USF study: Gag grouper are overfished in the Gulf; this new tool could help

(Press-News.org) Anglers along the Gulf Coast have long prized the hard-fighting, mild-tasting gag grouper (Mycteroperca microlepis), but some may have been surprised over the past few years by shortened seasons for this desirable reef fish. Due to concerns about the population of the species, the gag season lasted just 41 days in 2023, 15 days in 2024, and 14 days in 2025 — far shorter than the six-month seasons in previous years.

A new paper by researchers from the University of South Florida (USF) and Florida Fish and Wildlife Conservation Commission (FWC) may assist resource managers who make tough decisions about the lengths of fishing seasons. A statistical model created by the researchers offered more accurate harvest predictions and explicit estimates of the probability of exceeding quotas for the 2025 gag season.

“Our approach provides a flexible tool to support decision making, particularly for vulnerable, highly targeted stocks,” the authors wrote in the paper published in the February issue of North American Journal of Fisheries Management.

Gag grouper has been called a “poster child” for the challenge of recovering heavily exploited fish stocks. Fishing pressure and environmental stressors led NOAA to declare gag in the Gulf to be overfished in 2009, meaning the population had fallen below the sustainable threshold. The population was carefully rebuilt by 2014, but was again determined to be impaired following a stock assessment in 2021. Stricter quotas and shorter seasons were implemented to help the population recover.

Complicating management efforts are gag’s migratory behaviors, spatial distribution, and biological trait known as protogynous hermaphroditism.

Gag are born as females and begin their lives in estuaries like Tampa Bay, moving further offshore as they age. Some of the fish undergo a sex change as they get older and the largest gag are often males. Many of these large males reside on offshore reefs for the remainder of their relatively long lives.

These habits can make it challenging for agencies to get an accurate pulse on the health of gag populations. In fact, the 2014 assessment that found the gag population had recovered in the Gulf, predicted that just 2-3 percent of that population was male (down from historic levels of about 17 percent). Research by FWC published in 2020 showed that current regulations were “not sufficient for the male population to recover to historic levels.”

To help better manage this vulnerable population, researchers from the USF College of Marine Science and the FWC’s Fish and Wildlife Research Institute teamed up to develop an alternative approach to traditional fisheries forecasting.

“Harvest rates have traditionally been predicted using historical data, but that approach can be unreliable as regulatory changes can impact the behavior of anglers,” said A. Challen Hyman, lead author of the paper and research scientist at the USF College of Marine Science Center for Environmental Analysis Synthesis and Application (CEASA), which leverages data to better inform environmental policy and management.

Hyman and his colleagues instead used a statistical model that was trained on data from the past decade and accounts for changes in angler behavior that result from regulatory decisions.

“Our model allowed us to not only get a more accurate prediction of harvest but also to quantify risk, meaning fisheries managers can make decisions based on the chance of exceeding the quota,” he said.

The risk tolerance of resource managers fluctuates in response to the vulnerability of a particular species. If the fish stock is impaired or depleted, managers tend to be more conservative. A healthy stock, on the other hand, may warrant a longer season.

Population health is weighed against economic and social considerations for coastal communities — for example, how might regulations impact the commercial fishing industry or prevent anglers from catching their favorite sportfish?

The statistical model developed by Hyman and his colleagues was trained on data gathered since 2015 including the length of seasons, the date seasons began, and whether seasons for other highly desired species, such as red snapper, were open simultaneously. It predicted that anglers had a 50 percent probability of hitting the 2025 annual catch target in 12 days. Preliminary data from federal and state agencies suggest that prediction was accurate, as the 14-day season recorded just under the annual catch target.

“These findings are significant because they demonstrate an approach to fisheries forecasting that’s more accurate, efficient, and reliable than traditional methods,” said Tom Frazer, dean of the College of Marine Science, director of CEASA, and co-author of the paper. “Our hope is that this model can inform decisions about the management of gag and other recreational species, and ensure that those decisions are based on the best available science. At the end of the day, this will benefit both fish and fishermen.”

The findings are of particular interest to the Fishery Management Council, which makes decisions about the length of seasons based on the risk of exceeding quotas.

Moving forward, the researchers aim to better understand how recent technological advances, economic factors, and the number of anglers on the Gulf Coast will affect fish stocks.

“More powerful motors and improved electronics mean anglers are able to cover more water and also find fish more quickly,” Hyman said. “Those changes coupled with a growing number of anglers are likely to have considerable consequences for the rate at which gag are harvested and total amount of fish that are being removed from the population.”

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