W&M ScholarWorks VIMS Articles 2010 A Molecular Genetic Investigation Of The Population Structure Of Atlantic Menhaden (Brevoortia Tyrannus) Abigail J. Lynch Jan R. McDowell Virginia Institute of Marine Science John E. Graves Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/vimsarticles Part of the Aquaculture and Fisheries Commons Recommended Citation Lynch, Abigail J.; McDowell, Jan R.; and Graves, John E., "A Molecular Genetic Investigation Of The Population Structure Of Atlantic Menhaden (Brevoortia Tyrannus)" (2010). VIMS Articles. 554. https://scholarworks.wm.edu/vimsarticles/554 This Article is brought to you for free and open access by W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. 87 Abstract—Atlantic menhaden (Bre- A molecular genetic investigation voortia tyrannus), through landings, support one of the largest commercial of the population structure fisheries in the United States. Recent consolidation of the once coast-wide of Atlantic menhaden (Brevoortia tyrannus) reduction fishery to waters within and around Chesapeake Bay has Abigail J. Lynch raised concerns over the possibility of the loss of unique genetic variation Jan R. McDowell (contact author) resulting from concentrated fishing John E. Graves pressure. To address this question, Email address for contact author: [email protected] we surveyed variation at the mito- chondrial cytochrome c oxidase sub- Virginia Institute of Marine Science unit I (COI) gene region and seven School of Marine Science nuclear microsatellite loci to evaluate College of William and Mary stock structure of Atlantic menhaden. Rt. 1208 Greate Rd. Samples were collected from up to Gloucester Point, Virginia 23062 three cohorts of Atlantic menhaden at four geographic locations along the U.S. Atlantic coast in 2006 and 2007, and from the closely related Gulf men- haden (B. patronus) in the Gulf of Mexico. Genetic divergence between Atlantic menhaden (Brevoortia tyran- Two populations, one north and one Atlantic menhaden and Gulf menha- nus) is an ecologically and economi- south of Cape Hatteras, North Caro- den, based on the COI gene region cally important species along the U.S. lina, have also been proposed. This sequences and microsatellite loci, East Coast. As a filter-feeder and division was based on the presence was more characteristic of conspecific key prey fish, it provides a critical of small, sexually mature fish before populations than separate species. link between primary production and the arrival of the larger, migrating Hierarchical analyses of molecular variance indicated a homogeneous dis- larger piscivorous predators, such fish in North Carolina waters and tribution of genetic variation within as striped bass (Morone saxatilis), the presence of spawning fish off Atlantic menhaden. No significant bluefish (Pomatomus saltatrix), and northern Florida in late winter and variation was found between young- weakfish (Cynoscion regalis). The early spring (June and Nicholson, of-the-year menhaden (YOY) collected commercial fishery for Atlantic men- 1964). One coast-wide population early and late in the season within haden consists of a small bait fishery has been indicated by tag recovery Chesapeake Bay, between young-of- and a larger reduction fishery. Of studies (Nicholson, 1978), which have the-year and yearling menhaden col- the 20 menhaden reduction plants shown that Atlantic menhaden of dif- lected in the Chesapeake Bay during (where menhaden are “reduced” to fering ages and sizes share the over- the same year, between YOY and year- meal and oil) that were once oper- wintering grounds off Cape Hatteras ling menhaden taken in Chesapeake Bay in successive years, or among ating along the U.S. Atlantic coast, and undergo seasonal migrations and combined YOY and yearling Atlan- only the Reedville, Virginia, facility that larger fish travel farther north. tic menhaden collected in both years is currently active. The concentration The Atlantic States Marine Fisher- from the four geographic locations. of fishing effort for Atlantic menha- ies Commission currently assesses The genetic connectivity between the den in and around Chesapeake Bay Atlantic menhaden as a single coast- regional collections indicates that the has raised concerns among many wide stock. concentration of fishing pressure in environmentalists and sport fisher- In addition to the uncertainty re- and around Chesapeake Bay will not men about the possibility of “localized garding the stock structure of At- result in a significant loss of unique depletion” of Atlantic menhaden in lantic menhaden, the relationship genetic variation. the area. A potential consequence of between Atlantic menhaden and localized depletion could be the loss Gulf menhaden (B. patronus) is not of unique genetic variation within well understood. The mean values Atlantic menhaden, if there is spa- of several of the morphometric and tial partitioning of genetic variation meristic characters are significant- (stock structure) within the species. ly different between the two puta- Results of previous analyses of the tive species, although the ranges of Manuscript submitted 23 January 2009. stock structure of Atlantic menha- variation are coincident (Dahlberg, Manuscript accepted 3 November 2009. Fish. Bull. 108:87–97 (2010). den have been discordant. Two pop- 1970). Similarly, preliminary genetic ulations of Atlantic menhaden, one analyses indicate limited divergence The views and opinions expressed north and the other south of Long between the putative species, and or implied in this article are those Island, New York, were suggested therefore the use of larger sample of the author (or authors) and do not necessarily reflect the position of the on the basis of vertebral counts sizes and additional genetic charac- National Marine Fisheries Service, and transferrin allele frequencies ters have been recommended (Avise NOAA. (Sutherland, 1963; Epperly, 1989). et al., 1989; Anderson, 2007). 88 Fishery Bulletin 108(1) Table 1 Collection location, date of collection, and number of Atlantic menhaden (Brevoortia tyrannus) and Gulf menhaden (B. patronus) analyzed in this study and range of sample fork lengths. For all collections outside the Chesapeake Bay, young-of-the-year (YOY) and yearling samples are pooled. Collection Location Date n Fork length (mm) New England 2006 Gloucester, MA Aug. 2006 25 43–58 New England 2007 Gloucester, MA Aug. 2007 25 34–64 Mid-Atlantic 2006 Pennsville, NJ Aug. 2006 27 61–110 Mid-Atlantic 2007 Oakwood Beach, NJ June 2007 25 77–190 Chesapeake Bay YOY 2006 Gloucester Point, VA May 2006 25 27–67 Chesapeake Bay yearling 2006 Gloucester Point, VA Aug. 2006 18 120–200 Chesapeake Bay YOY (early) 2007 Gloucester Point, VA May 2007 25 34–84 Chesapeake Bay YOY (late) 2007 Gloucester Point, VA Aug. 2007 31 35–99 Chesapeake Bay yearling 2007 Gloucester Point, VA June 2007 18 114–184 U.S. South Atlantic 2006 Beaufort, SC Aug. 2006 28 41–113 U.S. South Atlantic 2007 Beaufort, SC April 2007 41 28–181 Gulf menhaden 2006 Galveston, TX Oct. 2006 25 not recorded Gulf menhaden 2007 Cameron, LA Oct. 2007 25 52–91 In this study, analyses of sequence data from the structure of Atlantic menhaden, and to evaluate the mitochondrial cytochrome c oxidase subunit I (COI) potential for loss of unique genetic variation resulting gene region and allele frequencies of seven nuclear mi- from “localized depletion” of Atlantic menhaden within crosatellite loci were used to investigate the genetic the Chesapeake Bay region. relationships of Atlantic and Gulf menhaden, the stock Materials and methods 90°W 80°W 70°W Sample collection Range of Atlantic menhaden Range of Gulf menhaden Young-of-the-year (YOY) and yearling Sampling locations Atlantic menhaden were sampled from New England (MA), the U.S. mid-Atlantic (NJ), Chesapeake Bay (VA), and the U.S. South Atlantic (SC) in 2006 and 2007, and YOY 40°N 40°N Gulf menhaden were sampled from the Gulf of Mexico in 2006 and 2007 (Table 1; Fig. 1). United States For all collections outside the Chesapeake Bay, samples of YOY and yearling Atlantic menhaden were pooled. For Chesapeake Bay Atlantic Ocean collections, scales were aged from a sub- 30°N 30°N sample of 20% of individuals taken in 2007 and length was used as a surrogate for the Gulf of remaining samples (where fish less than 100 Mexico mm fork length were considered YOY and fish greater than 100 mm fork length were 20°N 20°N considered yearling). The younger cohorts were sampled because they are less likely 0 600 miles to have migrated far from where they were 90°W 80°W 70°W spawned. Local experts identified menha- den on the basis of morphological characters Figure 1 and capture location. Muscle tissue samples Map of ranges of Atlantic menhaden (Brevoortia tyrannus) were taken from each individual and either and Gulf menhaden (B. patronus) and the approximate frozen or stored in DMSO buffer (Seutin et location of sites sampled in 2006–2007 for the analysis al., 1991) at room temperature. Voucher spec- of stock structure in Atlantic menhaden. imens were retained from all U.S. Atlantic Lynch et al.: A genetic investigation of the population structure of Brevoortia tyrannus 89 coast regions in 2007 to corroborate field identifications. the presence of null alleles and evidence of scoring er- Some of the identifications were retroactively verified rors. To ensure consistency,