Black Marlin
Istiompax indica
The giant of our billfish, trolled for on heavy tackle off KZN and at Bazaruto in Mozambique, and nearly always released.
Size: Males seldom grow past about 200 kg; the really big ones are females. Fish over 400 kg have been landed off Sodwana and Cape Vidal, and Bazaruto produces a fish of 450 kg or more in most seasons.
Where: The Indian Ocean coast from Mozambique to KZN, mostly in summer, where deep water and canyons come close to shore, as at Sodwana and Cape Vidal. Strays have been caught as far south as Cape Point.
How to spot it
A heavy, deep-shouldered marlin, dark blue to almost black on the back and silver below. The bill is shorter and thicker than a sailfish's, and the first dorsal fin is low, lower than the body is deep. The pectoral fins are stiff and stick out from the body; on a black marlin they cannot be folded flat, which sets it apart from blue and striped marlin.
Varieties and look-alikes
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Black Marlin - A low dorsal fin, a shorter, thicker bill and stiff pectoral fins that stick out and cannot be folded flat.
-
Sailfish - A huge, sail-like dorsal fin, much taller than the body is deep, and a long, thin bill.
What it eats
Tuna, bonito, other shoaling fish and squid, taken at the surface and deeper down.
Where it feeds
- Over deep drop-offs and canyons close to shore
- Around shoals of bonito and small tuna
- Near reefs and islands, such as at Bazaruto
- In warm, clean blue water
How to catch it
Black marlin are a boat fish for heavy tackle. Troll big skirted lures to find fish, or slow-troll a live bonito or small tuna; rigged skip baits of bonito also work. Use circle hooks and strong tackle, so the fight is short and the fish can be released in good shape.
| Way of fishing | How well it works |
|---|---|
| Bait on the bottomA sinker holds your bait still on the bottom. | Not used |
| Under a bobberA bobber is a small buoy on your line: it holds the bait off the bottom and dips under when a fish bites. | Not used |
| Natural or dead baitReal food on the hook: worms, liver, sardine, chokka. | Works well |
| Live baitA small live fish or other live creature on the hook. | Best |
| LuresArtificial baits you cast and reel in: spinners, spoons, plastics. | Not used |
| TrollingLures or bait pulled behind a moving boat. | Best |
| Fly fishingLight artificial flies, cast with a fly rod. | Not used |
Baits and lures that work
- Live baitfish
- Skirted trolling lures
- Fish strips or dead fish
Flavours it likes
Marlin hunt by sight and by feeling movement in the water. A big, lively bait or a lure that splashes and leaves a bubble trail draws them in, not scent.
When it bites
Time of day
| Time | Bite |
|---|---|
| Dawn | Good |
| Day | Good |
| Midday | Good |
| Dusk | Best |
| Night | Rarely |
Bites come through the day, often mid-morning and in the late afternoon. They are hardly ever caught at night.
Best months
- Best: January, February, March, November, December
- Good: April, May, September, October
Off KZN the marlin season runs from about November to May, best from November to March. At Bazaruto the big females gather from September to December, peaking in October and November.
What affects the bite
| Condition | What it likes | Effect on the bite |
|---|---|---|
| Water temperature | Best at 24–28 °C | Medium |
| Time of day | Best during the day | Low |
| Tide | Best when the tide turns | Low |
| Swell and surf | Best when the sea is calm | Medium |
| Air pressure | Best when it is falling | Medium |
| Cloud cover | Hardly matters | Low |
| Wind | Best with a light breeze | High |
| Rain | Hardly matters | Low |
| Water clarity | Best in clear water | Medium |
| Moon phase | Hardly matters | Low |
| Spawning | More fish gather while they spawn | Medium |
High means it makes a big difference to whether this fish bites. Low means it hardly matters.
Tips
- Catch fresh bonito for live bait first thing in the morning.
- Fish the edges of deep drop-offs and canyons where bait shows on the fish finder.
- Clear the deck and agree on everyone's job before the fish reaches the boat.
Good to know: Nearly every marlin caught off SA and Mozambique is released. Keep it in the water, cut the leader close to the hook if you cannot remove it, and tow it slowly forward to revive it. Check the current rules: marlin and sailfish are recreational fish that may not be sold, with a bag limit of 5 per person per day.
Are they biting today?
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