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Diversity, Abundance and Feeding Ecology of
Mangrove Crabs in Cameroon
Simon. N. Longonje
University of Buea, Cameroon
Email for correspondence: nlongonje@yahoo.com
Abstract
The diversity and abundance of crab species was studied
in the Cameroon estuary mangrove. Five zones located
from landward to seaward fringes were sampled twice a
month for 6 months, using standard excavation and crab
catching methods. In each zone 10x10m plots were
sampled and 1m 2 quadrat excavated. In total, 1,349
crabs in 13 species were recorded. Five species were
Sesarmidae (38.5%), four species were Grapsidae
(30.8%), two species were Ocypodidae (15.4%), one
species was Portunidae (7.7 %), and one species was
Gecarcinidae (7.7 %). Uca tangeri (Ocypodidae) and
Goniopsis pelii (Grapsidae) were the dominant species,
constituting 44.1% and 21.9 % respectively. The
dominating species in mudflat, young forest and
landward fringe were Uca tangeri, Goniopsis pelii and
Cardisoma respectively. The feeding ecology of several
species of mangrove crabs was studied through
tethering experiments and gut analyses. Feeding
preference was determined on fresh and senescent
leaves of Laguncularia racemosa, Avicennia germinans
and Rhizophora species while propagule predation was
investigated on Rhizophora mangle, R. harrisonii and R.
racemosa. Gut content analysis was done on
Metagrapsus curvatus, Sesarma huzardi, S. elegans, S.
alberti, G. pelii and Grapsusgrapsusto assess their
natural diets. The field observations suggest that 65.9%
of the propagules studied were predated and 71.3% of
the leaves damaged. Mangrove material was the main
component of crab’s diet: M. curvatus (45.4%) S.
elegans (55.0%), S. Alberti (62.5%), G. pelii (65.9%) S.
huzardi (47.8%) and G. grapsus (37.3%). Damage on
young mangrove trees was highly correlated to the
number of crabs on trees (r 2 = 0.75). The high damage
rate of mangrove materials indicate that crabs play a
significant ecological role in the functioning of the
mangrove ecosystem, by affecting mangrove
recruitment and biogeochemical functioning.
Assessment of Fauna Resources of Oli River Complex at
Kainji Lake National Park, Nigeria
Folusade Catherine Arowosafe
Federal University of Technology, Akure, Nigeria
Email for correspondence:folukate@gmail.com
Abstract
The Oli River of the Kainji Lake National Park provides
water for the wild animals throughout the year making
it a hotspot for ecotourism because of its unique
assemblages of flora and fauna more visible during the
dry season when the animals come for water at the
river. This research, focused on the natural resources of
Oli River complex. The resources in and around Oli River
were assessed. Oral interviews and Park records were
used in the process of data collection. The animal
diversity was assessed using direct and indirect
methods: the direct method used involved road count
method while indirect methods include faecal
droppings, footprints and calls. Random collection of
fish from different points in the river was used in
assessing the fish diversity. A total of 22 fish species in
11 families were identified. Animals identified around
the river include the Hippopotamus (24.2%), Kob
(16.7%), Roan antelope (16.7%), Duiker (10.6%), Reed
buck (4.6%), Warthog (15%), and Bird species (12.2%).
Findings revealed that there is concentration of effort to
reduce human activities such as poaching that could
affect the conservation of the animals found in the park.
As such management policies which allows game
viewing for tourist but do not permit sport fishing and
game hunting has gone a long way to meet the objective
of conserving the animals found in and around the Oli
River.
Keywords: Natural resources, Oli River, Ecotourism,
Conservation, Diversity
Keywords: Mangrove crabs, Community structure,
Feeding Behaviour, Biodiversity conservation, Cameroon
TAAG First African Student’s Conference, Nairobi. 2-4 July, 2013 21