Post on 10-Dec-2015
Biology and Ecology Biology and Ecology
of a Sawfishof a Sawfish
TaxonomyTaxonomyPhylum: ChordataPhylum: Chordata
Class: Chondrichthyans (sharks, rays and Class: Chondrichthyans (sharks, rays and chimeras)chimeras)
Subclass: Elasmobranchii Subclass: Elasmobranchii
Superorder: Batoidea (rays)Superorder: Batoidea (rays)Order: PristiformesOrder: Pristiformes
Family: PristidaeFamily: Pristidae
BiologyBiologyLife history strategyLife history strategyK-selected life history K-selected life history
strategy strategy Long-livedLong-lived
25-30 years25-30 yearsLarge sizeLarge size
Up to 7mUp to 7mLate sexual maturityLate sexual maturity
Approx. 10 years oldApprox. 10 years oldLow fecundityLow fecundity
8-24 pups8-24 pups
Distribution and HabitatDistribution and HabitatGlobal distribution in tropical and sub-Global distribution in tropical and sub-
tropical regionstropical regionsDistribution is currently fragmented with Distribution is currently fragmented with
most populations thought to be depletedmost populations thought to be depletedOccur in marine, freshwater and coastal Occur in marine, freshwater and coastal
habitats habitats Tolerance to freshwater dependent on Tolerance to freshwater dependent on
speciesspeciesPreference for shallow, inshore coastal and Preference for shallow, inshore coastal and
freshwater habitats but can occur to at least freshwater habitats but can occur to at least 80 m depth 80 m depth
DescriptionDescriptionClosely 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
BehaviourBehaviourSawfish are Sawfish are
nocturnalnocturnalSleep in the daySleep in the dayHunt at nightHunt at night
Sawfish are top Sawfish are top order predators order predators
Actively seek out Actively seek out prey items such as prey items such as Fish Fish CrustaceansCrustaceansSquid Squid
Use rostrum for Use rostrum for feeding byfeeding byStunning slow Stunning slow
moving schooling moving schooling fish with slashing fish with slashing motion motion
Locating and Locating and dislodging prey dislodging prey buried in sand or buried in sand or mudmud
Locate buried prey Locate buried prey by using sensors on by using sensors on rostrumrostrum
Will also eat dead Will also eat dead prey and strike at prey and strike at lureslures
AnatomyAnatomyRostrumRostrum Most distinguishing featureMost distinguishing feature Long flat and saw-likeLong flat and saw-like Made of cartilageMade of cartilage Contains pairs of teeth on Contains pairs of teeth on
sidessides Modified scalesModified scales
Used to detect and catch Used to detect and catch prey using motion and prey using motion and electro-sensors electro-sensors Allow detection from long Allow detection from long
distance and under distance and under sedimentsediment
Rostrum can also be used Rostrum can also be used to;to; rake through sediment to rake through sediment to
find preyfind prey Stun prey with slashing Stun prey with slashing
motionmotion Protect from predatorsProtect from predators
Also used to distinguish Also used to distinguish speciesspecies Number of teethNumber of teeth Shape of rostrumShape of rostrum
AnatomyAnatomyEyesEyesOn top of head so can On top of head so can
see when partially see when partially buriedburied
Eyesight good but often Eyesight good but often not useful due to murky not useful due to murky habitathabitat
Make up for this with Make up for this with sensitive sense organs sensitive sense organs in rostrumin rostrum
SpiracleSpiracleLocated behind the eyeLocated behind the eyeUsed to take in water Used to take in water
when lying on the bottomwhen lying on the bottom
AnatomyAnatomyFinsFins The sawfish has 4 different The sawfish has 4 different
types of fins all with different types of fins all with different usesuses
PectoralPectoral Pair of pectoral fins located Pair of pectoral fins located
behind the headbehind the head Used to lift fish when Used to lift fish when
swimmingswimming Helps with steeringHelps with steering Consists of cartilage spread Consists of cartilage spread
out in fan shapeout in fan shape Does not reach edge of fin Does not reach edge of fin Makes fin pliable Makes fin pliable
increasing increasing manoeuvrability manoeuvrability
Dorsal Dorsal
Dorsal means back or upper surfaceDorsal means back or upper surface
2 dorsal fins2 dorsal fins
Used for stabilisationUsed for stabilisation
Pelvic Pelvic
Pair of pelvic fins located on side behind Pair of pelvic fins located on side behind the pectoral finsthe pectoral fins
Used for stabilisation while swimmingUsed for stabilisation while swimming
CaudalCaudal
Also known as the tail finAlso known as the tail fin
Shape differs between speciesShape differs between species
Used to generate power and speed in Used to generate power and speed in swimmingswimming
AnatomyAnatomyPelvic Pelvic Pair of pelvic fins located on Pair of pelvic fins located on
side behind the pectoral finsside behind the pectoral finsUsed for stabilisation while Used for stabilisation while
swimmingswimming
CaudalCaudalAlso known as the tail finAlso known as the tail finShape differs between Shape differs between
speciesspeciesUsed to generate power and Used to generate power and
speed in swimmingspeed in swimming
Dorsal Dorsal Dorsal means back or Dorsal means back or
upper surfaceupper surface
2 dorsal fins2 dorsal fins
Used for stabilisationUsed for stabilisation
AnatomyAnatomyInternal AnatomySawfish don’t contain
swim bladder for buoyancy
Instead have an oil filled liver like sharks and rays
Underside of SawfishLike rays the flat
ventral or underside of sawfish containNostrils (nares)MouthGill slits
Jaw contains thousands of dome shaped teethUsed to crush small
fish and crustaceans e.g. Crabs and shrimp
Reproductive BiologyReproductive BiologyReproduce through Reproduce through
internal fertilisationinternal fertilisationMale contain claspers Male contain claspers
Modification of pelvic Modification of pelvic
finfinUsed to insert sperm Used to insert sperm
into femaleinto female
OvoviviparousOvoviviparousEggs are fertilised Eggs are fertilised
and grow within and grow within mothermother
Hatch within womb Hatch within womb and mother gives and mother gives birth to fully birth to fully developed pupsdeveloped pups
Reproductive BiologyReproductive BiologyAverage of 8 pups are born at around 65-90cmAverage of 8 pups are born at around 65-90cm
Gestation period (fertilisation to birth time) is approx. Gestation period (fertilisation to birth time) is approx. 5 months5 months
Number and size of pups increase with maturity of Number and size of pups increase with maturity of birthing motherbirthing mother
Pups born with a toothed rostrum which is covered by Pups born with a toothed rostrum which is covered by a enclosed membrane designed to protect mother a enclosed membrane designed to protect mother from teethfrom teeth
Growth rateGrowth rate Rapid in first year of lifeRapid in first year of life Slows considerably as maturity reachedSlows considerably as maturity reached
Saw fish are threatened throughout the worldSaw fish are threatened throughout the world
All Australian species are on the IUCN Redlist of All Australian species are on the IUCN Redlist of threatened species as critically endangered threatened species as critically endangered
Because they prefer an inshore benthic habitat for Because they prefer an inshore benthic habitat for breeding ,the juveniles are vulnerable to human breeding ,the juveniles are vulnerable to human interferenceinterference
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
Major threats includeMajor threats includeHuntingHuntingHabitat modification and Habitat modification and
pollutionpollutionEntanglement in fishing netsEntanglement in fishing nets
HuntingHunting Sawfish are hunted for theirSawfish are hunted for their
RostrumsRostrumsFinsFinsFleshFleshOther body partsOther body parts
These are sold for food and These are sold for food and use in traditional Asian use in traditional Asian medicines medicines
Rostrums are sold as valuable Rostrums are sold as valuable souvenirs, trophies or curios souvenirs, trophies or curios
Sawfish may also be collected Sawfish may also be collected as live specimens for as live specimens for aquariumsaquariums
Habitat modification and pollutionHabitat modification and pollutionBuilding of weirs and Building of weirs and
barrages can restrict barrages can restrict movement of sawfish movement of sawfish in riversin rivers
Other problems include Other problems include increased pollution from: increased pollution from: Land clearing - Land clearing -
increased sediment increased sediment runoff runoff
Use of fertilisers - Use of fertilisers - increased nutrient increased nutrient runoff runoff
Use of pesticides - Use of pesticides - reduced health and reduced health and death of organisms death of organisms
Urban and industrial Urban and industrial developmentdevelopment
Loss of soft Loss of soft bottom bottom feeding and feeding and breeding breeding habitats habitats also poses a also poses a threatthreat
Entanglement in fishing netsEntanglement in fishing nets
Entanglement may occur inTrawling netsShark netsRecreational
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