Reproduction Fisheries Continued Flashcards
Considerations when analyzing reproduction
Lifespan
Onset of maturity
Early
Late
Interplay = spawning opportunities
Number and size of eggs
Number of batches/season
Relationship with size/age
Not all eggs are the same!
Another term for sex identification
gross gonadal morphology
Female sex identification organ
Ovaries
Male sex identification organ
Testes
Physical Characteristics of Ovaries
Typically yellow or orange in coloration
Granular consistency
Vascularization
Central lumen
Physical Characteristics of Testes
Typically white or off-white in coloration
Smooth consistency
No central lumen
How can gonads help with understanding productive cycles and/or timing?
Size
Another term for assessing maturation
gross gonadal condition
What does GSI stand for?
Gonadosomatic Index
What does Gonadosomatic Index equal?
Gonad weight/somatic weight
Somatic Weight
Total body muscle - everything beyond the reproductive system.
What are some key characteristics for assessing maturation?
Gonads increase in size prior to spawning season
Remain large through spawning season
Become smaller in “resting phase”
What are the variables used to assess maturity?
Length or age at first maturity
What percentage is a standard often used to assess a population’s maturity?
Length or age at 50% maturity.
Example: 50% of the population is mature at a certain length or certain age.
What are the two stages of Ovarian Development?
Sexually Immature
Sexually mature
What are the stages of a sexually mature fish species?
Immature oocytes
Oocyte maturation (several stages as yolk incorporated)
Vitellogenesis (yolk production)
Production in the liver
Transport to ovary
Hydration of mature oocytes
Occurs shortly before spawning
Volume considerations
Ovulation (post-ovulatory follicle)
What are the stages of Oocyte Development based on American shad?
Primary growth
a small cell with a central nucleus;
Unyolked
all oocytes without yolk
Partially yolked
early stages of yolk deposition; some yolk granules are
Yolked
all contain many, small to large yolk globules
Hydrated
the largest oocytes
Atretic
Cell degeneration
Male gonad phases
Ripe
Resting
What are the three types of spawning strategies?
Synchronous spawners
Group synchronous spawners
Asynchronous spawners
Synchronous spawners
(e.g., Pacific salmonids, eels)
all mature oocytes, once formed, grow and ovulate in unison
determinant fecundity
Group synchronous spawners
(e.g., monkfish, cod)
at least two populations of oocytes can be distinguished at any one time: a population of larger oocytes (the ‘batch’) and a population of smaller, more heterogeneous oocytes from which subsequent batches are recruited
indeterminant fecundity
Asynchronous spawners
(e.g., anchovies, hake)
Multiple and daily spawning
oocytes of all stages are always present without dominant populations
indeterminant fecundity
Label the three types of spawning strategies.
How can spawning strategies help us understand maturity schedules?
The spawning frequency could impact when 50% of the population is considered mature.
How to determine the frequency of spawning?
originally modal analysis of oocyte sizes (three size classes of oocytes = three spawnings per season)
What is the issue with oocyte size to determine the frequency of spawning?
Post-ovulatory follicles (POFs) remain in the ovary for a period after ovulation and can be staged by histological examination
What was the Hunter & Goldberg analysis on the histological examination?
Conditioned northern anchovy to spawn
Used histological analysis to follow the fate of POFs
Could reliably stage POFs as 0 – 24 hr old, 24 – 48 hr old (evaluated with “blind” readers)
Why does all of this matter?
Determines fecundity
Fecundity
The number of eggs spawned in a reproductive season
Determinate fecundity
The standing stock of advanced oocytes is proportional to annual fecundity (synchronous spawners)
Indeterminate fecundity
The standing stock of advanced oocytes does not indicate annual fecundity (group-synchronous and asynchronous spawners)
How to estimate the fecundity of batch spawners?
Fecundity = (batch size) (spawning frequency) (spawning duration)
What is important to be aware of when assessing fecundity?
Not all developed eggs are necessarily spawned (atresia, resorption)
