R/FISH-105

Impact/Outcome:

This section describes how this project has advanced scientific knowledge and/or made a difference for coastal residents, communities, and environments. Maryland Sea Grant has reported these details to the National Oceanic and Atmospheric Administration (NOAA), one of our funding sponsors.

Summary: Researchers used data from a historic, large-scale fish tagging study to produce new analyses that improved understanding of the population dynamics of Atlantic menhaden and informed sustainable management of the commercial fishery for this species.

Relevance: The commercial fishery for Atlantic menhaden (Brevoortia tyrannus) is the largest on the U.S. East Coast. Menhaden are significant in the food web of the Chesapeake Bay and coastal ocean, serving as prey for species such as striped bass that provide economic value through harvests by recreational and commercial fishers. Resource managers need improved knowledge about the effect of the fishery, which is centered on the Chesapeake Bay, on the sustainability of the menhaden resource both in the estuary and along the Atlantic coast from New England to Florida. New understanding about menhaden population dynamics, including migration and mortality rates, could reduce uncertainty in estimates of stock status and advance ecosystem-based management of the fishery.

Response: Researchers carried out new analyses and modeling using data from a mark-recapture study of Atlantic menhaden conducted during the 1960s and 1970s. More than one million menhaden were tagged and over 200,000 tags were recovered. The researchers used these data and data about the effort and catch of the commercial menhaden reduction fishery to estimate age-based selectivity of the commercial fishery, natural and fishing mortality, and the spatial distribution of menhaden. Unlike previous analyses of this tagging dataset, this project estimated migration among five Atlantic coast zones and accounted for lost tags. The project team provided an education campaign for fisheries managers and the general public. Researchers from the Chesapeake Biological Laboratory at the University of Maryland Center for Environmental Science and the Beaufort Laboratory of the National Marine Fisheries Service (NMFS) collaborated on the study.

Results: This project supported the development of new, quantitative estimates of menhaden migratory patterns, an improvement over the solely qualitative descriptions provided in previous analyses of this tagging dataset. Among the findings were that fishing mortality was highest in the southern Atlantic region, and fish movement appeared to vary by season and age. These findings informed a stock assessment of Atlantic menhaden prepared by a technical committee for the Atlantic States Marine Fisheries Commission (ASMFC), which manages the fishery. The assessment concluded that the menhaden resource is not overfished nor experiencing overfishing relative to existing biological reference points. The ASMFC subsequently decided in 2015 to increase the total allowable catch by 10 percent over the 2014 level, which was consistent with the stock assessment.   The ASMFC also expressed interest in establishing ecological-based reference points for managing Atlantic menhaden that reflect its role as a forage species (prey for other species). The results of the MDSG research project will be useful for informing future spatial management of menhaden along the Atlantic coast and ultimately to help ensure that the menhaden fishery is sustainable.