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The research could support efforts to better monitor bycatch in commercial nets and manage menhaden, taking into account their importance to sport fish

Researchers from the National Oceanic and Atmospheric Association, the University of Miami and the University of Florida recently completed a study modeling the Gulf of Mexico ecosystem with a focus on Gulf Menhaden. The model was developed to assess the ecosystem impact of various Menhaden fisheries practices, with a focus on how Menhaden predators would respond to changes in forage availability and bycatch risks.

Researchers also quantified tradeoffs between menhaden harvest and predator biomass to develop ecological benchmarks — metrics that would help manage menhaden fisheries in the context of the fish’s importance to the overall ecosystem. ERPs are currently being used to manage the Atlantic Menhaden fishery after years of lobbying by anglers.

The TRCP already reported the preliminary results of this study in 2021. The final results published confirm the findings we shared at the time: Gulf menhaden support about 40 percent of the diets of king and Spanish mackerel and about 20 percent of the diets of mackerel, red drum, sea trout, seabirds and blacktip sharks.

The newly released results also show which predators are most sensitive to menhaden harvesting and why. King mackerel, Spanish mackerel, blacktip sharks and red drum are most affected by the resulting shortage of food in the water. Tarpon, sea trout and croak are most at risk of being caught and killed by the massive purse seine nets employed by the Menhaden reduction fishery.

In the Atlantic, striped bass are the predators most sensitive to the Atlantic Menhaden’s harvest. For this reason, stripers were the key species considered in the development of the 2020 ERP targets and thresholds, which aim to keep sufficient menhaden in the water to feed bass and other species such as bluefish, weakfish and dogfish.

In this Gulf model, king mackerel was the most sensitive predator species for harvesting Gulf menhaden, but interrelationships were found between menhaden and nine other predator groups. An ERP target could therefore be developed based on the ten most affected predator groups.

The authors suggested that a 20 percent reduction in commercial menhaden landings compared to 2018-2020 levels would leave enough menhaden in the water to support these ten predator species in their biomass goals.

Interestingly, the results indicated that biomass for many predators was more affected by commercial harvesting of menhaden than by fishing pressure on the predator species itself. This was most notable for red drum and quaker due to the effects of bycatch. Redfish is a popular target for anglers in the Gulf, but the Menhaden reduction fishery could catch more redfish as bycatch than the recreational sector as a whole.

Unfortunately, the Menhaden fishery in the Gulf has little to no current bycatch data and no in-season observation reports. The TRCP has been campaigning for updated bycatch analyzes in the Menhaden fishery on both the Gulf and Atlantic coasts and we hope this model will advance that process.

This model can be used to inform stakeholders and policy makers about the trade-offs between different management measures while accounting for predator-prey interactions, fishing pressure and bycatch. It could encourage the development of ERPs for the Gulf Menhaden fishery that mirror those of the Atlantic Menhaden fishery.

This updated science is an exciting step forward in the improved management of golf menhaden and the predators that rely on them. The TRCP and its partners will work diligently to gain more information on the role of the menhaden in the Gulf of Mexico ecosystem and how mackerel, red drum and sea trout are affected by the industrial menhaden fishery, which currently has no catch limit and very little has state and federal supervision.

Learn more about our efforts to preserve Menhaden in the Gulf and Atlantic.