Billfish

Black Marlin

Rigid pectoral fins that do not fold flat against the body.

Blue Marlin

A long spear-shaped bill.

Pacific Sailfish

A very tall sail-like first dorsal fin.

Striped Marlin

A long bill and streamlined body.

Swordfish

A long broad, flattened sword-like bill.

Nature Field Guide

Black Marlin

Spanish name: Marlín negro
Scientific name: Istiompax indica

What Do Pico & Tati Think?

Pico: “How can we tell this marlin apart?”

Tati: “Its stiff side fins are a useful clue.”

Identification

Key Features of the Black Marlin

Rigid pectoral fins that do not fold flat against the body.
A substantial head and comparatively stout bill.
A powerful streamlined body.

Habitat & range

Offshore Pacific waters.

Conservation & care

Observe marine wildlife without feeding, touching or chasing it. Keep litter and discarded fishing line out of waterways. Follow qualified guides and current local rules.

Threats & pressures

Fishing capture is a conservation concern for billfish. Tracking catches and releases helps assess pressures across a migratory range.

Nature Field Guide

Blue Marlin

Spanish name: Marlín azul
Scientific name: Makaira nigricans

What Do Pico & Tati Think?

Pico: “Its back is such a deep blue!”

Tati: “Let’s compare its fin and bill with the other marlin.”

Identification

Key Features of the Blue Marlin

A long spear-shaped bill.
A cobalt-blue back and silvery underside.
A pronounced front dorsal fin and crescent-shaped tail.

Habitat & range

Warm tropical and subtropical open water.

Seasonal Calendar

Regional presence

Costa Rican Pacific waters

Year-round

JanFebMarAprMayJunJulAugSepOctNovDec

FECOP reports year-round Costa Rican Pacific presence and a historical May–September Guanacaste fishing peak. Catch patterns are not exact migration or breeding dates.

Reported fishing peak

Guanacaste offshore waters

May, Jun, Jul, Aug, Sep

JanFebMarAprMayJunJulAugSepOctNovDec

FECOP reports year-round Costa Rican Pacific presence and a historical May–September Guanacaste fishing peak. Catch patterns are not exact migration or breeding dates.

Conservation & care

Observe marine wildlife without feeding, touching or chasing it. Keep litter and discarded fishing line out of waterways. Follow qualified guides and current local rules.

Threats & pressures

Blue marlin can be caught incidentally in longline fisheries targeting tuna and swordfish. Fishing pressure needs monitoring across its migratory range.

Nature Field Guide

Pacific Sailfish

Spanish name: Pez vela
Scientific name: Istiophorus platypterus

What Do Pico & Tati Think?

Pico: “Its fin looks like a sail!”

Tati: “That tall fin is our best first clue.”

Identification

Key Features of the Pacific Sailfish

A very tall sail-like first dorsal fin.
A long slender bill.
A slender blue-and-silver body.

Habitat & range

Warm Pacific marine waters, including offshore areas.

Seasonal Calendar

Regional presence

Costa Rican Pacific waters

Year-round

JanFebMarAprMayJunJulAugSepOctNovDec

FECOP reports sailfish can be encountered throughout the year in Costa Rica. Concentrations vary between northern and central/southern waters. This is regional presence, not a fixed migration season.

Conservation & care

Observe marine wildlife without feeding, touching or chasing it. Keep litter and discarded fishing line out of waterways. Follow qualified guides and current local rules.

Threats & pressures

Incidental capture in tuna fisheries and other fishing pressure can affect sailfish.

Nature Field Guide

Striped Marlin

Spanish name: Marlín rayado
Scientific name: Kajikia audax

What Do Pico & Tati Think?

Pico: “I can see blue stripes along its sides!”

Tati: “We should check the shape too—other marlin can show stripes.”

Identification

Key Features of the Striped Marlin

A long bill and streamlined body.
Vertical blue bars that may vary in intensity.
A tall front portion of the first dorsal fin.

Habitat & range

Tropical and subtropical Pacific and Indian Ocean waters.

Seasonal Calendar

Regional presence

Costa Rican offshore waters

Year-round

JanFebMarAprMayJunJulAugSepOctNovDec

FECOP reports striped marlin throughout the year in Costa Rican offshore waters. No fixed Tamarindo migration or spawning calendar is established here.

Conservation & care

Observe marine wildlife without feeding, touching or chasing it. Keep litter and discarded fishing line out of waterways. Follow qualified guides and current local rules.

Threats & pressures

Striped marlin are caught incidentally in pelagic longline fisheries. Fishing pressure differs between assessed Pacific stocks.

Nature Field Guide

Swordfish

Spanish name: Pez espada
Scientific name: Xiphias gladius

What Do Pico & Tati Think?

Pico: “Its bill looks like a sword!”

Tati: “It is flatter and broader than a marlin’s bill.”

Identification

Key Features of the Swordfish

A long broad, flattened sword-like bill.
A dark upper body and lighter underside.
A streamlined body with a crescent-shaped tail.

Habitat & range

Open-ocean surface and deeper waters.

Conservation & care

Observe marine wildlife without feeding, touching or chasing it. Keep litter and discarded fishing line out of waterways. Follow qualified guides and current local rules.

Threats & pressures

Commercial and recreational fishing affect swordfish. Managing this migratory species requires international cooperation; assessments vary by stock.