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What factors, other than first feeding can also constrain larval survival?

Predation, success of settlement.


What are the three different predator constraint on larval survival models?
What type of predator would be expected for each?
What is the growth strategy or a key factor?

1 - Linear, as the fish gets bigger, predation goes down
Predator - Invertebrate (copapod); jellyfish
Strategy - relatively fast growth of larvae to decrease vulnerability

2 - Vulnerability similar early on until a magic size is reached
Predator - filter feeder
Key factor - swimming ability changes with size, bigger can escape predator every time - predation is nearly zero

3 - Middle period most dangerous
Predator - visual predator
Growth strategy - delay pigment formation until swimming ability is better developed


Describe how fish outgrow their predator constraints for: invert and jellyfish predators.

Predator driving this is small.
When larger and swimming ability gets better, inverts and jellyfish cannot catch fish.
So, linear decrease in predation with size.


Describe how fish outgrow their predator constraints for: magic number.

Vulnerability is the same early on until a magic size is reached where swimming ability reduces predation to zero.
Swimming ability changes with size.


Describe how fish outgrow their predator constraints for: visual predators.

Predation is highest in the middle.
Don't want to grow too fast too soon but grow fast later in life to escape vulnerability.

Vulnerability is low early since yolk sac larvae are relatively transparent.

Develop pigment when grows and develops, but somites arent particularly developed for swimming - predation is highest here.

Once swimming ability is developed, easier to escape.


What is successful settlement for reef fish?

Adults are broadcast spawners, eggs have to land or settle on reef to survive.


What is successful settlement for flatfish?

When eye migrated to side of head, can now live on the bottom and less vulnerable to predation once settled.


What is a key determinant of cohort strength in reef fish?

Percentage that make it to a reef


What are all the possible reasons that reef fish even have a pelagic phase if the mortality is so high?
Which is the most important?

Dispersal to new habitats
Enhanced gene flow
Decrease competition


What is an issue with the dispersal to new habitats hypothesis?

Reef already has lots of resources and is a good habitat.
At the individual level, it doesnt make sense to risk not passing genes on since odds of survival of the embryo are low.


What is an issue with the enhanced gene flow hypothesis?

If offspring reach a new reef, can meet up and increase gene flow between the two habitats but, once again, the odds of survival are low that the benefit of enhanced gene flow is offset.


What is the issue with the competition hypothesis?

Would work on the species level (like the others) but, competition would have to be extremely high for this to make sense.
Fitness is too reduced by sending them off.


What is the No choice hypothesis?

Reefs have currents that are strong that bring in nutrients and clear out wastes.
When making babies, may be too much of an energetic investment to make offspring that can withstand the current so, they have to do broadcast spawning.


Is dispersal passive or active?



Give reasons for why dispersal is active.

Passive at embryo stage, but larvae are better at swimming than initially thought.
- these fish can swim against the current and return to natal reef or go to reefs nearby
- these fish can also sense the reef (smell, hear, etc.) so they can actively navigate


What is the equation to determine production?

Production = (R + G) - (M + F)
R - recruitment rate
G - growth rate
F - fishing pressure
M - natural mortality


What is production?

How many fish the fishery produces.


What is recruitment?

How many fish are added to the fishery, i,.e. how many fish make it past the critical period


What is fishing pressure?

How many fish are caught commercially and by local fishermen.


What is the equation for yield?

Yield = P - Rp


What is Rp?

Replacement rate = how many adult fish are needed to make offspring


Commercial fishermen argue ___ is too high.
The issue with the cod fishery was that ____ was too low.



What is the purpose of spines in larvae?

Make them look bigger to prevent predation


_____ are longer in larvae relative to body size. Why?

Don't have much trunk musculature early on so depend on fins to swim


What larval fish have stalks for their eyes?

Deepsea fish - enhances visual field