Last week, we looked at trying to catch fish on area reservoirs during the hot summer months and how water temperature and oxygen levels impact fishing success. Before we turn our attention to the different lake species and how each species reacts to water temperature and oxygen levels during summer, I want to explore the water temperature and dissolved oxygen levels in more detail.

Dissolved oxygen is a measure representing the amount of oxygen in the water. Most dissolved oxygen comes from the atmosphere, but it can be depleted by high water temperatures that deplete the ability of the water to hold oxygen. It can also be increased by rain and wind.

Most fish species can also adapt to low dissolved oxygen levels but when dissolved oxygen in the water drops to 5 mg/l or below, the fish are under stress.

Fish can survive and adapt to levels as low as 2-3 mg/l for short periods, but below that level, the fish will begin to die.

As the summer weather takes hold on Lakes Oconee and Sinclair, the water temperatures rise and dissolved oxygen levels steadily drop.

Looking at a temperature/dissolved oxygen study done by the Georgia Wildlife Resources Division on Lake Sinclair clearly shows the result of the summer heat on water temperatures and dissolved oxygen levels.

The study was done in the year 2000 and some changes have occurred (construction of the cooling towers) that could impact some of the numbers, but relatively speaking the study shows the high water temperatures and low dissolved oxygen that occurs in Lakes Sinclair and Oconee and the lack of stratification. Lower summer air temperatures and increased rainfall will have a positive impact on oxygen levels.

The study clearly showed that the highest water temperatures and greatest amount of dissolved oxygen levels were near or at the surface. But it also showed that there was little difference in water temperatures and dissolved oxygen levels at all other depths in the water column during the summer months.

I took particular interest in the study readings taken from an area near Optimist Island, which is near my lake home. This area of the lake is not influenced by the hot water discharge at Plant Branch but is influenced by inflow from Little River and other tributaries which can bring in slightly cooler water and greater oxygen levels, especially during periods of heavy rains.

The summer season officially begins June 21 and when readings were taken June 22, 2000, the water temperature at the surface was 84.2 degrees and dissolved oxygen was 5.2 mg/l. On June 22, the water temperature at 13 feet was 84.2 degrees and the dissolved oxygen was 5.0 mg/l. On July 27, the water temperature at the surface was 86.36 degrees and the dissolved oxygen was 6.2. On July 27 the water temperature at 13 feet was 85.64 degrees and the dissolved oxygen was 4.4.

Moving to August when we normally see the hottest air temperatures that normally equate to high water temperatures, the water temperatures actually dropped somewhat, and dissolved oxygen remained good at all levels except the very bottom of the lake.

On Aug. 25, the water temperature at the surface was 85.1 and dissolved oxygen was 5.9 mg/l. At 13 feet the water temperature was 84 degrees and the dissolved oxygen was 5.2 mg/l.

The water temperature in August of 2000 at the Optimist Island location was in fact almost the same from top to bottom and dissolved oxygen fluctuated between 5.9 mg/l at the surface and about 5.3 mg/l at all other levels.

I can only assume that we had a lot of rain in August of 2000 to have obtained those good August readings near Optimist Island in the Little River. That area would have been a good choice for anglers to fish in August of 2000.

Unfortunately, readings at other locations on the lake during August of 2000 showed a completely different story. At eight other sites where temperature and dissolved oxygen profiles were taken, the water temperature ranged from 86 degrees to 96.8 degrees and many of the disolved oxygen readings varied between 5.5 mg/l to 2.5 mg/l with a majority of the dissolved oxygen reading being below 5.0 where fish become stressed.

Water temperatures and dissolved oxygen readings at those eight different sites indicated that water temperature and dissolved oxygen levels were basically the same from top to bottom at each site which indicates no stratification or variance at different water depths.

This current summer has been extremely hot and I am sure water temperatures and dissolved oxygen levels, if measured now, would indicate that fish are very stressed — and few areas of either lake at any depths have good combinations of water temperature and dissolved oxygen. So where are the fish and where is an angler most likely going to have the best success?

Next week, we will look at where the lake species go during the heat of summer on lakes like Oconee and Sinclair that do not stratify and what lures or baits would be good choices for anglers to catch each species. See you next week.

Outdoor Columnist Bobby Peoples can be contacted via e-mail at brpeoples@windstream.net.