controlling reproduction II

Question 1

What is a welfare problem in rearing king salmon?

Answer 1

when the fish reaches puberty it prepares itself to go through osmotic changes to migrate from the sea to the freshwater thus trapped in a sea pen of an aquaculture facility –> can cause epidemic deaths of fish if not controlled

Question 2

Define puberty

Answer 2

transition from immature fish to sexually mature

(HPG axis largely ‘silent’ until sufficient somatic growth attained for reproduction
Puberty reflected by functional competence of HPG axis
Puberty shouldn’t be confused with seasonal maturation)

Question 3

Effects of size at puberty may be affected by different factors:

Answer 3

Mortality patterns
Fecundity
Offspring quality

(E.g. heavily fished stocks may reach puberty at smaller size and earlier age)

Question 4

name six issues with early puberty in farmed fish

Answer 4

• Males often mature at a smaller size than females
• Under captive conditions farmed fish often reach puberty at smaller size and age
• High energy feeds & associated adiposity ‘allow’ reproductive maturity
• Farming conditions can mask desirable traits such as delayed age & size at maturation for selective breeding
• Feed rates may drop around spawning
• Atlantic cod may lose 30% bodyweight during spawning
• Aggressive behaviouroften increases injury and infection
• Spawning Atlantic salmon have reduced survival and condition as well as changed morphology

Question 5

Name four issues with early puberty in Atlantic Salmon (Salmo solar)

Answer 5

-Atlantic salmon initially increase growth in early puberty
-Can expend up to 59% of energy during reproduction
-Near spawning season, lipid, protein and astaxanthinlevels drop
-Muscle quality drops (flavour, tone)
Increased risk of escapees breeding

Question 6

Name three issues with early puberty in Atlantic halibut (Hippoglossushippoglossus)

Answer 6

Males reach early puberty
Growth slows or even negative
No new muscle fibresrecruited

Question 7

What five environmental parameters are important cues for puberty

Answer 7

Photoperiod
Temperature
Food availability
Exercise
Social interactions

Question 8

What is the significance of the Photoperiod as a cue for puberty?

Answer 8

Seasonal window of time in which fish must be in sufficient condition for puberty or sexual maturation to proceed

• *Important physiological cues;** gonad maturity, adiposity, size
• *Photoperiod** appears to determine timing of ‘decision’

If spawning season is advanced using photoperiod, number of Atlantic salmon entering puberty can be reduced (Tarangeret al., 1998)

Question 9

What are some big issues in farming Sea bass (Dicentrarchuslabrax) in the Mediterranean

Answer 9

Precocious fish larger than non-precocious, but in second annual cycle, precocious males weigh up to 18% less (5% less FL) than non-precocious

-Male 20–40% less body weight at harvest than females (approx 18–22 months) = earlier onset of puberty

-Mediterranean fish farms may show extremely high percentages sex ratios skewed to males (70–90%)

Question 10

what triggers gonadotropin activity and where is it produced?

Answer 10

FSH and LH in the petruatery

Question 11

What is suggested by Felip et al. 2008 as a possiblility to arrest puberty?

Answer 11

Suggests that reduced 11-KT possibly due to limited FSH, may reduce germ cell proliferation and their entry into meiosis = arrest of puberty

Found that short window of LL during August–November (2months) = critical period to block gametogenesis