Shovelnose guitarfish are found along the Southwestern coast of North America, ranging from San Francisco to Guerrero, Mexico as well as within the Gulf of California and along the coast of Baja California. (Farrugia, et al., 2011)
This species is usually found in the surf zone and in shallow coastal waters (average depth 13 m), though individuals have been observed at depths of up to 91 m. This species prefers sandy or muddy bottoms and is occasionally found in sea grass beds, estuaries, and near rocky reefs. ("Shovelnose guitarfish (Rhinobatos productus)", 2012; Farrugia, et al., 2011; Froese and Luna, 2012)
Shovelnose guitar fish most resemble sharks in posterior body shape, with a flattened anterior like a ray. Their snouts are pointed and shovel-like, and they have broad pectoral fins. Their dorsal surfaces are smooth except for rows of small thorns around the eyes and tail. The tail is rather thick with a rounded caudal fin (characteristic of a benthic fish), lacking the lower lobe that most other sharks possess. Shovelnose guitarfish have two equally-sized dorsal fins positioned close to the end of the tail. This species' body color ranges from sandy brown to olive, with a white underside; the distal end of the snout is partially translucent. Their teeth are small and rounded, and range in number from 102 to 112. Females usually grow larger than males, reaching up to 137 centimeters when fully gown, while males may reach up to 120 centimeters. (Timmons and Bray, 1997)
Females retain their eggs inside their bodies until they hatch and give live birth to young that are miniature versions of adults. The sex ratio of the pups appears to be 1:1. Shovelnose guitarfish grow continuously until death. (Timmons and Bray, 1997)
Shovelnose guitarfish mate once a year and are monogamous. Males typically move into shallow waters by midsummer, shortly followed by females, for mating; following mating, the fish typically leave these areas. ("Shovelnose guitarfish (Rhinobatos productus)", 2012; Ebert, 2003)
This species mates seasonally, during summer months. On average, males reach sexual maturity at 8 years while females reach sexual maturity at 7 years. Beginning in midsummer, males migrate to bays and estuaries to mate, followed by females; they are absent from these areas during the fall and winter months. Gestation ranges from 9-12 months. Females re-enter bays and estuaries along Southern California and Baja, California to complete gestation and give birth, typically between June and October. Females are ovoviviparous, giving birth to litters of 6–28 pups that are 15-24 cm in length. ("Shovelnose guitarfish (Rhinobatos productus)", 2012; Froese and Luna, 2012; Martin, 2007; "Shovelnose guitarfish", 2012; Timmons and Bray, 1997)
There is no known parental investment after birth.
Average life expectancy of shovelnose guitarfish is 11 years, with a maximum reported age of 16 years. Lifespan can be limited in some populations due to bycatch by bottom trawling. There is no available information regarding lifespan in captivity. (Froese and Luna, 2012; Timmons and Bray, 1997)
These animals are solitary outside of mating aggregations. They are not known to be territorial. They tend to lie, partially buried, on sandy or muddy sea bottoms. They are known to feed in warmer waters and rest in cooler waters, which may be an adaptive behavior to regulate metabolic rate. ("Shovelnose guitarfish (Rhinobatos productus)", 2012; Farrugia, et al., 2011)
This is a migratory species, moving to protected areas to breed and give birth. Shovelnose guitarfish do not appear to maintain individual home ranges or territories. (Farrugia, et al., 2011)
Little data is available on communication between individuals of this species. Like other elasmobranchs, shovelnose guitarfish have highly developed senses to detect prey. The lateral line system that extends the length of the body detects pressure waves from movements of prey and other animals in the water, and electroreceptors on the underside of the snout (called Ampullae of Lorenzini) detect electrical discharges of infaunal prey buried within the sediments. (Bond, 1996)
Shovelnose guitarfish feed nocturnally on infaunal organisms such as worms, crabs, clams, and smaller fish. In Elkhorn Slough, California, their preferred prey is yellow shore crabs (Hemigrapsus oregonensis). (Talent, 1982)
This species has a countershaded body. By staying primarily on the sea floor, most often on muddy areas, the gray coloration on the dorsal surface helps to camouflage them from predatory birds and mammals. Much like rays, they may also bury themselves in sand to effectively conceal themselves from predators. (Farrugia, et al., 2011)
Shovelnose guitarfish fill the roles of both predator and prey in the coastal marine ecosystem, consuming second-order consumers such as fish and mollusks. They serve as prey to large bird species and sea lions, as well as being actively fished by humans along the California and Mexico coastline. They are hosts to multiple species of endoparasitic flukes and tapeworms, as well as at least one species of ectoprasitic copepod. (Dailey and Carvajal, 1976; Dailey and Mudry, 1968; Dojiri and Deets, 1988; Doran, 1953; Ebert, 2003; Sandoval-Castillo, et al., 2004)
Shovelnose guitarfish are actively fished along the Pacific coast of Baja California as well as within the Gulf of California. They are an important source of income to artisanal fishermen in the region because of their high market value. (Sandoval-Castillo, et al., 2004)
There is only one reported attack on a diver, when a male shovelnose guitarfish was interrupted during mating. Due to its blunt tooth structure, the bite was described as "gumming", and no significant injury resulted. (Ebert, 2003)
Although this species faces no serious threat in northern and central California, Mexican fisheries are impacting both population numbers and their habitats. These fisheries tend to catch adults as bycatch in their gill nets. On the west coast of Baja California, there is a greater chance of catching pregnant females in the gill nets. The actual effect of these fisheries has yet to be determined. On the Pacific coast of northern Mexico, shrimp farming activities are altering the bays and estuaries, which are key habitats for Shovelnose guitarfish feeding and mating activities. As of 2012, there are no laws in place to protect this species in U.S. or Mexican waters. This is due to a lack of data on the species. Currently, Mexico is working on legislation geared toward the general conservation of elasmobranchs, but there is not a specific conservation plan for this species. (IUCN, 2012)
Rodriguez Torri Navarro Robert, Chow Victoria (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Jeremy Wright (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
Animals with indeterminate growth continue to grow throughout their lives.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
an animal that mainly eats dead animals
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
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Márquez, F., W. Smith, J. Bizzarro. 2006. "Rhinobatos productus" (On-line). IUCN Red List of Threatened Species. Accessed March 14, 2012 at http://www.iucnredlist.org.
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Talent, L. 1982. Food habits of the grey smoothhound, Mustelus californicus, the brown smoothound, M. henlei, the shovelnose guitarfish Rhinobatus productus, and the bat ray Myliobatis californica in Elkhorn Slough, California. California Fish and Game, 68-4: 224-234. Accessed April 29, 2012 at http://ia600504.us.archive.org/17/items/californiafishga68_4cali/californiafishga68_4cali.pdf.
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