The Indo-Pacific sailfish is capable of tremendous bursts of speed over short distances, making it one of the fastest—if not the fastest—of all fish species. Tests in the 1920s estimated that this species is capable of short sprints of up to 111 kilometres per hour, although more conservative estimates of 37 to 55 kilometres per hour are more commonly accepted (4). An opportunistic predator, the Indo-Pacific sailfish takes a variety of food items, including fish, crustaceans and cephalopods, but its most common source of prey is schooling fishes, such as sardines, anchovies and mackerel (2) (3) (5). This species typically hunts alone, although groups have also been known to display cooperative feeding behaviour. When feeding upon schooling fish, the Indo-Pacific sailfish herds the shoal into a dense group called a ‘bait ball’ before swimming through the middle and making thrashing movements with head. The resulting impact with the sailfish’s bill kills or stuns large numbers of fish, which are then picked off as they sink through the water column (2). The fully grown Indo-Pacific sailfish has few natural predators, and while large sharks and killer whales have been known to prey on individuals hooked by longlines, predation on free-swimming specimens is likely to be rare (2).
The Indo-Pacific sailfish’s reproductive behaviour involves the male and female swimming in pairs, or several males chasing a single female, prior to spawning taking place. The female produces huge numbers of eggs, which hatch into tiny larvae, and develop the sail-like dorsal fin and elongated bill when only five centimetres long (4).
The Indo-Pacific sailfish spawns throughout the year in tropical and subtropical waters, with peak spawning taking place during the summer (3). Populations in the Pacific undergo seasonal spawning migrations, covering extremely large distances (2) (3).