Spawning Techniques?

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flowerpower

flowerpower

Feeder Fish
MFK Member
Jun 10, 2007
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NY
Hey guys, I just wanted to get some ideas and info on a spawning technique commonly used in the aquaculture industry:

"... Fish can be spawned in the laboratory by manually stripping gametes into petri dishes and then mixing milt and eggs with water."

Does this involve sacrificing one or both fish in order to extract sperm and egg or can one 'milt the cow' so to speak?

Thoughts?
 
Most often it is done by sacrificing the fish, though some of the larger species can be "milted" as you put it. Usually there is an injection of a hormone that ensures the eggs are at the proper stage of readiness, If I remember right from my classes, it's "Carp Pituitary Extract" and I think anyone can purchase that hormone (sold in powder or whole gland form) There is also a synthetic version called Ovaprim that is used.

I would imagine that both have been discussed here on the forum.

We did some induced spawning in sturgeon and injected both sexes, "milted" the males both by squeezing and by inserting a syringe into the urogenital opening (about 180 lbs at the time and nearly 6ft long). The females we did what was referred to as MIST or Minimally Invasive Surgical Technique. (The females were nearer to 250lbs and over 6.5ft long at the time) These fish are over 8 ft long today.

MIST involves cutting a slit in the abdominal region and sticking in a firm plastic tube that just fits over the tip of a large syringe. The syringe is used to sample eggs to see what stage they are at, and later to remove *most* of the eggs through suction.
 
groelzj said:
Most often it is done by sacrificing the fish, though some of the larger species can be "milted" as you put it. Usually there is an injection of a hormone that ensures the eggs are at the proper stage of readiness, If I remember right from my classes, it's "Carp Pituitary Extract" and I think anyone can purchase that hormone (sold in powder or whole gland form) There is also a synthetic version called Ovaprim that is used.

I would imagine that both have been discussed here on the forum.

We did some induced spawning in sturgeon and injected both sexes, "milted" the males both by squeezing and by inserting a syringe into the urogenital opening (about 180 lbs at the time and nearly 6ft long). The females we did what was referred to as MIST or Minimally Invasive Surgical Technique. (The females were nearer to 250lbs and over 6.5ft long at the time) These fish are over 8 ft long today.

MIST involves cutting a slit in the abdominal region and sticking in a firm plastic tube that just fits over the tip of a large syringe. The syringe is used to sample eggs to see what stage they are at, and later to remove *most* of the eggs through suction.
Click to expand...

Interesting read. Thanks for sharing.
 
Very interesting indeed.
How many female breeders have I lost over the years? What a waste.
What's the shelf life of a gamete?
I feel silly asking but the the thought evokes some serious questions (for me at least).
 
Gametes are usually only good until a few seconds after they hit the water. Most eggs need to be fertilized within seconds of exposure to water or they'll never get fertilized. As I recall, there's a little pore in the 'top' of the egg that closes up when the egg absorbs water. I'm not entirely sure if the sperm are rendered unusable as fast, they likely lose motility awhile after contact with water, but it might be tens of seconds rather than the maybe 3-10 second window you have with eggs.

I remember when we were stripping/removing eggs, it HAD TO BE DONE WITH ABSOLUTELY DRY HANDS! a drop of water would ruin the whole batch.

As far as shelf life of gametes goes, it's possible to cryopreserve gametes, but I think they have to be stored in liquid nitrogen, or at similar temperatures to ensure preservation. I'm pretty sure we received sturgeon sperm that way, can't remember if any of the eggs were gotten that way though. Unfrozen, I have no idea what the shelf life is, it's probably in a research paper somewhere though! Try searching through Google Scholar if you feel like it.

Jon
 
Thanks Jon. A wealth of information you've provided here. As a hobbyist I'm not sure how ethical these practices are but I'm sure someone has tried or will try this at some point. It seems as if someone with a certain amount of initiative could figure it out on their own with a little trial and error.
 
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