Shovelnose guitarfish (Rhinobatos productus)

Description

Shovelnose guitarfish fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Shovelnose guitarfish description

The shovelnose guitarfish has an unusual body shape, intermediate between that of a shark and a ray, and is named for its long, pointed, shovel-like snout and broad disc, with wide pectoral fins that give the body a distinctive triangular shape ^{(3) (4) (5) (6)}. The tail is relatively thick, with a moderately large caudal fin that lacks a distinct lower lobe, and there are two equal-sized dorsal fins located towards the tail ^{(2) (3) (5)}. A row of thorny projections runs along the midline of the back and tail. The shovelnose guitarfish ranges from olive to sandy brown in colour, with white underparts, and a clear, somewhat translucent area on either side of the snout ^{(3) (4) (5) (6)}. Males may grow to a smaller size than females ^{(5) (6)}.

Also known as

guitarfish, northern guitarfish, pointed-nosed guitarfish, shovelnose shark.

Size

Length: up to 1.7 m ^{(2) (3)}

Weight

up to 18.4 kg ⁽³⁾

Shovelnose guitarfish biology

Although generally solitary, female shovelnose guitarfish may gather in large numbers in shallow waters from June to October, to give birth ^{(4) (5) (7)}. By midsummer, males also move into these areas to mate with the females, after which both males and females usually leave the area ⁽⁵⁾. The female produces a single litter each year ⁽¹⁾, potentially giving birth to as many as 28 pups ^{(2) (5) (6)}, after a gestation period of 11 to 12 months ^{(5) (7)}. The young measure around 15 to 24 centimetres at birth ^{(2) (4) (5) (6)}. Male shovelnose guitarfish reach maturity at around 8 years, and females at around 7 years, with individuals living to at least 11 to 16 years ^{(5) (8)}.

The shovelnose guitarfish feeds on a variety of bottom-dwelling invertebrates, such as molluscs, crustaceans and worms, and also on small fish ^{(4) (5) (6) (9)}. Clam shells may be crushed in the jaws and spat out, before the soft, fleshy portions are consumed ⁽⁵⁾. There is a single report of a shovelnose guitarfish biting a diver, but the species is considered harmless to humans ^{(2) (5) (6)}.

Shovelnose guitarfish range

The shovelnose guitarfish is found in the eastern central Pacific Ocean, from central California, USA, to the southern Gulf of California, Mexico ^{(1) (2) (3) (5)}.

Shovelnose guitarfish habitat

Typically inhabiting shallow waters around beaches, bays and estuaries, the shovelnose guitarfish usually lies partially buried on sandy or muddy bottoms, and is occasionally also seen in sea grass beds. It usually occurs at depths of up to 13 metres, but has been recorded down to 91 metres ^{(2) (4) (5) (6)}.

Shovelnose guitarfish status

Classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾.

Shovelnose guitarfish threats

The shovelnose guitarfish is fished in the Gulf of California and on the Pacific coast of Baja California, and is also taken indirectly as bycatch in commercial and recreational fisheries ^{(1) (5) (7)}. In some areas, dried guitarfish are also reportedly sold in large numbers as curios in shell shops, with individuals of all sizes taken, but particularly newborn pups ⁽⁸⁾. Pregnant female shovelnose guitarfish become particularly vulnerable to bottom gillnets when congregating in shallow waters to breed ^{(1) (7) (8)}, and the species is often one of the most heavily targeted batoids (a group which includes guitarfish, sawfish, electric rays, skates and stingrays), with declines reported in some areas ⁽¹⁾. A long lifespan, long gestation period, late maturity and slow reproductive rate may make the shovelnose guitarfish particularly vulnerable to overfishing ⁽⁷⁾. Other potential threats include habitat change, such as the modification of many bays and estuaries in northwest Pacific Mexico to accommodate shrimp farming ⁽¹⁾.

Shovelnose guitarfish conservation

There are currently no specific conservation measures in place for the shovelnose guitarfish ⁽¹⁾. Various studies have investigated the life history of the species, providing basic information for its management ^{(7) (8)}, but fishing of batoids in Mexico is poorly monitored and lacks the species-specific details necessary to assess catch levels ⁽¹⁾. However, legislation is currently being developed here to establish national fishery management for shark, ray and skate species, and the IUCN have also recommended that fishery-independent surveys be undertaken, to provide population estimates for this and other bottom-dwelling species ⁽¹⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

To find out more about the conservation of guitarfish, and of other sharks and rays, see:

• Save Our Seas Foundation:
  http://www.saveourseas.com/
• IUCN Shark Specialist Group:
  http://www.iucnssg.org
• Shark Research Institute:
  http://www.sharks.org
• Shark Trust:
  http://www.sharktrust.org/

Authentication

Glossary

Bycatch

In the fishing industry, the part of the catch made up of non-target species.

Caudal fin

The tail fin of a fish.

Crustaceans

Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.

Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.

Gestation

The state of being pregnant; the period from conception to birth.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.

Molluscs

A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.

Pectoral fins

In fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.

References

1. IUCN Red List (July, 2009)
   http://www.iucnredlist.org
2. ReefQuest Centre for Shark Research (July, 2009)
   http://www.elasmo-research.org/education/shark_profiles/rhynchobatiformes.htm
3. Allen, G.R. and Robertson, D.R. (1994) Fishes of the Tropical Eastern Pacific. University of Hawaii Press, Honolulu, Hawaii.
4. Burnie, D. (2001) Animal. Dorling Kindersley, London.
5. Ebert, D.A. (2003) Sharks, Rays, and Chimaeras of California. University of California Press, Berkeley.
6. Eschmeyer, W.N., Herald, E.S. and and Hammann, H. (1999) A Field Guide to Pacific Coast Fishes of North America. Houghton Mifflin Harcourt, Boston.
7. Márquez-Farías, J.F. (2007) Reproductive biology of shovelnose guitarfish Rhinobatos productus from the eastern Gulf of California México. Marine Biology, 151: 1445 - 1454.
8. Timmons, M. and Bray, R.N. (1997) Age, growth, and sexual maturity of shovelnose guitarfish, Rhinobatos productus (Ayres). Fishery Bulletin, 95: 349 - 359.
9. Talent, L.G. (1982) Food habits of the gray smoothhound, Mustelus californicus, the brown smoothhound, Mustelus henlei, the shovelnose guitarfish, Rhinobatos productus, and the bat ray, Myliobatis californica, in Elkhorn Slough, California. California Fish and Game, 68(4): 224 - 234.