Aspects of the ecology and exploitation of the fishes of the Kosi Bay system, KwaZulu, South Africa.
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Date
1986
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Abstract
ln this study the exploitation of the fish fauna of the Kosi
estuarine system by man and natural predators is described
and estimates made of the off-take and its species
composition. The most important human exploitation, that by
the traditional Zulu fish traps, was monitored over a four
year period and the data collected were used to give an
insight into the marine fish populations of the system.
All the physical parameters, which it was thought could
influence the migrations of fish, were monitored and
correlations between these and the daily and monthly fish
trap catches were used to interpret fish movements into and
out of the system. Reasons for the annual migrations and day
to day movements of fish were investigated.
In order to establish relative off-takes by local fishermen
and sport anglers fish were tagged inside the system and the
recovery rates by the various fishing methods were used to
calculate estimates of the percentage off-takes of these
principal human exploitation methods. These data were also
used to obtain estimates of the population sizes of the major
marine fish species inside the system. Catch data were used
to indicate the levels of estuarine dependence of these
species. Where possible comparable data from other areas were
used to indicate whether or not similar trends in catch
abundance were obvious. The ecological and economic importance of the Kosi system
is discussed and its value to the local inhabitants stressed.
Competition between the various fishing techniques is
described and recommendations are made concerning future
fish exploitation. Natural predation rates are also discussed
and levels compared with those of other systems.
The fish food resources of the systems are considered in the
light of recently declining salinities, destruction of swamp
forests and increasing numbers of hippopotami. The
implications of these changing factors are discussed as is
their impact on the Kosi Bay fisheries.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1986.
Keywords
Estuarine ecology--Kwazulu-Natal--Kosi Bay., Fishery resources--Kwazulu-Natal--Kosi Bay., Theses--Zoology.