Invasion Biology Introduced Species Summary Project

Introduced Species Summary Project
Nile Perch (Lates niloticus)

Common Name: Nile Perch

Scientific Name: Lates niloticus

Classification:

Phylum or Division: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Centropomidae

Identification: The Nile perch is a fresh water fish that generally grows between 85 and 100 centimeters and weighs between 2 and 4 kilograms. However, this predator has been captured and seen at a size of 195 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.

Adult Nile perch 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.

The female Nile perch generally grows larger than the male. Certain bones such as the preopercle and pre- orbital are guarded with spines. The Nile perch is known to grow extremely fast during the first year of existence. The growth rate begins to decrease throughout the next four years of life.

Original Distribution: The Nile perch is indigenous to the Ethiopian region of Africa.

Current Distribution: They can most commonly be found in Lake Victoria, which is in East Africa. The Nile perch can also be found in other African river basins in Chad, Senegal, Congo and Volta. They can also be found in the Nile (hence the name) and Lake Maryut in Egypt.

The Nile perch can be found in numerous types of fresh water. Adult Nile perch inhabit lakes and rivers 10-60 meters in depths where there is a sufficient amount of oxygen. Small juveniles are confined to much more shallow areas in rivers and lakes that are closer to shore.

Site and Date of Introduction: The Nile perch was initially introduced into Lake Victoria in 1962. Subsequently, the decision to introduce the Nile perch into Australian waters was changed when its catastrophic effect on African waters was noted.

Mode(s) of Introduction: The Nile perch was intentially introduced into Lake Victoria for commercial fishing purposes, where it then reproduced enormously and spread throughout several aquatic environments in Africa.

Its popularity as a source of food is its great abundance. The Nile perch is an easy fish to catch, when using industrial fishing techniques. Their considerable size and palatable bone free meat make them an attractive food source.

Reason(s) 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.

Ecological Role: The 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 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.

Benefit(s): 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.

Threat(s): The 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 nonexistent.

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.

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.

Control Level Diagnosis: 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. 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. Recently their 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.

References:

http://animaldiversity.ummz.umich.edu/site/accounts/information/Lates_niloticus.html

http://www.dpi.qld.gov.au/fishweb/2374.html

http://en.wikipedia.org/wiki/Nile_perch

http://darwin.bio.uci.edu/~sustain/bio65/lec09/b65lec09.htm

http://www.gisl.co.uk/Megapesca/nileperch.html

Author: Jennifer Blake
Last Edited: January 10, 2005

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