Topics to be covered

1
Reproduction, Early Life Stages, Growth (Chapter
6 and additional material)

• Topics to be covered
• Reproduction
• Life cycles
• Growth

2
Reproduction, Early Life Stages, Growth

• Reproduction hormones of the reproductive
  system
• Brain-hypothalamic hormones
• Gonadotropin-releasing hormone (GnRH or LHRH).
  Note error in textbook this hormone is from the
  brain, not the pituitary
• Gonadotropin release-inhibitory factors (GnRIF
  such as dopamine)
• Pituitary hormones gonadotropins
• Follicle-stimulating Hormone (FSH) controls
  gonadal growth
• Luteinizing Hormone (LH) controls gamete
  maturation and release
• Gonadal hormones (steroids)
• 11-ketotestosterone (androgen) important for
  spermatogenesis
• 17?-estradiol (estrogen) important for oogenesis
• Progesterone or its derivatives (progestins)
  induce gamete maturation in males and females and
  ovulation in females

3
Reproduction, Early Life Stages, Growth
Reproduction general environmental regulation
4
Reproduction, Early Life Stages, Growth
Reproduction hormones that control release of
gametes
5
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

6
Reproduction, Early Life Stages, Growth
Reproduction captive natural spawning
7
Reproduction, Early Life Stages, Growth
Reproduction captive induced spawning
8
Reproduction, Early Life Stages, Growth
Reproduction captive induced spawning
9
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
  males and females (in some species, eyestalk can
  regenerate)
• Bivalves
• Spawning cues include change in water
  temperature, change in salinity, lunar cycles,
  pheromones

10
Reproduction, Early Life Stages, Growth

• Early 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
  begins)
• Larval development
• Larva-juvenile transition (metamorphosis)
• Juvenile (pre-pubertal) growth

11
Reproduction, Early Life Stages, Growth

• Early 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

12
Reproduction, Early Life Stages, Growth

• Early 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

13
Reproduction, Early Life Stages, Growth

• Growth
• 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
  assimilated
• F amount of food consumed
• M catabolism (energy release)
• G growth (anabolism)
• Expanded equation C (Mr Ma SDA) (F U)
  (Gs Gr)
• C rate of energy consumption
• Mr standard metabolic rate (rate of energy use
  by a fasting animal at rest)
• Ma metabolic rate increase (over standard) due
  to activity
• SDA metabolic rate increase (over standard) due
  to digestion and assimilation of food
• F waste due to egestion (feces)
• U waste due to excretion (urine)
• Gs somatic growth rate

14
Reproduction, Early Life Stages, Growth

• Growth
• 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

15
Reproduction, Early Life Stages, Growth

• Growth
• Measuring growth
• Growth measurements are needed to monitor health
  and predict harvest time
• For accurate estimations, take measurements on at
  least 100 individuals
• 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
• Condition factor weight/(length)3
• Dry weight wet weight minus water (in oven at
  about 50C until water evaporated). It is most
  accurate method for assessing animal tissue
  growth, since changes in tissue water content may
  occur due to stress, etc.
• Ash-free dry weight dry weight inorganic ash
  (up to 24 h at 500C). 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.
• Proximate composition determination of different
  categories of compounds in tissues. Most
  commonly measured categories include
  carbohydrates, proteins, lipids.

16
Reproduction, Early Life Stages, Growth

• Growth
• 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)