Pond Boss Forums INTRO Questions & Observations Trout

Shawn -- how fish farms produce their fish depends on quite a few things, and the options vary by type of fish.

Some fish have more "primitive" ovaries where ripe eggs are loose in a simple bag or ovary sac and there is no complex connective tissue to hold the eggs. My choice of words doesn't seem very good here. However, these tend to be eggs of a similar size, and they are in a ovary that just has a thin wall, and nothing much inside except the eggs.

The fishes with "primitive" ovaries, or maybe I should just call them simple ovaries, can be hand stripped when the fish are ripe. Fishes such as trout and salmon, northern pike, and walleyes all fall into this group.

Some commercial trout farmers that hatch their own eggs simply hold and feed trout, perhaps in a raceway, until the eggs are ripe. Then, you strip eggs from females and milt from males, and fertilize the eggs. The eggs then are hatched; again this depends on species of fish. Trout eggs are often hatched in a series of screened trays with water flowing through them. Eggs must be "picked" daily to remove the dead ones, as fungus that starts on the dead eggs can move to the live eggs. Eggs from walleye and northern pike are often hatched in hatching jars.

Fish tend to ripen their eggs based upon photoperiod (length of day and night periods) and water temperature. As I mentioned earlier, there are strains of rainbow trout that spawn in spring, and others that spawn in fall. You can also really mess up your fish by changing water temperatures and and photoperiod (say inside a building) and get them to spawn earlier than normal or delay until later than normal.

Other fishes have more complex ovaries, and we tend to let them spawn themselves and then collect the fry. A good example is largemouth bass. They have a complex ovary, and eggs of different sizes in the ovary. Even when a female is absolutely ripe, it's hard to squeeze more than a few dozen eggs from her. So, for this group of fishes, we tend to let them do their own thing!

Whew!! This is either too long, or too short!! I could write more, but I suspect this may have answered your initial question???? :-)

Chris -- thanks for helping with the "local" knowledge.

Dave