Fish reproduction razia 2
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Transcript of Fish reproduction razia 2
Topics to be covered• Reproduction• Life cycles• Growth
Reproduction, Early Life Stages, Growth(Chapter 6 and additional material)
Reproduction – hormones of the reproductive system
• Brain-hypothalamic hormones (note error in textbook) Gonadotropin-releasing hormone (GnRH) Gonadotropin release-inhibitory factors (GnRIF; such as
dopamine)• Pituitary hormones: gonadotropins
FSH: controls gonadal growth LH: controls gamete maturation and release
• Gonadal hormones (steroids) 11-ketotestosterone (androgen) 17-estradiol (estrogen) Progesterone or its derivatives (progestins, they induce
gamete maturation and ovulation; Maturation-Inducing Hormone = MIH)
Reproduction, Early Life Stages, Growth
Reproduction – general environmental regulation
brain
gonad
Fish
pituitary
steroid hormones
Environment
seasonal photoperiod profileseasonal temperature profile
food availabilitycontaminants
other liver
LHFSH
•androgens•estrogens
Vg
gonadaldevelopment
•progestins
Reproduction, Early Life Stages, Growth
Brain
Pit
Gonad
dopamine
-LHRH
+
LH
Gametes
Reproduction – hormones that control release of gametes
Reproduction, Early Life Stages, Growth
Reproduction – captive spawning
• Captive spawning is preferred over collection of natural seed because,
Greater control over timing of seed availability Greater control over number of available seeds
• Many of the current aquacultural species do not spawn naturally in captivity
• Often, problem is with the spawning of captive female, not male, fishes
• Methods for natural and hormonally induced spawning of captive fishes and other aquacultural organisms have been developed based on knowledge of their reproductive physiology
Reproduction, Early Life Stages, Growth
Reproduction – captive natural spawning
Zebrafish spawning
• photoperiod - 14L:10D• temperature - 28~29 °C• spawning container overnight
spawning containers
fish in spawning containers
Reproduction, Early Life Stages, Growth
Reproduction – captive induced spawning
MIH
MIH
R.W. Rottmann et al. 1991
LHRH = GnRH
Reproduction, Early Life Stages, Growth
Reproduction – captive induced spawning
R.W. Rottmann et al. 1991
MIH
hCG = human chorionic gonadotropin
Reproduction, Early Life Stages, Growth
Reproduction – shellfish
• Decapod crustaceans X-organ/sinus gland system of eyestalk produces gonad-
inhibiting hormone Eyestalk ablation removes gonad-inhibiting hormone and
causes completion of gametogenesis in male and female decapod crustaceans (in some species, eyestalk can regenerate)
• Bivalves Spawning cues include change in water temperature,
change in salinity, lunar cycles, pheromones
Reproduction, Early Life Stages, Growth
Reproduction, Early Life Stages, GrowthEarly life stages
• Fertilization leads to Zygote• Depending on species, embryogenesis occurs over period of hours
to weeks• Following hatching, several stages of development can be described:
Embryo-larval transition (endogenous feeding) Larval development Larva-juvenile transition (metamorphosis) Juvenile (prepubertal) growth
Embryo-larva transition
Reproduction, Early Life Stages, GrowthEarly life stages
• Embryo development (endogenous nutrition) Days to weeks
Need to clean egg mass following fertilization Use clean water for incubation (filtered water) Keep good levels of oxygen Appropriate temperature
• Embryo-larva transition (fishes – endogenous nutrition) Days to weeks
Culture techniques similar to embryo• Larval development
Days to weeks Onset of exogenous feeding; providing appropriate food
becomes major aspect of rearing (microalgae for molluscs and shrimps; rotifers and brine shrimp nauplii for fish and older shrimp larvae)
Nitrogenous waste can become problem; need close monitoring of general water quality - rearing often occurs in large tanks to help with water quality
Density of larvae reduced as they grow
Reproduction, Early Life Stages, GrowthEarly life stages (continued)
• Larval development is abbreviated or non-existent in some species (direct development)
Embryos hatch already bearing juvenile form• Larva-juvenile transition: metamorphosis
Slight to marked changes in morphology, physiology and behavior, depending on species
• Juvenile development Postmetamorphic juvenile fishes are progressively weaned
off live feeds on to artificial diets Initial culture is in hatchery tanks
• Grow out Final phase of culture when juveniles are grown until
harvested
Reproduction, Early Life Stages, GrowthGrowth
• Bioenergetics Energy equations (note: specifics here are different from text
but overall meaning is same) Simple equation: p x F = M + G
p = proportion of food consumed that is assimilatedF = amount of food consumedM = catabolism (energy release)G = growth (anabolism)
Expanded equation: C = (Mr + Ma + SDA) + (F + U) + (Gs + Gr)C = rate of energy consumptionMr = standard metabolic rate (rate of energy use by a fasting animal at rest)Ma = metabolic rate increase (over standard) due to activitySDA = metabolic rate increase (over standard) due to digestion and assimilation of
foodF = waste due to egestion (feces)U = waste due to excretion (urine)Gs = somatic growth rateGr = reproductive or gonadal growth rate
Reproduction, Early Life Stages, GrowthGrowth
• Patterns of growth of an organism can be described in several ways: Absolute growth: increase in size (length or weight), equal
Y2-Y1
Absolute growth rate: increase in size per unit time, equal (Y2-Y1)/(t2-t1) Initially small, but as animal grows in size, there is
increased capacity to take in and assimilate food Relative growth: increase in size relative to initial size,
equal (Y2-Y1)/Y1
Relative growth rate: increase in size per unit body size per unit time, equal (Y2-Y1)/[Y1(t2-t1)] Initially rapid, but slows down with development
Infle
xion
poi
nt
Reproduction, Early Life Stages, GrowthGrowth
• Measuring growth: Growth measurements are needed to monitor health and
predict harvest time Measures
Length: linear dimension using calipers or ruler - quick and easy Wet weight: most common assessment of whole body growth of
fishes - quick and easy Dry weight: wet weight minus water (in oven at ≤100°C). Can
usually be applied only on dead organism; it is most accurate method for assessing animal tissue growth, since changes in tissue water content may occur due to stress etc.
Condition factor: weight/(length)3
Ash-free dry weight: dry weight – inorganic ash (up to 24 h at 500°C). It is the dry weight of organic matter in the animal. Useful for animals with large inorganic components (e.g., bivalves) where it is relatively difficult to measure organic tissue content. Sometimes simply expressed as ash weight.
Proximate composition: determination of different categories of compounds in tissues. Most commonly measured categories include carbohydrates, proteins, lipids.
Reproduction, Early Life Stages, GrowthGrowth
• Measuring growth in fishes: Length measurements
Total length (TL): tip of snout to tip of longest caudal fin rays. Difficult to measure accurately if caudal fin is damaged
Fork length (FL): tip of snout to fork (median caudal fin rays). Used in fishes with clear forks
Standard length (SL): tip of snout to base of caudal fin (or tip of notochord in larval fish)
Notes on Chapter 6 reading material
• Subsections 6.3.1, 6.3.2, and 6.3.3, 6.4.2: general knowledge of topic covered in these subsections is necessary, but no need for details
• Formulas in subsection 6.4.1 are not required reading (you must instead know formulas covered in class)
• Under subsection 6.4.4, discussion of bivalves and decapod crustaceans is not required reading
• Table 6.2 is not required reading
Reproduction, Early Life Stages, Growth