Elasmobranchii (sharks and rays) > Carcharhiniformes
(Ground sharks) > Sphyrnidae
(Hammerhead, bonnethead, or scoophead sharks)
Etymology: Sphyrna: Greek, sphyra = hammer (Ref. 45335).
Environment / Climate / Range
Marine; brackish; reef-associated; depth range 10 - 80 m (Ref. 244), usually 10 - 25 m (Ref. 9253). Subtropical; 45°N - 36°S, 121°W - 32°W (Ref. 55302)
Length at first maturity / Size / Weight / Age
Maturity: Lm ?, range 80 - 90 cm
Max length : 150 cm TL male/unsexed; (Ref. 5217); common length : 80.0 cm TL male/unsexed; (Ref. 5217); max. published weight: 10.8 kg (Ref. 40637); max. reported age: 12 years (Ref. 26248)
Front of head semicircular in outline. No other hammerhead has front of head in semicircle. (Ref. 26938).
Western Atlantic: North Carolina, USA to southern Brazil, including Cuba and the Bahamas. Caribbean and Gulf of Mexico; rare in Bermuda (Ref. 26938). Eastern Pacific: southern California, USA to Ecuador.
Found on the continental and insular shelves, on inshore and coastal areas, over mud and sand bottoms, also on coral reefs. Often occur in shallow water including estuaries, shallow bays and over coral reefs (Ref. 9987). Spends night time hours on shallow grass flats, searching for nocturnally active invertebrate prey, moves into deeper water during the day (Ref. 27549). Feed mainly on crustaceans, also on bivalves, octopi, and small fish. Viviparous, with 6 to 9 young per litter. Size at birth about 35 to 40 cm. Not territorial. Always occurs in small groups. Considerable sexual segregation occurs. Shows diel rhythm of activity. Utilized for human consumption and processed for fishmeal.
Viviparous, placental (Ref. 50449), with 6 to 9 young per litter. Size at birth about 35 to 40 cm.
Compagno, L.J.V., 1984. FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2 - Carcharhiniformes. FAO Fish. Synop. 125(4/2):251-655. Rome: FAO. (Ref. 244)
IUCN Red List Status (Ref. 96402)
CITES (Ref. 94142)
Threat to humans
Fisheries: commercial; gamefish: yes
Estimates of some properties based on models
Phylogenetic diversity index (Ref. 82805
= 0.5029 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00186 (0.00098 - 0.00353), b=3.16 (2.99 - 3.33), based on LWR estimates for species & (Sub)Family-body shape (Ref. 93245
Trophic Level (Ref. 69278
): 3.9 ±0.0 se; Based on diet studies.
Resilience (Ref. 69278
): Very Low, minimum population doubling time more than 14 years (K=0.17-0.34; tm=3; tmax=12; Fec=3).
Vulnerability (Ref. 59153
): Moderate to high vulnerability (50 of 100) .