Hormones in Aquacultre/Fish Hormones in Aquacultre/Fish ReproductionReproduction

Hormones in Aquacultre/Fish Hormones in Aquacultre/Fish ReproductionReproduction

Dr. Craig KasperDr. Craig KasperDr. Craig KasperDr. Craig Kasper

IntroductionIntroduction

• New inovative hatchery techniques have evolved as New inovative hatchery techniques have evolved as global demand for fish increases.global demand for fish increases.

• Many fish spawn in environments that are nearly Many fish spawn in environments that are nearly impossible to simulate in a hatchery. impossible to simulate in a hatchery.

• Hormone-induced spawning is the only reliable method Hormone-induced spawning is the only reliable method to induce reproduction in these fishes.to induce reproduction in these fishes.

• Now fish may be spawned nearly any time of year Now fish may be spawned nearly any time of year providing environental conditions and cues are correct providing environental conditions and cues are correct for the target species.for the target species.

Hormones/FishHormones/Fish

• Hormone induced spawning of fish is nearly 75 years Hormone induced spawning of fish is nearly 75 years old! old!

• Surprisingly, many techniques haven’t changed much Surprisingly, many techniques haven’t changed much during this period.during this period.

• Fish such as carp, catfish, seabass, redfish and snook Fish such as carp, catfish, seabass, redfish and snook were used as test fish. were used as test fish.

• Induced spawning for many other fish became merely a Induced spawning for many other fish became merely a modificaiton of what was already being done.modificaiton of what was already being done.

Why Why InduceInduce Fish to Spawn? Fish to Spawn?

• Hybrid productionHybrid production• Sterile fish (polyploidy)Sterile fish (polyploidy)• Sychronous spawningSychronous spawning

(simplifies production)• Max. production of fryMax. production of fry• Produce fish outside Produce fish outside

normal season normal season ($$$!!)

Fish HandingFish Handing

• Of course be careful!! REM: These are Of course be careful!! REM: These are broodfish and money is at stake!broodfish and money is at stake!

• Fish should be captured, handled and spawned Fish should be captured, handled and spawned with the greatest care possible. (Females will with the greatest care possible. (Females will reabsorb eggs if roughed up!)reabsorb eggs if roughed up!)

• Optimal environmental conditions are required to Optimal environmental conditions are required to maximize spawning potential.maximize spawning potential.

Sexual Maturity RevisitedSexual Maturity Revisited

• Ensuring the sexual maturity of your fish is Ensuring the sexual maturity of your fish is important.important.

• Males can be checked for milt easily, but Males can be checked for milt easily, but females are more difficult (may require a females are more difficult (may require a microscope)microscope)

Environmental ConditionsEnvironmental Conditions

• photoperiodphotoperiod• water temperaturewater temperature• water quality (e.g., dissolved oxygen, pH, hardness, water quality (e.g., dissolved oxygen, pH, hardness,

salinity, alkalinity)salinity, alkalinity)• flooding and water currentflooding and water current• tides/lunar cyclestides/lunar cycles• weather cycles (e.g., atmospheric pressure, rainfall)weather cycles (e.g., atmospheric pressure, rainfall)• spawning substrate (e.g., aquatic plants, sticks, gravel, spawning substrate (e.g., aquatic plants, sticks, gravel,

mats, caverns)mats, caverns)• nutritionnutrition• disease and parasitesdisease and parasites• presence of other fish.presence of other fish.

Egg/Sperm AquisitionEgg/Sperm Aquisition

1. Tank spawning1. Tank spawning

2. Hand stripping (taking eggs)2. Hand stripping (taking eggs)

3. Surgically removing the eggs3. Surgically removing the eggs

1. Tank Spawning w/hormones1. Tank Spawning w/hormones

• Simplest method for obtaining a hatchery spawn. Simplest method for obtaining a hatchery spawn.

• Brood fish of both sexes are placed together in the Brood fish of both sexes are placed together in the spawning tank following injection(s).spawning tank following injection(s).

• Brood fish should not be disturbed and subdued lighting Brood fish should not be disturbed and subdued lighting is recommended. is recommended. (Frank Sinatra doesn’t hurt…)(Frank Sinatra doesn’t hurt…)

• The female ovulates when she is physiologically ready.The female ovulates when she is physiologically ready.

• Male will stimulate the female to release eggs.Male will stimulate the female to release eggs.

Tank Spawning…Tank Spawning…

• Fertilization improved if males are Fertilization improved if males are preconditioned (injected prior). preconditioned (injected prior).

• Males can be used for several tank spawns.Males can be used for several tank spawns.

• Two or three males/female/tank can be used to Two or three males/female/tank can be used to ensure fertilization. (unless aggressive)ensure fertilization. (unless aggressive)

• If tank size permits, then more “groups” may be If tank size permits, then more “groups” may be in one tank.in one tank.

Tank Spawnig AdvantagesTank Spawnig Advantages

• Skilled workers (predicting the exact time of ovulation or Skilled workers (predicting the exact time of ovulation or checking females)checking females)

• Verifying ovulation is unnecessaryVerifying ovulation is unnecessary

• Rapid deterioration of eggs in the ovary after ovulation is Rapid deterioration of eggs in the ovary after ovulation is not a problem.not a problem.

• Unnecessary to check and strip the fish (<injury).Unnecessary to check and strip the fish (<injury).

• Less labor required!Less labor required!

Tank Spawning DisadvantagesTank Spawning Disadvantages

• Egg collector or suitable spawning substrate neededEgg collector or suitable spawning substrate needed

• Dirt/debris with the eggs, or egg clumping = fungusDirt/debris with the eggs, or egg clumping = fungus

• Some females may not release all their eggs!Some females may not release all their eggs!

• Estimation of fecundity difficult.Estimation of fecundity difficult.

• Can’t used method for polyploidyCan’t used method for polyploidy

Hand Stripping Hand Stripping

• Also a common technique.Also a common technique.

• Broodfish kept separate.Broodfish kept separate.

• Ovulation verified when eggs flow freely from the vent Ovulation verified when eggs flow freely from the vent (most spp.) (or with ultrasound!)(most spp.) (or with ultrasound!)

• One hour prior to anticipated spawning females are One hour prior to anticipated spawning females are checked again.checked again.

• Tropical species every 45 minutes or less, temp.)Tropical species every 45 minutes or less, temp.)

Hand stripping…Hand stripping…

• The fish is turned belly up and gentle fingerThe fish is turned belly up and gentle finger pressure is applied to the abdomen starting atpressure is applied to the abdomen starting at the pectoral fins, movingthe pectoral fins, moving slowly toward the vent.slowly toward the vent.

• Do not try to squeeze or forceDo not try to squeeze or force the eggs from the fish (injury)!the eggs from the fish (injury)!

• If you only get a few eggs, If you only get a few eggs, then put ‘er back! then put ‘er back! She ain’t ready!She ain’t ready!

If you make a mistake…If you make a mistake…

Sacrificing your broodfish for poor technique is never a good feeling.

Hand StrippingHand Stripping

• Water can’t touch the eggs at this point!!Water can’t touch the eggs at this point!!

• Water activates sperm and closes the Water activates sperm and closes the micropylemicropyle (hole (hole where sperm enter egg.) where sperm enter egg.) For many fish, this closure takes For many fish, this closure takes place within only 45 to 60 seconds.place within only 45 to 60 seconds.

• Solution: Keep a towel handy!Solution: Keep a towel handy!

• Stripping of eggs used the same technique as checking Stripping of eggs used the same technique as checking for “ripeness.” Firm pressure and steady flowing motions for “ripeness.” Firm pressure and steady flowing motions are better than driving them out with force.are better than driving them out with force.

Surgical RemovalSurgical Removal

• Yes, sometimes it becomes necessary to do Yes, sometimes it becomes necessary to do this.this.

• Anatomy of some fish won’t allow efficient strip Anatomy of some fish won’t allow efficient strip spawning.spawning.

• For example, sturgeon and paddlefish have no For example, sturgeon and paddlefish have no ovarian sac; the eggs are released into the ovarian sac; the eggs are released into the abdominal cavity during ovulation.abdominal cavity during ovulation.

Surgical RemovalSurgical Removal

FertilizationFertilization

• Once you’ve got the eggs, repeat the same “stripping” Once you’ve got the eggs, repeat the same “stripping” technique with a male fish.technique with a male fish.

• Milt can be added to eggs and them slightly aggitated by Milt can be added to eggs and them slightly aggitated by swirling, mixing with glass rod, or turkey feather.swirling, mixing with glass rod, or turkey feather.

• Next add some water. Hardening of the eggs will occur Next add some water. Hardening of the eggs will occur within several minutes in some spp.within several minutes in some spp.

• Move eggs to the appropriate McDonald jar, etc.Move eggs to the appropriate McDonald jar, etc.

Sticky Eggs?Sticky Eggs?

• In the wild, eggs stick together or adhere to substrate, In the wild, eggs stick together or adhere to substrate, but in the hatchery this isn’t desirable.but in the hatchery this isn’t desirable.

• Silt-claySilt-clay

• BentoniteBentonite

• Fuller’s EarthFuller’s Earth

• Diatomaceous Earth is bad (sharp edges of diatoms Diatomaceous Earth is bad (sharp edges of diatoms damage eggs). damage eggs).

Sticky Eggs…Sticky Eggs…

• The silt-clay suspension (saturated) is combined The silt-clay suspension (saturated) is combined with fertilized eggs at 2 to 4 parts suspension to with fertilized eggs at 2 to 4 parts suspension to 1 part fertilized eggs. (~20 minutes)1 part fertilized eggs. (~20 minutes)

• Other options:Other options:Tannic acidUrea and saltSodium sulfite(for receipe and mixing instructions see SRAC

handout #426)

Hornmone InjectionHornmone Injection

Brain-hypothalamus-pituitary-gonadBrain-hypothalamus-pituitary-gonad

• The internal mechanism that regulates the process of The internal mechanism that regulates the process of reproduction in fish is the reproduction in fish is the brain-hypothalamus-brain-hypothalamus-pituitary-gonad pituitary-gonad chain (Figure 1).chain (Figure 1).

• The hypothalamus producesThe hypothalamus produces gonadotropin releasing hormonegonadotropin releasing hormone (GnRH) and also gonadotropin(GnRH) and also gonadotropin release inhibiting factors.release inhibiting factors.