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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Average mass: 6.64 kg.
Range length: 90 to 137 cm.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: female larger
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.
Range lifespan
Status: wild: 11 to 16 years.
Average lifespan
Status: captivity: unknown. years.
Typical lifespan
Status: wild: 16 (high) years.
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.
Range depth: 2 to 91 m.
Average depth: 13 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: benthic ; coastal ; brackish water
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.
Biogeographic Regions: nearctic (Native ); pacific ocean (Native )
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).
Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans; other marine invertebrates
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore , Vermivore, Scavenger )
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.
Commensal/Parasitic Species:
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.
Positive Impacts: food ; body parts are source of valuable material
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.
Negative Impacts: injures humans (bites or stings)
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.
Development - Life Cycle: indeterminate growth
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.
Communication Channels: tactile
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical ; electric
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.
Mating System: monogamous
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.
Breeding interval: This species breeds once a year during warmer months, beginning in June.
Breeding season: Breeding occurs during the summer months.
Range number of offspring: 6 to 28.
Average number of offspring: 11.
Range gestation period: 9 to 12 months.
Average age at sexual or reproductive maturity (female): 7 years.
Average age at sexual or reproductive maturity (male): 8 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); ovoviviparous
There is no known parental investment after birth.
Parental Investment: no parental involvement
The shovelnose guitarfish, Pseudobatos productus, is a ray in the family Rhinobatidae.[2][3] It becomes mature at an estimated seven to eight years old. Males are between 90–100 cm (35–39 in) long, while females are around 99 cm (39 in) at that age.[4] The ray can live up to 11 years, and full-grown sizes are around 120 cm (47 in) for males, and females reach 137 cm (54 in).[5] They range from central California south to the Gulf of California.[1] Morphological and genetic variations occur in the mitochondrial DNA in those found in the Gulf of California, evidencing their isolation from the rest. Because of this, the conservation of this species must be carefully managed to preserve the biological diversity.[6] The shovelnose is considered to be a primitively developed ray, with many features of both sharks and rays.
Pseudobatos productus has magnetic particles in its vestibular receptors, and the magnetic particles are believed to be exogenous in origin. The magnetic particles' spatial arrangement may aid in the sensitivity of the receptors to movements.[7]
The visual system of the shovelnose is more extensive and developed than other Elasmobranchii, with multiple large projections connecting to the brain. Almost the entire dorsal and ventral hypothalamus is connected to the visual system, but still maintains a similar lack of differentiation as with sharks.[8]
The shovelnose guitarfish was first considered to be a shark because of its dorsal fins' shape.
This species can be caught from the surf, within shallow California waters. Sand crabs, various bivalves such as mussels, and other live or dead bait are recommended for catching the fish.[9]
The common cuts of meat used from the shovelnose guitarfish are the trunk, tail, and loin, mostly from mature individuals. It has been referred to as "shark steak" within markets, and is usually served fried; with other iterations such as cocktails and kebabs being prepared. It is sold as fish and chips in Santa Barbara, California on piers. Dried specimens of all sizes are also frequently sold in shell shops throughout central to Baja California.[4][10]
Shovelnose guitarfish
Media related to Pseudobatos productus at Wikimedia Commons
The shovelnose guitarfish, Pseudobatos productus, is a ray in the family Rhinobatidae. It becomes mature at an estimated seven to eight years old. Males are between 90–100 cm (35–39 in) long, while females are around 99 cm (39 in) at that age. The ray can live up to 11 years, and full-grown sizes are around 120 cm (47 in) for males, and females reach 137 cm (54 in). They range from central California south to the Gulf of California. Morphological and genetic variations occur in the mitochondrial DNA in those found in the Gulf of California, evidencing their isolation from the rest. Because of this, the conservation of this species must be carefully managed to preserve the biological diversity. The shovelnose is considered to be a primitively developed ray, with many features of both sharks and rays.
Pseudobatos productus has magnetic particles in its vestibular receptors, and the magnetic particles are believed to be exogenous in origin. The magnetic particles' spatial arrangement may aid in the sensitivity of the receptors to movements.
The visual system of the shovelnose is more extensive and developed than other Elasmobranchii, with multiple large projections connecting to the brain. Almost the entire dorsal and ventral hypothalamus is connected to the visual system, but still maintains a similar lack of differentiation as with sharks.
The shovelnose guitarfish was first considered to be a shark because of its dorsal fins' shape.
