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The study aiming to explore the impacts
of the sea weeds invasions on the availability of fishes in the Lake Victoria.
The chapter have seven aspects which
including; the back ground of the study, statement of the problem, objectives
of the study, research questions, scope of the study, significance of the study and the definitions of the term
used in the study.
1.2 Back ground of
the study
Lake
Victoria is the largest fresh water lake in the word, spanning over 688000km2
and fall under the jurisdiction of Tanzania, Uganda, and Kenya; (Burs, 2015,
p.6). (Muguti, 2013, p.1) cemented that, the lake occupying the upper watershed
of Rwanda, and Burundi through river Kagera and Nile river basin; The lake lies
between 2.5̊ S and 1.5̊ N latitudes and Longitudes of 32̊ W and 35̊ E of
Equator. The lake occupy catchment area
of 250,000 km2
The majority of
this jurisdictions falls under Tanzania and Uganda rules whom they control Tanzania
51% and Uganda 43% of the lake respectively, the report (2014, p.10) show that
Lake Victoria is shared by also Kenya for 6%, and is the largest tropical lake.
Its shore line approximately 3450km long, where by Tanzania 33%, Uganda 51%, and
Kenya 16%.
Historically,
lake Victoria originated as a results of region tectonic tilting as estimated
to 400000 years old, it arose from a dry landscape 14600 a calendar years ago
(14.6 ka) with an extremely highly primary production in its first 50years,(
Munguti, 2013, Pp1)
This body of
water named after Queen Victoria of the United Kingdom (UK) by then, by John
Hunting Speke who was the 1st European to sight the lake 1850`s.
About 80% of
its water comes from rains, 20% from small streams flowing into the lake, (UK,
Report of 1874).
Lake Victoria
supports more than 20000 marine fishes species, the major groups includes
Dagaa55.4%, Nile, 27.3%, Haplomines 8.0 % and Tilapiines 6.5% by URT, (2014,
P.10).
The lake
accommodates more than 200000 fishers, where by Tanzania 49%, 31% Uganda, and
20% Kenya these data was at the beginning of 2014, and up to the of 2014
fishers and processors in industries
were more than 600000. By Turyheebwa, (2014, p. 7).
All these
communities earn their daily cakes from the Lake Victoria, however the
surviving of population depending on the fish harvest in the lake.
Apart from fishes as among component of ecosystem in
Lake Victoria there also other marine communities like lake weeds, and macro
plankton plants which acting as aquatic parasites,
they always sharing the same nutrient, foods through both photosynthesis, and feeding from lake edible species,
as food webs
These days it is common to observe varieties of majority
planktons in lakes, seas, river banks and oceans.
Always these aquatic plant species attached in
any objects like stones, logs, and most of them floating freely in and on the
water surfaces but also leafs overlap
the top of seas, lakes, rivers and ocean surfaces. The situations leading to
the green surface water, and sometimes prevent the penetration of sun light,
heat, and other forms of energy from the sun. The green
overlapping surface absorb all the carbon from the surroundings, and
when decaying the release carbons monoxides beneath the lakes and hence affect
the fishes, and other marine ecosystems because
it lead to oxygen holes or gaps which are vital
for the surviving of marine organisms. Because of this situation, the
reproduction of fishes decreasing rapidly and this threatening to days’ and
tomorrow’s availability of fishes in many lakes including Lake Victoria.
The
rapid increase of sea weeds in the Lake Victoria triggering on decreasing of
fishes daily; example Fish stock trends
in Lake Victoria Fish stock assessment in the lake from 1969, has been
affected by the invasive see weeds (Biomes), hydroaustic surveys from 1999 shown
that Nile perch and Dagaa are rapidly decreased relative about 2.1 million
tons, as cited in (Kayanda et al., 2010) by. Nicholas, (2014, p 40),
while average of Rastrineobola agent area had increased over, 1 million between
2005- 2008 Nile perch communities declined from 1.9 million tons in
[Source, Nicholas, (2014, P, 41)]
Changes
in the biomass of (a) Nile perch and (b) Rastrineobola
argentea
(Dagaa),
in Lake Victoria, 1999-2008. The Grey shading represents total biomes, Red
point stand for species biomass, (± standard deviation)
Because of these squabbles, we need to a research so as to
find the possible solutions against the invasions of seaweeds in Lake Victoria.
Globally, the Alga detected in Japan before 1960`s
on spat of the oyster crassostreagigas. Meinesz, (2007, P. 1)
Brown Seaweed Sargassum Muticum
detected in 1973 on the Isle of Wight (South Coast of Britain), two years later
before its discovery on the south side of the English Channel at Saint
Vaast-la-Hougue France.
In 1984, Green algae
(Caulerpa texifolia) were firstly detected in Monaco as an invader beneath
a public aquarium where it was cultivated. Meinesz,
(2007, P.3)
These green algae might have been carried from the
Red Sea by Currents (more than 2500km from Monaco) or was a native from
Mediterranean sea as a : “Metamorphosis”
of Caulerpa Mexicana sonder exKÜtzing
kwon on the eastern shores of the Mediterranean sea nearly 3000km from Monaco
since 1945. By Meinesz, (2007, p.3)
As cited in (Silvar et al.2002 and Valentine &
Johnson., 2003) Undraria Pinnatifida detected in
Europe in 1971 especially in United Kingdom (UK), North Atlantic Ocean in Britany,
Netherlands, New-Zealand, Australia, Argentina ,Northern Pacific, and in Mediterranean Sea.
Similarly in 2000, a SCUBA diving scientist working
on marine Phaner Organisms in California (San Diego) discovered Caulerpatexfolia by chance. At the time of discovering
in California more than 1000m2 of the lagoon were already covered by
these species.
According to Otieno, (2015, P. 2) in Africa these
plants reported in Africa first in Egypt 1893. Examples of these weeds were
Eichhornia Crassipes Solon, is one of the most preralent invasive aquatic
plants known to cause major ecological, social and economic changes in marine
ecosystems. (Namibian Research Institute ‘University students’ 2000, P.2) reported
the Sea Weeds that, seaweed belong to one of the primitive groups in plant
kingdom- the Algae. They attached to different objects or freely floating, they
grow at varying depths in the sea.
In East Africa, aquatic weeds species particularly Eichhorniacrassipes preralent entered Lake Victoria through River
Nile from Egypt on 1893 and by 1990`s it had spread throughout African fresh
water lakes.
Oyono & Otieno,(2015, P.2) shows that, Water Hyacinth entered lake Victoria in 1989 via
Kagera River which has its mouth in the Ugandan portion of the lake Victoria
which is a source of Nile River and therefore hyacinth penetrated the lake from Egypt through Nile channels
These hyacinth commonly in tropical and sub tropical
water bodies where a nutrient levels are often high due to agricultural runoff,
deforestation, and insufficient waste water treatment. As cited in (Ntiba ,et, al.
2001) by Oyono and (Otino, 2015) Water hyacinth has very high growth rate that
it double its area in only five days and this is why it threatening the
surviving of fishes and need to be studied immediately in lake Victoria now.
Water hyacinth has social, economic and
environmental impacts, negatively affect the water quality.
Gichuki, et, al, (2010, p.1) observed that aquatic
species especially Macrophytes dynamics in
Nyanza Gulf of lake Victoria is ongoing since 1990`s after the invasion of
water hyacinth. Maccrophytes are higher plants grow in water or soil. It is
commonly along shores of water bodies like dames, lakes and along river banks
Source from the field:The world
map showing areas affected by sea weeds
Santa Catarina Coast,
Brazil, showing the sites affec
Statement of the research
The
question of sea weeds invasions on many world lakes now become a questions of
every one, every country in the world. The majorities of sea weeds are now
spread rapidly in many oceans and lakes including Lake Victoria. Examples of
marine planktons are blue algae, green algal, brown algal, red algal, Macrophytes, Water Hyacinth, Eichhorniacrassipes preralent, and Caulerpatexfolia (Green algae). The major focus of
the study is to assess on “The impacts of the Sea weed invasions on the
availability of fishes in lake Victoria; case study of Nyamagana district”.
The sea weeds is the independent variable, this mean that all Sea Weeds
manufacture their own food (Autotrophic organisms),through photosynthesis, and any changes within the sea weed populations in the
lake Victoria leading to changes on the availabilities of fishes in the lake,
where by these changes can be positive or negative changes. The availability of
fishes in the lake Victoria is the dependent
variable, this indicating that
the breading, increase, and survival of fishes is highly influenced by
presence or absence of weeds in the lake. Since both sea
weeds and fishes feeds nutrients like minerals, and tend to feed each other, fishes feed on planktons, receive oxygen
exhaled by planktons, overcrowded weeds form the green surface hence prevent
penetration of light from the sun, and if died and decayed produce carbon
dioxide gas which affect and threat the surviving of fishes in lake Victoria
Reasons for doing the
research includes; to find out the reason behind the current deficient of
fishes in lake Victoria, to search how
overflow of the sea weeds in lake Victoria affects fish breading, surviving of
the already existing and its availability, the impacts of the decreasingly of fishes
yields on the social, health, and economic stability of the surrounding
communities, and lastly to suggest out the possible solutions to minimize, or to end the problem of sea weeds invasions in lake Victoria
particularly Nyamana… Luchelele zone
Research gaps are openly
appeared in the following researches, The British research
Of (1974) indicated that
the only source of fishing stock decline in the Lake Victoria is the use of
Gill Nets Meshes, which tend to capture eggs, fetus / fetus and big fishes.
Therefore they ignored
other factors like agricultural activities, invasions of sea weeds in the lake,
and impacts of climatic changes.
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