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Population genetics structure of juvenile Mugil cephalus around Zanzibar and Bagamoyo (Tanzania) reveals multiple genetic demes
Södertörn University College.
Stockholm University, Faculty of Science, Department of Zoology. (Ecology)
Stockholm University, Faculty of Science, Department of Zoology. (Ecology)
(English)Manuscript (Other academic)
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 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 Mugil cephalus collected from six sites around Bagamoyo (Tanzanian mainland) and Zanzibar Island, East Africa. Fish were caught in low tide using a seine net. All fish collected were juveniles with a total length ranging between 7 and 14 cm (mean length of about 10 cm). Samples were analyzed using Amplified Fragment Length Polymorphism (AFLP), and the Bayesian assignment test implemented in the STRUCTURE 2.2 software was applied to detect if sites were composed of several genetic demes. Our results indicate that all sites contain several different genetic demes suggesting that juvenile collection from a single site may neither harm the genetic diversity of wild M. cephalus nor reduce its disease resistance within an aquaculture system. By collecting juvenile fish from a single site one will in effect harvest juveniles from several genetic lineages.

Keyword [en]
Mugil cephalus, Population genetic structure, deme, Western Indian Ocean, aquaculture
National Category
Fish and Aquacultural Science
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-27397OAI: oai:DiVA.org:su-27397DiVA: diva2:214033
Projects
Sida-SAREC Marine Bilateral Programme between Sweden and Tanzania
Available from: 2009-05-01 Created: 2009-05-01 Last updated: 2010-01-14Bibliographically approved
In thesis
1. Fish community patterns in Tanzanian mangrove creeks
Open this publication in new window or tab >>Fish community patterns in Tanzanian mangrove creeks
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human beings have exploited the biota of mangrove systems for centuries and fish continue to be one of the main products harvested from these habitats. The assumption of mangroves functioning as recruitment areas for juvenile fish from neighbouring habitats such as seagrass beds and coral reefs is a common argument for conservation and management of mangrove ecosystems. Yet, mangrove systems are increasingly in decline worldwide primarily because of destructive anthropogenic activities. In the present thesis, fish assemblages in various mangrove creeks in Tanzania were investigated. Specifically, it dealt with the distribution, abundance and trophic structure of fishes in space and time as predicted by habitat characteristics and environmental conditions occurring naturally and following human-induced changes of clearing for construction of ponds for salt production and fish farming. In addition, the variation in population density and genetic connectivity of the economically important striped mullet (Mugil cephalus) was examined. In undisturbed creeks the fish abundance and assemblage composition showed inconsistent spatial patterns within and among different creeks that appear to be strongly influenced by species-specific responses to dominant bottom substrate types and to some extent to water depth and clarity. Seasonality had little impact on most fish assemblage variables. The genetic analysis showed mixed demes of Mugil cephalus and significant separation between Zanzibar Island and Tanzania mainland. Anthropogenic effects were found on the structural and functional organisation of fish assemblages resulting in lower densities, species numbers, diversity and number of trophic groups in the reservoirs compared to less disturbed sites. These changes in fish assemblage composition seem to be caused by an increase in salinity and water temperature as well as by the loss of refuge and feeding grounds. The findings in this thesis will contribute to coastal management planning for conservation and suggests integration of various activities (like fish farming and salt production) in order to maximise the economical use of deforested areas.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2009. 38 p.
Keyword
Mangrove ecosystems, fish assemblages, Mugil cephalus, population genetics, spatial and seasonal variability, human disturbance, East Africa
National Category
Natural Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-27168 (URN)978-91-7155-879-4 (ISBN)
Public defence
2009-05-27, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-05-06 Created: 2009-04-23 Last updated: 2009-05-05Bibliographically approved

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