Photographer: unknown Affiliation:U.S. Geological Survey Source:www.bugwood.org Copyright: CC BY-NC 3.0
This fish is has a compressed oval body with two dorsal fins that appear as a single fin. The front one has 16 sharp spines and the rear fin has 12-13 soft rays. The tail is fan-shaped. The anal fin has three spines at the front and 10-11 rays that taper to a point at the rear. The mouth is terminal, and the large eye is reddish. Coloration is distinct. Juveniles have no spots but there is prominent black spot on the back of the dorsal fin. The bars present as juveniles fade away with age and 6-9 irregular square dark blotches appear along the midline of the flanks of adults. Some show pink or red coloration on the throat when spawning. Males and females slightly differ in appearance. Males have somewhat longer dorsal and caudal fins, both of which display shimmering white spots not found in females. Spotted tilapias are smaller than most other African cichlids and it is the most abundant. Florida specimens typically are between 6 to 8 inches but they may grow to 12 inches or more and weigh up to 3 pounds. Most fish larger than 10 inches are males.
Spotted tilapias disperse rapidly and quickly become the dominant fish in numbers in habitats to which they are introduced, thereby reducing the biodiversity. With the large population numbers they compete with native fish for food. They may also compete with native fish such as sunfishes for spawning areas, since they aggressively defend their nests and broods.
Tilapia mariae feed primarily on algae and detritus. They form pair bonds right before spawning and stay in these pair bonds to care for the eggs and fish fry. In Florida, spawning generally occurs between November and March and may be synchronized with the lunar cycle. Each female produces 200-2000 turquoise eggs that stick to the gravel bottom. Two days after the eggs are laid; all infertile eggs are eaten by the female. Both parents guard and feed the hatchling until they are free-swimming about 9 days later. These fish are sexually mature at 7 inches.
The first known occurrence in the United States goes back to April 1974 in South Miami. It quickly became established in the canals and then in the Everglades National Park by the late 1980s. Similarly in Nevada, introduction was related to an aquarium release. Spotted tilapias have been abundant in Rogers Spring, in Lake Mead, Nevada since 1980. In 1997, one specimen was collected in South Texas in Cameron country from a drainage ditch.
West Africa (Ghana to Cameroon)
U.S. Habitat: warm, slow-moving waters. They thrive in the canals in South Florida and the warm springs of Nevada. Water temperatures below 52oF are not tolerated.
Distribution
U.S. Present: AZ, CA, FL, NV and TX
In the 1980s, Florida attempted to control this fish species by introducing yet another exotic fish, the South American peacock cichlid (Cichla ocellaris) to feed upon it. However, the two species have reached predator-prey equilibrium. In the 2010s, using exotic animals to “control” other invasive species is highly discouraged. Only after years of studying by the USDA are exotic animals or parasitoids even considered as bio-0control agents. Prevention of further spread is the main goal of management. Now it is illegal to transport of possess live tilapia in Florida. This fish is edible, so fishermen are encouraged to catch them and eat them accordingly.
Text References
Brooks, W. R., & Jordan, R. C. 2010. Enhanced interspecific territoriality and the invasion success of the spotted tilapia (Tilapia mariae) in South Florida. Biological Invasions, 12(4):865-874.
Courtenay Jr, W. R., & Hensley, D. A. 1979. Range expansion in southern Florida of the introduced spotted tilapia, with comments on its environmental impress. Environmental Conservation, 6(2):149-151.
Courtenay Jr, W. R., & Deacon, J. E. 1983. Fish introductions in the American Southwest: a case history of Rogers Spring, Nevada. The Southwestern Naturalist, 221-224.
Siemien, M. J., & Stauffer, J. R. 1989. Temperature preference and tolerance of the spotted tilapia and Rio Grande cichlid. Archiv fuer Hydrobiologie, 115(2):287-303.
Woodward, Susan L., and Joyce Ann. Quinn. 2011. Spotted Tilapia. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood, 196-97. Print.
Internet Sources
http://www.invasive.org/browse/autimages.cfm?aut=55668
http://myfwc.com/wildlifehabitats/profiles/fish/freshwater/nonnatives/spotted-tilapia/
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