Mulloway are a large native inshore marine fish that are currently being evaluated by NSW Fisheries for their potential in aquaculture. The current study developed and applied molecular genetic markers to assess the geographical scale at which future hatcheries should be developed for the species. In addition, it evaluated the impact that current breeding practices in NSW have had on genetic diversity in culture cohorts. The study showed that wild Australian populations of this species constitute a single management unit (genetic stock), but that current hatchery practices employed in NSW are eroding natural genetic diversity. Thus a single hatchery could provide cultures stock to the whole Australian industry without compromising wild populations but that hatchery management practices will need to be modified in the future, to minimise levels of inbreeding.

The Nile tilapia Oreochromis niloticus is native to Africa and middle East, and is an important source of nutrition for many in sub-Saharan Africa. Understanding the genetic diversity within and differentiation among wild populations can help identify O. niloticus populations that are imperiled and require directed management, especially because of increasing threats to the species' long-term persistence in the wild, including habitat destruction, overfishing, climate change, and hybridization with farmed populations. Knowledge of the genetic variation among wild populations also can contribute to foundation and selection of genetically diverse populations for aquaculture. I assessed the genetic variation among tilapia populations using fin-clips collected between December 2014 and July 2017 from 14 farmed sources, mostly originating from cage farms on the Volta Lake, and 13 wild sources from nine river basins in Ghana. I also conducted a laboratory growth experiment in Ghana with two wild populations to evaluate the tolerance of different genotypes to high temperatures, to inform their development for aquaculture in West Africa. I found that pure O. niloticus populations persist in the wild but some have been extensively introgressed with the closely related species, O. aureus, which has not previously been documented in Ghana. Additionally, some wild populations appear to have recently declined significantly in numbers, likely due to overfishing and habitat modification, the latter primarily as a result of illegal alluvial mining ongoing in Ghana. Analysis of the farmed populations revealed that at least two farms were growing the unapproved genetically improved farmed tilapia (GIFT) and related strains, and that escaped individuals are admixed into some wild populations. The results of my laboratory experiment showed that O. niloticus populations occurring in northern Ghana already may be adapted to warmer temperatures and could be developed and used purposefully in aquaculture, taking advantage of their adaptation. To protect remnant pure O. niloticus populations in the wild, timely conservation decisions should be made and implemented. Protecting wild O. niloticus populations also would ensure that pure germplasms are available to develop aquaculture stocks from native populations. / Ph. D. / The Nile tilapia Oreochromis niloticus is an important food source for many people in Africa. However, many wild populations may be at risk of population decline and extinction because of increasing human activities such as overfishing and farming of non-native strains. Understanding the genetic differences among wild populations and comparing them with farmed strains can inform protection of wild populations and also help develop aquaculture strains using native populations as genetic resources. I assessed the genetic differences among tilapia populations using fin-clips I collected between December 2014 and July 2017 from 14 farmed sources, mostly originating from cage farms on the Volta Lake, and 13 wild sources from nine river basins in Ghana. I also conducted a laboratory study with two wild populations to test their tolerance to high water temperature. My research showed that pure O. niloticus populations still occur in Ghanaian rivers, but some have reproduced widely with a similar species, O. aureus, which is not known to occur in Ghanaian rivers. I also found that some wild populations may have reduced population sizes because of overfishing or because their environments have been impacted by illegal mining occurring in almost all Ghanaian rivers. My results indicated that at least two farms were growing the genetically improved farmed tilapia (GIFT) and related varieties, some of which have escaped the farms and mixed with wild populations. The results of my laboratory experiment showed that O. niloticus populations occurring in northern Ghana may be adapted to warmer water temperatures and could be selectively bred and used in aquaculture. The information generated from my research should help in making timely conservation decisions, which should help protect the remnant pure O. niloticus populations in the wild and contribute to developing aquaculture responsibly.

Primers for 10 polymorphic DNA microsatellite loci were developed and characterized for the endangered oyster mussel Epioblasma capsaeformis from the Clinch River, TN. Microsatellite loci also were amplified for individuals collected from the following additional populations or species: (1) E. capsaeformis from Duck River, TN; (2) E. florentina walkeri from Indian Creek, upper Clinch River, VA; (3) E. florentina walkeri from Big South Fork Cumberland River, TN; and (4) E. torulosa rangiana from Allegheny River, PA. Allelic diversity ranged from 9-20 alleles/locus, and averaged 13.6/locus for all 5 populations investigated. Average expected heterozygosity (HE) per locus ranged from 0.78-0.92, and averaged 0.86. A genetic characterization of extant populations of E. capsaeformis and E. florentina walkeri was conducted to assess taxonomic validity and to resolve conservation issues related to recovery planning. These mussel species exhibit pronounced phenotypic variation, and are difficult to characterize phylogenetically using DNA sequences. Monophyletic lineages, congruent with phenotypic variation among species, were obtained only after extensive analysis of combined mitochondrial (1378 bp of 16S, cytochrome-b, ND1) and nuclear (515 bp of ITS-1) DNA sequences. In contrast, analysis of variation at 10 hyper variable DNA microsatellite loci showed moderate to highly divergent populations based on FST values, which ranged from 0.12-0.39. Quantitative genetic variation was observed in fish host specificity, with transformation success of glochidia of E. capsaeformis significantly greater (p<0.05) on the greenside darter Etheostoma blennioides, and that of E. f. walkeri significantly greater (p<0.05) on the fantail darter E. flabellare. Lengths of glochidia differed significantly (p<0.001) between species, with sizes ranging from 241-272 μm. Underwater photographs of mantle-pads and micro-lures of female mussels documented fixed phenotypic variation between species. The texture and color of the mantle-pad of E. capsaeformis is smooth and bluish-white, while that of E. f. walkeri is pustuled and brown, with tan mottling. Based on extensive molecular, morphological, and life history data, a population of E. capsaeformis from the Duck River, TN is described and proposed as a separate species, and a population of E. f. walkeri from the upper Clinch River, VA is described and proposed as a separate subspecies. Genetic management guidelines were developed to assess taxonomic status, genetic variation of donor-recipient populations targeted for augmentation, and field and laboratory protocols to maximize genetically effective population size, minimize genetic changes in captive-reared progeny, and prevent the release of juvenile mussels into non-native drainages. A pragmatic approach to species recovery is advocated; one that incorporates the principles of conservation genetics into breeding programs, but prioritizes the immediate demographic needs of critically endangered mussel species. / Master of Science

No description available.