ST. MARYS — Low dissolved oxygen levels have caused fish to die in Grand Lake St. Marys.
Grand Lake St. Marys Park Manager Brian Miller said low dissolved oxygen levels are robbing fish of oxygen. Last week's heat wave also caused the water temperatures to top 80 degrees in some locations.
"We checked the dissolved oxygen levels this morning in the East Bank Marina and fishing ponds, and at 8 a.m. we had levels of zero," Miller said. "In the lake proper, we have 0.4 so with those types of levels, the fish will be stressed."
When algae in the lake dies, it causes the dissolved oxygen levels in the lake to drop. Miller said the majority of the dead fish are shad.
"There are some small amounts of game fish," Miller said. "We are seeing it widespread through the lake in different areas."
Cooler temperatures this week may help matters. However, Miller said sunlight is needed in order to kick start photosynthesis.
"Last week, we had the dog days of summer — this is historic," Miller said. "We always have algae in the lake and when it dies off, it takes the dissolved oxygen, which in turn starves the aquatic life. The shad are a soft fish and cannot handle stress and they are usually the first to go. We have seen some game fish, but not at the numbers of the shad."