Changes

= Introduction =

== Introduction ==

Among the most significant advancements in the field of aquaculture during recent decades is the development of techniques to induce reproduction in fish. These techniques have allowed farmers to profitably breed and raise species that do not naturally reproduce in captivity, and to manipulate the timing of reproduction to suit production cycles.

Among the most significant advancements in the field of aquaculture during recent decades is the development of techniques to induce reproduction in fish. These techniques have allowed farmers to profitably breed and raise species that do not naturally reproduce in captivity, and to manipulate the timing of reproduction to suit production cycles.

Where successful, techniques for altering the spawning cycle of fish have become a valuable tool.

Where successful, techniques for altering the spawning cycle of fish have become a valuable tool.

= Strategies =

== Strategies ==

There are two main strategies used to induce reproduction.  Often the two strategies are used sequentially, the first to manipulate maturation, then the second to induce ovulation.

There are two main strategies used to induce reproduction.  Often the two strategies are used sequentially, the first to manipulate maturation, then the second to induce ovulation.

* This is only effective in fish that are already in breeding condition and have mature eggs in which the germinal vesicle has migrated.

* This is only effective in fish that are already in breeding condition and have mature eggs in which the germinal vesicle has migrated.

= Induction using Hormones =

== Induction using Hormones ==

Numerous hormones have been used to induce reproduction. Two methods have emerged over the past few years that seem to offer the best chance for success at the least expense. They are injection of a GnRH analog with dopamine antagonist, and injection of gonadotropin.

Numerous hormones have been used to induce reproduction. Two methods have emerged over the past few years that seem to offer the best chance for success at the least expense. They are injection of a GnRH analog with dopamine antagonist, and injection of gonadotropin.

== GnRH Analogue with Dopamine Antagonist ==

=== GnRH Analogue with Dopamine Antagonist ===

 

* Leutinizing Hormone Releasing Hormone (LHRH) is the name of a mammalian hormone that has been employed successfully to induce the reproductive hormonal cascade.  

* Leutinizing Hormone Releasing Hormone (LHRH) is the name of a mammalian hormone that has been employed successfully to induce the reproductive hormonal cascade.  

* Recently, synthetic analogues of LHRH ('''LHRHa''') have been developed that are more effective.  

* Recently, synthetic analogues of LHRH ('''LHRHa''') have been developed that are more effective.  

* When LHRHa and a dopamine antagonist are used in conjunction, reproductive success dramatically increases.

* When LHRHa and a dopamine antagonist are used in conjunction, reproductive success dramatically increases.

== Gonadotrophin ==

=== Gonadotrophin ===

Two types of gonadotropin extracts have been used to induce ovulation in fish: Human Chorionic Gonadotropin (HCG) and fish pituitary extract.

Two types of gonadotropin extracts have been used to induce ovulation in fish: Human Chorionic Gonadotropin (HCG) and fish pituitary extract.

* Pituitary extracts are made by removing the pituitary from a fish and extracting the hormones, which may then be injected into another fish.  

* Pituitary extracts are made by removing the pituitary from a fish and extracting the hormones, which may then be injected into another fish.  

** Comes in a purified form

** Comes in a purified form

= Brooder Selection =

== Brooder Selection ==

Fish with gametes that have not yet been released by the gonads are called “green.” The term “ripe” is used to describe fish with gametes that have been released from the ovary into the ovarian lumen. Ripe fish can be stripped, green fish cannot.Brooders should be fast growing, disease free, and sexually ripe. There are several indicators of ripeness:

Fish with gametes that have not yet been released by the gonads are called '''“green”'''. The term '''“ripe”''' is used to describe fish with gametes that have been released from the ovary into the ovarian lumen. Ripe fish can be stripped, green fish cannot.Brooders should be fast growing, disease free, and sexually ripe. There are several indicators of ripeness:

== Females ==

=== Females ===

* The abdomen is rounded and soft.  

* The abdomen is rounded and soft.  

* Secondary sexual characteristics are evident.  

* Secondary sexual characteristics are evident.  

== Males ==

=== Males ===

* '''Milt''' (seminal fluid of fish) is released when the abdomen is pressed gently.  

* '''Milt''' (seminal fluid of fish) is released when the abdomen is pressed gently.  

* Secondary sexual characteristics are evident.

* Secondary sexual characteristics are evident.

= Stripping =

== Stripping ==

 

* Stripping should be carried out as soon after ovulation as possible.  

* Stripping should be carried out as soon after ovulation as possible.  

* Water, faeces and blood should not be allowed to mix with the gametes as they are stripped.

* Water, faeces and blood should not be allowed to mix with the gametes as they are stripped.

== Technique ==

=== Technique ===

 

==== Female ====

* To strip the fish, the female should be held around the caudal fin with one hand, while applying slight pressure to the abdomen with the other hand.  

* To strip the fish, the female should be held around the caudal fin with one hand, while applying slight pressure to the abdomen with the other hand.  

* If only a few appear, the female is still '''green''' and should be returned to the holding tank.

* If only a few appear, the female is still '''green''' and should be returned to the holding tank.

* If there is a stream of eggs, the abdomen should be messaged from front to back to strip out all the eggs.

* If there is a stream of eggs, the abdomen should be messaged from front to back to strip out all the eggs.