Originally posted by PaPond:
If fish can be stressed by the supercooling of the deeper water by aeration, then how do cage culture fish fare when they are essentially trapped in a pen close (within 5 feet) to the surface, where theoretically the water is the coldest. Are there different guidelines for aeration if you're floating a cage of trout or HSB in a northern pond? Since water starts its natural migration to the surface at 39 degrees, and reaches the surface when it is at or very close to 32, the surface waters must be pretty nippy for the caged fish. Are they stressed similarly to the fish supercooled by bottom aeration over the winter?
PaPond,
From someone that's been doing seasonal cage culture for several years and overwintered caged fish one winter I can give you some information based on experience. I've have also included a website that covers cage culture in depth that talks about overwintering fish if you can find the right link. Don't remember which exact link it is at the present time but here is the website:
http://aquanic.org/beginer/systems/cages.htm I don't overwinter fish in a floating cage unless I have to as it IS stressful on them and can be risky where one gets ice cover. Typically folks that overwinter fish in cages do so in climes where their ponds don't freeze over. Additionally since their ponds do not freeze over, but the water gets fairly cold, lack of oxygen and too cold of water are not an issue as it would be with ice and snow cover and much colder temps. In fact, they are able to hold more fish (trout) per cubic foot because of this increased oxygen level. I have also observed no ill effect to mixing of the water column to trout when I have done it. In fact I actually fed them in the open water caused buy the diffuser! Since the metabolism of the trout is still active in water in these southern climes, the trout can be continued to be fed and this is conducive to good health and optimum growth. No experience with hybrid striped bass.
From a past experience overwintering feed trained smallmouth fingerlings (was only able to purchase them in the fall) I would suggest if you have to overwinter fish in a cage, cover the cage with the same material the cage is made out of, and suspend the cage a foot of two off the bottom. The first year I tried to overwinter smallmouth in a cage, the cage actually sunk below the surface from the weight of ice build up, and most of the smallmouth escaped because I left the cage on surface.
I am presently overwintering another batch of 200 smallmouth fingerlings in one 7 X 7 foot cage and about 350 bluegills in another 7 X 7 foot cage. The smallmouth are too small to release into the pond with several hundred over 8 inches to 20 inch feed trained largemouths as they would be decimated. The bluegill I want to sex come late spring and plant only the males in a small pond I had recently dug. Hence protecting the feeding them in the floating cages.
What I have done is after securing the top of the cage with the same material the sides are made of so the fish cannot escape, I have attached two strands of nylon rope about three feet long to a couple of ajacent corners of the cage and to the other end of each of these ropes two floats (orange juice or detergent or mineral spirit gallon jugs). On the other opposing side of the cage are two more nylon ropes of the appropriate length attached to my pier. Once the jugs are removed that were originally attached to the cage to keep the top of the cage above water, the cages sinks until the ropes stop it's progress. (I have drilled holes in the PVC frames when originally constructed to allow the PVC to fill with water which causes them to sink evenly) Since the water depth there is 9 feet and the cage bottom where the fish reside is 4 feet, (cage is 4 feet high) by sinking the tops of the cages top 3 feet below the water surface the fish are residing 7 feet down at 2 feet off the bottom.This should allow them to overwinter O.K. and I will let anyone know of the results if they are interested.
I will NOT aerate anywhere near the cages as I want them to have a somewhat warmer water refuge. I may aerate very close to shore in a shallow end of the pond though due to my large density of bass in the pond.
