Origin of the Present Delaware River Striped Bass Population as Shown by Analysis of Mitochondrial DNA

Abstract

Management options for the Delaware River population of striped bass Morone saxatilis depend on whether or not the population forms a discrete stock. The recent increase in striped bass in the Delaware River follows decades of scarcity and concern about the possible extinction of the original population. The increase may have resulted from one or more of the following: Expansion of a remnant population, repopulation by migrants from the Chesapeake Bay, or repopulation by migrants from the Hudson River. To determine the origin of the present Delaware River striped bass population, we analyzed mitochondrial DNA (mtDNA) from 191 striped bass collected in the Delaware River between 1990 and 1992. Our results indicate the Delaware River striped bass population is genetically intermediate between the Chesapeake Bay and Hudson River populations; mtDNA major-length genotype frequencies of the Delaware River sample were significantly different (P < 0.05) from those of the Hudson River stock, whereas mtDNA minor-length genotype frequencies of the Delaware River sample differed significantly from those of the Chesapeake Bay stock (P < 0.005). This intermediacy, together with information from historical surveys that suggest the original population did not become extinct, favors the hypothesis that the present Delaware River striped bass stock represents expansion from the original Delaware River stock.