Information briefs and risk analyses for species under consideration ...

HAMMERHEAD SHARK
Species: Sphyrna zygaena
Common name: Smooth hammerhead shark
Species code: HHS
Stock area: 1-10
Introduction
1 This paper seeks to identify whether smooth hammerhead shark should be considered
for introduction into the QMS. The assessment concludes there is little risk to
maintaining the existing regime in the short term. Further, the species should be
evaluated against some sort of prohibited utilisation standard before being
re-considered for introduction into the QMS.
Biological information
Morphology, growth, reproduction and recruitment
2 The smooth hammerhead shark (hereafter hammerhead shark) has an elongate lateral
body shape with the distinctive feature of a wide flattened head. Colouration is olivegrey
or dark grey above and white below. Fins are plain, dusky or blackish tipped.
The maximum size attained in New Zealand waters is 3.5m. Hammerheads become
sexually mature when 2.5 to 3m long and pregnant females may give birth to up to 40
live young.
Spatial and temporal distribution and key areas (feeding, spawning,
migration)
3 Hammerhead shark is a highly migratory species (HMS) as defined by the United
Nations Convention on the Law of the Sea (UNCLOS).
4 The species inhabits inshore and offshore waters over the continental shelf. It
occupies both a pelagic and benthic habitat, and may be semi-oceanic. Hammerhead
shark is a northern species, and probably occurs very rarely in South Island waters.
The young are often found on the sea surface with such aggregations common in the
Hauraki Gulf.
5 Hammerhead shark prefer to feed on skates, stingrays and other small sharks, but also
predate bony fishes, shrimps, crabs, barnacles and cephalopods.
Habitat interactions
6 As mentioned, juveniles are known to aggregate on the surface of shallow coastal
waters such as the Hauraki Gulf where they may be vulnerable to a wide range of
human impacts (e.g. sedimentation, pollution, dredging and interactions with moving
vessels) that degrade their habitat and possibly their health. No other information is
available.
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