Population Structure Of River Herring In Albemarle Sound, North Carolina, Inferred From Geometric Morphometrics And Otolith Shape Analysis

Abstract

Alewife Alosa pseudoharengus and Blueback Herring Alosa aestivalis, collectively known as River herring, use tributaries of the Albemarle Sound, North Carolina as spawning and nursery habitats. Stocks of these anadromous fish have experienced dramatic declines in North Carolina, and show no sign of recovery. Although the state has designated considerable resources to the management of river herring, we still do not fully understand river herring utilization of North Carolina's estuaries, and know little about the structure and composition of populations. Determining the population, or 'stock' structure of species is crucial for the proper distribution of management efforts. We utilized two robust stock identification methods to identify distinct groups of River Herring. Using geometric morphometric analysis, we found that groups of juvenile Alewife and Blueback herring from different tributaries of the Albemarle Sound had significantly different overall body shapes, despite apparent mixing between groups. Overall body shape of adult Blueback Herring was not significantly different at the tributary level, but did differ significantly at the state level between North Carolina and New Jersey. Elliptical Fourier analysis of otolith shape revealed the same pattern as geometric morphometric analysis on adult Blueback Herring, with significant differences in otolith shape at the state level but not the tributary level. Our results suggest that a portion of spawning adult River Herring returning to the Albemarle Sound may return to non-natal tributaries to spawn.