SOUTH GULF COVE — A week ago, South Gulf Cove homeowners started seeing dead fish floating in their canals.
The recent cool fronts and low dissolved oxygen levels are suspected as the killers of largemouth bass, bluegills and other small sunfish, mullet, and exotic species like tilapia in the South Gulf Cove canal system.
A week ago, Charlotte County Public Works stocked the canals with sterile grass carp for weed control, Public Works spokesperson Tracy Doherty said. Some of those carp also died in the fish kill, according to the reports Doherty received.
SGC residents George and Jodi Torkoly moved into their new canal-front home on Stuart Street in May. They hadn’t expected to see dead fish floating in the canal, as they did last week. George said he pulled a small, six to eight-inch largemouth bass out of the water. Numerous small, silver-dollar sized sunfish floated among the cattails Monday and one large tilapia bobbed in the middle of the canal behind the Torkolys home.
The Florida Fish and Wildlife Commission first received a report of the fish kill.
While toxic algae blooms are known to spark massive freshwater and saltwater fish kills, the FWC identifies other potential causes:
• Cold weather events reducing the oxygen produced from photosynthesis by green plants and algae, resulting in a normal fall die-off of plants and algae due to cold water. Those green plants surviving a cold snap produce less oxygen due to their metabolism slowing down in cold water.
• Low dissolved oxygen — also called LDO or DO — refers to the volume of oxygen in the water. Oxygen enters the water through the photosynthesis of aquatic vegetation and by the transfer of oxygen across the air-water interface. When the oxygen level in the water drops too low, the fish suffocate.
• Fish kills caused by transmitted diseases when and where fish are already stressed by poor water quality or overcrowding. Little can be done once a disease strikes and spreads except to wait for it to run its course and see what fish populations are left.
• While not as frequent as oxygen depletion, human causes include the pollution of water bodies with pesticides, herbicides, or other chemicals. They are not as common as those caused by oxygen depletion. Sewage spills and illegal dumping have also led to fish kills.
• The causes of some fish kills remain “unknown” due to aquatic anomalies or are reported by a caller who does not always have enough information for the FWC to determine a “probable cause.”
While some residents say they saw county spraying pesticides in the area, county officials say they spray only environmentally friendly materials.
For more information about fish kills, visit myfwc.com. To report a fish kill, call the FWC Fish Kill Hotline at 800-636-0511.