Hickory Shad Alosa mediocris (Mitchill) Stock Identification Using Morphometric and Meristic Characters

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Jordan P Smith (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: The Hickory Shad Alosa mediocris is an anadromous fish species of the family Clupeidae. Little is known about its distribution , life history , and status. Adult Hickory Shad are found seasonally during spring spawning in estuaries and coastal watersheds along the East Coast of the United States from Maryland to Florida , and during late summer as far north as Connecticut. To provide information on stock identification and watershed fidelity the distributional patterns of 17 morphometric and four meristic characteristics of adult Hickory Shad were analyzed from spawning populations along its range. A total of 687 specimens were examined along the latitudinal gradient from the Susquehanna River , Maryland , to the Wekiva River , Florida. Due to low sample sizes (n<13) for some rivers as well as missing measurements or counts , some specimens had to be excluded from multivariate analysis. Prior to statistical analysis morphometric characters were corrected for size-dependent variation using an allometric formula. After correction morphometric characters were natural log transformed to better approximate multivariate normality. Correlation analysis on transformed measurements and SL confirmed the results obtained from the allometric method; yet showed fork length and total length were strongly correlated (>0.80) and therefore excluded. Multivariate analysis of variance of pooled morphometric and meristic characters showed a significant effect of sex (P <0.05) therefore , all analyses were separated by sex. Analysis of variance showed highly significant difference (P <0.003) for 15 characters between 10 locations for males and 12 characters between 12 locations for females. Non-significant characters were excluded and only significant characters for males and females were used for subsequent analysis including Principle Components Analysis (PCA) and Discriminant Function Analysis (DFA). PCA extracted 6 and 4 components (eigenvalues> 1) cumulatively explaining 63.67% and 60.88% of the variance for males and females , respectively. Bartlett's Test of Sphericity was significant (P <0.05) and Kaiser-Meyer-Olkin Measure of Sampling Adequacy was 0.60 for males and 0.68 for females , which confirmed appropriateness of the data for PCA. Principal component 1 for males and females was most correlated (> 0.4) with the head region and fin lengths. Using Quadratic Discriminant Function Analysis (QDFA) , 77.9% and 80.3% of males and females , respectively , were correctly classified to their rivers of collection using separate-groups covariance matrix and equal prior probabilities. Individual river classification varied between 58.6% - 100%. The Tar-Pamlico River had the lowest percent correct classification for both male (58.6%) and female (62.0%) QDFAs. Tributary level discrimination was achieved in two instances: the James and Appomattox rivers , and the Roanoke and Cashie rivers. Overall , results of this study suggest that meristic and morphometric characters are a viable and potentially lower cost method to identify separate spawning populations (stocks) of Hickory Shad. Fishery management agencies desire more basic life history information to better manage the species. One large gap in knowledge is the untested assumption of natal homing in Hickory Shad; though the results of this study cannot directly confirm this assumption , the significant variation between river populations provides support for natal homing. The results of this work offer foundational information for creating a unique management plan for Hickory Shad.

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Thesis

Language: English

Date: 2018

Keywords

Morphometric, Meristic

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