Indo-Pacific sailfish

Description

The Indo-Pacific sailfish (Istiophorus platypterus) is a sailfish native to the Indian and Pacific Oceans.It is dark blue on top,brown-blue laterally,silvery white underbelly;upper jaw elongated in the form of a spear;first dorsal fin greatly enlarged in the form of a sail,with many black cones,its front squared off,highest at its midpoint;pelvic fins very narrow,reaching almost to the anus;body covered with embedded scales,blunt at end;lateral line curved above pectoral fin,then straight to base of tail.They have a large and sharp bill,which they use for hunting.They feed on tuna and mackerel,some of the fastest fish in the Ocean.The Indo-pacific sailfish is related to the marlin.It is theorized by marine biologists that the 'sail' (dorsal fin array) of the sailfish may serve the purpose of a cooling and heating system for this fish;this due to a network of a large number of blood vessels found in the sail and because of "sail-raising" behaviour exhibited by the sailfish at or near the surface waters after or before high-speed bursts.