Aquaculture research achievements and impacts 2015

By Dr. Hanping Wang, Senior Scientist
Summary of Achievements: In 2015, in collaborations with the Oregon State University, University of Wisconsin-Stevens Point, Lincoln University of Missouri, University of Benha University, and several other international institutions, we accomplished twelve research studies and projects resulting in 12 manuscripts being submitted; we finished the 3-year on-farm on-station tests of improved yellow perch vs. local unimproved fish, and finalized the report; we published five peer-reviewed journal articles and six proceedings abstracts; received two grants; trained five graduate students, post-doctoral fellows and scholars; completed/submitted seven new grant proposals; and made eight presentations at international conferences.  A book titled Sex-Control in Aquaculture is in the progress.
Yellow Perch Breeding: The fifth generation of fast-growing lines of yellow perch was created for the aquaculture industry through marker-assisted cohort selection.  Approximately 1,000,000 genetically improved seeds were delivered to the aquaculture industry in 2015 and so far over 2,000,000 genetically improved seeds have been distributed to farms for test and demonstration.  Neo-male male populations of yellow perch with a female genotype have been created, and a fast-growing all-female strain has been developed for the aquaculture industry by crossing neo-males with regular females.   The all-female population should be able to grow 50% faster than unimproved regular mixed populations.  Four projects related to sex-control and breeding were completed and four manuscripts on these projects are in preparation or in revision.
Bluegill Breeding: Twenty-four selected and improved females and 24 selected males were pair-mated, and 12 batches of expected all-males were produced.  Once the sex is confirmed, the fish will be distributed to two locations and to compare sex ratios and production characteristics.  Temperature effects on sex ratio have been found in some geographic populations, producing more males in high temperatures, more females in low temperatures.  The findings were published in Aquaculture.  Follow-up investigation using four different geographic populations strongly suggests that both temperature-dependent sex determination and genetic sex determination exist in bluegill.
This paper is in the revising phase and being considered by The Biological Bulletin for publication. The results from these two experiments provide a valuable base for developing all-male broodstock for bluegill, which could grow 35-50% faster than mixed populations.
Identify the best genetically distinct largemouth bass populations for the industry: We investigated the genetic structure of largemouth bass from 20 wild populations and five cultured stocks across the United States and China using eight microsatellite loci.  Our major findings are as follows: (1) Allelic richness was lower among cultured populations than among wild populations; (2) Effective population size in hatcheries could promote high levels of genetic variation among individuals and minimize loss of genetic diversity; (3) The majority of largemouth bass populations had a significant heterozygosity excess, which is likely to indicate a previous population bottleneck; (4) The phylogeny based on eight microsatellites revealed a clear distinction between northern and southern populations.  The information provides a valuable basis for development of aquaculture genetic breeding programs in largemouth bass.
On-farm and on-station tests of improved yellow perch in ponds:  A 3-year project of the on-station and on-farm tests of genetically improved yellow perch on three sites and in two states was finished, data analyzed, and report submitted. This is an important step for Commercialization of genetically improved strains. The testing results showed improved fish exhibited 27.6% - 42.1% higher production, and 25.5% - 37.5% higher growth rates, while having 12.3% - 27.8% higher survival than local strains, on the average, across the three sites.
Genomic sequence and tool development: In collaboration with Oregon State University, we completed RAD/DNA sequencing of five strains, and whole genome sequencing of two strains in yellow perch to develop SNPs and identify genomic diversity of those strains for further improve perch growth and other economic traits; we completed RNA sequencing of regular males, regular females and neo-males, and different growth phases of yellow perch to identify genes associated with sexual size dimorphism and sex determination, and to develop an all-female population using improved fish; a total of 41,479 microsatellite markers were identified from 18,210 unigene sequences for breeding programs; we also completed whole genome sequencing of two strains of bluegill to develop SNPs and investigate genomic base of sex determination for developing mono-sex population.  In addition, we completed RAD/DNA sequencing of white and black crappie to develop SNPs and identify genomic diversity of those species for a future crappie and sunfish breeding program. 
Improvement of egg hatching rate for industry: We completed a project on determining efficacy of formalin, iodine, and sodium chloride for the improvement of egg hatching rate and fry survival prior to the onset of exogenous feeding in yellow perch.  The study revealed that formalin was a more effective disinfectant to improve the hatching rate and survival to first feeding fry of yellow perch than iodine and sodium chloride.  To improve the hatching rate, a concentration of 150 to 250 mg L-1 for 30 min is recommended to disinfect the eggs of yellow perch daily from the beginning to the eyed stage.  The results were published in Aquaculture Research and will be used by fish farmers to improve the egg hatching rate and fry production of yellow perch.
Improvement of perch fry survival rate for industry: Seven feeding regimes were tested in 2015, with each having two replicates, via combination of mouth-opening prey, initial age of weaning, duration of weaning, duration of co-feeding, and different larvae formula feed.  Several related studies were completed: 1) By monitoring egg size produced by different strains/families, we have identified some strains/families that produced significantly larger-mouth gape progeny and larger eggs than others; 2) Variation of egg size is dramatically different among strains of our genetically improved fish, indicating there is a large range of selection for large eggs; 3) We found predation and ingestion of prey at the beginning of feeding is limited by the mouth gape in fish larvae which determine larvae survival.  Survival varied considerably between replicates and among feeding regimes.  Massive mortality was observed at two stages for all feeding regimes/tanks. 
The first massive mortality was observed right after stocking from the hatching tank to nursing tank.  About 30-75% larvae died the next day after stocking due to handling. The second massive mortality was observed from 10- to 30-days post-hatch (DPH) of fry.  No mortality was found after 45 DPH and all fish could ingest commercial starter feed (>0.8 mm) for larvae.
International training program: Leading research in aquaculture genetics and breeding at the OSU South Centers has attracted more than twenty-five scientists and international scholars to work in the Aquaculture Research Center and Genetics Lab at Piketon.  In 2015, the lab trained five visiting Ph.D. students, post-doctorial researchers and international scholars, and one of them received their Ph.D in 2015.  They also significantly contributed to the aquaculture program’s success at The Ohio State University South Centers.