Winter aeration: Still Learning - 03/07/10 11:27 PM
Perch and bluegill morts from three different cages.
Large 9 to 10 inch bluegills from one cage.
A view showing how far ice as melted so far as today of 3/07/10 looking out. High today was 49 F. Possible thunderstorms in the forecast. Ice is absolutely not safe to step on anywhere on the pond.
A view looking back the other way 3/07/10.
A view of typical water kept open during the winter give or take by the diffuser.
As you can see I lost some fish in the fish cages this winter possibly because they were too close to the diffuser I set in shallow water. However it's not as bad as it looks as I have lots more in the cages that seem to be O.K. In fact I am feeding my yellow perch in the cages with hydrated feed even though more than half the pond is still ice covered, and couple of the cages still have ice around them. The surviving perch look good and are feeding well. I also have large free swimming male bluegills and female yellow perch in the pond that are probably fine.
What does this mean to those of you that have ponds and use a diffuser in shallow water to prevent winterkill? Possibly nothing as your fish can stay deep and back away from any potential super chilling of the water if that indeed was the cause. The caged fish at about the four foot level didn't have that option.
One factor may have been that perch larger than 10 inches don't fair well in cages in winter. According to Dr. Perca (Bill Cody) in a recent email,
"I don't have good luck with perch larger than 10"-10.5" in my cages. Larger perch seem to be more territorial(?) and a larger percent have more body abrasion as they get bigger. I think it is due to interaction and competition in the cage. Any cage stress is not helped by super cooled water."
I'm considering putting my male perch that I typically kept in cages, in a seperate pond as with the female bluegills. And any fish that must be overwintered in cages I will put farther away from the diffuser. It also appears smaller fish fare much better (see below).
Some interesting observations with the cages and subsequent morts or lack thereof:
(The higher the numerical value the farther away from the diffuser).
Cage # 1 -- Had a low density of bluegills approximately 3 to 4 inches had no morts whatsoever. It was inside the edge of the ice or in open water a significant part of the winter closest to the diffuser.
Cage #2 Two year old gills 5 to 7 inches (not YOY) had about a 20 percent mortality.
Cage # 3 Larger mostly male YP and some females had about a 50 percent mortality.
Cage # 4 200 + small YOY 09 in number of 5 to 8 inches had 10 percent mortality tops.
Cage # 5 with large bluegills 8 to 10 inches I lost 7 out of about 25.
Cage #6 with a high density about 250 bluegills 3 to 4 inches I lost one.
Large 9 to 10 inch bluegills from one cage.
A view showing how far ice as melted so far as today of 3/07/10 looking out. High today was 49 F. Possible thunderstorms in the forecast. Ice is absolutely not safe to step on anywhere on the pond.
A view looking back the other way 3/07/10.
A view of typical water kept open during the winter give or take by the diffuser.
As you can see I lost some fish in the fish cages this winter possibly because they were too close to the diffuser I set in shallow water. However it's not as bad as it looks as I have lots more in the cages that seem to be O.K. In fact I am feeding my yellow perch in the cages with hydrated feed even though more than half the pond is still ice covered, and couple of the cages still have ice around them. The surviving perch look good and are feeding well. I also have large free swimming male bluegills and female yellow perch in the pond that are probably fine.
What does this mean to those of you that have ponds and use a diffuser in shallow water to prevent winterkill? Possibly nothing as your fish can stay deep and back away from any potential super chilling of the water if that indeed was the cause. The caged fish at about the four foot level didn't have that option.
One factor may have been that perch larger than 10 inches don't fair well in cages in winter. According to Dr. Perca (Bill Cody) in a recent email,
"I don't have good luck with perch larger than 10"-10.5" in my cages. Larger perch seem to be more territorial(?) and a larger percent have more body abrasion as they get bigger. I think it is due to interaction and competition in the cage. Any cage stress is not helped by super cooled water."
I'm considering putting my male perch that I typically kept in cages, in a seperate pond as with the female bluegills. And any fish that must be overwintered in cages I will put farther away from the diffuser. It also appears smaller fish fare much better (see below).
Some interesting observations with the cages and subsequent morts or lack thereof:
(The higher the numerical value the farther away from the diffuser).
Cage # 1 -- Had a low density of bluegills approximately 3 to 4 inches had no morts whatsoever. It was inside the edge of the ice or in open water a significant part of the winter closest to the diffuser.
Cage #2 Two year old gills 5 to 7 inches (not YOY) had about a 20 percent mortality.
Cage # 3 Larger mostly male YP and some females had about a 50 percent mortality.
Cage # 4 200 + small YOY 09 in number of 5 to 8 inches had 10 percent mortality tops.
Cage # 5 with large bluegills 8 to 10 inches I lost 7 out of about 25.
Cage #6 with a high density about 250 bluegills 3 to 4 inches I lost one.