Hormones in Aquacultre/Fish Reproduction Dr. Craig Kasper

Introduction New inovative hatchery techniques have evolved as global demand for fish increases.New inovative hatchery techniques have evolved as global demand for fish increases. Many fish spawn in environments that are nearly impossible to simulate in a hatchery.Many fish spawn in environments that are nearly impossible to simulate in a hatchery. Hormone-induced spawning is the only reliable method to induce reproduction in these fishes.Hormone-induced spawning is the only reliable method to induce reproduction in these fishes. Now fish may be spawned nearly any time of year providing environental conditions and cues are correct for the target species.Now fish may be spawned nearly any time of year providing environental conditions and cues are correct for the target species.

Hormones/Fish Hormone induced spawning of fish is nearly 75 years old!Hormone induced spawning of fish is nearly 75 years old! Surprisingly, many techniques havent changed much during this period.Surprisingly, many techniques havent changed much during this period. Fish such as carp, catfish, seabass, redfish and snook were used as test fish.Fish such as carp, catfish, seabass, redfish and snook were used as test fish. Induced spawning for many other fish became merely a modificaiton of what was already being done.Induced spawning for many other fish became merely a modificaiton of what was already being done.

Why Induce 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 outsideProduce fish outside normal season normal season ($$$!!)

Fish Handing Of course be careful!! REM: These are broodfish and money is at stake!Of course be careful!! REM: These are broodfish and money is at stake! Fish should be captured, handled and spawned with the greatest care possible. (Females will reabsorb eggs if roughed up!)Fish should be captured, handled and spawned with the greatest care possible. (Females will reabsorb eggs if roughed up!) Optimal environmental conditions are required to maximize spawning potential.Optimal environmental conditions are required to maximize spawning potential.

Sexual Maturity Revisited Ensuring the sexual maturity of your fish is important.Ensuring the sexual maturity of your fish is important. Males can be checked for milt easily, but females are more difficult (may require a microscope)Males can be checked for milt easily, but females are more difficult (may require a microscope)

Environmental Conditions photoperiodphotoperiod water temperaturewater temperature water quality (e.g., dissolved oxygen, pH, hardness, salinity, alkalinity)water quality (e.g., dissolved oxygen, pH, hardness, 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, mats, caverns)spawning substrate (e.g., aquatic plants, sticks, gravel, mats, caverns) nutritionnutrition disease and parasitesdisease and parasites presence of other fish.presence of other fish.

Egg/Sperm Aquisition 1. Tank spawning 2. Hand stripping (taking eggs) 3. Surgically removing the eggs

1. 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 spawning tank following injection(s).Brood fish of both sexes are placed together in the spawning tank following injection(s). Brood fish should not be disturbed and subdued lighting is recommended. (Frank Sinatra doesnt hurt…)Brood fish should not be disturbed and subdued lighting is recommended. (Frank Sinatra doesnt 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… Fertilization improved if males are preconditioned (injected prior).Fertilization improved if males are 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 ensure fertilization. (unless aggressive)Two or three males/female/tank can be used to ensure fertilization. (unless aggressive) If tank size permits, then more groups may be in one tank.If tank size permits, then more groups may be in one tank.

Tank Spawnig Advantages Skilled workers (predicting the exact time of ovulation or checking females)Skilled workers (predicting the exact time of ovulation or checking females) Verifying ovulation is unnecessaryVerifying ovulation is unnecessary Rapid deterioration of eggs in the ovary after ovulation is not a problem.Rapid deterioration of eggs in the ovary after ovulation is 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 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. Cant used method for polyploidyCant used method for polyploidy

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 (most spp.) (or with ultrasound!)Ovulation verified when eggs flow freely from the vent (most spp.) (or with ultrasound!) One hour prior to anticipated spawning females are checked again.One hour prior to anticipated spawning females are checked again. Tropical species every 45 minutes or less, temp.)Tropical species every 45 minutes or less, temp.)

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 at pressure is applied to the abdomen starting at the pectoral fins, moving the 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 aint ready! She aint ready!

If you make a mistake… Sacrificing your broodfish for poor technique is never a good feeling.

Hand Stripping Water cant touch the eggs at this point!!Water cant touch the eggs at this point!! Water activates sperm and closes the micropyle (hole where sperm enter egg.) For many fish, this closure takes place within only 45 to 60 seconds.Water activates sperm and closes the micropyle (hole where sperm enter egg.) For many fish, this closure takes 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 for ripeness. Firm pressure and steady flowing motions are better than driving them out with force.Stripping of eggs used the same technique as checking for ripeness. Firm pressure and steady flowing motions are better than driving them out with force.

Surgical Removal Yes, sometimes it becomes necessary to do this.Yes, sometimes it becomes necessary to do this. Anatomy of some fish wont allow efficient strip spawning.Anatomy of some fish wont allow efficient strip spawning. For example, sturgeon and paddlefish have no ovarian sac; the eggs are released into the abdominal cavity during ovulation.For example, sturgeon and paddlefish have no ovarian sac; the eggs are released into the abdominal cavity during ovulation.

Surgical Removal

Fertilization Once youve got the eggs, repeat the same stripping technique with a male fish.Once youve got the eggs, repeat the same stripping technique with a male fish. Milt can be added to eggs and them slightly aggitated by swirling, mixing with glass rod, or turkey feather.Milt can be added to eggs and them slightly aggitated by swirling, mixing with glass rod, or turkey feather. Next add some water. Hardening of the eggs will occur within several minutes in some spp.Next add some water. Hardening of the eggs will occur within several minutes in some spp. Move eggs to the appropriate McDonald jar, etc.Move eggs to the appropriate McDonald jar, etc.

Sticky Eggs? In the wild, eggs stick together or adhere to substrate, but in the hatchery this isnt desirable.In the wild, eggs stick together or adhere to substrate, but in the hatchery this isnt desirable. Silt-claySilt-clay BentoniteBentonite Fullers EarthFullers Earth Diatomaceous Earth is bad (sharp edges of diatoms damage eggs).Diatomaceous Earth is bad (sharp edges of diatoms damage eggs).

Sticky Eggs… The silt-clay suspension (saturated) is combined with fertilized eggs at 2 to 4 parts suspension to 1 part fertilized eggs. (~20 minutes)The silt-clay suspension (saturated) is combined with fertilized eggs at 2 to 4 parts suspension to 1 part fertilized eggs. (~20 minutes) Other options:Other options: Tannic acid Urea and salt Sodium sulfite (for receipe and mixing instructions see SRAC handout #426)

Hornmone Injection

Brain-hypothalamus-pituitary-gonad Brain-hypothalamus-pituitary-gonad The internal mechanism that regulates the process of reproduction in fish is the brain-hypothalamus- pituitary-gonad chain (Figure 1).The internal mechanism that regulates the process of reproduction in fish is the brain-hypothalamus- pituitary-gonad chain (Figure 1). The hypothalamus producesThe hypothalamus produces gonadotropin releasing hormone gonadotropin releasing hormone (GnRH) and also gonadotropin (GnRH) and also gonadotropin release inhibiting factors. release inhibiting factors.