BLACK MARLIN (Makaira indica)
A number of different types of billfish are caught in the waters off northern KwaZulu-Natal.
The most common are: black marlin, blue marlin, striped marlin, broadbill, swordfish and
sailfish which are part of populations which extend throughout the Indian and Pacific Oceans.
IDENTIFICATION The body colour is metallic blue-black with a white belly.
It has a relatively short, round bill with the lower jaw curving downwards. The pectoral fins
are curved and cannot be moved in fish larger than 55 kg. The tail is semicircular in adults and
the lateral line is not visible.
DISTRIBUTION Distributed throughout tropical and sub-tropical waters of the
Indo-Pacific. They are highly migratory and often found close to land in water less than 200m deep.
Black marlin are most common off KwaZulu-Natal during summer, especially around submarine canyons
that reach close to the shore.
FEEDING This fast predator will eat virtually any fish, especially tuna, bonito
and kingfish. The prey is either slashed with or impaled by the bill.
REPRODUCTION The females grow much larger than the males. Females reach maturity
at more than 200 kg and males mature between 50 - 80 kg. In KwaZulu-Natal waters, there are a
higher proportion of females then males (6.7 females to 1 male). No reproductively active
individuals have been recorded in South African waters and no spawning areas have yet been
identified in the Indian Ocean. The eggs and larvae are found in surface waters of tropical oceans,
often found closely associated with the seaward side of reef edges.
GROWTH This fish reaches 448 cm total length and the maximum recorded weight is
707 kg. In the Indian Ocean the males live up to at least 13 years of age and the females reach
over 20 years of age (275 kg).
FISHERY This is an important recreational species, caught by ski-boat anglers
primarily off KwaZulu-Natal. Little commercial harvesting is done from mainland southern Africa
although foreign long-line fleets (Japan, Taiwan and Korea) harvest catches in the south western
Indian Ocean. There has been an increase in landings from the Indian Ocean and a substantial
decline in catch rates in the Pacific 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 in the Indian Ocean is not known but there has
been a substantial decline in catches of the species in the Pacific Ocean. Research is needed on
age and growth, stock distribution, reproduction and catch trends.
Rudy van der Elst and Bruce Mann are acknowledged for the scientific information on which this
publication is based.
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