Historical records reveal potential extirpation of four
hammerhead sharks (Sphyrna spp.) in Mexican Paciﬁc
Juan Carlos Pe
Received: 12 April 2013 / Accepted: 17 April 2014 / Published online: 23 April 2014
Ó Springer International Publishing Switzerland 2014
Abstract Populations of hammerhead sharks
(Sphyrna and Eusphyra) have declined in many
regions of the world. Six of the eight hammerheads
known to date are distributed in the Mexican Paciﬁc:
S. corona, S. lewini, S. media, S. mokarran, S. tiburo
and S. zygaena. These species, with exception of S.
corona, were abundant in the Gulf of California in
1960s. I analyze records from ﬁshery-dependent and
ﬁshery-independent surveys, and records from ichthy-
ological collections to determine the presence and
frequency of hammerheads in the Mexican Paciﬁc.
The most frequent hammerheads in ﬁshery-dependent
and ﬁshery-independent surveys were S. lewini and S.
zygaena. It appears that S. media, S. mokarran and S.
tiburo might have been extirpated from the Gulf of
California. In the last two decades, records of S.
mokarran (n = 61) were restricted to Central and
Southern Mexican Paciﬁc, and records of S. tiburo
(n = 3) and S. media (n = 3) were restricted to the
Southern region. Given the continued ﬁshing pressure,
inferred declines and the probable extirpation of
populations, S. tiburo and S. media should be
reassessed for the IUCN red list as Endangered or
Critically Endangered. Sphyrna corona should be
reassessed as Endangered or Critically Endangered,
because it is endemic to the Eastern Paciﬁc and recent
records have been obtained only from Colombian
waters. The Endangered status of S. mokarran is
conﬁrmed for this region.
Keywords Hammerheads Á Population
declines Á Conservation status Á Eastern north
The hammerhead sharks (Eusphyra and Sphyrna), so
named because of the unusual lateral expansion of the
head, comprise a moderately large family of sharks
occurring in tropical and temperate waters throughout
the world (Gilbert 1967). The ﬂat, hammer- or shovel-
shaped heads of these sharks is so characteristic that
they cannot be confused with any other sharks (Castro
2011). The genus Sphyrna includes species with
common names different to hammerhead, such as
Bonnethead, Scoophead and Scalloped bonnethead.
Based on the study of Quattro et al. (2006
) who found
genetic evidence for a second scalloped hammerhead
(similar to Sphyrna lewini) in the east coast of USA,
Castro (2011) purports that the family Sphyrnidae
comprises at least nine species, seven or eight of which
are found in North America.
In 1900, six of the eight (or nine) hammerhead
species known to date were already described
J. C. Pe
Laboratorio de Pesquerı
as, Departamento de Ciencias de
la Sustentabilidad, El Colegio de la Frontera Sur
(ECOSUR), Av. Rancho, Polı
gono 2-A, Ciudad
Industrial, Lerma, CP 24500 Campeche, Mexico
Rev Fish Biol Fisheries (2014) 24:671–683