Wetland & Fish Ecology - Enviro Dynamics Namibia

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Acacia hebeclada subspecies tristis, Ziziphus mucronata, (buffalo thorn), Hyphaene
petersiana (makalani palm) and Combretum imberbe, (leadwood).
All trees that do not mind standing in water for short periods of time, found at the
edges of floodplains.
Terrestrial/floodplain species in the area that is alternately flooded or dry;
typical plants include:
Sedges, grasses like Eragrostris trichophora and lilies e.g. Dipcadi crispum.
Shallow water/pool rooted aquatic plants can be emergent, submerged, or have
floating leaves; typical plants include:
Marsilea ferns, Aponogeton junceus (waterblommetjies), Utricularia, and a variety of
sedges (Cyperaceae) and grasses that can grow in water like Diplachne amboesis.
Deep water pool species also rooted e.g. Nymphaea nouchali (waterlilies).
Saline pool and pan species in areas where little grows due to high salinity;
typical plants include:
Salt tolerant grasses such as Sporobulos iocladus and Odyyssea paucinervis.
In a detailed study of the iishana, over two wet seasons, from 1996 to 1997, Clarke
(1998a) found that early October rains of as little as 20mm was enough to wet these
pools and trigger hatching of Crustacea such as Triops, a tadpole shrimp, and
Lovenula falcifera, calanoid copepods that dominate the crustacean fauna.
Lovenula, like the other ephemeral pool crustacean are specially adapted to survive
in temporary waters, they can tolerate increasing temperature and water chemistry
concentrations as the pools dry and even more importantly can complete their lifecycles
within 3-4 weeks enabling them to lay drought resistant eggs before the pools
dry out (Bethune, 1982). These pools typically dried up within a few weeks, and
remained dry until the early January rains, which again triggered crustacea to hatch
as well as causing the first emergence of the aestivating bull frogs Pyxicephalus
adspersus. Some 44 different species of crustaceans occur in these pools, with
Lovenula falcifera, a calanoid copepod, as the dominant species (Clark 1998a,
Clark & Rayner 1999), (See list of Crustacea and where they occur in Appendix 2b).
Invertebrate species from the Cuvelai, based on museum records show that 60
crustaceans including16 endemic ostracod species are known from the
Cuvelai/Etosha system (Curtis et al. 1998). Eleven snail species have been recorded
(Curtis, 1991, Curtis et al. 1998).
The rains normally continue through January, February and March, keeping the pools
filled and with time attracting insect invertebrates too (Clark, 1998b). Some 72
species of aquatic insects including 4 endemic beetles have been recorded from
the Cuvelai system (Curtis et al. 19980. A more recent study on the aquatic
Draft Environmental Impact Assessment: Oshakati Flood Mitigation Project
Specialist Study: Wetland Ecology and Fish Ecology Imputs
July 2012