A Maze of Multi-Faceted Effects
Red tide occurs when the algae Karenia brevis blooms, releasing neurotoxins into Florida’s Gulf Coast waters and air. These harmful algal blooms disrupt marine ecosystems and the communities that depend on them. While managing these events is challenging, scientists are developing new strategies to navigate these complex impacts.
Red tides kill marine animals, including gag and red grouper, by exposing them to toxins and reducing oxygen in the water. Toxins also bioaccumulate in the food web, forcing mobile species to evacuate affected areas.
Beyond ecological damage, severe blooms inflict heavy economic tolls. A 2017–2019 bloom cost Florida an estimated $2.7 billion in tourism revenue. Anglers face increased operational costs and profit losses as they avoid affected areas. These financial pressures also negatively impact mental health, community identity, and industry retention.
A new review paper, led by the University of Miami Cooperative Institute for Marine and Atmospheric Studies and NOAA Fisheries, synthesized the existing literature on this topic. It explored avenues for incorporating red tide impacts into the fishery management process. It supports the implementation of the Gulf Council’s Fishery Ecosystem Plan, which formalizes ecosystem-based fishery management in the region. The synthesis made significant progress in the realm of red tides by:
- Assessing ecological, economic, and sociocultural impacts of red tides on federal fisheries
- Suggesting a shift to more proactive management
- Providing advice to the Council to help fisheries be more resilient in the face of these shocks
- Highlighting knowledge gaps and research opportunities regarding red tide
Navigating the Obstacles: Accounting for Red Tide
Scientists and fisheries managers have extensively studied how to account for the effects of red tides in stock assessments and consider it when making management decisions. Scientists routinely account for these impacts in catch advice. However, red tide impacts many other aspects of fisheries—prey populations, habitat, fishing behavior, demand for seafood products, and human health. There is very little research to guide, and no clear mechanism for how to deal with these broader impacts in the fisheries management realm.
Prioritizing Adaptation, Research, and Partnerships
In the paper, the authors suggest managers explore policy options that foster adaptive capacity for the industry, such as:
- Developing emergency rules to remove barriers to quota leasing
- Exploring temporary permit switches to allow fishermen the flexibility to make up for revenue displacement and loss during blooms
Developing marine insurance mechanisms, similar to federal crop insurance, could also be a way to provide financial support when the fishing industry experiences a significant red tide.
They also emphasized that we still have more to learn about red tide. Better research is needed to understand lethal and sublethal thresholds, behavioral responses, and recovery times for affected species, as well as the economic impacts. Cooperative research and citizen science could enhance data collection efforts and improve fish kill reporting and characterization of mortality across age/size classes.
“We likely need multiple, varied actions to bolster both the industry and the ecosystem,” said lead author Brendan Turley, assistant scientist with the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies. “A holistic and proactive approach will help build resilience to withstand the natural, episodic impacts of severe red tides.”
Lastly, the authors recognize that the catalysts for red tides fall outside the jurisdiction of fishery managers. A combination of physical oceanography and land-based nutrient inputs contribute to blooms. Some of these aspects are completely outside of human control, but others rely on decision-makers outside of the fisheries realm. The team proposes interjurisdictional partnerships between marine resource managers and land-based environmental agencies that oversee water quality policy. These partnerships could address the root causes of bloom severity before they occur.
History of Red Tides in Fisheries Management
Red tides have made it challenging to provide stability in fisheries management decisions. Historically, managers have had to frequently adjust annual catch limits to allow stocks to recover following each event. Each of these events presents a period of unquantified red tide-induced mortality. For example, from 2017 to 2018, the red grouper quota decreased by 61 percent. Similarly, gag quota dropped 79 percent from 2022 to 2023. These massive fluctuations highlight the instability red tide inserts into both the ecosystem and the fishery. To better quantify and account for the impacts, NOAA Fisheries initiated an effort to gather information from those with first-hand knowledge on this topic: the fishermen.
Local ecological knowledge has been instrumental in guiding the decision to include extra mortality in stock assessments. For example, the 2018 red grouper assessment took place during an extensive red tide bloom that caused heightened concern from the fishing community. Although analysts didn't have a clear way to measure the bloom's impact, they produced several model predictions in response to public input to provide a range of recommended fishing limits. This allowed the Gulf Council's Scientific and Statistical Committee to select a likely limit based on both the data and local angler knowledge.
Florida Fishermen Collect Data to Help Red Tide Response
Analysts used a similar approach for the 2021 gag grouper assessment. They used data on fish mortality rates to explore two different ways red tide affected different size classes. They ran predictions with varying levels of red tide mortality, informed by the West Florida Shelf ecosystem model funded via the RESTORE Science Program. The Council chose a moderate prediction that avoided long recovery times for the fish stock, helping to mitigate further economic impacts to fishing communities. The formal inclusion of red tide in these two assessments has proven our ability to successfully account for red tide mortality in Gulf grouper management.
“Including red tide in the assessment models is a great advancement because the extra mortality due to red tides is no longer attributed to fishery mortality—which had unfairly penalized the fishermen,” said Brendan Turley, lead author of the paper and assistant scientist at the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies
A Path Through the Labyrinth: Recommendations for the Future
After assessing the current state of scientific knowledge and history of management strategies for red tide, the team deciphered a few recommendations for moving forward:
- Exploring alternative harvest control rules’
- Leveraging adaptive management strategies
- Filling research gaps
Shifting From Single-Species Management
For single-species fisheries management, the paper recommends evaluating whether existing harvest control rules are sufficient to prevent fluctuations from episodic mortality (like from red tide). Fishermen have emphasized they need stable, predictable annual catch limits, enabling reliable long-term investment by the industry while still preventing overfishing. While these single-species actions may help smooth out the rollercoaster of annual catch limits during episodic events, it’s likely not the magic fix for all things red tide.
“Red tide cannot be effectively managed through a single-species approach alone,” summarized Skyler Sagarese, co-author and research ecologist at NOAA’s Southeast Fisheries Science Center. “An ecosystem-based fisheries management approach is critical to understand the wide-reaching effects of red tides on fish and fisheries, and ultimately to reduce hardships felt by coastal communities.”
