As WBS pointed out some time back, we have fresh water shrimp in the Zululand area, and i have been trying to find some information regarding these shrimp. They seem to be Caridina nilotica, and i include a paragraph from the document, to be found at: http://eprints.ru.ac.za/159/01/slaughter-msc.pdf
(see page 81).
"3.1.8 Overview of Caridina nilotica distribution, life history and biology
Caridina nilotica occur in the rivers and lakes of southern Africa (Hart, 1981). The
genus Caridina is the only member of the Atyid shrimps in southern Africa (Hart,
1982). According to Barnard (1950) quoted by Hart (1983), the distribution of
C.nilotica in South Africa extends as far south as the Umzimvubu river and as far
west as Lake Ngami. Hart (1983) stated that specimens of C.nilotica had been
collected in the Keiskamma and Bushmans River (Eastern Cape), representing a
southerly extension of its distribution. In 1984, a further southerly extension to
C.nilotica distribution was determined when specimens were found in the Gamtoos
River (Coetzee, 1985). Hart (1983) found that C.nilotica have a temperature activity
range of 11,5 to 31,5 ° C and concluded that temperature tolerance may be a
significant factor affecting this organisms’ distribution. In southern Africa, shrimp of
the genus Caridina are ecologically important as herbivores and scavengers (Hart,
1981). C.nilotica has a specialised feeding system and feeds as a scraper of surfaces
of organic macrophytes and other substrates, feeding on microbiota (Hart, 1980). As
scavengers, the species may enhance the production of submerged macrophytes by
removing debris and epiphytic microphlora (Hart, 1981). These shrimp may also be
an important source of food for small fish (Hughes, 1992). C.nilotica comprises a
significant proportion of zooplankton in Lake Victoria (Hart, 2001, quoting Lehman
et al., 1996). Time from "˜egg to egg’ takes approximately three months (personal
observation and Muller, pers.comm., 2004) and individuals transform from male to
female with increasing age (Okuthe et al., 2004)."
A small dam near my house had an abundance of these shrimp, but at a recent visit, I did not see as many as before. My son remarked that they are more abundant in winter, I think his observation may be accurate.
Hope this information helps!