Lecture 21- Marine vertebrates and issues for their conservation Flashcards
What is the ecological context of marine vertebrates?
- some live entirely in the sea
- some use both marine and terrestrial environments
- all dependent on the sea for foraging
- conservation/management programs more complex in marine vs terrestrial alone, often very difficult in the ocean+ species distributions often go beyond territorial waters
What is the classification of marine mammals?
- Therian mammals, subclassEutherian mammals
- orders Cetacea and Sirenia, Carnivore= but not closely related
What is the order Cetacea?
- whales and dolphins
- live entirely in aquatic environments, forage and breed in water, often have very extensive geographic distributions
- in Australian waters=baleen whales= 9species, toothed whales and dolphins= 35 species
What is the order Carnivora (seals)?
- F:Otariidae= eared seals eg. fur seal
- F: Phocidae= earless seals eg elephant seals
- use both marine (for foraging) and terrestrial (breeding environments
- many species breed in large colonies onshore
What are the management issues with seals? (7)
- Lone seals hauling out near towns-unusual (crowd control needed so people don’t get bitten and then shoot the seal)
- Harvesting
- Population status
- Tourism (approach and disturbance)
- Pollution (oil spills or exploration)
- Disease (Phocine distemper)
- Fisheries management(-entanglement in nets.-raiding fish farms (get shot), -potential competition for food with commercial fishing industry
What is the story with seals and nets entanglement?
- one source of mortality, young seals at higher risk
- education targeting fishing industry
Does seal diet change over time?
- yes, could be related to changes in fish stocks
- but not commercial fish populations are very difficult to monitor so unclear
What animals are in the order Sirenia?
- 1 species in Australia
- the dugong
- declining in numbers
What is the dugong distribution?
- coast of Australia,PNG, Maylaysia, Indonesia, India, South Africa and the Red Sea
- in areas of high human populations
- occurs in many poorer nations (there used as food)
- fewer dollars for conservation and management
What is the dugong life history like?
- max life span= 70 years
- sexual maturity= 9-17
- gestation: 13 months
- lactation: 18 months
- calving interval: 3-7 years
- very slow reproductive rate thus very low population growth rate
What are the assumptions of the model of population growth used in population management in dugongs?
- females breed at same rate through life
- stop breeding at 50
- females live less than 60
- sex ratio 1:1
- no migration (now known to be incorrect)
What do dugongs feed on?
-seagrass, which occurs in shallow coastal waters, this exposes them to risk (interactions with humans)
What are the threats to dugongs?
- increased hunting pressure (aboriginals hunt them)
- illegal harvest
- drowning in nets and boat strike
- habitat destruction (coastal development and boating activities
- boat strike and capture stress
Why is aboriginal hunting a threat to dugongs?
- using traditional methods (the post and the spear) is ok, can only catch a limited number
- now using speedboats and rifles= leads to overcatching
What are the general conservation issues for marine mammals?
- seals, whales, dolphins, dugongs
- may be highly mobile and may also have large geographic distributions thus often cross territorial boundaries
- high potential for detrimental interactions with commercial fisheries industries
- conservation and management is often difficult in marine system (have to agree across several countries etc.)
What are the characteristics of seabird?
- class Aves
- use both marine and terrestrial environments (none live entirely in the sea)
- all dependent on the sea for foraging
- distributions often go beyond territorial waters
- many seabird species are declining
- conservation/management programs easier in terrestrial environments, often very difficult in the ocean
What is the diversity of seabirds in Australia?
- have quite a few
- eg. petrels, albatross, pelica, terns and noddies etc.
- some breed here and some just visit
What is the diversity of penguins?
- swimming seabirds
- world total=17
- in Autralia 1 breeding(little penguin), 4 visit(king, erect-crested, fiordland, rockhopper)
- pretty wide distribution in the southern ocean waters
- Galapagos penguin is endangered
What is the behaviour of seabirds like?
- use of marine and terrestrial environments
- nest on land= often colonial
- feed at sea=difficult to follow, unknown where they forage
- immatures and non-breeding season adults of some species may spend months/years on the wing, rarely coming to land (albatross)
What is the diet of seabirds?
- often feed on pelagic schooling animals near the surface (such as fish, squid, krill etc) e.g. gannets, penguins
- others scavenge (on land or at sea, and/or are seabird predators e.g. gulls, skuas, giant petrels, frigate birds
What are the seabird feeding methods at sea? (4)
- underwater pursuit diving (from surface-penguins, cormorants; from air-shearwaters)
- plunge divers (plunge from the air: gannets and terns)
- feeding from the surface (sit on water and push head under: fulmars, petrels, albatross)
- feeding from air (dip down in flight: some terns)
Which group of birds is declining very rapidly?
- seabird species/populations are declining more rapidly than other bird groups
- partly because it is hard to help them on the sea
What are the marine threats to seabirds? (5)
- oil spills
- overfishing
- loss of key food species (e.g. fish disease)
- entanglement in fishing gear
- difficult to study their biology while they are at sea
What are the terrestrial threats to seabirds? (4)
- introduced species
- habitat loss/disturbance
- fire
- climate change
Why is the albatross in decline?
- many breed on sub-Antarctic islands
- long parental care, long maturation
- e.g. wandering albatross, 11 months from laying to fledge, start breeding 9+ years= low population growth rate
- mortality due to long-line fishing (get caught and drown)
What are the wandering albatross wanderings like?
- satellite tracking- ARGOS system
- 180g transmitter on bird, signal picked by satellites c.12 times a day, you can monitor fixes in the computer from your desk
- extraordinarily long foraging trips
- up to 15 200km in 30 days (1 trip)
- 380 km in 4 days during brooding
- ranging/foraging behaviour make albatross difficult to protect
How are short-tailed shearwaters in danger from oil spills?
-foraging, fly/dive therefore less at risk from oil on sea surface and beaches
How are penguins in danger from oil spills?
- foraging penguins: swim at surface and dive, plus walk up the beach to return to colony, therefore at serious risk from oil on sea surface and beaches
- little penguins: foraging: swim at surface /dive
- nest on shore therefore must walk up the beach through oil
How do you help the oil spill penguins?
- collect oiled birds
- prevent further ingestion of toxic oil (via the cute little sweater things)
- clean and feed them
- fitness training and check for waterproofing
- release!;)
