Broodstock management

Question 1

What is the most important aspect to mitigate when aiming for success of reproduction in captivity?

Answer 1

Stress

Broodstock management requires reducing stress and providing essential environmental parameters for spawning induction

Question 2

Important environmental cues other than light and temperature include:

Answer 2

Temperature

Salinity (Anadromous fish such as salmon have reproductive difficulties if left in hyperosmotic environment -> hydration and ovulation may fail)

Substrate (Environmental substrates may be important for alleviating stress, also relevant structures or hides for cryptic species)

Exercise (Anguilla anguillamigrate 5500 km to Sargasso sea
Captive eels will not enter vitellogenesis
Dopinhibition of GtHs -> Palstraet al. 2007 exercised eels for equivalent distance led to development of oocytesinto lipid droplet and cortical alveoli)

Social interactions (Social interactions and courtship important for successful reproduction
Fish may require appropriate depth for courtship
Sex ratios important)

Question 3

What are possible effects on salmon when left in a hyperosmotic environment? Why?

Answer 3

Hydration and ovulation may fail

Salmon are anadromous

Euryhaline fish may tolerate range of salinities

Question 4

What is triploidy?

how does it work?

How does it affect fish?

What is cellular gigantism?

Answer 4

Triploid fish have an extra set of chromosomes, typically sterile

Induction can be achieved using temperature or pressure

Less likely to develop gonad = better flesh quality, faster growth

lower impact of escapees on wild stocks

Some concerns relating to cellular gigantism (welfare problem for fish as more likely to suffocate under stress due to higher O2 consumption)

Question 5

What are some solutions to produce an all male stock?

Answer 5

XY male and XX female

Feminisation of males to produce XY female phenotype

Irradiate XY male sperm to inactivate chromosomes

Activate XY eggs with irradiated sperm

Block meiotic II division using shock to create diploid XY egg

Cull 50% XX keep 50% YY

Cross YY males with XX females for all XY progeny

Question 6

What are the three main points of the reproductive cycle where dysfunction may occur

Answer 6

1. Failure to enter vitellogenesis (e.g. Eels, tuna)
2. Failure to complete final oocyte maturation (most common)
3. Failure to spawn ovulated eggs (e.g Halibut)

Question 7

What are some effects of male reproductive dysfunction?

Answer 7

not as common as in females

• captive male fish may show reduced milt volume and fliudity
• can lead to difficulty for artificial fertilsation or reduced fertilisation of in tank spawning
• GnRHa implants increased milt 28 –35 days v 7 days of GnRH injectionn

Question 8

What is one way to approach reproductive dysfunction?

Answer 8

One way to approach reproductive dysfunction is to over ride the HPG and use hormonal intervention

hormones are also useful for synchronising hormones.

Question 9

What are the two different hormonal approaches?

Answer 9

Question 10

What are the three different types used in first generation hormonal manipulation?

Answer 10

1. Pituitary homogenates
2. Pituitary extracts (LH, hCG)
3. Purified, recombinants GtHs

hCGs are hormones that are found in the urine of pregnant women

Question 11

what is a way to manipulate hormones of a second generation?

Answer 11

GnRHa much more effective then GnRH (5 min hl)

Implant via injection

can be used across wide species range

can become a DA blocker

small molecule

Cheaper than commercial GtHpreps

Question 12

What aspects would hormones used to have when used for hormonal manipulation?

Answer 12

minimum oocyte size

appropriate hormone dose

Question 13

What can be a side effect of hormonal manipulation when spawning and ovulating is increased?

Answer 13

quality of eggs can decrease

Question 14

What is a common issue in commercial hatcheries?

Answer 14

poor fertilisation

Question 15

What are three issues that may affect broodstock gamete quality?

Answer 15

genetics

stress

nutrition

Question 16

What was the result of an experiment where AA was increased?

Answer 16

fecundity increased

fertilisation rate increased

hatching rate was higher

Question 17

what are five indicators for egg quality

Answer 17

Transluscence
Bouyancy(Pelagic eggs)
Lipid droplet position
Egg size (not necessarily linked to survival)
Blastomeremorphology (8 cell stage)

Question 18

what are five indicators of sperm quality?

Answer 18

Milt volume
Spermatocrit
pH, osmolality
Total duration of movement
CASA (computer assistance sperm analysis)

Question 19

how are all female offspring produced?

Answer 19

XY male and XX female

All female production by masculinisation (MT-methyl testosterone) of XX females

Cross XX (male phenotype) with XX females
All progeny = XX

Question 20

WHat is gynogens?

Answer 20

Sperm (n) is treated with UV light to destroy the genetic material it contains. The polar body is not expelled (second set of chromosomes) as the egg (2n) cells are put under pressure.

the sperm kicks off the cell division whilst both chromosomes sets are contained within the egg cell creating a clone of the mother