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How does a sailfish use its sail?

August 3, 2017
BY DONNEL A. TATE , Lahaina News

Rare to Hawaiian waters, the Indo-Pacific sailfish inhabits tropical and temperate waters near landmasses, coral reefs and islands. where warm currents are close inshore. Pelagic and migratory, sailfish usually travel alone or in groups.

Schooling instinct is developed very strongly in the sailfish. They mainly school for food and spawning activity. They are the peacock of the sea with glorious colors and a graceful winged shape.

It has a huge, high, sail-like membrane first dorsal fin, colored slate or cobalt blue with a scattering of black spots. With its pointed bill and graceful, elongated body, the Indo-Pacific sailfish (Istiophorus platypterus) is one of the world's most charismatic fish species. The body coloration is predominantly metallic blue, darker on the upper parts and lighter on the sides, with around 20 bluish gray or pale lavender vertical bars along the flanks along with diffuse brown markings.

Article Photos

Deckman Andrew Buckland (left) and Capt. Brad Coombs caught this 48.8-pound sailfish on July 22.

Other distinct features are a single and prominent lateral line along the median line of the flanks. Most noticeable, the pelvic fins are very long with a membrane (longer than any other billfish).

So why does it have the sail, and what is its use? Those who have been near these fish as they hunt and ball up their prey can see the answer. That apparently flimsy, supposedly balance-destroying sail, when upright, turns the slender-bodied sailfish into a silhouette of a monster fish, increasing the visible body depth in combination with the long-rayed pelvic fins.

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" behavior exhibited by the sailfish at or near the surface waters after or before high-speed bursts.

The most action is found where sailfish are located on or near the surface. They appear to feed mostly in mid-water along the edges of reefs or current eddies. They eat squid, octopus, mackerels, tunas, needlefish, flying fish, mullet and other small fishes.

Sailfish are a blend of marine savagery and efficiency in the way they hunt. Sailfish ball their bait schools. One will work the surface by jumping anti-clockwise in a tight circle with sail and fins folded. This apparently random free-jumping is part of an organized ruthless, cooperative feeding pattern. This surface jumping helps ball up the baitfish into tight masses.

Other sailfish in the school will circle below the surface at various levels with dorsal fins and pelvic fins fully extended to look as big as possible to assist in rounding up the bait. Then they gently take their prey from the outside of the column of bait in their circling.

Its fighting ability and spectacular aerial acrobatics, along with fast surface runs, have established its reputation as a top sport fish, but it tires quickly and is considered a light tackle species. Sailfish have been clocked at over 60 mph, a speed unheard of in any other fish, although more conservative estimates of 25 to 35 mph are more commonly accepted.

Indo-Pacific sailfish attain a much greater size than their Atlantic counterparts do. Sailfish grow rapidly in early years and exhibit sexual dimorphism, with females growing to larger maximum size than males.

Sailfish live an average of three to four years, with some living as long as eight years. Sailfish grow quickly, reaching the adult stage at about four months. They are seven inches in the first month, 20 inches by the second month and over four feet in six months, weighing 6-8-pounds. In a year, they will be six feet long, weighing around 20 pounds.

The Indo-Pacific sailfish's reproductive behavior 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 in 36 hours and develop the sail-like dorsal fin and elongated bill when only five centimeters (two inches) long.

The Indo-Pacific sailfish spawns throughout the year in tropical and subtropical waters, with peak spawning taking place during the summer. Populations in the Pacific undergo seasonal spawning migrations, covering extremely large distances.

There is a resident population of sailfish in Hawaiian waters, but not large enough that they are caught on a regular basis. There has been at least one per year for Lahaina Harbor, with 80 sailfish weighed and four released since 1979.

The Hawaii state record is a 151-pound fish taken in 2013 from Punalu'u, Hawaii. The Lahaina Harbor record is a 113-pound fish taken in 1979 aboard the Sport Diver with Capt. Tad Luckey. The second largest was a 100-pound fish taken in 1986 aboard the Finest Kind with Capt. Dave Hudson.

 
 
 

 

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