APPLIED FISHERIES AND ECOSYSTEM MODELING FOR MANAGING MARINE RESOURCES IN A CHANGING ENVIRONMENT

Managing fisheries resources is challenged by complex food web and habitat interactions, frequently occurring natural and manmade stressors, and strong socio-cultural dependencies. This complexity has introduced uncertainty into management outcomes, iwth effects on food production, sustainable seafood supplies, citizen incomes, and our ability to maintain healthy ecosystems. Contemporary and emergent challenges exist for fishery managers. For example, managers face a tradeoff between harvest of forage fish and impacts on predator populations that support their own valuable fisheries. There is also a need to account for effects of multiple environmental and manmade stressors (e.g. red tide, invasive species, oil spills, and climate change) in fisheries stock assessment and management. To adequately address these issues and the tradeoffs they present, managers must move beyond single species stock assessments to more holistic, ecosystem-based tools that inform decision-making.There are specific examples of these challenges in marine and estuarine ecosystems of Florida, the Gulf of Mexico, and U.S. Atlantic coast. Menhaden (Brevoortia spp.) are an important forage fish for a suite of predators that support valuable recreational fisheries, but they are also harvested commercially and processed into animal feed, lubrication components, and vitamin supplements. Approximately 800,000 mt of menhaden are harvested annually on the Gulf and Atlantic coasts with an ex-vessel price of over $140 million/yr. Recent amendments to fisheries management plans now require ecosystem approaches to ensure that enough menhaden are left in the ocean to meet the needs of their predators, which support valuable sport fisheries. To do so requires novel food web-based modeling.As another example, red tides have become more frequent and severe on the West Florida Shelf in recent years, leading to declines in valuable commercial and recreational fisheries for gag and red grouper (Mycteroperca microlepis and Epinephelas morio, respectively), which in 2017 had a combined ex-vessel value of $16.7 million in Florida and were targeted on over a million trips by recreational anglers. Contemporary estimates of red tide mortality are routinely needed in order to set appropriate catch levels in the following year. This requires spatially explicit models that account the duration and overlap of red tide blooms with species distribution patterns, fish movement and bloom avoidance, and impacts on the forage base.Lastly, demands for freshwater resources in Florida are expected to increase drastically over the coming decades as more land is converted for agricultural use and urban centers expand to accommodate a growing human population. The demands for water could be exacerbated under certain future climate scenarios. Estuarine ecosystems that support valuable commercial and recreational fisheries, as well as local economies, are expected to be altered under such scenarios. Ecosystem models that integrate land use change and climate impacts on estuarine food webs and fisheries resources are necessary to understand and mitigate against future impacts. The overall goal of this project is to provide information and tools (the models) that enable managers, scientists, and stakeholders to become better stewards of our shared natural resources. The models will be used to improve population assessments, screen policy options for unintended consequences, prioritize research, and calculate new management reference points that account for ecosystem interactions and the uncertainty therein. To achieve this goal, the following tractable objectives will be accomplished over the next five years:Fisheries managers will consider ecological interactions, environmental effects, and policy tradeoffs when managing forage fisheries.Ecosystem models will have improved ability to account for spatially explicit processes and stressors (i.e. red tides) that routinely occur in the Gulf of Mexico.Fishery managers will be provided with innovative tools to evaluate stock status and management strategies for stone crabs in Florida.