Biology

    Red snapper (Lutjanus campechanus) is distributed throughout the Gulf of Mexico (GoM) and the U.S. Atlantic coast to North Carolina. The GoM stock is divided into two sub-stocks: eastern and western GoM, separated roughly by the Mississippi River. The highest density of ages 0-1 red snapper is found in the northern GoM at a depth between 18-55 m from the Alabama-Florida border to the Texas-Mexico border. They prefer shell substrate over sand substrate. The newly settled fish smaller than 40 mm total length (TL) is mostly found in open habitat, but begins moving onto the reefs as their lengths approaching 100 mm TL. Red snappers at age 2 or older can be found across the shelf to the shelf edge and show an affinity for the vertical structure, especially from ages 2-10 years. Red snappers older than ages 8-10 years are no longer totally dependent on structured habitats and are capable of forage over open habitats with the threat from predation. They tend to spend most of their time over soft bottoms, especially areas with sea bottom depressions and lumps. An NMFS bottom-longline survey suggests that red snapper tend to be most abundant at depths from 55 to 92 m and that older and larger red snapper are found more frequently in the western GoM and younger and smaller fish are found in the eastern GoM. Adult red snappers tend to experience a seasonal depth-related movement toward shallower water (inner-mid shelf) in the spring/summer months and offshore (mid-outer shelf) in the winter months. This movement may be related to the spawning-related activity. Red snappers experience high rates of growth when they are young, but start to slow down when they reach ages 8-10 years old. There is little evidence for strong sexual dimorphism in growth. The average maximum attainable length in the von Bertalanffy growth equation is less than 900 mm TL. Females tend to mature at relatively smaller lengths and at younger ages in the eastern GoM compared to those in the western GoM. The red snapper spawns from Apr. through Jan. and peaks in June and July over most of its range. On average, a female of age 10 can produce over 60 million eggs per year. Young (to age-8) red snapper in the eastern GoM tend to have a higher reproductive output compared with those of the same age individuals in the western GoM.

Management Strategy Evaluation

    Management strategy evaluation uses simulation methods to quantify the risk associated with a suite of potential fisheries management actions. Management of the GoM red snapper resource over the last three decades has been controversial and contentious. Numerous amendments affecting the red snapper fishery and resulting harvest, as well as emergency and interim rules, have been made since the early 1980’s when the Reef Fisheries Management Plan was created for the GoM. Although the stock has begun to rebuild recently, increases in recreational anglers and limited quotas have led to short fishery seasons, frustrated anglers, and calls to rescind strict regulations. Meanwhile, the most recent stock assessment report for red snapper (SEDAR 2015) indicated a number of uncertainties that may impact the reliability of current or alternate management strategies. The need to develop a management strategy evaluation tool that can test the robustness of long-term management strategies and short-term regulations has been indicated in the recent stock assessment reports. For complex fisheries like GoM red snapper, a customized decision-support tool is needed, based on a broader MSE framework that allows for a more holistic evaluation of alternative management strategies.

Research Plan

    The main deliverable of this project is the decision-support tool presented within a graphical user interface. In Stage One, an operating model (OM), which includes the intricacies of the current stock assessment and various aspects of snapper management, is developed and serves as the foundation for the decision-support tool. The operating model simulates the complex population dynamics, fishery processes, management procedures, and various sources of uncertainty. Following model development and validation, extensive simulations are conducted in Stage Two to evaluate the performance of alternative management strategies. Specifically, the decision-support tool has the following functions: 1) evaluating the efficacy of alternate long-term management strategies such as harvest control rules, 2) assessing the usefulness of short-term regulations such as size limits, and 3) examining the robustness of the management strategies and regulations to the uncertainty resulting from process error, observation error, assessment error, and implementation error. Because the OM is spatially structured, sub-stock dynamics can be simulated and regional management can be explored. Stage Three involves outreach and promotion of the decision-support tool, including the development of the graphical user interface, which will be easily manipulated by stakeholders to explore the implications of alternative management scenarios. The expected end-users include the Gulf of Mexico Fisheries Management Council, the NOAA Southeast Regional Office and Southeast Fisheries Science Center, various state agencies (e.g., the Florida Fish and Wildlife Commission), and organizations representing other stakeholders in the GoM.