Lec 17 Eggs and Larvae Flashcards
what does ontogeny mean?
development
Fish eggs and larvae are considered part of the plankton, meaning
they cannot swim against currents
although some larval fishes have been shown to swim vertically in the water to take advantage of dif currents
What do larval fishes eat?
phytoplanton, algae, copepods, larvaceans, and other fish
How do eggs/larvae differ from adults? Name 4
- anatomically
- physiologically
- behaviorally
- ecologically
Why is it important to know the early life history of fishes?
To have proper management of fisheries. Even of non commercial fishes because they belong in the same ecosystem with commercial fishes
How is the sampling of fish eggs and larvae helpfully?
Provides info about fish species, populations and communities.
Can determine yearly fish population.
Can be used to determine geographic distribution of spawning adults
What are vertical egg tows?
A net that is used to collect eggs, it’s lowered to 70 m and retrieved at a constant rate
What is a neston tow
method to collect larvae by sampling just the upper 10 cm of water.
Afterwards, they’re washed by formalin to preserve the eggs.
What is extrusion?
Loss of organisms after capture
How may collectors limit the amount of extrusion occuring?
By considering the mesh size and speed of the two
How is avoidance of sampling gear possible by larvae?
Larvae may avoid collection by their size and speed to travel away from the negs, and the size and speed of the net being used to collect them
Describe the early development stage of fish eggs
fertilization to blastopore closure
Describe the middle development stage of fish eggs
blastopore closure to embryo tail bud free of yolk
Describe the late development stage of fish eggs
embryo tail bud free of yolk to hatching
What occurs during the pre flexion development of the larvae?
absorption of yolk sac to start of notochord flexion
What occurs during the flexion development of larvae?
start of notochord flexion to completion of notochord flexion
What occurs during the post flexion of the development of larvae?
completion of notochord flexion to start of metamorphosis
What are characteristics used to describe fish eggs? (6)
- Shape
- Size
- Chorion texture
- Size and shape of oil globules
- Perivitelline space
- Embryonic charac (late stage only)