Browsing by Author "Nehemia, Alex"

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Anthropogenic activities along the lake nyasa catchments alter the habitat and genetic diversity of a lake salmon, opsaridium microlepis
(Heliyon, 2024) Nehemia, Alex; Mwakalesi, Alinanuswe J.
The Lake Salmon, Opsaridium microlepis is an economically important fish along the Lake Nyasa. However, the species is under threat of extinction due to anthropogenic activities such as agri culture, mining, urbanization, and deforestation. Consequently, the fish species is currently regarded as a threatened species, and the International Union for Conservation of Nature (IUCN) has red-listed the species due to an apparent decline in abundance. The current study assesses the potential impact of human activities on the genetic diversity of O. microlepis using partial mito chondrial cytochrome oxidase subunit I (COI) sequences and microsatellite loci. The results indicate that genetic diversity is lower in the areas affected by human activities compared to relatively pristine areas. The results from this study may suggest that human activities taking place in the catchments are likely to contribute to the alteration of the genetic diversity of O. microlepis species. Thus, immediate measure is required to control anthropogenic activities in the areas to protect the species and other aquatic organisms from possible threats of extinction.
DNA barcoding reveals endangered and protected elasmobranchs in Tanzanian fish markets
(Western Indian Ocean Journal of Marine Science, 2023) Rumisha, Cyrus; Simwanza, Rehema J.; Nehemia, Alex; Mdegela, Robinson H.; Kochzius, Marc
Western Indian Ocean countries have banned elasmobranch finning and enacted legislation to of Marine Science 22(1): 57-65protect endangered elasmobranchs, however finned and morphologically deformed specimens [doi: 10.4314/wiojms.v22i1.6]are still landed and traded on Tanzanian fish markets. Such specimens are difficult to identify Received:morphologically, and it is possible that protected elasmobranchs are among these. This study September 19, 2022used DNA barcoding to uncover protected elasmobranchs in 102 specimens traded on Tan- Accepted:zanian fish markets. The sampled specimens revealed 23 elasmobranch species, 12 of which April 04, 2023(52.1 %) were classified as endangered (EN) or critically endangered (CR) on the IUCN Red List. Published:Three of the identified species (great hammerhead Sphyrna mokarran, oceanic whitetip shark June 16, 2023Carcharhinus longimanus, and pelagic thresher Alopias pelagicus) are protected by Tanzanian laws. Copyright:Hence, it is advised that steps be taken to strengthen law enforcement at landing sites and fish Owned by the journal.markets in the country. Furthermore, the Third Schedule of Fisheries (Amendment) Regula- The articles are open accesstions of 2009 should be updated to include 11 EN and CR elasmobranchs that are not on the list. articles distributed underAdditionally, national and regional elasmobranch conservation plans should be developed to the terms and conditions of the Creative Commons Attribution (CC BY 4.0) licence. prevent the exploitation of endangered elasmobranchs.
DNA barcoding validates new sightings of tridacna elongatissima in Tanzania and Mozambique (Western Indian Ocean)
(Springer, 2022) Velkeneers, Xander; Dissanayake, P. A. K. N.; Huyghe, Filip; Nehemia, Alex; Ratsimbazafy, Hajaniaina Andrianavalonarivo; Kochzius, Marc
There are currently 12 recognised extant species of giant clams (Cardiidae: Tridacninae) inhabiting the tropical waters of the Indo-Pacific. Six species have been newly described or rediscovered since 1982, such as the recently resurrected species Tridacna elongatissima in the Western Indian Ocean. In order to investigate the distri- bution range of this species, 24 specimens have been col- lected and identified by DNA barcoding. This study provides the first record for T. elongatissima in Tanzania and expands both the northern (Zanzibar, Tanzania) and southern (Ponta de Ouro, Mozambique) ranges of this species.
Genetic erosion in the snail littoraria subvittata (reid, 1986) due to mangrove deforestation
(Journal of molluscan studies, 2016) Nehemia, Alex; Huyghe, Filip; Kochzius, Marc
In tropical coastal ecosystems mangrove forests are important as feeding, spawning, breeding and nursery grounds for many marine species. High human population pressure in coastal areas has led to the loss and deterioration of mangrove habitats. Solar salt production can affect these habitats along the East African coast. Littorinid snails live on mangrove trees, forming an important component of the mangrove ecosys- tem and have been used as bioindicators of environmental health and community stress. Littoraria subvittata is the most abundant littorinid species in mangroves along the East African coast. Partial mitochondrial cytochrome oxidase subunit 1 (COI) gene sequences of 298 individuals were used to assess the impact of mangrove deforestation at salt ponds on the genetic diversity and structuring of L. subvittata populations, as well as to infer the demographic history of the species. Nucleotide and haplotype diversities were found to be lower in samples from mangroves at salt ponds than in samples from natural mangroves. The mean nucleotide diversity was 0.049 ± 0.036% and 0.115 ± 0.068% in mangroves at salt ponds and natural mangroves, respectively. The mean haplotype diversity was 0.23 ± 0.14 and 0.50 ± 0.14 in mangroves at salt ponds and natural mangroves, respectively. Analysis of molecular variance (AMOVA) detected a sig- nificant population structure (Ф st = 0.049; P < 0.0001) for the combined populations. Hierarchical AMOVA detected a significant population genetic structure only between populations from mangroves at salt ponds and natural mangroves (Φ ct = 0.022; P < 0.05), but not between any other groupings. Populations from natural mangrove sites showed a significant genetic structure (Ф st = 0.054, P < 0.0001), while populations from sites at salt ponds could not be differentiated (Ф st = −0.0026, P = 0.64). Reduced effective population size was observed in most samples from mangrove sites at salt ponds compared with natural mangrove. The direction of migrants was mostly from salt ponds to natural mangroves. These results show that salt ponds have a negative impact on the genetic diversity of L. subvittata populations and modify the population’s genetic structure.
Length-Weight relationship and condition factor of tilapia species grown in marine and fresh water ponds
(Agriculture and Biology Journal of North America, 2012) Nehemia, Alex; Maganira, Justin D.; Rumisha, Cyrus
The aim of this study was to describe the differences in Length-Weight relationship and condition factor of Tilapia zillii and Oreochromis urolepis urolepis reared in full strength sea water (FSSW) and fresh water (FW) ponds. The environmental condition in FSSW and FW ponds were also analyzed to determine their impacts on Length-Weight relationship and condition factor on both species. The regression coefficient "b" exhibit negative allometric growth in FW and positive allometric growth in FSSW for both species. The value of exponent "b" and condition factor (K) for T. zillii in FW and FSSW (in the bracket) were found to be 2.94 (3.3) and 2.07 (0.74) respectively. On the other hand the value of exponent "b" and condition factor (K) for O. urolepis urolepis in FW and FSSW (in the bracket) were found to be 2.81 (3.46) and 0.86 (0.53) respectively. Though both species performed well in FW, the study also revelead that farming of these tilapia species in FSSW can be feasible if water quality parameters are properly monitored.
Population expansion but limited gene flow in kuhl's blue-spotted maskray along the Tanzanian coast
(2024) Nehemia, Alex; Shabani, Maulidi; Malisa, Allen Lewis
The blue-spotted maskray Neotrygon kuhlii (Müller & Henle, 1841) is a member of the Dasyatidae family of stingrays which grows slowly. Members of this group mature late and have a low fecundity rate. The ICUN Red List of Threatened Species lists N. kuhlii species as data deficient (DD) because information on its ecology and life history is not readily available. The purpose of this study was to determine the genetic diversity, demographic history and population structure of N. kuhlii, all of which are critical information for efforts aimed at conserving the species. The investigation was carried out along Tanzania's coastline using 595 base pairs of partial mitochondrial cytochrome oxidase subunit I (COI) sequence. The haplotype diversity ranged between 0.37 and 0.70 and nucleotide diversity between 0.11% and 0.50%. The findings show that samples from Unguja had higher mean molecular diversity indices than those from other sampling sites. Nonetheless, samples from Mafia and Unguja were found to have the largest effective population size. Genetic variations were found between the subpopulations under study, suggesting limited genetic connectivity among the studied subpopulations. The COI sequences of N. kuhlii from most subpopulations studied showed signs of past population expansion, which are typical for most Western Indian Ocean (WIO) fauna. The findings highlight the need for enhanced management and conservation strategies for N. kuhlii and other coastal stingray species in Tanzania, particularly in areas where sampling sites showed low levels of genetic diversity and effective population size.
Population Genetic Structure and Demographic History of Opsaridium microcephulum along Lake Nyasa
(University of Dar es Salaam, 2023) Nehemia, Alex; Mwakalesi, Alinanuswe J.
The Sanjika, Opsaridium microcephalum is among the fish species that serve as a major source of proteins and income to people along Lake Nyasa. However, the information on its genetic diversity and structure particularly in the Tanzania part of the Lake is limited. Therefore, the assessment of the genetic diversity and structure of O.microcephalum along the Lake Nyasa part of Tanzania was conducted in the current study using a fragment of the mitochondrial COI gene from 92 individuals of O. microcephalum. The findings showed that an average haplotype diversity and average nucleotide diversity were 0.8065 ± 0.0314 and 0.002380 ± 0.001640, respectively. The molecular Variance (AMOVA) indicated significant genetic variations among the subpopulations studied (Overall Φst = 0.31560, p < 0.001). The lowest haplotype diversity was recorded at Manda and the highest haplotype diversity was recorded at Buloma. The lowest nucleotide diversity was recorded at Manda and the highest was recorded at Lupingu. The differences in genetic diversity can be a possible indicator of different localised evolutionary forces that require attention to conservationists for the sustainable management of O. microcephalum.
Survival and Growth of Tilapia zillii and Oreochromis urolepis urolepis (Order Perciformes; Family Cichlidae) in Seawater
(wiomsa) Nehemia, Alex; Mmochi, Aviti J.; Mtolera, Matern S. P.