Lecture 30- Overview

Question 1

What is the life cycle of the Australian Short-fin eel?

Answer 1

• catadromous, spawn in sea and the migrate to rivers where they live most of their lives
• migrate near New Caledonia, deep water
• have leptocephalus larvae, then glass eels= they return to freshwater -sillver and yellow eel= mostly colour transformations

Question 2

What are the factor having an impact on the short finned eel?

Answer 2

-global declines in freshwater eels due to: 1. Ocean basins- spawning and larval migrations 2. Coastal oceans- dispersion and detection of river plumes 3. Intertidal- sand transport and river mouth closure 4. Estuaries- facultative diadromy and growth 5. Small scales- swimming and upstream migration!

Question 3

What could some other factors responsible for the eel decline?

Answer 3

-parasitism, damming and water extraction= reduction environmental quality, overexploitation= fishing -current changes due to climate change

Question 4

What is the migration of the american eel like?

Answer 4

adult eels don’t feed when they migrate so have to have all the energy they need

• ocean scale migration
• the juveniles rely on physical transport to get back to europe -not a one off, some adults spawn repeatedly
• 3-4 years for larvae to get back to europe

Question 5

How is river mouth closure bad for eels?

Answer 5

-rivers= chemical odour of the river change maybe cannot detect anymore and can’t get to it

Question 6

Why is sand transport potentially bad for eels?

Answer 6

-what are the transportation process of sand - get river mouth closure -can’t get to the river the small eels, or cannot detect the presence of the river -the openings dangerous, carefully done

Question 7

What did the eel ooliths show?

Answer 7

• higher striaum if hatch in sea water= red
• facultative catadromy= so some individuals not moving all the way to the freshwater

Question 8

How is eel migration affected by humans?

Answer 8

-there may be issues with barriers, they cannot scale some barriers -put fish travel ways in!