Browsing by Author "Anane-Taabeah, Gifty"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Aquaculture-Mediated Invasion of the Genetically Improved Farmed Tilapia (Gift) into the Lower Volta Basin of GhanaAnane-Taabeah, Gifty; Frimpong, Emmanuel A.; Hallerman, Eric M. (MDPI, 2019-10-02)The need for improved aquaculture productivity has led to widespread pressure to introduce the Genetically Improved Farmed Tilapia (GIFT) strains of Nile tilapia (Oreochromis niloticus) into Africa. However, the physical and regulatory infrastructures for preventing the escape of farmed stocks into wild populations and ecosystems are generally lacking. This study characterized the genetic background of O. niloticus being farmed in Ghana and assessed the genetic effects of aquaculture on wild populations. We characterized O. niloticus collected in 2017 using mitochondrial and microsatellite DNA markers from 140 farmed individuals sampled from five major aquaculture facilities on the Volta Lake, and from 72 individuals sampled from the wild in the Lower Volta River downstream of the lake and the Black Volta tributary upstream of the lake. Our results revealed that two farms were culturing non-native O. niloticus stocks, which were distinct from the native Akosombo strain. The non-native tilapia stocks were identical to several GIFT strains, some of which showed introgression of mitochondrial DNA from non-native Oreochromis mossambicus. We also found that the non-native cultured tilapias have escaped into the wild and interbred with local populations, and also observed potentially admixed individuals on some farms. Our results highlight aquaculture as a vector in the spread of invasive non-native species and strains, and underscore the importance of genetic baseline studies to guide conservation planning for wild populations.
- Characterization of the molecular genetic variation in wild and farmed Nile tilapia Oreochromis niloticus in Ghana for conservation and aquaculture developmentAnane-Taabeah, Gifty (Virginia Tech, 2019-02-01)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.
- Harnessing the opportunities and overcoming constraints to widespread adoption of cage aquaculture in GhanaAnane-Taabeah, Gifty (Virginia Tech, 2012-04-25)Understanding cage aquaculture adoption decisions and factors affecting adoption is necessary to ensure that fish production from cage aquaculture in Ghana is both significant and sustainable. The goal of this study was to provide a framework for understanding cage aquaculture adoption decisions and to identify factors affecting adoption, to inform decision makers as they formulate policies aimed at promoting cage aquaculture adoption in Ghana. I surveyed 122 respondents comprising current cage fish farmers, farmers who have abandoned cage aquaculture, and potential adopters of cage aquaculture such as, fish traders, fishermen and land-based fish farmers. Respondents answered questions related to knowledge, interest, constraints in cage aquaculture, and demographics. I used non-metric multidimensional scaling and discriminant function analysis to identify unique groups within the respondents, classify respondents according to their position in the innovation-decision continuum, and identify factors affecting cage aquaculture adoption. Based on their differences in knowledge and interests, I placed respondents into one of three stages of the cage aquaculture innovation-decision process model I developed: (1) Unawareness, (2) Knowledge, Persuasion, and Decision (KPD), and (3) Implementation (Confirmation and Abandonment). Respondents in the KPD and Implementation stages had knowledge, were more interested in cage aquaculture, and were aware of constraints in cage aquaculture, whereas respondents in the Unawareness stage lacked knowledge and interest in cage aquaculture, and did not clearly understand the constraints. Respondents who were males, belonged to the tribes Ewe and Akan, and who had fishing experience tended to be more interested in cage aquaculture. The lack of capital, high input costs, inability to adequately market fish, theft, lack of information sources, conflict over water use, and cage destruction by storms, were identified as the main constraints to cage aquaculture adoption in Ghana. The results of the study suggest that programs aimed at encouraging new entrants into cage aquaculture should focus on demographic characteristics such as gender, and tribe. However, demographic characteristics may affect adoption decisions and it may be important to consider them as such. Some recommendation to address the major constraints in cage aquaculture include: the Fisheries Directorate should (1) develop an efficient extension program that farmers can access regularly, especially, for farmers with no other information sources, (2) provide feed subsidy to enable farmers produce fish at competitive prices, (3) facilitate the formation of fish farmers' cooperative groups that would purchase large quantities of feed, (4) encourage local production of high quality fish feed, and (5) develop credit facilities that can be accessed by individuals interested in cage aquaculture to assist potential farmers who would, otherwise, not be able to adopt cage aquaculture . In addition, fish farmers should (6) be proactive in marketing their fish by identifying potential niche markets prior to production, and (7) join cooperative groups to ease the burden of accessing loans to increase production.