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Genetic Identification and Population Structure of Juvenile Mullet (Mugilidae) Collected for Aquaculture in East Africa
Södertörn University, School of Life Sciences, Biology.
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2012 (English)In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 11, no 1, 41-54 p.Article in journal (Refereed) Published
Abstract [en]

There is a growing demand for wild caught juvenile fish to supply the market for aquaculture. However, little is known about the genetic effects of juvenile collection from wild populations. There are a number of imminent threats to both aquaculture systems and wild fish populations. Juvenile collection from a single population can for example reduce population’s evolutionary potential as well as the disease resistance within an aquaculture pond. In this study, we investigated the local genetic structure of juvenile mullets collected from five sites around Bagamoyo (Tanzanian mainland) and Zanzibar Island, East Africa. Fish were caught in low tide using a seine net. The fish were morphologically identified, and then genetically identified using direct sequencing of the CO1 gene with cross referencing with the Barcode of Life Database (BOLD) systems.  Molecular variance analyses were used to infer genetic subdivision based on geographic sampling site as well as inferring population structure through the Bayesian assignment test implemented in STRUCTURE 2.3. Our results showed that samples morphologically identified as Mugil cephalus where in fact Valamugil buchanani and we also found evidence of an introgression genome event, where the gene flow from one species may have affected the general gene pool. The Bayesian analysis revealed a clear genetic population structure among the sampled fish; the main difference was the presence of a unique mainland cluster. Our findings may have important implications for management and conservation of mullet fishes in the region and elsewhere.

Place, publisher, year, edition, pages
2012. Vol. 11, no 1, 41-54 p.
National Category
Research subject
Environmental Studies
URN: urn:nbn:se:sh:diva-18924OAI: diva2:622909
Sida - Swedish International Development Cooperation Agency, SWE-2005-321
Available from: 2013-05-23 Created: 2013-05-23 Last updated: 2014-06-17Bibliographically approved
In thesis
1. Genetic connectivity of fish in the Western Indian Ocean
Open this publication in new window or tab >>Genetic connectivity of fish in the Western Indian Ocean
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

An almost unbroken fringing reef runs along the east coast of Africa, the lagoon inside the reef is the foundation of almost all artisanal fisheries. It is a low-tech fishery conducted by many people. Some areas can have up to 19 fishermen per square kilometer. High fishing pressures, coupled with declining fish stocks has led to changes in mean size and reproductive age of many exploited species. There is a vital and urgent need for scientifically based management systems, including the utilization of genetic information to guide management practices.

This thesis aims to investigate the presence of genetic structures in the western Indian Ocean. In order to do that we first investigated the historical patterns of connectivity throughout the region (paper I). In papers II and III we focused on local scale connectivity in Kenya and Tanzania and finally in paper IV we investigate the large-scale contemporary gene flow throughout the Western Indian Ocean. In paper III we also investigate the temporal genetic variation at one site and compare it to the small-scale genetic variation along a stretch of the Kenyan coastline. Some overall conclusions that can be drawn from my body of work are: there are genetic structures present in the western Indian Ocean even though the apparent lack of physical barriers. Major oceanic currents aid evolutionary dispersal patterns. A single geographic site need not be genetically homogenous or temporally stable. Island sites are genetically more homogenous than mainland sites.

In conclusion, there are clear and distinct genetic structures present especially in Siganus sutor, the most targeted fish for the artisanal fishery in East Africa.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2013. 43 p.
Södertörn doctoral dissertations, ISSN 1652-7399 ; 84
population genetics, indian ocean, siganus sutor, valamugil buchanani, scarus ghobban, connectivity, aflp, mtDNA, d-loop, CO1
National Category
Research subject
Animal Ecology
urn:nbn:se:sh:diva-22799 (URN)978-91-7447-729-0 (ISBN)978-91-86069-74-2 (ISBN)
Public defence
2013-09-27, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, 13:00 (English)

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2014-03-21 Created: 2014-03-21 Last updated: 2015-07-17Bibliographically approved

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