Invasive Species

By: Jhosue Yepez

The Nile Perch

The Nile Perch generally grows between 85 and 100 centimeters and weighs between 2 and 4 kilograms. However, this fish has been captured and seen at a size of 210 centimeters and is able to reach a weight of 200 kilograms. It is one of the most immense fresh water fish, and can live for up to 16 years.

Location:• The Nile Perch is native to a number of freshwater African lake and river systems. It was introduced to Lake Victoria in the 1950's.•The Nile perch can also be found in other African river basins as: Chad, Senegal, Congo and Volta. They can also be found in the Nile and Lake Maryut in Egypt.

The problem:•As the fish isn't native from the area the lake's ecosystem was not prepared for it. •Meanwhile the population of the fish was controlled through commercial fishing for several years. The population exploded in late 1980's.•This massive grown up of the fish population leaded to the extinction or near extinction of several hundred native species.

The devastating impact that this animal created was based because of his capacity of being the biggest and not eatable predator in the river, also because an study released that the appetite of the fish was enormous, he ate members like fish, crustaceans, insects, and zooplankton.

Reasons why it has become established

The Nile perch is a dominating predatory fish. They are able to inhabit both fresh and tropical water. They become sexually mature at the age of three years and reproduce in large numbers (they can produce 16 million eggs at one time!!) with juveniles requiring no parental care.

Its ecological roleThe Nile perch is a fierce predator that 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 immense creature now searches for larger fish than the usual minute supply. This ability to take 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.

BenefitsThe 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.

The threatsThe introduction of the Nile perch into Lake Victoria has had a catastrophic effect on the ecosystem. Hundreds of fish native to the lake have become extinct, by the 1980’s, 300 of these fish were nonexistentThe 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.

DiagnosticsDue to their rapid reproduction and dominating force, according to the IUCN’s Invasive Species Specialist group the Nile Perch is considered one of the world’s worst 100 invasive species. If dramatic measures are not taken to eliminate this species, they will continue to cause ecological disaster.

Control MethodsCommercial fishing activities are currently the only control method for the Nile perch in Lake Victoria. 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 killed by the introduction of the Nile perch into Lake Victoria are showing increasing populations.

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