California Fish Species

Nile Tilapia

• Scientific Name

  Oreochromis niloticus
• Native

  Non-Native
• Identification

  

  • Deep, elongate, laterally compressed bodies
  • 30-34 cycloid scales on the lateral line
  • Bluntly pointed snout with a slightly oblique mouth that rarely extends past the outer margins of the eye
  • 15-18 spines and 12-14 rays on the dorsal fin
  • 3 spines and 7-12 rays on the anal fin
  • Truncate caudal fin
  • Females and non-breeding males are normally a pale gray to washed out yellow with a series of bands on the side
  • Normal coloration also includes caudal fin with distinctive stripes, dorsal fin with a gray to black margin often tinted with red
  • Spawning males are flushed with red throughout the head and sides
• Life History

  No definitive information is currently available for wild Nile tilapia in California. It is a common species for aquaculture farming where they are likely to have escaped from into the Colorado River. They can survive temperatures as high as 39-40°C but are less tolerant of high salinities than other tilapia. Fry will start on a diet of zooplankton and small insects but will become almost completely herbivorous when the reach 5-6 cm. As they get larger their diet will focus on phytoplankton like cyanobacteria but will also include bacteria, aquatic plants, and the small invertebrates that can be found on such plants.

   

  Nile tilapia reach maturity when they are 18-30 cm in length and breeding begins when temperatures pass 18-19°C. Spawning occurs when males claim a territory and dig a shallow pit for a nest. He then displays in front of the female school convincing a female to follow him back to the nest. The pair will swim in circles before the female first deposits her eggs onto the nest and then takes them into her mouth. The male responds by releasing his milt which the female also takes into her mouth to fertilize the eggs. Once complete the male chases that female away and begins displaying for another. The female incubates the eggs in her mouth until they hatch and keeps the young there until they are free swimming and capable of being released into the water. The young stay with their mother for a few days after release during which time they can retreat to the safety of her mouth when a predator approaches. At the end of this period the young form massive schools in shallow water while the female returns to the adult school to find another mate. Nile tilapia are known to reach lengths of 40-65 cm and weights of 4-7 kg.

• Links to Other Research

  N / A
• Watershed

  N / A