When I was hired as the Sea Grant Extension Agent for Escambia County, I conducted a needs assessment with my advisory committee to determine the local issues that most needed education and outreach. They responded with several, but water quality was number one. I followed by asking what their largest water quality concerns were. They responded with health advisories and fish kills. I have been tracking health advisories each year since and you can see this year’s report at https://blogs.ifas.ufl.edu/escambiaco/2022/12/30/health-advisories-for-the-pensacola-bay-system-2022-annual-report/. This is the report for those fish kills.
I am sure their concern for fish kills stems from the large kills that occurred in our local bayous during the 1960s and 70s. I remember seeing large kills littering the lower portions of Bayou Texar when I was in high school. More often than not, they were primarily Gulf menhaden (Brevoortia patronus). This species has a very low tolerance for hypoxic conditions (low dissolved oxygen) and it is believed this was the primary cause of many of these fish kills.
Hypoxia can be triggered by several things – some of them natural, like very warm water – but they can also be human-induced with the introduction of excessive nutrients to the system. Excessive nutrients can trigger a process called eutrophication. Eutrophication begins with excessive nutrients which in turn trigger an algal bloom. These blooms will darken the water reducing needed to sunlight to the submerged seagrasses thus reducing those – which are much needed by the estuarine animals. Though algae produce oxygen during the daytime, they consume it at night and can significantly lower the concentration of dissolved oxygen in the water. As the night wanes on, the DO drops, with the lowest levels being close to dawn. Most estuarine creatures begin to stress when the DO concentrations get below 4.0 mg/L. Some will surface gasping for air. Others will leave the bayou. Some will die. Menhaden are particularly sensitive to this and will die in the thousands, sometimes millions. The dead fish – and algae, they do not live long – are decomposed by the bacteria in the sediments, which reduces the dissolved oxygen concentration even further.
Since the 1970s there have been many things the city and county have done to try and reduce the amount of nutrients reaching our local waterways. Getting more homes off leaking old septic systems, creating stormwater ponds instead of straight discharge of stormwater, and providing pet waste bags at local parks. They have also worked on restoring the natural hydrology of the system so that nutrients are not “trapped” and accumulate. All of these seem to have helped reduce the number of fish kills reported each year. The large kills of the 1960s and 70s have not happened in a long time. In fact, there has only been one large fish kill during my time as the Sea Grant Agent and that was in Bayou Chico. It was determined it was induced by naturally warm water, and not from excessive nutrients. Many local and state agencies monitor nutrients in the water. The Bream Fishermen’s Association has been doing it for decades. Sea Grant trains volunteers to do so in a project called Lakewatch. You can see the 2022 Lakewatch report at https://blogs.ifas.ufl.edu/escambiaco/2022/08/17/come-on-in-the-water-is-fine-well-its-better/. But what about the number of fish kills this year? How did that go?
We track fish kills through the Florida Fish and Wildlife Conservation Commission’s website (FWC). Fish Kill Report Application (myfwc.com). Below are the results from Escambia/Santa Rosa counties for 2022.
|Source of Fish Kill||Number of Fish Kills reported||Notes:|
|All sources||16||7 from Escambia; 9 from Santa Rosa
2 from Pensacola; 1 from Pensacola Beach; 2 from Perdido Key; 1 from Cantonment; 1 from Milton; 1 from Navarre; 7 from Gulf Breeze
11 were reported as fish kills; 4 were reported as “abnormal behavior/fish still alive (all of these were from Whisper Lake in Gulf Breeze and involved soft shell turtles); 1 was a marine mammal kill – a dolphin on Pensacola Beach
4 reports did not identify species; 3 reported freshwater fish including largemouth bass; 2 reported baitfish; 1 reported redfish; 1 reported hammerhead shark
|Some form of human induced pollution||2||1 was on May 3 from Lost Key Beach and Golf Club – their pond.
1 was from October 24 from Indian Lake Pond near Cantonment.
|Low Dissolved Oxygen; algal bloom; sewage spill||2||The same two above. Neither were caused by a sewage spill.|
16 fish kills for the year seems high, but only 2 of those were triggered by human induced pollution: the others from a variety of causes including discarded bait. This is good news. Both pollution related kills were in small private ponds and were triggered by low dissolved oxygen or algal blooms. This suggests that in both cases excessive nutrients could have been the cause and, since not connected to sewage spills, COULD be from fertilizers used nearby. With the new developments going on around Indian Lake and the golf course associated with Lost Key, these would be good assumptions – and easily fixed. Note – that only one kill was reported from both locations. This suggest that the problems may have already been addressed.
This report also suggests that the large fish kills of the 60s and 70s are not as large a problem today as they were. The management practices adopted seem to have made a difference and they should continue. The Lakewatch nutrient report suggest that though there are fewer fish kills in the bayous, there is still need for improvements in nutrient reduction in Bayou Chico and Texar. The recent efforts to improve Carpenter’s Creek may help reduce nutrients in Bayou Texar. Much is going on in and around Bayou Chico and we will have to continue to monitor both nutrients and fish kills there to see if these will help.
If you have any questions concerning this report, please contact Rick O’Connor at the Escambia County Extension office – firstname.lastname@example.org (850)475-5230 ext.1111.