Nile Perch in Lake Victoria

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Introduction
Lake Victoria is largest lake in Africa, seventh largest in the world by volume. And second largest freshwater lake in the world. (PRINGLE, 2005) The lake is surrounded by three different country’s Tanzania, Uganda and Kenya. Figure 1 depicts Lake Victoria and the surrounding countries. All three countries share the lake and its resources, but one of the biggest issues is that the governing laws involving the resources and the lake regulations are different in each country. (Lowe-McConnell, 1994) As an economic stand point the lake produces an annual catch of roughly 400-500,000 tons of fish bringing in around US$250,000-500,000. (Blake, 2005) The lake itself has around 2 million people that either directly or indirectly depend on fishing activities to support their lives. Lake Victoria is the head waters to the Nile River. The Nile perch (Lates niloticus) can be distinguished by their silver coloring and blue tint. They have sharp black eyes which are surrounded by a luminous yellow outer ring. The juvenile Nile perch can be seen with very dark markings beaming from their eyes with extensive dark markings on their body which in time will fade with age. (Blake, 2005) The female Nile perch generally grows larger than the male. Certain bones such as the pre-opercle and pre- orbital are guarded with spines. The Nile perch is known to grow extremely fast during the first year of existence. (Blake, 2005) The growth rate begins to decrease throughout the next four years of life. The Nile perch was introduced into Lake Victoria in the 1950s from lakes Turkana (Kenya) and Albert (Uganda) where it is native. This date is heavily debated. Unlike many introductions, which occur by accident or are made quietly by private citizens, the introduction of Nile perch into Lake Victoria was put in action by the highest levels of the British administration in colonial East Africa. (PRINGLE, 2005)Scientists and ecologist both tried to convince the government that the introduction of the Nile perch would have long terms effects on the ecosystem. The eventual introduction of the Nile perch represents the failure of ecologists to communicate and implement their vision for Lake Victoria. (Schwartz, 2006)Although this failure was at least partially due to the lack of knowledge of the government who wanted to help the economy more than anything. The purpose for the introduction of the Nile perch was to widen the range of a sporting fish, to add edible fish and to strengthen the economic productivity of Lake Victoria's fisheries, which had until then rested on small tilapia and cichlids. (Chege, 1995) The dark side to this introduction was the real purpose of this fish was to wreak havoc on the cichlid population. Within a few years people started to notice that the Nile perch was really started prey ravenously on the haplochromines cichlids. (Furney, 2013) In fact, they did this so efficiently that entire species began to disappear before the eyes of frustrated ichthyologists; many species vanished before they could even be formally described. With the Nile perches has effectively caused the disappearance of about 40% of the roughly 500 haplochromine cichlid species (PRINGLE, 2005). Haplochromine meaning, any cichlid of the tribe Haplochromini. (Dictionary.net) The industrial fishing operations around the lake have sky rocketed. In the early 1990 the Nile perch yields are starting to declined due to intense fishing,
Overfishing
Nile perch stocks in Lake Victoria have declined dramatically since the time of the fish population boom. The main cause for this over fishing is the high amount of industrial fishing plants. Ten factories around the lake have closed and the remaining 25 are operating below capacity, according to the Jinja, a Uganda based inter-governmental organization. At the Department of Economics at University of Dar es Salaam (UDSM) several researchers have studied the problem with over fishing in general and the Lake Victoria fisheries in particular. (Blake, 2005)
Economic boost
Introduction of the exotic Nile perch into Africa’s Lake Victoria accelerated decline of the diverse, cichlid species and altered food web structure, but created valuable fisheries. As the Nile perch population expanded and predation rates increased, many of the endemic fish species disappeared, total fishery yield increased nearly fourfold, and fishery-related employment approximately doubled although it is perceived as an ecological disaster by scientists, the introduction of the Nile perch is viewed as an economic booster by successful businessmen and powerful government officials. Hauled by the ton from the open lake by large, commercial boats, the fish are sold to nearby foreign-owned processing plants where they are rapidly cleaned, filleted, boxed and frozen, and sent off to prohibitively expensive restaurants in Nairobi and to the delicacy freezers of stores in the Middle East and Europe. The Nile perch has indeed become a money-spinner. The introduction of the Nile perch has had a significant effect on the fishing industry. Not only has this species produced an increase in complete fishery, it has also helped increase employment with fishery- related jobs as well. Large factory fishing corporations have prospered greatly due to the development of the Nile perch. (Chege, 1995)
Ecological Role: The Nile perch plays a major role on the predation of the remaining fish species in Lake Victoria the Nile perch has had a devastating impact in its initial and introduced habitats. They feed on their own species as well as others, including crustaceans, mollusks and insects. As the fish matures its appetite increases. This ravenous creature now searches for larger fish than the usual minute supply. This ability to prey on different size fish enables it to dominate many habitats and have a catastrophic effect on the many species it encounters as it moves from area to area in search of food.

Issues/Problems The introduction of the Nile perch into Lake Victoria has had a catastrophic effect on the ecosystem. The eutrophication of the lake is starting to occur with the decrease of algae eating fish, the algae is growing at an alarming rate, there by choking the lake. The increasing amounts of algae, in turn, increase the amount of dead plant material) that falls to the deeper portions of the lake before decomposing. As a by-product of this the oxygen levels in the deeper layer of water are being depleted which in turn is producing dead zones that are popping up for often. With all the industrial pants hundreds of fish native to the lake have become extinct, by the 1980’s, 300 of these fish were nonexistent. (PRINGLE, 2005) The Nile perch also carries numerous parasites in its gills and different areas of its body, which can lead to the spread of disease among other species resulting in the loss of biodiversity. (Schwartz, 2006) In addition to the degradation that is caused by the Nile perch through competition, predation and parasites, is the increase in deforestation in the region, due to the large quantities of firewood that are required to dry the fish. (Blake, 2005)
Management
Due to their rapid reproduction and dominating force in their habitats I strongly rank this threat as highest priority. According to the IUCN’s Invasive Species Specialist group the Nile Perch is considered one of the world’s worst 100 invasive species. (Blake, 2005) If dramatic measures are not taken to eliminate this species, they will continue to cause ecological disaster.
Control Method Commercial fishing activities are currently the only control method for the Nile perch in Lake Victoria. (Blake, 2005) Recently there have been signs of over fishing. Over the past twenty years, the quantity of the Nile perch caught in Lake Victoria as a percentage of total fish caught have slowly been declining. The average size of the Nile perch has also declined over this period. In addition, several species of fish that were decimated by the introduction of the Nile perch into Lake Victoria are showing increasing populations. (Rapport, 1995) Some off the key aspect of management that need to put in place or continued are as followed
 International cooperation is necessary in order to make Lake Victoria’s resources sustainable. In 1992, representatives of Kenya, Tanzania and Uganda formed the Lake Victoria Organization to co-ordinate rescue efforts. One of these efforts is aimed at the cichlids. To save these tiny fish from further extinction. (Chege, 1995)
 Conservation of habitat and biodiversity will only succeed if water quality is improved – Stricter laws on the industrial sites, need to be enforced to help keep the nutrient levels and toxic contamination at a safe limit.
 Stock management strategies linked to regulation of fishing effort are needed. The Nile perch has established itself a top fish food chain in Lake Victoria, and in order for the Nile perch to be a sustainable option for Africans, the fishing regulations need to be controlled better.
 Representative habitats in the lake should be conserved with focus on high diversity areas. The Cichlid species should be the main focusing point. The Cichlid species have adapted too many changes within Lake Victoria, and in order to keep what Cichlids species remain around the conservation of the ideal habitat needs to be protected more.
Conclusion
Ecological changes in this system now occur rapidly, and are due largely to human actions, and have profound socioeconomic effects. There is a lot of the history of the Nile perch in Lake Victoria. Just like most other introduced non-native fish species in a body of water the introduction rate has accelerated greatly over time. Although not all introduced fishes have appreciable effects on their new ecosystems, many exert significant ecological, evolutionary, and economic impacts. For researchers, managers, and policy makers interested in conserving freshwater diversity, understanding the magnitude and array of potential impacts of non-native fish species is of utmost importance. (McConnell, 1994) Although a great deal of knowledge is known about the Nile perch, but this body of knowledge truly dwarfs in comparison to what we still need to learn. Specifically, the need for additional scientific research to fill knowledge gaps

Work Cited
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