Fish growth and development, relevant stuff Flashcards
What are the four stages of embryo development after fertilization?
Blastulation
Gastrulation
Neurulation
Somite formation
What is blastulation?
Cell division to form hollow ball
What is gastrulation?
Differentiation and layer formation.
What is neurulation?
Forming basic nervous tissues. (make brain, spinal cord and peripheral nerves)
What is somite formation?
Forms muscle segments.
Generally, the series of steps in embryo development occur, internally or externally?
externally
What is epiboly?
First cell movements of the blastoderm cells over the yolk.
What cell layers does involution form?
Endoderm, mesoderm, ectoderm
When do both epiboly and involution occur?
Gastrulation
What does involution mean?
As cells crawl over the yolk sac in epiboly, these cells crawl over one another, generating cell layers.
What does the endoderm form?
Guts
What does the ectoderm form?
Mostly the skin
What does the mesoderm form?
Muscles
What is the process that forms the neural tube?
Cavitation.
What cell layer forms the nervous tissue?
Ectoderm
Describe formation of the neural tube in fish.
Neural plate in the middle of the ectoderm will thicken and cavitate,
What is an embryo?
Fertilized egg prior to cell layer formation.
What is a yolk-sac larva?
When the embryo hatches out of egg and is feeding of the yolk.
Not feeding externally
What is a larva?
Free swimming, doesnt look like adult.
Yolk has been used up, feeding externally.
What is a juvenile?
Looks like mini adult, typically has scales (one of the last developmental steps)
Similar markings to adult.
Cannot reproduce.
What is an adult?
Has internal parts necessary for reproduction.
Can conceivably reproduce and is done developing.
What is an alevin?
Salmon term for yolk-sac larva.
What is a fry?
Salmon term for larva.
Between the alevin and fry stage, other than the yolk sac difference, what is the main difference?
Change habitats.
Alevin - gravel
Fry - move up in water column
What is a parr?
When salmon start getting colourations, pigmented bars. - form of camo
Still in stream.
Juvenile
What is a smolt?
For salmon that migrate.
Older juvenile making transition to marine environment.
Change to saltwater chloride cells
More silvery
What is a leptocephalus?
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).
Why do we care about larval forms?
Because this will determine how productive the fishery will be.
Growth is _______ in fishes.
indeterminate
What is growth influenced by?
Temperature
DO
Food
Genetics
Is fish size correlated with age?
No, can have two fish of the same age with vastly different sizes.
How does temperature affect growth?
Each species has an optimal temperature for growth.
Affects metabolism.
How does DO affect growth?
The more DO the more it grows.
Is there a genetic contribution to growth?
Yes, but also environmental component.
What does a walford plot measure?
Changes in size over time.
In a walford plot, what is the maximum size?
Where the 1:1 line intersects the plot line.
How are growth rates estimated for walford plots?
Scales and otoliths rings.
What is the growth coefficient?
K = -ln(slope)
Why are growth rates important?
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.
What is an assumption for determining growth rates?
Growth rates are constant from year to year.
What is the von Bertalanffy growth equation?
L(t) = Lmax(1-e^(-K(t-t0)
What does the walford plot allow one to know?
How long it will take to reach market size
max size
Growth rate of a given species
Thus –> fish catch limits
What is the critical period hypothesis?
One life stage will have the highest mortality and will be the limiting or critical stage that determines year class strength.
What is the point of no return?
Time after which effects of starvation are irreversible.
What is the critical feeding hypothesis?
Modification of critical period hypothesis.
Assumes that first-feeding is the critical stage that limits cohort strength.
How does the government apply the critical feeding hypothesis to determine year class strength and set catch quotas?
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.
What is the point of no return?
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.
So what is important to look at for determining if fish are susceptible to the point of no-return?
Prey abundance and size of prey.
