Browsing by Author "Njiru, James"

Now showing 1 - 4 of 4
  • Publication
    Publication
    An Overview of Heavy Metal Pollution in the Western Indian Ocean (WIO) region of Kenya: A Review
    (Journal of Aquatic Terrestrial Ecosystems, 2023-06-20) Nyamora, Jane Moraa; Njiru, James; Nyakeya, Kobingi; Getabu, Albert; Muthumbi, Agnes
    This study is a review on heavy metal pollution in the Western Indian Ocean (WIO) region of Kenya. The review examines heavy metal pollution of copper, lead, cadmium, iron and zinc that are toxic to marine life and human health; and identifies gaps for future monitoring and assessment. Each pollutant was addressed in order to determine their status in the environment, sources and their effect on biological systems, marine organisms, and human health. Although the concentration levels of these metals are still low and within the recommended standards of global regulating bodies, there is little information in relation to their effects along the food web, human health and how they affect the population dynamics of fish species. Apart from regular monitoring and assessment further research on their effects in the food web and an assessment of human health is recommended.
  • Publication
    Publication
    Some aspects of the reproductive biology of Labeo victorianus (Boulenger, 1901) from Kuja-Migori River basin, Kenya
    (Journal of Fisheries, 2022-03-19) Kembenya, Elijah; Getabu, Albert; Njiru, James; Omondi, Reuben
    Labeo victorianus is an endemic species to Lake Victoria basin and also a species threatened with extinction status. This study investigated reproductive biology of L. victorianus from Kuja- Migori River basin, Kenya with a view to determining the length weight relationship (LWR), condition factor, fecundity, egg diameter gonado-somatic index (GSI), length at 50% maturity (LM50) and sex ratio. Sampling was done by electrofishing from January 2018 to June 2019. The LWR showed a negative allometric pattern (p < 0.05). The mean condition factor for combined sexes was 1.02. Fecundity ranged from 47842 – 101902 eggs (mean ± SD: 83663 ± 2605 eggs) and correlated highly with body size (r2 = 0.9137). Egg diameter ranged from 0.5 – 0.7 mm. Mean GSI was 6.3 ± 1.6 and 2.8 ± 0.45 for females and males respectively. The LM50 was estimated at 18 cm total length (TL) and 20 cm TL for males and females respectively. Sex ratio did not differ from the expected 1:1. This species has a high fecundity with small sized eggs and males attain sexual maturity earlier than females. The findings of this study provide useful information towards sustainable conservation of L. victorianus in the Lake Victoria basin.
  • Publication
    Publication
    Spatial-temporal composition, abundance and diversity of algal communities in River Malewa of Lake Naivasha Ramsar Basin, Kenya
    (Integrity Research Journals, 2022-04-30) Obegi, Beatrice; Njiru, James; Getabu, Albert; Gichana, Zipporah
    ABSTRACT: Algae and algal communities are potentially vulnerable to climate change and consequently can be depleted or be extinct hence the current debate on global biodiversity. Using a 30 µm phytoplankton net, triplicate samples were picked monthly from 10 stations in River Malewa from November 2020 to December 2021. A total of 360 samples were picked the whole study period. The study examined taxonomy, composition, abundance, diversity, and distribution. Counting and identification was done using Sedwick- rafter cell counting chamber with a Binocular compound microscope. Results indicated 89 species of phytoplankton were identified. 86 species were identified in the river while additional 3 more species were identified in the lake. Bacillariophyceae (Diatoms) dominated in lotic sites with 50%, Cyanophyceae was 17%, Chlorophyceae 16% and Myxophyceae was 6% while the least dominant was Euglenophyceae with 4%, Chrysophyceae (3%), Xanthophyceae, Rhodophyceae and Dinophyceae with 1% each. Two points at the lake showed a high dominance in Chlorophyceae with 63%, Xanthophyceae 21% and Chrysophyceae 14%, while Bacillariophyceae was 1% and the rest of the groups were 0%. The abundance showed RM1 and RM4 had abundance of 4.8 x 105 cells/mm3. Site RM9 and RM10 being lacustrine recorded highest abundance with 1.24 x 106 and 1.29 x 106 respectively. RM3 recorded abundance of 6.2 x 105 cells/mm3, RM3 was 7.3 x 105 cell/mm3 and RM5, RM6, RM7 and RM8 recorded abundance of 8.5 x 105, 9.2 x 105, 7.5 x 105 and 7.9 X 105 cell/mm3 respectively. High value of Shannon-Wiener's index (H ') was recorded in RM6 (1.556), followed by RM4 (1.521), RM7 (1.504), and lowest was RM 10 (1.141), RM5 (1.299), RM1 (1.398), RM3 (1.403), RM2(1.474) and RM8 (1.473). Management issues and effects of existing human pressures, such as damping, urbanization and nutrient enrichment on river ecosystems should be studied to fill gaps in knowledge on phytoplankton monitoring on rivers and streams.
  • Publication
    Publication
    Using the Multi-metric Index of Biotic Integrity methodological approach to determine the major river catchment that most pollutes a lake
    (Aquatic Ecosystem Health, 2021-12-20) Aura, Christopher; Nyamweya, Chrisphine; Njiru, James; Omondi, Reuben; Manyala, Julius; Musa, Safina; Owiti, Horace; Guya, Fredrick; Ongore, Collins; Ogari, Zachary; Mwamburi, Job; Health and Management, Aquatic Ecosystem
    We present the Multi-metric Index of Biotic Integrity methodological approach that allows for the ranking of major river catchments based on pollution status in the Kenyan portion of Lake Victoria, Africa. The study has a broader applicability to all of Lake Victoria, other African Great Lakes, and all lakes that have riverine discharge. The method presented utilizes water quality and environmental data, local knowledge, and pre-existing literature. The parameters considered were sampled from 2016 to 2018 during the dry season (July sampling) and the wet season (March sampling). Separation power of Mann-Whitney U test (p < 0.05) qualified 11 discriminant metrics for both macroinvertebrate and fish samples into the scoring system of 1, 3 and 5 in the formulation of final Multi-metric Index of Biotic Integrity methodological approach. Rivers in the northern section had lower Multi-metric Index of Biotic Integrity methodological approach scores, as compared to southern counterparts. The Multi-metric Index of Biotic Integrity methodological approach ranking herein was validated by community perceptions on pollution levels. River Nzoia catchment emerged as the most polluted, followed by River Yala, River Kuja, and Sondu-Miriu. Siltation, domestic washing, litter and refuse emerged as the main agents of pollution. Management authorities ought to reinforce a balanced utilization of the vital water resources to minimize future impacts, and promote catchment wide practices that ensure ecological health sustainability of the lake ecosystem.