Slender, oceanic requiem shark with a notably silky‑smooth skin created by densely packed dermal denticles. First dorsal fin moderately tall, origin behind pectoral free tips; second dorsal possesses a long free rear tip. Pectorals long, narrow, falcate. Snout long and rounded; eyes large with nictitating membranes. Colour uniform dark bronzy‑grey above, white below; no distinct fin markings except faint dusky tips in juveniles. Adults average 2.2–2.6 m TL (maximum 3.5 m) and 150‑170 kg. Teeth: upper narrow, serrated; lower slender, semi‑erect. Sexual dimorphism minimal—females slightly larger, males with claspers.
Females larger/heavier; males with claspers.
Males 2.1 m; females 2.4 m (max 3.5 m)
60–170 kg
≈ 22 yr (vertebral ageing)
Data deficient
Data deficient
Males 6–7 yr (≈ 210 cm TL); females 7–9 yr (≈ 230 cm TL)
Parturition in coastal shelf waters May–July; mating inferred preceding dry season offshore
4 – 16 pups (mean 8) every 1–2 yr
Slender, oceanic requiem shark with a notably silky‑smooth skin created by densely packed dermal denticles. First dorsal fin moderately tall, origin behind pectoral free tips; second dorsal possesses a long free rear tip. Pectorals long, narrow, falcate. Snout long and rounded; eyes large with nictitating membranes. Colour uniform dark bronzy‑grey above, white below; no distinct fin markings except faint dusky tips in juveniles. Adults average 2.2–2.6 m TL (maximum 3.5 m) and 150‑170 kg. Teeth: upper narrow, serrated; lower slender, semi‑erect. Sexual dimorphism minimal—females slightly larger, males with claspers.
Offshore epipelagic (surface – 400 m) of warm oceans; abundant around Costa‑Rica Dome, Cocos Ridge seamounts, FAD arrays and tuna purse‑seine sets; juveniles utilise outer continental‑shelf and insular shelf breaks (30–100 m).
Apex / upper‑mesopredator feeding on skipjack and yellowfin tuna, mackerels, flyingfish, squid; opportunistically scavenges cetacean and whale‑shark carcasses.
Social Structure & Behaviour
Activity pattern: cathemeral; follows prey‑rich thermocline (50–150 m) by day, surfaces at night.
Group size: solitary or loose schools (5–50) around FADs, seamount plateaus and tuna schools.
Mating behaviour: suspected offshore; males bite female pectorals.
Site fidelity: seasonal return to Cocos–Galápagos corridor seamounts documented.
Communication: body‑arching and pectoral drop threat postures toward divers/competitors.
Named for the silky texture of skin—denticles reduce drag, enabling efficient cruising.
Can sustain burst speeds > 3 m s⁻¹ when corralling tuna.
Satellite tags show diel vertical migrations: surface at night, 200–400 m by day following prey.
Juveniles exhibit counter‑shading with faint white fin edges that fade in adults.
Costa Rica banned finning (2006), yet silky accounts for > 40 % of shark by‑catch at national tuna fleet.
Native
Decreasing
Robust requiem shark with fusiform body and high, slightly rounded first dorsal fin whose origin lies over (or just anterior to) the free rear tip of the pectorals. Snout long, broad and rounded; eyes circular with nictitating membrane. Dorsum uniform grey‑brown, ventrum white; no prominent flank markings.