Flashcards in Lecture 2- Freshwater fish Deck (25):
What are the three key threatening processes for freshwater fish in Australia?
-river regulation (dams)
What is the definition of a freshwater fish?
-occupy non-marine habitat for a significant part of life cycle
What does diadromous mean?
-species that spend some time in salt water as well as freshwater
=some on the other hand are obligate freshwater species
What is the definition of freshwater fish?
-lives in water with salinity less then 3 parts per thousand 3 ppt= internationally accepted limit for H20
-but in Australia many inland waters are higher than 3ppt for example some up to 60 ppt and fish can tolerate it, but even then called freshwater fish because they are inland enclosed
-lives inland, but still many migrate...
What are the three origins of freshwater fish in Australia?
-Ancient origins= Gondwanan relics (only 3 families and only 4 species)
-Marine colonisers= northern waters (11 families)
=southern waters (7 families)
-most of the fish from there, came form the sea
-other= uncertain (about 2 families...)
-introduced species= 5 families (trout, carp, mosquito fish)
Did freshwater fish evolve in freshwater?
-only 4 species (the gondwanan relics) developed in freshwater
-lungfish (queensland) , nth and sth saratoga (north tropics), salamander fish(lives in seasonal wetlands, they go dry in summer, the fish encases itself in mud and wait for rain)
-majority of Australian freshwater species evolved from marine ancestors
How is Saratoga proof of Gondwana?
- there are related species in Asia, South America and Africa
What are some examples of marine colonisers in northern waters?
-catfish= barbels around mouth, eel tail
-eels= catadromous, the larave= they stay in the sea and then as adults migrate
-pygmy perch= threatened species, Yarra and one river in WA
What are some examples of marine colonisers in southern waters?
-galaxids= like small salmon, 5-25 cm long
-blackfish= 2 endemic species, carnivorous bottom feeder
-lampreys=jawless, parasitic fish
What about Murray cod?
-lives 50-60 years
What is the species richness of freshwater fish in Australia?
-low, only 206 exclusively freshwater native
-about 70% endemic
-71 non freshwater dependent species
-26 exotic/ introduced species
compare: Africa- 1900 freshwater species
Why are there so few freshwater fish species in Australia?
-very dry continent, 80% arid zone
What are the three main zoogeographic subregions?
-monsoonal, warm= north,long periods of rain= december= march lot of rain and for the rest of the year completely dry,dry season/ wet season
-arid, ephemeral water bodies=middle, they may get water only every 20 years, but still some fish
-high rainfall, cooler, permanent water=south
What are the characteristics of rivers on the North coast?
North coast= Torresian
-wide flood plain
What are the characteristics of rivers inland?
-source on west of Great Divide
-fluctuating, unpredictable levels
-warm, slow and turbid
What are the characteristics of rivers on the South coast?
-east coast= Bassian
-source on east of Great Divide
-fall rapidly to the sea
-clear and cool
-relatively stable flow
What are the two types of lakes in Australia?
-salt lakes (eyrean), hot, shallow and ephemeral
-mountain lakes (bassian), cold, deep and permanent
What are the three types of diadromous?
-anadromous= in fresh only to spawn, rest of life in sea (lampreys, Tas whitebait)
-catadromous= spawn in ocean an and move to fresh for rest of life and tehn spawn again (eel, barramundi)
-amphidromous= fish that live in both dependant on food, not reproduction, non-breeding migration, both ways
What is the migratory pattern of the lamprey?
-eggs hatch into larvae in the river, larvae live in river mud for 5-6 years filter feeding on organic detritus
-larvae metamorphosis into the adult form and migrate to sea
-adults live at sea
-adults return to rivers to spawn and die
=if you build a dam! can't get to freshwater spawning habitats
-suck blood and flesh from other organisms
What is the migratory pattern of the short-finned eel?
-adults= live in rivers, then swim to vanuatu and spawn in the sea (3000-4000 km migration)
-then larvae in the sea= paper larvae= feed on plankton and drift with the current that goes back along the coastline, then when big enough move inshore, live in rivers and eventually swim to vanuatu to spawn
What is the migratory pattern of the barramundi?
-adults spawn at at estuary mouth, eggs and larvae develop in high salinity water, post larvae enter supratidal wetland habitats, some mature in estuary and some continue upstream and exit the wetland habitat sand mature in freshwater
-when they migrate etc 95% males, once 80cm they change into females= the fish that go all the way the freshwater. then move to marine to spawn, the ones who don't make it to the freshwater= remain males
-but any bigger than 80cm is female even in freshwater, but there are some larvae there all the tome the small males to spawn
What is the barramundi ear bone good for?
-earbone= calcium carbonate, not like normal bone, more like a rock, once finished never remade, all the minerals in water leave a trace and then you take it out and check the chemistry of it and check were the fish has been
How is river regulation a threat to freshwater fish species in Australia?
-dams and weirs
-stop spawning and feeding migrations of fish, reduces habitat for some species
How do salinisation, pollution and eutrophication (excess nutrients from agriculture) pose a threat to freshwater fish?
--95% of Australia's original wetlands degraded or lost due to rural development and mining
-particularly severe around populated coastal areas and farming areas
-salinisation is caused by land clearing resulting in rise of the salt-laden water table (murray river)