Review of Stock Discrimination Techniques for Striped Bass

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Abstract
Attempts to discriminate stocks of striped bass Morone saxatilis have spanned five decades. We review and evaluate the approaches used, outline research trends, and suggest research needs and potential future applications of stock discrimination techniques. There have been moderate gains over the years in the ability to discriminate among stocks, primarily due to the use of biochemical techniques. An important mixed-stock fishery for striped bass off the northeastern USA has focused the majority of stock discrimination efforts on identification of Atlantic coast populations. Many techniques have been applied alone or in combination. Phenotypic studies have involved the presence of specific parasites, meristic and morphometric characters, trace element composition of scales, scale morphology, and densitometric analysis of isoelectrically focused eye lens proteins. Genotypic techniques have included cytogenetics, protein electrophoresis, isoelectric focusing, restriction endonuclease analysis of mitochondrial DNA, DNA fingerprinting, and immunogenetics. No technique consistently identified the stock ancestry of individual striped bass; most classified correctly at about the 70–80% level. Although new genetic techniques may increase the ability to resolve stocks, perhaps their greatest value lies in providing the means to catalogue relatively fixed genotypic stock identifiers. Eventual establishment of a library of genetic information on striped bass would free stock discrimination efforts from the ongoing adjustments required for environmentally or ontogenetically sensitive phenotypic discriminators. This goal has been complicated by the widespread stocking of nonnative stocks to supplement wild populations. The homing of spawning fish to natal rivers should be quantified and the period that young fish are resident in natal rivers should be determined to evaluate assumptions that fish really are of “known” origins when they are used to identify stock discriminators. Other recommended research includes a reanalysis of the stability and usefulness of meristic characters for studies of the relative contributions of stocks to the mixed coastal population, and simultaneous comparison of alternative stock discrimination techniques on the same fish specimens. Future efforts in discrimination should be directed towards regular estimation of Atlantic mixed-stock components and toward assessment of the contributions that hatchery-produced striped bass make to native populations.

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