Natural phenomenon killing Claytor Lake striped bass

[ghostcomanche©®]

Scientists say an unusual condition at Claytor Lake is killing mass amounts of striped bass, leaving anglers frustrated – and confused.


Virginia Department of Game and Inland Fisheries Biologist John Copeland said he’s been fielding calls all week about fish either struggling near the surface of the water, or floating dead.


He said he saw more than 20 affected bass himself over a period on Wednesday.


The cause is a weather-related issue that Copeland said has happened at the lake about four times in the past 16 years. Typically, it happens during periods of hot, dry weather. Scientists still aren’t sure why it’s happening now, after such an abnormally wet summer.


Copeland explains stripers prefer water between 64 and 75 degrees. When the weather gets hot, the fish dive about 60 feet below the surface in search of cooler temperatures.


The problem is that oxygen levels at those depths have fallen to about 1 parts per million this year, according to data from the Virginia Department of Environmental Quality.


Stripers can only tolerate oxygen levels down to 2 ppm.


Copeland says the fish will stay deep in the water until there’s virtually no oxygen, and then are forced to rise toward the surface too quickly.


The fish experience rapid pressure change, which causes their air bladders, used to regulate buoyancy, to inflate.

The fish have no way of releasing the air, so they become stuck on the surface.


“They can’t go back down, but they’ll try,” Copeland said, describing what he saw from his boat this week. “They go down, but they pop back up a few minutes later.”


Water at the surface of the lake is far too warm for the fish, so they stay there until they die.


Copeland said he doesn’t recommend eating floating fish. And those struggling near the surface aren’t going to bite. But he said Claytor Lake is fine for fishing other species.


He said he first heard about the infrequent occurrence known as the “temperature/oxygen squeeze” in 2002. He saw it again in 2007, then 2010. This year, people began reporting dead fish last weekend.


Copeland has examined samples of the fish, finding no parasites or signs they had recently been caught.

He said it seems to affect larger stripers between 6 and 15 pounds. Other fish species, including striped bass hybrids, are less susceptible.


“People will see a difference in their catch rates for stripers in the next six months, next couple years until the population rebuilds from annual stocking,” Copeland said. “Good news is smaller fish aren’t as affected so there will be more smaller fish growing.”


Copeland said he is now aware of the issue impacting fish at Smith Mountain Lake.

www.roanoke.com/news/local/pulaski_county/natural-phenomenon-killing-claytor-lake-striped-bass/article_bfed4cd6-c78d-5300-a155-472a2a87b3d2.html

[striperjohn]

this is another thread under the Rockfish Dock party started by Johnr.

[bushwacker]

The last line states. Copeland said he is not aware of the issue impacting fish at Smith Mountain Lake. Not now aware.

[BentRod]

They need to look into an O2 diffuser like Cherokee installed years back. It would likely result in a restricted area like Cherokee has in the summer, but at least maybe the fish would survive the squeeze.

www.knoxnews.com/sports/hodge-no-fishing-zone-no-big-deal-anymore-ep-408002901-358613011.html?d=mobile

[Gator]

That's a good read, Bentrod. I'm curious as to what TWRA/TVA findings were for the most recent study.

[BentRod]

Same issue. I knew a few guys who fished in the study - the fish still concentrate there heavily in the summer months bc of the rich O2 and catch and release is not effective. It's still banned in the late summer months as far as I know.

[mwardncsu]

Before I realized there was a misprint in that article online early which implied this was also happening on Smith Mountain, I reached out to our SML biologist (Dan Wilson) for clarification this morning - received a response this evening.

This is not an unusual occurrence and happens periodically in some lakes and often in others. It becomes a problem in lakes that have limited habitat for striped bass (abundant cool oxygenated water all summer), is a high flow through system (water passes quickly through the lake), or both . Kerr Reservoir doesn't have much cool oxygenated water all summer any year and Claytor has limited summer habitat which becomes even more limited during wet years or summers with higher flows that tend to flush out preferred striped bass water that is cooler and well oxygenated. Both of these are dictated by lake hydrology and water coming into the lake (receiving water varies but too many variables to quickly discuss). Claytor is a high flow through system compared to SML and water is pulled deep for power generation but sustains adequate striped bass water during normal years but if the river flows are too high, much of the prferred striped bass water gets sucked out.

SML does not have this problem because it has a long retention time (averages: SML = 452 days, Claytor = 27 days) which prevents the good striped bass water from being sucked out or removed during critical periods so we do not see these issues.

Easy cliff notes for Claytor vs SML; water passes through Claytor quickly and too quickly during high precipitation years to sustain optimum striped bass habitat all summer; SML has so little water pulled from the lake, in comparison to its size, that we always have a substantial amount of preferred striped bass water available regardless of precipitation.