LAKEPORT >> Dead fish have been floating to the surface of Clear Lake for more than a week. The culprit? County officials now point the finger at Mother Nature.
After the Lake County Water Resources Department received several reports of dead fish washing up on the shores, there was reason for concern. Fish die offs occur in Clear Lake, sometimes due to the dumping of chemicals or an accidental spill.
Upon investigation, Phil Moy, Director of Water Resources, determined that it appears the fish likely succumbed to a rapid temperature change in shallow water during spawning.
The fish he observed were predominantly adult crappies, a few bass and several large carp. These are all fish that spawn in the spring in shallow water.
“Until recently, we were enjoying a cool spring then suddenly had a spate of rather hot weather,” Moy said. “The rapid temperature change in nearshore waters where these fish spawn, in addition to the normal stresses of spawning, likely caused the mortalities.”
Moy began the investigation on May 10. He tallied dead crappie and carp on the north shore of the lake and an accumulation of dead crappie, carp and few bass at Austin Park in Clearlake. Residents and anglers have seen dead fish of various size, including at least one carp estimated at over 20 pounds floating in a Lakeport cove. For Moy, the evidence at Austin Park was telling.
“It is unlikely the fish all died in the waters off Austin Park,” Moy reported. “The fish were predominantly accumulated on north-facing shorelines with some adjacent to the water and some father up on the shore, suggesting a strong north wind and waves carried them from other parts of the lake.”
Noting the fish were in various states of decomposition, he concluded that the cause of the mortalities was more chronic than acute — that is, taking place over a longer time frame than a single rapid event.
The distribution of dead fish all of similar species distributed around the lake also suggests the die-off was not a singular event involving a single location, but rather a lake-wide phenomenon. In consideration of the rapid cool to hot weather changes, Moy believes this further suggests thermal environmental stress rather than a toxic algal bloom.
