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Posted by john smink on June 26, 2019 at 06:58:38:

In Reply to: Re: +++++ ALERT!!!!LAKE HARTWELL STRIPER FISHERS++++++++ posted by bubba on June 24, 2019 at 20:47:52:

DRN presented annual shocking surveys for the last maybe 10 years. Striper counts are as high as they have ever been since beginning shocking surveys. By almost double 2017 values. However, size class has shifted to smaller fish. Electro shocking surveys indicate a 60% decrease in stripers over 6 lbs. They estimate the fish kill took 60% of stripers over 6lbs. Fisheries management has not had any affect on this loss of large fish. Angling fish mortality is estimated to be 17%. however, results from the first three months of tagging data suggest fishing mortality is higher than 17%. More time is needed to determine actual fishing mortality on Lake Hartwell. But the limit is 10 now and the total fish population is as high now as it has been in the last 10 years. Some folks believe the guide industry is responsible for loss of the larger fish. The data does not support this belief. There are more striper in the lake now than the last 10 years according to electro shocking surveys. Unfortunately, I don't think there was a single guide at the meeting. If there was, they did not identify themselves or stand up for their fellow guides. The issue is critical summer habitat. Their is a refuge zone in the lake for these large stripers. We all know it is water temps in the 55-65F with DO above 2 ppm. This critical habitat come August is roughly between 100 and 120 FOW. Unfortunately, the intake for the hydro turbines are positioned slap dag in the middle of this critical zone. Data was presented that clearly showed this critical zone decrease week by week starting in August and by September the zone was completely void of oxygen. This results in a fish kill. Stripers only have temperature sensors and seek the cold water. They do not have O2 sensors and as the 02 depletes with water withdraw for hydro electric generation, they do not move and suffocate.

Two major fish kills have happened in the last 10 years. 2013 and 2018. Both heavy rainfall years. The presenters say this is because all the warm water is displacing the cold water and fish kills will continue in heavy summer rainfall years. This however is not true. Warm water can not displace cold water. They have different densities. Warm water is less dense and will stay on the surface. Cold water is denser and will stay on the bottom of the lake. That is why water temperature is always colder the deeper you go in the water column.

The problem and the only problem for the hartwell striper fishery is the intake for the turbines is, well they could not exactly say where the intake was. The CORE lake manage was at the meeting and would not verify exactly where the intake is. It is somewhere between 100 and 125 FOW. He didn't have much to say because it is this withdraw that sucks all the cold oxygenated water out of the lake leaving cold oxygenated depleted water. The bottom of the lake will always be absent of O2 due to the biological or sediment oxygen demand. This oxygen depleted benthic zone is only replenished with water when and if the lake completely turns over. However, the O2 at the bottom of the lake will shortly return to zero as the BOD or SOD will continue to consume this O2.

There are a few solutions, and (they) did not want to hear about the solutions. They had an excuse for every solution. Oxygen lines is one solution. But DNR rebuttal was too expensive, or O2 lines are causing other problems in the other southern lakes that have o2 lines. This was not supported by science or data, only by fisherman opinion. Another solution is change the withdrawl point from the critical striper zone to higher in the water column where the water is warmer. This was shot down because their is a so called cold water fisher below the dam. Well, trout don't need 55F water. They can live just fine in 75 degree water as long as o2 remains above 5ppm. The turbines have O2 generating baffles to support the needed O2 levels for this so called cold water fisher. Moving the intake was shot down as "we can't move the intake". Well we put a man on the moon 60 years ago. This would be a one time expense to add hydraulic risers to the intake. Move them up the water column to protect the 100-125 FOW striper zone. Put it at 60 FOW. or wherever it needs to be for the cold water fisher. The cold water fisher does not need 55F water. It can survive with much higher temps. Before the dam, I don't think the river ran 55 in the summer and fall. Summer river temps are generally a few degrees warmer than average summer time night time low temps. So the water leaving the dam does not need to be 55. Historically this was not the case. Another solution which was not raised at the meeting is to install large pumps that pump up cold water from the depths of the lake, and this can be O2 starved water and mix it at the surface with warm oxygenated water. This creates a critical habitat zone in the upper parts of the lake and they can keep the intake where it is. Electric is free to the CORE, you can not store electric, it must be used. Use it to run the pumps. This is a one time expense of pump installation with minimal annual maintenance.

Lake Murry O2 lines were installed at a cost of 13 million with an annual operational budget of 500K. This is small change compared to the revenue generated from the hydro plant. Investigate cost of hydraulic risers, investigate cost of mixing pumps, investigate cost of O2 lines. All (they) wanted to do was discount any remediation action.

Bottom line is, we will have a fish kill every year we have average or above rainfall during the summer and early fall. The only years we can expect not to have a fish kill is summer drought years and nobody wants that to be the solution.

They were between 100 and 125 people at the meeting. Might have been about 15 DNR biologist, techs, and lake managers at the meeting.

the CORE manager did not have much to say as he knows darn well the entire fish kill revolves around where the hydrolic intake is for the electric turbines. If the intake was moved up in the water column, it wouldn't matter how much rain we got in the summer or fall. Warm water can not displace cold water.


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