Hammerhead Shark
Also known as: Sphyrnidae (family name) · Scalloped hammerhead (Sphyrna lewini, the species most often recorded in the Philippines)
Definition
The hammerhead sharks are a family (Sphyrnidae) of sharks named for the distinctive cephalofoil, a laterally flattened, hammer-shaped head with an eye at each end. Distributed in tropical and warm temperate seas, including Philippine waters, they include the scalloped hammerhead (Sphyrna lewini), which schools in aggregations sometimes seen by divers at offshore reefs and seamounts. The cephalofoil is believed to aid sensory reception and maneuvering. (Wikipedia)
Identities
| Source Type | Identity |
|---|---|
| Wikipedia | Hammerhead shark |
| Wikidata | Q208490 |
| DBpedia | N/A |
| ProductOntology | N/A |
| Wiktionary | N/A |
| Library of Congress Subject Headings (LCSH) | N/A |
| MeSH | N/A |
| NCBI Taxonomy | Sphyrnidae |
| AGROVOC | N/A |
| Google Scholar | hammerhead shark Philippines Sphyrna lewini fishery bycatch |
| ConceptNet | fish |
| OpenCyc | N/A |
Also Known As
- Sphyrnidae (family name)
- Scalloped hammerhead (Sphyrna lewini, the species most often recorded in the Philippines)
Examples and Analogies
- A head like a sensory antenna array: The wide cephalofoil spreads the shark’s electroreceptors over a broader swath of seafloor, functioning like a metal detector with a very wide search coil as the shark sweeps for buried prey.
- Schools like birds: Scalloped hammerheads gather in polarized schools by day and hunt singly at night, a rhythm familiar to anyone who has watched egrets roost together yet feed apart.
Usage Scenarios
1. Dive Tourism Encounters
Live-aboard expeditions to offshore protected areas such as the Tubbataha Reefs Natural Park market the possibility of schooling hammerhead sightings, anchoring high-value seasonal tourism.
2. Fisheries Management
Fisheries managers account for hammerheads as bycatch in gillnets and longlines when setting measures under the amended Philippine Fisheries Code and complying with international trade rules for shark products.
Strategies
- Protect aggregation sites through marine protected areas timed to seasonal schooling, the most efficient point to shield breeding populations.
- Strengthen species-level catch reporting so that landing statistics distinguish hammerheads from other sharks, enabling meaningful quotas.
- Develop fin traceability to choke the trade channel that makes hammerheads economically attractive to retain.
Security and Safety Measures
- Divers should observe sharks at a distance without chasing, blocking, or hand-feeding, following briefings from licensed guides at protected sites.
- Fishers handling hooked hammerheads should cut leaders on large animals rather than dehooking them in water, protecting both shark and crew.
Historical Context
Hammerheads were long treated as abundant inshore-offshore predators, but industrial fishing in the late twentieth century drove steep declines, and international bodies responded with trade controls, including the listing of scalloped hammerheads under CITES. In the Philippines, the rise of shark-focused dive tourism and the passage of national shark and ray conservation measures gradually shifted hammerheads from vermin-like bycatch to a managed, tourism-valued resource.
Challenges and Controversies
Bycatch and Fin Trade
Hammerheads caught incidentally in nets and longlines are often retained for high-priced fins, and weak port-side inspection undermines trade regulations.
Tourism Pressure
Dive boats crowding aggregation sites risk altering natural behavior, prompting debate over site caps and seasonal closures within marine parks.
Related Topic
Philippine Shark Conservation