L4 - Fish Migration

Question 1

Give 4 reasons why fish migrate

Answer 1

1) breeding grounds bring maturing adults together to the same place
2) to follow food availability
3) escape adverse environmental conditions - el Nino
4) follow favourable environmental conditions

Question 2

What are the 3 types of migration?

Answer 2

Diadromous - migrations are between sea and freshwater

Catadromous - where a fish grows and matures in freshwater, but breeds in the sea

Anadromous - fish grow in the sea but migrate to breed in freshwater

Question 3

Give 4 advantages of cata/Anadromous migration

Answer 3

• relatively low predation of juveniles at spawning grounds
• aggregation of spawning adults
• high growth rate to adulthood
• high fecundity - large adult body size

Question 4

Give 7 disadvantages to ada/cataromous migration

Answer 4

• physical barriers
• physiological barriers
• energy cost
• high adult mortality
• long juvenile stage - late maturity
• predation in estuaries in high
• mortality of un-adapted juveniles

Question 5

What animals are an example of:

a) Anadromous migration
b) Catadromous migration

Answer 5

a) Anadromous migration - Atlantic salmon
- salmon are born and live their juvenile lives in freshwater
- they then migrate to the sea to live their adult lives
- the migrate back up their birth site to breed again , and then die
- another example is sturgeon

b) Catadromous migration - European eels
- breed in marine environment and they ascend rivers to grow to maturity in freshwater
- adult eels undergo physiological changes to become silver eels and then migrate downstream to the sea, across the Atlantic, and to the saragresso sea where they breed and die