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Biology and Ecology of a Sawfish. Taxonomy Phylum: Chordata Phylum: Chordata Class: Chondrichthyans (sharks, rays and chimeras) Class: Chondrichthyans.

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Presentation on theme: "Biology and Ecology of a Sawfish. Taxonomy Phylum: Chordata Phylum: Chordata Class: Chondrichthyans (sharks, rays and chimeras) Class: Chondrichthyans."— Presentation transcript:

1 Biology and Ecology of a Sawfish

2 Taxonomy Phylum: Chordata Phylum: Chordata Class: Chondrichthyans (sharks, rays and chimeras) Class: Chondrichthyans (sharks, rays and chimeras) Subclass: Elasmobranchii Subclass: Elasmobranchii Superorder: Batoidea (rays) Superorder: Batoidea (rays) Order: Pristiformes Order: Pristiformes Family: Pristidae Family: Pristidae

3 Biology Life history strategy K-selected life history strategy K-selected life history strategy Long-lived Long-lived years years Large size Large size Up to 7m Up to 7m Late sexual maturity Late sexual maturity Approx. 10 years old Approx. 10 years old Low fecundity Low fecundity 8-24 pups 8-24 pups

4 Distribution and Habitat Global distribution in tropical and sub-tropical regions Global distribution in tropical and sub-tropical regions Distribution is currently fragmented with most populations thought to be depleted Distribution is currently fragmented with most populations thought to be depleted Occur in marine, freshwater and coastal habitats Occur in marine, freshwater and coastal habitats Tolerance to freshwater dependent on species Tolerance to freshwater dependent on species Preference for shallow, inshore coastal and freshwater habitats but can occur to at least 80 m depth Preference for shallow, inshore coastal and freshwater habitats but can occur to at least 80 m depth

5 Description Closely related to rays with modified bodies similar to sharks Also similar to and often confused with sawsharks Distinguished by presence of gills on the underside of head

6 Behaviour Sawfish are nocturnal Sawfish are nocturnal Sleep in the day Sleep in the day Hunt at night Hunt at night Sawfish are top order predators Sawfish are top order predators Actively seek out prey items such as Actively seek out prey items such as Fish Fish Crustaceans Crustaceans Squid Squid Use rostrum for feeding by Use rostrum for feeding by Stunning slow moving schooling fish with slashing motion Stunning slow moving schooling fish with slashing motion Locating and dislodging prey buried in sand or mud Locating and dislodging prey buried in sand or mud Locate buried prey by using sensors on rostrum Locate buried prey by using sensors on rostrum Will also eat dead prey and strike at lures Will also eat dead prey and strike at lures

7 Anatomy Rostrum Most distinguishing feature Most distinguishing feature Long flat and saw-like Long flat and saw-like Made of cartilage Made of cartilage Contains pairs of teeth on sides Contains pairs of teeth on sides Modified scales Modified scales Used to detect and catch prey using motion and electro- sensors Used to detect and catch prey using motion and electro- sensors Allow detection from long distance and under sediment Allow detection from long distance and under sediment Rostrum can also be used to; Rostrum can also be used to; rake through sediment to find prey rake through sediment to find prey Stun prey with slashing motion Stun prey with slashing motion Protect from predators Protect from predators Also used to distinguish species Also used to distinguish species Number of teeth Number of teeth Shape of rostrum Shape of rostrum

8 Anatomy Eyes On top of head so can see when partially buried On top of head so can see when partially buried Eyesight good but often not useful due to murky habitat Eyesight good but often not useful due to murky habitat Make up for this with sensitive sense organs in rostrum Make up for this with sensitive sense organs in rostrum Spiracle Located behind the eye Located behind the eye Used to take in water when lying on the bottom Used to take in water when lying on the bottom

9 Anatomy Fins The sawfish has 4 different types of fins all with different uses The sawfish has 4 different types of fins all with different usesPectoral Pair of pectoral fins located behind the head Pair of pectoral fins located behind the head Used to lift fish when swimming Used to lift fish when swimming Helps with steering Helps with steering Consists of cartilage spread out in fan shape Consists of cartilage spread out in fan shape Does not reach edge of fin Does not reach edge of fin Makes fin pliable increasing manoeuvrability Makes fin pliable increasing manoeuvrability Dorsal Dorsal means back or upper surface Dorsal means back or upper surface 2 dorsal fins 2 dorsal fins Used for stabilisation Used for stabilisationPelvic Pair of pelvic fins located on side behind the pectoral fins Pair of pelvic fins located on side behind the pectoral fins Used for stabilisation while swimming Used for stabilisation while swimmingCaudal Also known as the tail fin Also known as the tail fin Shape differs between species Shape differs between species Used to generate power and speed in swimming Used to generate power and speed in swimming

10 Anatomy Pelvic Pair of pelvic fins located on side behind the pectoral fins Pair of pelvic fins located on side behind the pectoral fins Used for stabilisation while swimming Used for stabilisation while swimmingCaudal Also known as the tail fin Also known as the tail fin Shape differs between species Shape differs between species Used to generate power and speed in swimming Used to generate power and speed in swimming Dorsal Dorsal means back or upper surface Dorsal means back or upper surface 2 dorsal fins 2 dorsal fins Used for stabilisation Used for stabilisation

11 Anatomy Internal Anatomy Sawfish dont contain swim bladder for buoyancy Instead have an oil filled liver like sharks and rays Underside of Sawfish Like rays the flat ventral or underside of sawfish contain Nostrils (nares) Mouth Gill slits Jaw contains thousands of dome shaped teeth Used to crush small fish and crustaceans e.g. Crabs and shrimp

12 Reproductive Biology Reproduce through internal fertilisation Reproduce through internal fertilisation Male contain claspers Male contain claspers Modification of pelvic fin Modification of pelvic fin Used to insert sperm into female Used to insert sperm into female Ovoviviparous Ovoviviparous Eggs are fertilised and grow within mother Eggs are fertilised and grow within mother Hatch within womb and mother gives birth to fully developed pups Hatch within womb and mother gives birth to fully developed pups

13 Reproductive Biology Average of 8 pups are born at around 65-90cm Average of 8 pups are born at around 65-90cm Gestation period (fertilisation to birth time) is approx. 5 months Gestation period (fertilisation to birth time) is approx. 5 months Number and size of pups increase with maturity of birthing mother Number and size of pups increase with maturity of birthing mother Pups born with a toothed rostrum which is covered by a enclosed membrane designed to protect mother from teeth Pups born with a toothed rostrum which is covered by a enclosed membrane designed to protect mother from teeth Growth rate Growth rate Rapid in first year of life Rapid in first year of life Slows considerably as maturity reached Slows considerably as maturity reached

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15 Saw fish are threatened throughout the world Saw fish are threatened throughout the world All Australian species are on the IUCN Redlist of threatened species as critically endangered All Australian species are on the IUCN Redlist of threatened species as critically endangered Because they prefer an inshore benthic habitat for breeding,the juveniles are vulnerable to human interference Because they prefer an inshore benthic habitat for breeding,the juveniles are vulnerable to human interference They are also known to They are also known to actively seek out dead baits or strike at lures making them vulnerable to recreational fishing

16 Major threats include Major threats include Hunting Hunting Habitat modification and pollution Habitat modification and pollution Entanglement in fishing nets Entanglement in fishing nets

17 Hunting Sawfish are hunted for their Sawfish are hunted for their Rostrums Rostrums Fins Fins Flesh Flesh Other body parts Other body parts These are sold for food and use in traditional Asian medicines These are sold for food and use in traditional Asian medicines Rostrums are sold as valuable souvenirs, trophies or curios Rostrums are sold as valuable souvenirs, trophies or curios Sawfish may also be collected as live specimens for aquariums Sawfish may also be collected as live specimens for aquariums

18 Habitat modification and pollution Building of weirs and barrages can restrict movement of sawfish in rivers Building of weirs and barrages can restrict movement of sawfish in rivers Other problems include increased pollution from: Other problems include increased pollution from: Land clearing - increased sediment runoff Land clearing - increased sediment runoff Use of fertilisers - increased nutrient runoff Use of fertilisers - increased nutrient runoff Use of pesticides - reduced health and death of organisms Use of pesticides - reduced health and death of organisms Urban and industrial development Urban and industrial development Loss of soft bottom feeding and breeding habitats also poses a threat Loss of soft bottom feeding and breeding habitats also poses a threat

19 Entanglement in fishing nets Entanglement may occur in Trawling nets Shark nets Recreational fishing line Sawfish are vulnerable to entanglement as the rostrum is easily entangled in nets and fishing line The sawfish thrashes around to get free causing further tangling When unable to swim the sawfish is unable to move water over gills and may drown


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