The The INVASS model, a conceptual framework to depict the invasion of the top-predator fish Cichla ocellaris in a large river floodplain

Abstract

The peacock cichlid Cichla ocellaris is a piscivorous fish, native to the Amazon region and introduced throughout the Americas, leading to adverse impacts on native fish assemblages. Applying the INVASS model, an approach conceived primarily to structure knowledge on terrestrial plants, we systematically describe which mechanisms are critical at each step of C. ocellaris invasion in the floodplain of the Upper Paraná River (UPRF). Through invasion Step 1, it was found that both intentional introductions and accidental escapes from fish farms were the key factors for the arrival of C. ocellaris in the UPRF. Intensive bi-parental care and the invader ability to form aggressive shoals seem to be the most favorable traits that allowed C. ocellaris to surmount invasion Step 2. Multiple spawns and a long reproductive season, coupled with a quick growth to a reproductive maturity largely contributed to the continuous establishment of the invader in the UPRF, overcoming thus invasion Step 3. Since peacock cichlids have been favored by cascading reservoirs upstream and experienced few threats in the UPRF, we anticipated that C. ocellaris is now crossing Step 4 of the invasion process, considerably increasing the risk of other systems still preserved —but also interconnected— being invaded.

Keywords

• river-floodplain system
• introduction
• dispersal
• invasion steps
• non-native fish