Lecture 20- Migration, homing and Orientation

Question 1

define migration

Answer 1

is the movement of large numbers of a species from one place to another, usually leaving none behind. This is usually directional and purposed based (food or mating).

Question 2

migration vs dispersal:

Answer 2

compared with dispersal migration is less risky given you are returning to a know habitat, that is a known distance away with know mates

Question 3

define dispersal:

Answer 3

is the spreading of individuals away from others, often parents or siblings, which are left behind in the original area. this is usually random with the goal of locating and securing habitat thus decreasing competition and inbreeding!

Question 4

what is homing?

Answer 4

The ability of an animal to navigate towards a pre-determined location

Question 5

dispersal is most common in what?

Answer 5

fry or juvenille fishes

Question 6

dispersal is often a response to what?

Answer 6

overcrowding and lack of local resources

Question 7

successful dispersal is —–

Answer 7

rare, most individuals will die during their trip

Question 8

migration compensates for what fact?

Answer 8

that a single geographic area is not able to meet all of a fishs life history needs. If everything a fish needed was within close proximity there would be no need to migrate

Question 9

what percent of fish species migrate?

Answer 9

2.5%

Question 10

describe oceanodrmous:

Answer 10

migrations occur entirely in saltwater

Question 11

many oceanodromou fishes are termed what??

Answer 11

highly migratory species (HMS) because of their ocean basin-sized migration routes ex.) atlantic bluefin tuna

Question 12

define potamadromous:

Answer 12

migrations that occur within freshwater. these types of migrations are generally daily or seasonal migrations for foods or seasonal migrations for high oxygen habitat for juvenilles ex.) walleye

Question 13

define diadrmous:

Answer 13

migrations that cross the seawater freshwater boundary

Question 14

what are three three subcategories of diadromous:

Answer 14

1. anadromy occurs when most of the fishes feeding and growth occurs in saltwater and fully grown adults move back into freshwater to spawn ex.) salmon
2. ) catadromy: occurs when most of a fishes feeding and growth occurs in freshwater and the fully grown adults move into saltwater to spawn. ex.) true eels
3. ) amphidromy: occurs when there is a brief excursion from freshwater to seawater during the juvenille stage to feed but the majority of feeding and growth and spawning occurs in freshwater. more rare but may be seen around islands

Question 15

migrations are triggered by one or a combination of the following factors. List them in order of importance:

Answer 15

1. Photoperiod- pineal eye
2. temperature
3. water velocity
4. lunar cycles (might play a bigger role than we think it does)

Question 16

sharks have been known to use what as a homing and oreintation signal?

Answer 16

geomagnetic orientation

Question 17

fishes may orient using information derived from changes in the suns azimuth. however this means what for the fish?

Answer 17

because these change on a fairly and seasonal scale fishes that orient using the sun must possess an internal biological clock and calendar to compensate for these changes

Question 18

define rheotaxis:

Answer 18

fish that use water currents to oreintate

Question 19

Positive rheotaxis:

Answer 19

is when a fish faces the current and swim upstream

Question 20

negative rheotaxis:

Answer 20

is when a fish swims with the current

Question 21

why is stream destruction bad for salmon?

Answer 21

because it changes the odour of the stream and can result in fish abdandoing it and going back to the ocean.