Flashcards in Lecture 21- Marine vertebrates and issues for their conservation Deck (29)
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)
1.Lone seals hauling out near towns-unusual (crowd control needed so people don't get bitten and then shoot the seal)
4.Tourism (approach and disturbance)
5.Pollution (oil spills or exploration)
6. Disease (Phocine distemper)
7.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
-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)
-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?
-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?
-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)
1. underwater pursuit diving (from surface-penguins, cormorants; from air-shearwaters)
2.plunge divers (plunge from the air: gannets and terns)
3.feeding from the surface (sit on water and push head under: fulmars, petrels, albatross)
4.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)
1. oil spills
3. loss of key food species (e.g. fish disease)
4. entanglement in fishing gear
5. difficult to study their biology while they are at sea
What are the terrestrial threats to seabirds? (4)
1. introduced species
2. habitat loss/disturbance
4. 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