Fish growth and development, relevant stuff

Question 1

What are the four stages of embryo development after fertilization?

Answer 1

Blastulation
Gastrulation
Neurulation
Somite formation

Question 2

What is blastulation?

Answer 2

Cell division to form hollow ball

Question 3

What is gastrulation?

Answer 3

Differentiation and layer formation.

Question 4

What is neurulation?

Answer 4

Forming basic nervous tissues. (make brain, spinal cord and peripheral nerves)

Question 5

What is somite formation?

Answer 5

Forms muscle segments.

Question 6

Generally, the series of steps in embryo development occur, internally or externally?

Answer 6

externally

Question 7

What is epiboly?

Answer 7

First cell movements of the blastoderm cells over the yolk.

Question 8

What cell layers does involution form?

Answer 8

Endoderm, mesoderm, ectoderm

Question 9

When do both epiboly and involution occur?

Answer 9

Gastrulation

Question 10

What does involution mean?

Answer 10

As cells crawl over the yolk sac in epiboly, these cells crawl over one another, generating cell layers.

Question 11

What does the endoderm form?

Answer 11

Guts

Question 12

What does the ectoderm form?

Answer 12

Mostly the skin

Question 13

What does the mesoderm form?

Answer 13

Muscles

Question 14

What is the process that forms the neural tube?

Answer 14

Cavitation.

Question 15

What cell layer forms the nervous tissue?

Answer 15

Ectoderm

Question 16

Describe formation of the neural tube in fish.

Answer 16

Neural plate in the middle of the ectoderm will thicken and cavitate,

Question 17

What is an embryo?

Answer 17

Fertilized egg prior to cell layer formation.

Question 18

What is a yolk-sac larva?

Answer 18

When the embryo hatches out of egg and is feeding of the yolk.
Not feeding externally

Question 19

What is a larva?

Answer 19

Free swimming, doesnt look like adult.

Yolk has been used up, feeding externally.

Question 20

What is a juvenile?

Answer 20

Looks like mini adult, typically has scales (one of the last developmental steps)
Similar markings to adult.
Cannot reproduce.

Question 21

What is an adult?

Answer 21

Has internal parts necessary for reproduction.

Can conceivably reproduce and is done developing.

Question 22

What is an alevin?

Answer 22

Salmon term for yolk-sac larva.

Question 23

What is a fry?

Answer 23

Salmon term for larva.

Question 24

Between the alevin and fry stage, other than the yolk sac difference, what is the main difference?

Answer 24

Change habitats.
Alevin - gravel
Fry - move up in water column

Question 25

What is a parr?

Answer 25

When salmon start getting colourations, pigmented bars. - form of camo Still in stream. Juvenile

Question 26

What is a smolt?

Answer 26

For salmon that migrate. Older juvenile making transition to marine environment. Change to saltwater chloride cells More silvery

Question 27

What is a leptocephalus?

Answer 27

``` Larval form of elipomorphs. Eels Larva, no yolk sac anymore. Head with lots of swimming muscles Don't have a gut, feed and breathe through skin. Swim to freshwater (spawn in marine). ```

Question 28

Why do we care about larval forms?

Answer 28

Because this will determine how productive the fishery will be.

Question 29

Growth is _______ in fishes.

Answer 29

indeterminate

Question 30

What is growth influenced by?

Answer 30

Temperature DO Food Genetics

Question 31

Is fish size correlated with age?

Answer 31

No, can have two fish of the same age with vastly different sizes.

Question 32

How does temperature affect growth?

Answer 32

Each species has an optimal temperature for growth. | Affects metabolism.

Question 33

How does DO affect growth?

Answer 33

The more DO the more it grows.

Question 34

Is there a genetic contribution to growth?

Answer 34

Yes, but also environmental component.

Question 35

What does a walford plot measure?

Answer 35

Changes in size over time.

Question 36

In a walford plot, what is the maximum size?

Answer 36

Where the 1:1 line intersects the plot line.

Question 37

How are growth rates estimated for walford plots?

Answer 37

Scales and otoliths rings.

Question 38

What is the growth coefficient?

Answer 38

K = -ln(slope)

Question 39

Why are growth rates important?

Answer 39

For setting catch limits. Each year, do surveys for how many baby fish there are in a species and estimate how long it will take to reach market size.

Question 40

What is an assumption for determining growth rates?

Answer 40

Growth rates are constant from year to year.

Question 41

What is the von Bertalanffy growth equation?

Answer 41

L(t) = Lmax(1-e^(-K(t-t0)

Question 42

What does the walford plot allow one to know?

Answer 42

How long it will take to reach market size max size Growth rate of a given species Thus --> fish catch limits

Question 43

What is the critical period hypothesis?

Answer 43

One life stage will have the highest mortality and will be the limiting or critical stage that determines year class strength.

Question 44

What is the point of no return?

Answer 44

Time after which effects of starvation are irreversible.

Question 45

What is the critical feeding hypothesis?

Answer 45

Modification of critical period hypothesis. | Assumes that first-feeding is the critical stage that limits cohort strength.

Question 46

How does the government apply the critical feeding hypothesis to determine year class strength and set catch quotas?

Answer 46

``` Most commercial fish are external fertilizers and their offspring will have yolk-sac larvae. Government surveys for both yolk-sac larva and larval adults. This is the critical period from which the transition from feeding from the yolk sac to external feeding occurs. - Argue that most of the mortality occurs at this point. The proportion of survival indicates year class strength. ``` Catch quotas are then set based on this number but, the number or reproductive fishes necessary to keep the population stable and thriving is taken into account as well.

Question 47

What is the point of no return?

Answer 47

Baby (walleye for this example) can survive without food for a limited amount of time when they lose their yolk-sac. The point of no return is when the effects of starvation are irreversible i.e. when the timing of larval feeding and prey availability is too far apart. What occurs is that these larvae will digest their GI tracts if they don't get food past a certain point. Also, the size of the prey matters for first feeding. Since their mouths are small, size of prey has to be small enough for them to feed.

Question 48

So what is important to look at for determining if fish are susceptible to the point of no-return?

Answer 48

Prey abundance and size of prey.