Pterygiophore Interdigitation Patterns and Morphometry of Larval Hybrids of Morone Species

In order to determine characteristics that would facilitate assignment of larvae and juvenile fish to the correct species of Morone, we examined osteological patterns and morphometric ratios of larvae and juveniles of striped bass M. saxatilis and white bass M. chrysops as well as their F 1 , F 2 , and backcross generations. Similarities in patterns of pterygiophore interdigitation between pure Morone species and their hybrids did not allow for separation based on primary pattern sequences alone. Statistical analyses of these patterns allowed for sorting of groups into subcategories but not for assignment of individual larvae to species. We corroborated pattern sequencing found by other investigators for pure‐strain stocks and developed a new approach to confirming pattern‐sequencing data. There was definite overlap in patterns expressed between pure species and hybrids. Bone morphometry was not a good character for classifying all hybrids into individual taxonomic categories but was good for classifying pure strains. A model developed by discriminant function analysis worked well for striped bass and white bass and for their F 1 hybrids but it was not successful for F 2 hybrids and backcrosses. Thus, larval and juvenile hybrids of the Morone complex may be confused with sympatric pure‐strain stocks even when identifications are based on interdigitation patterns or bone morphometry. This confusion may only further complicate management where stocking programs have been initiated to enhance or restore native stocks of striped bass and where hybrids have been introduced.