Pristiophorus cirratusCommon sawshark(Also: Doggies; Little sawshark; Longnose saw shark; Saw dog)

Geographic Range

Pristiophorus cirratus is found in the waters around southern Australia’s outer continental shelf, and is endemic to that region. This includes the eastern portion of the Indian Ocean and the southwest portion of the Pacific Ocean. They are found in the area described by the latitudes 20° to 41° south and longitude 112° to 150° east. (Hilton-Taylor, 2006)

Habitat

Longnose sawsharks prefer a variety of marine habitats including the open sea and coastal regions. They are typically found at depths below 40 meters. (Compagno, 2006)

  • Range depth
    40 to 310 m
    131.23 to 1017.06 ft

Physical Description

Pristiophorus cirratus is characterized by a long, thin, and flattened snout. The snout is lined with alternating long and short teeth. Unusual nasal barbels protrude about halfway down the snout. Near the barbels are the ampullae of Lorenzini, which are specialized organs for detecting electrical fields. Two dorsal fins are present, with the second being slightly smaller than the first. They lack an anal fin. Five gill slits are present on each side of the head, while most sawsharks have gills on the bottom of the head. The upper body is a blotchy combination of dull yellow, grey, and brown. (Cropp, 1964; Hilton-Taylor, 2006; Martin, 2006)

  • Sexual Dimorphism
  • female larger
  • Range mass
    18.7 lbs or 8.5 (high) kg
    lb
  • Range length
    4.9 ft or 1.49 (high) m
    ft

Development

Longnose sawsharks are born in litters of 3 to 22 individuals. They are born with their teeth folded back, which mostly likely is an adaptation to prevent possible injury to the mother during the birthing process. The teeth straighten shortly after birth. Sawsharks are born fully developed, looking like smaller versions of adults. Newborn sawsharks are generally 31 to 34 cm in length. Sawsharks do not undergo a metamorphosis and exhibit determinate growth. (Martin, 2006)

Reproduction

Longnose sawsharks breed seasonally. It is unknown if they are monogamous or promiscuous. It is unknown what affect mating behavior has on social structure.

Longnose sawsharks breed once every two years, and most breeding occurs in coastal areas. Each breeding season yields an average of 10 young (range of 3 to 22). The gestation period for longnose sawsharks is approximately 12 months. Longnose sawsharks are ovoviviparous, meaning that the eggs develop within the mother's body and then hatch within the mother before they are released. (Compagno, 2006)

  • Breeding interval
    Individual longnose sawsharks breed biennially (in alternating years).
  • Breeding season
    Longnose sawsharks have a yearly breeding/spawning season.
  • Range number of offspring
    3 to 22
  • Average number of offspring
    10
  • Average gestation period
    12 months
  • Range time to independence
    1 to 2 years
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

In the pre-birth stage, while the young are still within the womb, nourishment and provisioning are provided by the mother. In the post-birth stage, the parents provide food and protection. The exact duration of parental investment is unknown, but it is complete before the individual's next breeding season.

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
  • pre-weaning/fledging
    • provisioning
    • protecting

Lifespan/Longevity

Longnose sawsharks have been known to survive for up to 15 years in the wild. Lifespan in the wild is often limited by trawl fishing. (Compagno, 2006; Compagno, 2006)

  • Range lifespan
    Status: wild
    15 (high) years

Behavior

Longnose sawsharks are motile. Little is known about their social structure, but they do form schools. A notable behavior of longnose sawsharks is the use of their snouts (lined with sharp teeth) to side-swipe their prey. Longnose sawsharks are generally sedentary. (Compagno, 2006)

  • Range territory size
    Approximately 100 (high) km^2

Home Range

Longnose sawsharks do not travel extended distances. Even if travelling to breed, their home range rarely exceeds 100 square kilometers. (Hilton-Taylor, 2006)

Communication and Perception

Longnose sawsharks communicate using sight, touch, and electric signals. They perceive their environment with mediocre eyesight, use their barbels to touch the ocean floor, and use their ampullae to sense electrical fields. They communicate with other animals visually and use their barbels and ampullae when searching for prey. (Hilton-Taylor, 2006)

Food Habits

Longnose sawsharks feed on bony fish,including cornet fishes (Fistularia), shrimp, small squids, and various crustaceans. Longnose sawsharks uses their barbels and snout to detect prey on the ocean floor, and then immobilize their prey by hitting it with a side-swipe of their snout, which is lined with sharp teeth.

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

The main anti-predator adaptation of longnose sawsharks is their coloration. Their blotchy grey and brown markings help them blend in with the ocean floor. Human beings are the main predator of longnose sawsharks, although larger sharks are occasional predators. Humans have severely damaged shark populations due to commercial fishing. (Hilton-Taylor, 2006)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Longnose sawsharks are not a keystone species, although their absence would have an impact on creatures living on the ocean floor because they serve as prey for longnose sawsharks. Longnose sawsharks often serve as hosts for tetraphyllidean tapeworms.

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Longnose sawsharks are commercially fished for their high-quality meat. (Wikipedia, 2006)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Longnose sawsharks have no adverse economic impact on humans.

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Effective efforts have been made to protect longnose sawsharks. Commercial fishing of longnose sawsharks has been reduced due to the implementation of a Total Allowable Catch rule. Also, a three mile stretch of Victorian waters have been closed to all shark fishing, which provides some safe habitat for longnose sawsharks. (Hilton-Taylor, 2006)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Daniel Krcmaric (author), University of Notre Dame, Karen Francl (editor, instructor), Radford University.

Glossary

Pacific Ocean

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.

World Map

benthic

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.

bilateral symmetry

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

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.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

electric

uses electric signals to communicate

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

iteroparous

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).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Compagno, L. 2006. "Pristiophorus cirratus Longnose Sawshark" (On-line). Accessed February 27, 2006 at http://filaman-.ifm-geomar.de/summary/speciessummary.php?id=721.

Cropp, B. 1964. Shark Hunters. New York: The Macmillan Company.

Fisheries Global Information System, 2006. "Fisheries Global Information System" (On-line). Accessed February 27, 2006 at http://www.fao.org/figis/servelt?Firefservlet.

Hilton-Taylor, C. 2006. "The IUCN Red List of Threatened Species" (On-line). Accessed February 27, 2006 at http://redlist.org/search/details.php?species=39327.

Martin, A. 2006. "Order Pristiophoriformes: Sawsharks- 8 Species" (On-line). Accessed February 27, 2006 at http://www.elasmo-research.org/education/sharkprofile/pristiophoroformes.htm.

The British Library, 1999. "Southern Australian Shark Fishery Management" (On-line). Accessed February 27, 2006 at www.bl.uk/services/document/edd.html.

Walker, T. 1999. Southern Australian Shark Fishery Management. FAO Fisheries Technical Paper, 378: 48.

Wikipedia, 2006. "Sawshark" (On-line). Accessed March 23, 2006 at http://en.wikipedia.org/wiki/sawshark.