catfish DNA for identification of single nucleotide variants. The insert lengths of clones in a random-sheared large-insert DNA library were too variable to provide high quality information for enhancement of the catfish physical map. Alternate methods are now under evaluation for organizing joined DNA fragments (contigs) as chromosomes. Broodstock from 10 families with high levels of survival to Edwardsiella (E.) ictaluri challenge were used to produce channel and hybrid catfish families to assess the genetic components of disease resistance. Details of subprojects can be found in 6402-31000-009-01N, 6402-31000-009-03S, 6402-31000-009-07R, and 6402-31000-009-08R.
5. Significant Activities that Support Special Target Populations
The USDA Census of Aquaculture conducted in 2000 classified 84% of catfish farms as small businesses, with annual sales of less than $500,000. Of the 1,370 catfish farms in the United States, 38% (515) reported annual revenues of less than $25,000. This data is not available in the 2005 Census of Aquaculture. Increased foreign competition and higher feed and fuel prices have reduced the profit margins for these small businesses. Development of catfish lines with superior performance for commercially important traits, utilization of these lines in commercial culture, and utilization of production technology originating from the Catfish Genetics Research Unit will help solve production problems, increase efficiency and profitability for both small and large catfish farmers, and provide a quality product for consumers. Most catfish producers with limited acreage buy fingerlings from large breeders that are very likely to utilize improved brood stocks, and the development and use of improved catfish lines can quickly affect the profits of small producers. Because small farms do not enjoy the same economies of scale experienced by larger operations, breeding fish with improved production traits will be highly beneficial to small farmers. Average consumers also benefit from the increased availability of higher-quality, safer domestic products at a reduced price.
Wang, S., Peatman, E., Abernathy, J., Waldbieser, G.C., Lindquist, E., Richardson, P., Murdock, C.A., Small, B.C., Quiniou, S., Liu, Z. 2010. Assembly of 500,000 Inter-Specific Catfish Expressed Sequence Tags and Large Scale Gene-Associated Marker Development for Whole Genome Association Studies. Genome Biology. 11:R8.