Modern Hatchery Procedure

by Fly Fisherman

“Oh, so that’s a trout hatchery! Nothing tough about raising fish is there? Get some eggs, let ‘em hatch into minnows, give ‘em all the truck they’ll eat so they’ll grow big and fat, then they cart ‘em out to a stream, dump ‘em and we catch ‘em. What’s so all-fired complicated about it?”
The author is sure he didn’t hear you say that. In fact I cannot believe that any fisherman, anywhere, would be that naive. Many of us have visited trout hatcheries and, sure, we’ve been interested in observing the surface operations that might have been going on. We got a kick out of watching the gregarious little fellows in their troughs and channels. It was amusing to see the baby seven- and eight-inchers, and our fishing temperature jumped a few notches watching the twelve-and fourteen-inchers cavorting in their pond. But how many of us were curious about the internal background of these activities, the gears and the workings that makes what we see tick? Well, how about watching an egg come to life and following it through some of the intricate paths or channels it travels before it is introduced into the waters that we fish?

As we approach our first observation station allow me to state that this little trip will, of necessity, be as brief as we can make it. Some of the points will he broadly covered but we’ll attempt to divulge most of the ground which should be of interest to us, as lay anglers. The possible “meat” of this digest, if brought out in its most complete and encompassing form, would require not one book but volumes and, although important, would be of vital concern only to those directly immersed in the activities and the workings of the trout culturists, the force we depend upon to keep our streams “alive.”
Watch that worker so carefully strip the eggs from that female trout. Every precaution is taken to avoid any possible injury to the fish or to the eggs in the fish.

He is wearing protective gloves and you will note the basin in which the eggs are being placed contains no water, it has been dampened only. When the eggs from three or four female or hen fish are in the container, the milt or sperm of the male or cock fish, which is similarly stripped, is placed with the eggs and stirred enough to secure coverage contact with every egg. This complete procedure must be accomplished in the matter of a very few minutes. Should there be any of the eggs broken in the transfer from the fish to the keg, in which they are placed, the batch will be reduced in the possible number that will be made fertile. It seems that the liquid content of the eggs spreads itself about covering the micropyle of many whole eggs and this prevents the entrance of spermatozoon to those eggs and they remain infertile. The stripper does not attempt to get the very last eggs from the female because this action is a contributing factor toward breaking the skin of the egg or of injury to the brood fish.

Immediately following the fertilization of the eggs they are washed carefully and placed in their receptacles where a current of clean water constantly flows over them, as it would in nature. They are closely watched from this point on until the “bumping” period which ranges from sixteen to twenty days away.
While we’re waiting for this time to pass we might go back and explain briefly another progressive action that is beginning to be used in the egg stripping process. Many hatcheries are using anesthetics, where advisable, on the female trout before the eggs are taken from her. Incidentally, the same procedure is followed in many cases now, when trout are being fin clipped or tagged for identification. The trout are immersed in a solution of urethan for two or three minutes which puts them in a quiet, relaxed state. In the tagging process, following the operation, they also place the fish into another bath, a malachite green mixture, for a moment, and they are then returned to their regular water. We are told that the anesthetizing of fish is now being done by some hatcheries before they are plant dropped from planes into inaccessible lakes and waterareas. The anesthetic is non-toxic and all experiments indicate that the fish are not harmed in the least.

In shipping fertilized eggs from one point to another they are transported in fifteen gallon containers, called “kegs,” and generally are in batches of around 100,000 to 150,000. Water covers the eggs to a depth of six to ten inches and is changed regularly—as often as each hour.
Let’s now observe the “bumping” of the eggs. In this process they are siphoned off from one container to another and as they pass through a short length of hose each egg strikes or bumps the finger of the individual conducting the operation. The fall of the egg is little more than an inch or so, they’re quite delicate and it does not take much abuse to damage them.
About an hour after the bump the infertile eggs turn white and the batch, or “stack,” of eggs is placed on a screening tray and cleaned of these infertiles.

Temperature is the important ingredient that determines the incubation interval of the egg. An old saw used to say, “Fifty days at fifty degrees.” This, of course, isn’t always correct but it does approximate the time. When the stack does start hatching it may cover a period of days before the process is complete.
There follows several days, after the hatch, in which the tiny new trout does not eat. The egg, of which the fish is a part, is still attached to his underside and his sustenance comes from this. In salmon trouts, the little fish is known as an alevin at this point.
When the fry or tiny trout, now with the egg completely absorbed, is ready to take food, and while learning to eat, he is fed a fine fish meal first, then finely ground beef liver or heart. As he increases in size to the fingerling stage the trout is gradually given other foods in addition to the liver and beef diets. During this early growth the feeding periods range from hourly down to scheduled dinner hours, still several times a day. This will finally terminate into one daily feeding when the trout reaches about the eight-inch stage.

Comments on this entry are closed.

Previous post:

Next post: