Articleshttp://hdl.handle.net/1834/912024-03-29T11:16:01Z2024-03-29T11:16:01ZImpact of Human Physical Disturbance on Mangrove Forest Structure at the Gazi Bay, KenyaKihia, C.M.http://hdl.handle.net/1834/107332021-05-19T06:15:19Z2014-01-01T00:00:00ZImpact of Human Physical Disturbance on Mangrove Forest Structure at the Gazi Bay, Kenya
Kihia, C.M.
Human physical disturbance is prevalent in mangrove forests of the Western
Indian Ocean. This study investigated the impact of human physical
disturbance on the structure of mangrove forests by comparing forest
attributes such as density, taxon richness, stem diameter and tree height
between disturbed and relatively undisturbed sites. Physical disturbance was
evaluated through tree harvesting intensity, roads and footpaths and other
human activities, such as digging for fish bait at the sites. Disturbed sites
recorded significantly (ANOVA, P<0.001) higher tree cutting intensity than
comparable undisturbed sites, corresponding to lower forest complexity and
changes in dominant tree species. Disturbance increased prevalence of
Avicennia marina and Ceriops tagal species at the landward margin of
disturbed sites. Disturbed sites also recorded significantly lower abundance
of harvestable trees and stand volume (223 stem.ha-1, 14.56 m3
.ha-1,
respectively) than undisturbed sites (288 stem.ha-1, 19.69 m3
.ha-1,
respectively). In addition, accessible sites recorded lower marketable trees,
heights, pole size classes (mazio 4-6cm, boriti >10cm) and species
(Rhizophora and Bruguiera), being dominated by juvenile and stunted
Ceriops and Avicennia. These results indicate that overexploitation of
mangrove forests affects the species composition and structural complexity
of the forest and hence may impair forest functioning and regeneration and
subsequently, sustainable exploitation. Thus, human physical disturbance
leads to exponential decline in forest complexity and requires management
intervention.
2014-01-01T00:00:00ZFisheries in the Southwest Indian Ocean: Trends and Governance ChallengesKimani, E.N.Okemwa, G.M.Kazungu, J.M.http://hdl.handle.net/1834/105142021-05-19T06:14:57Z2009-01-01T00:00:00ZFisheries in the Southwest Indian Ocean: Trends and Governance Challenges
Kimani, E.N.; Okemwa, G.M.; Kazungu, J.M.
Laipson, E.; Pandya, A.
This assessment presents an overview of the current and prospective fisheries in the context of other transnational issues that affect the Southwest Indian Ocean (SWIO) region. It also examines key governance challenges, as well as trade-offs that can be made in the short and long term to meet the needs and interests of local fisher communities, national governments, and the international trade mechanisms that shape the region’s maritime policies. Finally, it reviews the work of regional and global fishery organizations in managing the IO fisheries.
2009-01-01T00:00:00ZScleractinian Coral Fauna of the Western Indian Ocean.Obura, D.http://hdl.handle.net/1834/90072021-05-19T06:15:51Z2008-01-01T00:00:00ZScleractinian Coral Fauna of the Western Indian Ocean.
Obura, D.
Obura, D.O.; Tamelander, J.; Linden, O.
Scleractinian coral species surveys were conducted at
10 sites in the western Indian Ocean, between 2002
and 2006. Each site varied from approximately 50-200
km in extent and was sampled with from 7 to 27
dives. Accumulation curves based on successive
samples at each site were used to construct logarithmic
regression curves, which provide estimated species
numbers at each site at an arbitrary value of 30
samples per site, assumed to reflect the total number
of species. The highest diversity of corals was found in
southern Tanzania to northern Mozambique (from
Mafia Island to Pemba town), with 280-320 species
estimated per site. Species diversity was lower in the
central Indian Ocean islands (140-240 species) and
declined steadily to a minimum in northern Kenya
(150 species). These patterns are consistent with the
central coast (around 10oS in Tanzania/Mozambique)
accumulating and retaining species due to the South
Equatorial Current (SEC) and mixing/reversing
currents locally, respectively. The islands may have
restricted diversity due to low area but nevertheless be
stepping stones to the East African mainland coast.
Lower diversity northwards into Kenya may reflect
distance and low dispersal from the center of diversity
at 10oS, and poorer conditions due to the Somali
Current influence in the north. Observer effects and
unclear taxonomy of scleractinian corals may
significantly affect the dataset, as may faunal changes due to bleaching or other impacts at individual sites
during the course of the study. Finally, it is likely that
the diversity gradient northwards into Kenya is
replicated southwards into southern Mozambique and
South Africa, providing a means to test latitudinal
changes in diversity and species distributions.
2008-01-01T00:00:00ZMangrove conservation and management: a structural regime for the Kenyan coastline.Ouko, E.M.Manohar, S.http://hdl.handle.net/1834/89062021-05-19T06:15:34Z1998-01-01T00:00:00ZMangrove conservation and management: a structural regime for the Kenyan coastline.
Ouko, E.M.; Manohar, S.
Hoorweg, J.
Structural attributes of mangrove forests; were studied at Shimoni, Gazi, Mida Creek and Ngomeni swamps along the Kenyan coast. The study was conducted using the transect method and the diameters, densities, forking, tree height, crown diameters and regeneration of mangals were recorded. The mangrove stand at Shimoni had the highest complexity index of 20.17 while Ngomeni, Mida Creek and Gazi stands had complexity indices of 14.49, 12.29 and 5.97 respectively. Shimoni had the highest M.S.D. at 17.7cm. Both Mida Creek and Gazi with M.S.D. ofS.9cm and 7.7cm respectively were ranked higher d1an Ngomeni which stood at 7.Ocm and indicated that Ngomeni harboured a young population. R. mucronata, A. marina and C. tagal had the highest Importance Value Index (l.V.!.) within the four stands except at Shimoni where B. gymnorrhiza was ranked second to R. mucronata. The lowest ranked species were S. alba, X. granatum and L. racemosa with an exception only at Shimoni where S.alba was ranked third. L racemosa was absent in Shimoni, Gazi and Ngomeni swamps. The results of this study indicate that there is an urgent need for a multi-disciplinary approach for the conservation and management of this complex mangrove ecosystem.
1998-01-01T00:00:00Z