River Herring Nursery Habitat in Albemarle Sound, North Carolina, Inferred from Otolith Microchemistry
Zapf, Daniel Hunter
River herring is a collective term used to describe two similar alosine species: alewife Alosa pseudoharengus and blueback herring A. aestivalis. Both of these anadromous species are native to the Atlantic coast of North America and spawn in North Carolina rivers. Consistent with populations along the east coast of North America, river herring populations in North Carolina have experienced drastic declines. Therefore, it is essential to identify nursery habitats used by these species. The goal of this study was to assess river herring nursery habitats in Albemarle Sound by examining growth of juvenile river herring and estimating survival to the adult stage using otolith microchemistry. Water samples were collected from the Alligator, Chowan, Perquimans, Roanoke, and Scuppernong rivers in the summer of 2010. Sr:Ca, Ba:Ca, and Mn:Ca ratios differed significantly between habitats. Magnesium (Mg) was detected consistently only in the Alligator River and was therefore excluded from most analyses. Juvenile river herring were collected from riverine and non-riverine Albemarle Sound habitats from June-October 2010. Concentrations of Mg, manganese (Mn), strontium (Sr), and barium (Ba) at the outer edge of otoliths were measured to determine habitat specific signatures that were used to classify river herring captured in non-riverine habitats to their river of origin. Total length, condition, and growth rates of juvenile river herring differed significantly between habitats. Concentrations of Mg, Mn, Sr, and Ba in otoliths differed significantly between rivers, allowing juvenile river herring to be classified to their river of capture with between 75-100% accuracy. Based on the growth metrics used, alewife nursery habitat was best in the Alligator, Chowan, Pasquotank, and Roanoke rivers along with non-riverine northwest and southwest Albemarle Sound habitats. Alewife nursery habitat was poor in the Little, North, Perquimans, Scuppernong and Yeopm rivers. Blueback herring nursery habitat was best in the non-riverine northwest and southwest Sound. Riverine habitats, particularly the Scuppernong and Perquimans rivers, provided poorer nursery habitat for blueback herring. However, juvenile alewife and blueback herring seemed to move out of the Chowan and Perquimans rivers into western Albemarle Sound habitats suggesting they may seek out nursery areas of higher quality than natal rivers can provide. Adult blueback herring were captured in the Chowan, Perquimans and Scuppernong rivers. Using river specific elemental signatures obtained from juvenile river herring otoliths, adult blueback herring were classified to their river of origin. High percentages of adults returning to Albemarle Sound were predicted as originating from the Alligator, Chowan, and Roanoke rivers. Homing rates ranged from 0-60%, with highest rates of homing to the Chowan River, and lowest rates to the Perquimans and Scuppernong rivers. This analysis and the analysis of juveniles show that the Alligator, Chowan, and Roanoke rivers along with western Albemarle Sound habitats are high quality river herring habitats, which corresponds well with the strategic habitat areas (SHAs) designated by the state of North Carolina.
Zapf, Daniel Hunter. (January 2012). River Herring Nursery Habitat in Albemarle Sound, North Carolina, Inferred from Otolith Microchemistry (Master's Thesis, East Carolina University). Retrieved from the Scholarship. (http://hdl.handle.net/10342/3962.)
Zapf, Daniel Hunter. River Herring Nursery Habitat in Albemarle Sound, North Carolina, Inferred from Otolith Microchemistry. Master's Thesis. East Carolina University, January 2012. The Scholarship. http://hdl.handle.net/10342/3962. July 17, 2018.
Zapf, Daniel Hunter, “River Herring Nursery Habitat in Albemarle Sound, North Carolina, Inferred from Otolith Microchemistry” (Master's Thesis., East Carolina University, January 2012).
Zapf, Daniel Hunter. River Herring Nursery Habitat in Albemarle Sound, North Carolina, Inferred from Otolith Microchemistry [Master's Thesis]. Greenville, NC: East Carolina University; January 2012.
East Carolina University