Friday update from Miami-Dade County on recent fish kill

The Department of Regulatory and Economic Resources, Division of Environmental Resources Management (RER-DERM) has been investigating a fish kill across the northern basin of Biscayne Bay. Response efforts are detailed below.

Original report and assessment

The originally affected areas included 64^th Street. North to Broad Causeway, and areas of Miami Beach, including Tatum Waterway South to 63^rd Street. Reports of struggling fish were still being received yesterday morning, as well as reports of dead fish within the affected area. The event is ongoing, although reports received from the public, along with staff observations of live, struggling fish, have decreased. Reports of dead fish from DERM field staff included areas along the 79^th Street. Causeway, North Bay Village, Miami Shores, San Souci, and Malloy Channel near 79^th Street., slightly beyond the areas reported on Wednesday.

Follow-up assessment

Yesterday, DERM field staff observed low to no wind, substantial outbound flows of brown and heavily turbid water from the Little River and Biscayne Canal, and strong dead fish odors from Biscayne Canal south to Little River. Levels of dissolved oxygen at the mouths of both Little River and Biscayne Canal are near zero, with values in the adjacent open bay between 3-4 mg/L. This is an improvement from Wednesday’s results, which were at near zero, but remained low when compared to values measured the first week of October during DERM’s monthly sampling, for which values in northern Biscayne Bay in the vicinity of the fish kill were between 5.70 – 6.43 mg/L. Aquatic organisms can become stressed at oxygen levels below 5 mg/L. Temperatures were found to be lower during this fish kill event than they were during the September 2021 fish kill, with all temperatures now below 86 F. During last year’s fish kill, recorded temperatures were mostly above 86 F. Warmer water holds less oxygen, depriving marine life of available oxygen.

Analysis and cleanup

The samples collected by DERM will allow staff to analyze nutrients and other parameters, including levels of oxygen, salinity, and water temperature. By comparing water quality results from recent sampling prior to the fish kill event with current conditions, DERM can detect differences and identify concerns leading to a further understanding of the cause of this incident. DERM field biologists are also documenting sightings of live and dead fish to determine the extent of the areas impacted and recording current weather conditions. The DERM laboratory is playing a critical role in processing the samples and working to report back the data to technical staff in an expeditious manner after all analyses have been completed.

Also yesterday, DERM’s biomass removal contractor, Kearns Construction Company, initiated a cleanup of the accumulated fish in the areas identified in DERM staff’s observations, including the Pelican Harbor area and North Bay Village around 79^th Street. Kearns’s Construction Company will continue those efforts again today. These cleanup activities are integral to the restoration of water column health by ensuring that decomposing fish do not consume additional oxygen in the water, further degrading the water quality. Given the importance of these efforts, the DERM team has confirmed that the City of Miami Beach has also activated their vendor to collect dead fish on the eastern side of the bay.

The Health of Biscayne Bay

It is important to note that DERM staff understands that there are multiple, cumulative conditions that can lead to a fish kill event. However, fish kills are largely unpredictable. There are conditions that make fish kills more likely, but there are currently no short-term solutions to avoiding these incidents from occurring. Conditions that can contribute to a fish kill consist of lower winds, leading to a lack of necessary mixing in the water column; higher water temperatures reducing the amount of available oxygen in the water column; and low oxygen/high nutrient waters discharging into the bay from canals, which create additional pressures on the receiving waters to reconcile the increased nutrients with low oxygen water. Therefore, DERM’s efforts are focused on identifying the causes and conditions under which this fish kill incident occurred. These fish kills are evidence of the urgency and importance of this community’s collective efforts to restore Biscayne Bay to good health.

Miami-Dade County continues to invest in critical, long-term, comprehensive solutions to improve the wellbeing of Biscayne Bay. These include the ongoing septic to sewer transition, water infrastructure upgrades, pollution reduction policies, increased water quality testing, and enhanced monitoring and updates to the public via the annual Biscayne Bay Report Card.

How the community can help protect the Bay

Residents have several options for reporting a fish kill. The DERM hotline, 305-372-6955, and email, [email protected], are available 24/7. Residents can also report via 311. Use the 311Direct App (Android or Apple), 311 Online at www.miamidade.gov/311direct or call 311. DERM is best able to respond quickly when they are contacted directly, and provided with information that includes an address or precise location. Photos and videos are also helpful.

Miami-Dade County reminds residents that their daily actions can help or harm Biscayne Bay and the local watershed. Following these tips consistently contributes to a healthier environment.