IDENTIFICATION
The general body colour is cobalt blue above a white belly with faint vertical bars on the flanks.
The bill is heavy and round like the black marlin but the lower jaw is only slightly down-curved.
The tapered pectoral fins fold flat against the body. The tail is sickle shaped and there is no visible lateral line.

DISTRIBUTION
The species is distributed throughout tropical and sub-tropical waters of the Indo-Pacific but the Indian Ocean appears to have a discreet population. They undergo extensive migrations into higher latitudes during summer and return to the equator during winter.

FEEDING
This pelagic predator feeds extensively on shoaling game-fish, especially tuna, bonito and dolphinfish.

REPRODUCTION
The females grow much larger than the males. Females reach maturity at 60 - 80 kg while males mature from 40 kg. In KwaZulu-Natal the catches are comprised predominantly of larger females. Spawning occurs during summer and autumn in distinct breeding populations which occur between the latitudes 30oN and 30oS. The eggs and larvae are found in surface waters of tropical oceans, often found concentrated on the seaward edges of reefs.

GROWTH
The females reach 420 cm and up to 900 kg whereas the males reach 150 kg. Both males and females found in the Indian Ocean reach an age of at least 21 years.

FISHERY
This is an important component of long-line fisheries in the Indian Ocean. Capture by sport fishermen in South Africa is relatively uncommon and all specimens are landed during summer, with most being hooked further offshore than other billfish species. There has been a dramatic decrease in catch per unit effort in the Pacific fishery and a decline in the percentage composition of long-line catches in the Indian Ocean.

MANAGEMENT
• Categorised as a recreational species.
• Recreational and commercial anglers are allowed 5 per person per day.
• There is no size limit and no closed season.
The current status of this fish population is not known in the Indian Ocean but catches are declining. Research is needed on age and growth, stock distribution and assessment, reproduction and migration.

Rudy van der Elst and Bruce Mann are acknowledged for the scientific information on which this publication is based.