Fish continued to perish in Lake Elsinore for a second day Wednesday, Aug. 5, as a heat wave is exacerbating deteriorating water quality.
City workers scooped out about 400 pounds of carcasses Wednesday, bringing the two-day total to about 1,000 pounds, said Management Analyst Nicole Dailey, who is orchestrating a multi-agency response plan called Lake Watch 2015.
Whereas observers spotted mostly dead or dying carp and threadfin shad minnows on the lake Tuesday, other bigger kinds surfaced the following day, indicating a worsening of the environment.
“We are seeing a variety of species — bass, carp, shad, bluegill and catfish,” Dailey said. “There’s definitely been some big catfish, big bass and shad that are bigger than we’d expect.”
As they did before, city crews worked quickly again Wednesday to gather and dispose of the carcasses before they spoil public enjoyment of the lake.
The die-off has remained relatively small, but city and lake officials are worried it could expand.
“We’re still seeing fish coming up gasping for air,” Dailey said. “We’re still very concerned because of the high temperatures today and limited cooling throughout the night.”
Lake Elsinore, the largest freshwater natural water body in Southern California, is the only lake in the region that appears to be experiencing pronounced problems with fish dying, said Senior Environmental Scientist Mike Giusti of the California Department of Fish and Wildlife.
Even Imperial County’s Salton Sea, a saltwater lake notorious for fish mortality, is relatively stable, though such an event could happen there any day, Giusti said.
Because of its shallow depth, he said, Lake Elsinore is more vulnerable than other freshwater bodies such as Canyon Lake and Lake Hemet, both upstream on the San Jacinto River.
“Most of the other lakes are much deeper for one thing,” Giusti said. “They don’t have the high algae concentration that is in Lake Elsinore. … At night, when algae no longer photosynthesizes, it’s discharging more carbon dioxide, which causes the dissolved oxygen levels to drop and with very low dissolved oxygen levels, that’s when you see the fish kills.”
Various factors are contributing to the downturn, starting with the drought.
Elsinore has shrunk to about 20 feet deep at best. Its surface is at 1,236 feet above sea level, the lowest the lake has been since February 2005.
Studies performed by UC Riverside marine biologist Michael Anderson determined the lake’s health starts declining when it drops under 1,240 feet above sea level.
As a natural lake, it almost entirely depends on rain storms for an infusion of water. Runoff flows into Canyon Lake, forcing it to overflow into Lake Elsinore. That hasn’t happened for several years.
In past decades, Lake Elsinore has dried out, but that possibility is minimized by the use of reclaimed water and well water by the Elsinore Valley Municipal Water District.
As a result of the reduced water, it is becoming choked with nutrients that feed algae. Meanwhile, the population of threadfin shad that feed on zooplankton — which in turn consume and control algae — has exploded, said Mark Norton, administrator of the Lake Elsinore and San Jacinto Watersheds Authority.
In an April survey, Anderson determined the 3,000-acre lake contained about 56,600 fish per acre, nearly all of which were shad. While the authority in conjunction with the city has dealt with carp overpopulation in the past by netting and removing them, shad are too small and numerous for that option to work, Norton said.
“To really freshen up Lake Elsinore, we really need a big rain storm to fill up the lake again and actually get it flowing out again through Temescal Wash to wash out the nutrients and sediment that has built up in the lake,” Norton said.