the role of tourism in natural resource management in the okavango ...

Fish populations in the entire Okavango River Basin are much smaller than in many
other freshwater systems. This is primarily due to the river water's low nutrient levels
which, means that there are fewer algae and planktonic plants that would normally
provide an abundance of food for fish in richer waters. Fish biomass is extremely
variable from one habitat to another but an average of approximately 120 kilograms
of fish per hectare is probably a reasonable estimate of fish stocks in the Panhandle,
while much of the Delta supports an average of between 100 and 200 kilograms of
fish per hectare. Fish stocks in most other healthy river systems and floodplains are
two to four times higher (Mendelsohn and el Obeid, 2004).
Fish stocks in the Okavango Delta are generally thought to be in good health, and
fish populations are generally not over utilised. The number of people catching fish
in the Delta is less than half the total on the Kavango River in the Caprivi Strip, and
large areas of the Delta are simply not accessible to fishermen. It is also likely,
however, that the succession of years with relatively low flows over the past two
decades has had a substantial effect on fish numbers. With smaller floods and
f100dplains remaining inundated for shorter periods, fewer fish would have produced
eggs and the survival rates of fish fry would have dropped. This relationship between
fish yields and flood levels has been established in many African wetlands, but more
research is needed to understand the impacts of human fishing pressures and
patterns of flooding on fish populations in the Okavango (Mendelsohn and el Obeid,
2004).
5.3.3.2 Soil Resources
In one form or another, soils are important to all life in the Delta, and the Okavango
River Basin as a whole. They provide the medium from which plants obtain water
and nutrients, and the properties of the soils determine what plant species are
present and hence the value and diversity of vegetation communities. Soil properties
differ in terms of their depth, structure and chemical composition, and these impact
upon the amount of water soils retain, the depth to which roots extend, and what
nutrients are available. These factors are particularly relevant to crop cultivation, and
the generally poor quality of soils in the Okavango region has major impacts on the
types of crops grown and their yields (Mendelsohn and el Obeid, 2004).
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