Lake Victoria in East Africa is home to many species of fish called cichlids. In 1954 the predatory Nile perch was introduced to Lake Victoria. The Nile perch became the dominant fish species in the lake by the mid-1980s. The number of cichlid species in the lake decreased as the Nile perch population increased. The perch preyed heavily on cichlid species that fed on algae and debris on the bottom of the lake. Algae in the lake increased, and oxygen levels decreased. The surface area of the gills of some cichlid species has increased in over 20 years. A. Increased gill surface area has allowed the cichlids to change their diet and avoid competing with the Nile perch.
B. Increased gill surface area has allowed the cichlids to be camouflaged and avoid being eaten by the Nile perch.
C. Increased gill surface area has allowed the cichlids to leave Lake Victoria and establish populations in nearby bodies of water.
D. Increased gill surface area has allowed the cichlids to better absorb the limited oxygen in the water.