April & August, 1999 
7 
christened "Minamata" disease because of the havoc it 
wreaked in Minamata Bay in Japan several years back 
Other point source pollution includes waste materials 
from fish smoking and slaughter houses and the literal 
dumping of solid wastes which arc returned to our 
beaches. 
Non-point source pollution results from materials 
earned into Lake Victoria by streams, nvers and surface 
run off. It is usually, however, more difficult to control 
It contains agro-chcnncal pollutants like pesticides, 
fertilisers, fungicides from agricultural areas along with 
huge amounts of nutrients, e.g , silt, nitrogen and 
phosphorus Often these chemicals have become 
indispensable in the agricultural industry which is highly 
developed around Lake Victoria. Oilier inland industries 
and factories arc guilty of this type of pollution by 
dumping their wastes into streams and rivers ihm 
finally discharge them into the lake 
In Kenya, sugar industries in iho western sugarbelt 
region like Mumias. Nzoia, Chcmilil, Muhoroni and 
South Nyanza Sugar Companies arc notorious for 
dumping effluents imo adjacent rivers like Nyando, 
Nzoia and Migori which end up in Lake Victoria 
Pollution in the lake has increased the rate of 
eutrophication which has resulted in die emergence of 
algal blooms through the increase of biological oxygen 
demand (BOD). These have in effect provided 
favourable conditions for the uncontrolled growth of 
the infamous weed, water hyacinth The water hyacinth 
has proceeded to colonise areas important to native 
aquatic plants and also hinders the penetration oi light 
to the under water surfaces-a factor csscntml for the 
growth of underwater plants This impacts negatively 
the food chain within the lake ecosystem and disrupts it 
substantially. 
The latest threat to the lake, the effects of which 
have been severely chronic with overwhelming and far- 
reaching implications, is the invasion of the lake by 
“alien" aquatic weeds like die Sahiniu vilxintu mnifMa. 
W/iier lettuce Pima stratioies and the water hyacinth 
Eichomia enusipes. These thice alien weed species 
have infested Lake Victoria at different times and to 
varying degrees. However, of the three nquntic weed 
species, water hyacinth stands tall ns the most 
widespread and threatening to the ecology of Luke 
Victoria and by extension to the lives of many people 
and animals. 
As attractive as it appears, with magnificently dark 
green leaves and beautiful blue/purplc flowers, its 
uncontrolled growth has resulted iti thick mats of 
vegetation which have, in effect, colonised more than 
half the of the lake surface The beauty of this weed is 
a complete irony when its hazardous effects are 
considered and it reads like a paradox of beauty for 
suffering. A member of the family Frintedcriaccac and 
a native of the South American Amazon basin, it is 
theorised to have been brought to tropical Africa mainly 
ns an ornamental plant and. of course, it has found its 
way into many lakes The success of this weed in Tropical 
lakes, including Victoria, is attributed to many factors. 
Firstly and most important, unlike the indigenous 
floating aquatic plants, which are in natural equilibrium 
with the parasites and predators in their environment, 
this alien species proliferates outside its natural habitat 
because it is freed from the controlling influence of its 
natural enemies. Secondly, the water Hyacinth has found 
a new-nutrient rich habitat in Lake Victoria because 
this lake, being highly polluted, has a correspondingly 
high degree of eutrophication. The above factors, 
combined with the rapid spread of the water hyacinth 
(both through stnlcns and large quantities of long-lived 
seeds), can rcsuli in the population sometimes doubling 
lit from 5 to 15 days. The water Hyacinth's spread in 
Lake Victoria is unmistakable, although it is more 
prevalent on the Kenyan and Ugandan waters and than 
on the Tan/aman side It is mainly due to the choking 
effect of this notorious weed that the problems of Lake 
Victoria have been brought to the attention of ihe rest 
of Ihe world, by both the print and electronic media 
after the hue and cry of local dwellers 
Over exploitation and misuse of the lakes resources, 
strictly speaking, docs not come per se. but is usually 
the unintended consequence of development For 
instance over-exploitation of the resources of Lake 
Victoria is one such major problem and threat that 
cannot be overemphasised. More often than not the 
resources in question arc either (ab)used or (mis)uscd 
to satisfy the short term gams of the exploiters 
Situated in a densely populated region, Ukc Victoria 
provides nutritious food in the form of fish and other 
edible aquatic species, thereby forming a socio- 
economic base for ihose living in the lake basin region 
Fish, being popular with the local people, has become 
an innocent victim of over exploitation Fishing lias 
tremendously increased over a period of years, usually 
with an impressive annual yield. The high yield in fish 
catch is heavily Influenced by the increase in catch ol 
Nile perch Nile perch Lares niloticus is consumed 
locally and also exported to markets within the European 
Union. Hence it is by far the most commercially 
i mponant fish species in Lake Victoria The increase 
m fish production has positively impacted the lake 
community as ii is an important protein source Over- 
fishing is attributed to not only die increasing demand 
of a growing populanon, but also to the sudden shift 
from traditionally harmless subsistence fishing methods, 
using traps, baskets, papy rus nets, hooks and spears, to 
technologically advanced, intensive, non-selective and 
highly sophisticated commercial fishing methods that 
employ the use of power boats, cotton, nylon and 
tnullifilatuent gill nets, bench seines and trawlers. The 
off-take of fish species is thought to be slowly exceeding 
the maximum sustainable yield (MSY), a factor that 
can effectively lead to their extinction 
The other problem of fishing and fisheries in Lake 
Victoria is attributable, to the severe alteration of the 
drainage basin tnrough agricultural, vcgetational. urban 
and industrial changes, often without due regard to the 
traditional breeding patterns and breeding regions of 
the fishes. A case in point is the building, by the Kenya 
government in the early eighties, of the Mbita Causeway, 
linking the main land and Rusinga Island. It is theorised 
