06-22-2007, 12:12 PM
[cool][#0000ff]Wherever there are perch, there are dieoffs...sometimes in different sizes and year classes...sometimes across the board...like at Jordanelle two years ago. The same thing often happens with crappies in their smaller sizes.[/#0000ff]
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[#0000ff]There are about 3 potential causes...1. food supply 2. disease 3. sudden temperature changes.[/#0000ff]
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[#0000ff]The food supply is the biggie. Many of our lakes do not have a lot of weed growth, with any kind of resident invertebrate population for the perchlets to feed on all during the year. Some lakes have areas of mud flats that produce hatches of aquatic insects or small worms, and the fry do fine until they can grow large enough to feed on the fry of their own and other species. But, whenever there are slim pickings in a given area, and the young fish cannot make a living, they die off. They do not know enough to migrate to better feeding areas.[/#0000ff]
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[#0000ff]In many cases, once the fry absorb their yolk sacs, they have to live on zooplankton, copepods and other tiny stuff. In a lake with poor nutrients, there is simply not enough of the bitty bits to support a large population of new hatchlings. Die off. That is a big thing with the crappies at Willard. The gizzard shad vacuum up so much of the invertebrate food material that the young of walleyes, crappies and other species sometimes do not make it through the fry stage.[/#0000ff]
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[#0000ff]Perch are not as temperature sensitive as other species, but if a bunch of fry are caught in shallow water, during a major cold snap, they could stress and die. [/#0000ff]
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[#0000ff]In talking with a couple of DWR biologists about dieoffs among larger perch, I was told that there are assorted fish viruses and other ailments that can affect the fish within a specific area of the lake..or lakewide. And, many times, the diseases attack mostly the fish that are weakened by stress from hunger or temperature fluctuations. [/#0000ff]
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[#0000ff]So, without a CSI analysis, it is difficult to say for sure exactly what is causing any particular mortality situation. But, without some form of natural control, we would be up to our bilge pumps in perch. It is for sure that natural causes kill off far more fish than anglers.[/#0000ff]
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[#0000ff]There are about 3 potential causes...1. food supply 2. disease 3. sudden temperature changes.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]The food supply is the biggie. Many of our lakes do not have a lot of weed growth, with any kind of resident invertebrate population for the perchlets to feed on all during the year. Some lakes have areas of mud flats that produce hatches of aquatic insects or small worms, and the fry do fine until they can grow large enough to feed on the fry of their own and other species. But, whenever there are slim pickings in a given area, and the young fish cannot make a living, they die off. They do not know enough to migrate to better feeding areas.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]In many cases, once the fry absorb their yolk sacs, they have to live on zooplankton, copepods and other tiny stuff. In a lake with poor nutrients, there is simply not enough of the bitty bits to support a large population of new hatchlings. Die off. That is a big thing with the crappies at Willard. The gizzard shad vacuum up so much of the invertebrate food material that the young of walleyes, crappies and other species sometimes do not make it through the fry stage.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]Perch are not as temperature sensitive as other species, but if a bunch of fry are caught in shallow water, during a major cold snap, they could stress and die. [/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]In talking with a couple of DWR biologists about dieoffs among larger perch, I was told that there are assorted fish viruses and other ailments that can affect the fish within a specific area of the lake..or lakewide. And, many times, the diseases attack mostly the fish that are weakened by stress from hunger or temperature fluctuations. [/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]So, without a CSI analysis, it is difficult to say for sure exactly what is causing any particular mortality situation. But, without some form of natural control, we would be up to our bilge pumps in perch. It is for sure that natural causes kill off far more fish than anglers.[/#0000ff]
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