Browsing by Author "Rumisha, Cyrus"

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    Mitochondrial DNA revealed a single stock structure of the Spotted sardinella Amblygaster sirm (Walbaum, 1792) (Teleostei; Clupeidae) in Tanzanian coastal waters
    (Springer Berlin Heidelberg, 2023-06-12) Fabiani, Godfrey; Mtonga, Cretus; Chauka, Leonard; Rumisha, Cyrus; Muhando, Christopher
    The Spotted sardinella Amblygaster sirm are small pelagic fish that are important protein source to coastal communities in the Indo-West Pacific. In this study, a cytochrome c oxidase subunit 1 (COI) gene of A. sirm from Tanzania was amplified to assess the species’ genetic structure and demographic history. All individuals collected were identified using both morphological examination and genetic barcoding as A. sirm. A total of 19 haplotypes were found in the dataset, with low overall nucleotide (π = 0.13 ± 0.001) and moderate haplotype diversities (h = 0.45 ± 0.07). AMOVA revealed a very low and non-significant genetic differentiation in the dataset (Fst = 0.002, Фst = −0.004, p > 0.05), indicating a lack of population structure. The minimum spanning haplotype network revealed additional evidence for the lack of population structure, which grouped all the sampled haplotypes into one cluster, regardless of their geographical regions. The Tajima’s D, Fu’s Fs tests, and mismatch distribution analyses supported a hypothesis of recent demographic expansion. The lack of population structure identified suggests that the fishery should be treated as a single-stock management unit, consistent with the existing management regime for the species in Mainland Tanzania that currently does not consider genetic structure in managing the fishery. The lack of population structure suggests that populations with low genetic diversity, such as Dar es Salaam, can rebuild by recruiting from other sites if regulations against unsustainable fishing are strictly enforced.
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    Population genetics of the hound needlefish Tylosurus crocodilus (Belonidae) indicate high connectivity in Tanzanian coastal waters
    (Taylor & Francis, 2023-07-13) Mgeleka, Said; Silas, Mathew; Mtonga, Cretus; Rumisha, Cyrus; Viinamäki, Elina; Polte, Patrick; Sköld, Mattias; Winder, Monika; Gullström, Martin
    . The hound needlefishTylosurus crocodilus(Belonidae) is a highly demandedfish in the localmarkets of Tanzania, but the growing coastal population threatens its sustainability. As belonidsare highly migratoryfishes utilising various parts of the seascape, increasedfishing pressuremay disrupt connectivity patterns on different spatiotemporal scales and disaggregatepopulations. Using the COI gene, this study assessed the genetic population structure,connectivity patterns, and historical demography ofT. crocodiluscollected in seven sites spreadalong Tanzanian coastal waters. Results showed fourteen haplotypes with low overallnucleotide and haplotype diversity. Pairwise FSTcomparisons revealed no significant differencesamongthesampledsites,exceptforthenorthernmostsite(Tanga)andanislandinthesouth(Songosongo). Analysis of molecular variance (AMOVA) revealed a non-significant geneticstructure among populations (FST= 0.01782), suggesting thefishery across Tanzanian watersexploits the same population. Moreover, there was no correlative relationship between geneticand pairwise geographic distances, rejecting the isolation by distance hypothesis. However,neutrality tests and mismatch distribution analysis revealed that recent demographic expansionmight exist. Empirical evidence of panmixia suggests high genetic connectivity. In combinationwith low genetic diversity, management shouldbe directed to actions that prevent geneticdiversity loss and the effect of genetic drift on populations.