Common
Names: Shovelnose Guitarfish,
Californian Guitarfish, Shovelnose Ray.
Latin
Name: Rhinobatos productus
Family:
Rhinobatidae
Identification:
Body disc longer than width. Snout
pointed with slight concavity before rounded tip.
Body tapers into broad tail
topped by two dorsal fins of equal size. Thorns (enlarged denticles) around eyes
and extending in a single row along centre line of back and tail. Well developed
caudal fin roughly triangular with indistinct lower lobe. Dorsum color olive to
sandy brown with vague darker blotches. Ventrum pale.
Size:
Maximum
length 170cm. 15-23cm at birth
Habitat:
Intertidal
Inshore
waters and estuaries to 13m but recorded at 91m. On sand or mud bottoms.
Occasionally in sea grass beds.
Abundance
and distribution: Eastern Pacific from central California (San
Fransisco) to the Sea of Cortez.
May be locally abundant forming
large aggregations.
Behavior: Lays
partially buried in sand when not foraging for food. Hunts for benthic
invertebrates including poychaete worms, clams, amphipods, crabs and shrimp.
Adults also consume some bony fishes. Swims by using powerful caudal fin.
Reproduction:
Guitarfishes are ovoviviparous (yolk
sac viviparity).
Female Shovelnose Guitarfish give birth in shallow sandy bays in late
spring/summer.
El Nino years tend to induce
earlier reproductive cycles.
Gestation lasts about 12 months
after which up to 28 young may be born.
Observations:
Photographs:
La Jolla Shores, San Diego, California.
Similar
species: The Speckled Guitarfish (Rhinobatos
glaucostigma) from southern Baja and further south can be identified by a
scattering of small light sots over its back. The Banded Guitarfish (Zapteryx
exasperata) which ranges from southern California south, has a more rounded
anterior margin and darker and more distinct blotches across its snout and much
of its body.
Reaction
to divers: Generally skittish and difficult to approach. Although these
guitarfish usually move away when approached there is one record of a diver
being bitten by a guitarfish that was disturbed while chasing a female at La
Jolla Cove.
Diving logistics:
Shovelnose Guitarfish move in and out of bays in southern California during the
summer and fall. A promising but non guaranteed spot to
snorkel with them is off the beach at the Marine Room at La Jolla. In late
summer they can be so thick that as you approach them their mass exodus brings
the visibility down to almost zero.
Other diving locations submitted by readers:
Further
reading:
Sharks, Rays, and Chimaeras of
California. David A. Ebert
Reef Sharks and Rays of the World. Scott W. Michael. Sea Challengers.
Sharks
and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.
