Predatory behaviors of Caranx melampygus (Carangidae) feeding on spawning reef fishes: a novel ambushing strategy

Carangid fishes, commonly known as jacks, are important predators of reef fishes in tropical and sub-tropical oceans. The behavioral strategies used by Caranx melampygus while preying on spawning aggregations of coral reef fishes were studied for 2 yrs at Johnston Atoll (Central Pacific). Visual observation of 173 attack events revealed two different hunting behaviors. A "midwater" hunting behavior typical of large transient predators consisted of midwater high speed attacks on spawning fishes, and yielded a capture success rate of 2%. An "ambush" hunting behavior consisted of attacks on spawning fishes from hiding locations in the substrate and yielded a higher capture success rate of 17%. During ambush hunting, C. melampygus adopted a dark coloration and displayed aggressive behaviors toward other intruding conspecifics while defending a specific section of the reef. This previously undescribed, specialized ambushing behavior is atypical of fast swimming carangids and illustrates the behavioral flexibility of this important reef predator.