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 Fish. Bull., U.S. 84:771-798. 



Roger T. Hanlon 



Philip E. Turk 



Phillip G. Lee 



Won Tack Yang 



The Marine Biomedical Institute 

 The University of Texas Medical Branch 

 200 University Boulevard 

 Galveston, TX 77550-2772 



CHANGES IN THE POPULATION STRUCTURE 



OF MALE STRIPED BASS, MORONE SAXATILIS, 



SPAWNING IN THE THREE AREAS OF THE 



CHESAPEAKE BAY FROM 1984 TO 1986 



The striped bass, Morone saxatilis, supported im- 

 portant commercial and recreational fisheries until 

 recently. Population declines over the past 15 years 

 have prompted fishing restrictions in most states 

 along the Atlantic coast of the United States and 

 a complete moratorium in Maryland. Spawning suc- 

 cess of M. saxatilis has been poor since 1970, ex- 

 cept for 1982 when the juvenile index reported by 

 the Maryland Department of Natural Resources 

 which was near the 50-yr average for Chesapeake 

 stocks (Boone and Uphoff 1983). 



Knowledge of the population structure of the 

 striped bass is important to restoration efforts. 

 Many attempts have been made to identify distinct 

 stocks along the Atlantic coast and within Chesa- 



peake Bay. Morphological studies have found evi- 

 dence of discrete stocks within the Chesapeake 

 system (c.f. Setzler et al. 1980 for review), while 

 studies of allozyme variation have been ambiguous 

 (Morgan et al. 1973; Grove et al. 1976; Sidell et al. 

 1980). Electrophoretic studies have found only 

 limited allozyme variation and, thus, discrimination 

 of stocks has been problematical. To further under- 

 stand the reproductive patterns of striped bass in 

 the Chesapeake Bay, an analysis of mitochondrial 

 DNA (mtDNA) genotypes among spawning in- 

 dividuals was initiated in 1984. For the most part, 

 mtDNA is maternally inherited and and provides in- 

 formation concerning matriarchal ancestry. The 

 results of this analysis for the overall striped bass 

 fishery will be reported elsewhere, but support the 

 conclusion that distinct stocks exist in the Chesa- 

 peake Bay. As part of this survey, it was deemed 

 important to examine the distribution of mtDNA 

 genotypes of striped bass among 1982 year class in- 

 dividuals as they recruited into reproducing popula- 

 tions and to determine if the distribution of these 

 genotypes changed in subsequent years. I report 

 here on the distribution of mtDNA genotypes in 

 1982 year class males during their first (1984) and 

 third spawning seasons (1986). 



Methods 



Striped bass were gill netted from the Chesapeake 

 Bay at the mouth of the Sassafras River (Worton 

 Point, 23, 24, 26 April 1984 and 7, 9 May 1986), the 

 Potomac River (2 May 1984 and 29 April 1986) and 

 Choptank River (9 May 1984 and 13 May 1986) 

 during the spawning season. Age and sex deter- 

 minations were made by counting scale annuli and 

 visually inspecting the gonads, respectively. The ac- 

 curacy of scale annuli for aging striped bass was 

 reviewed by Setzler et al (1980). MtDNA was iso- 

 lated from the livers according to the methods of 

 Chapman and Powers (1984) and digested with the 

 restriction endonucleases Hind III, Eco RI, and Bel 

 I. The digested mtDNA fragments were separated 

 on 0.8% agarose gels. To insure consistent scoring 

 of genotypes, 1984 samples were rerun against 1986 

 samples. Homogeneity of mtDNA frequencies with- 

 in localities and among years was tested by G^ 

 tests with pooling of expected classes less than five 

 (c.f. Sokal and Rolf 1969). 



Results and Discussion 



Variation in M. saxatilis mtDNA was character- 

 ized by fragment length polymorphisms that can be 



FISHERY BULLETIN: VOL. 85, NO. 1. 1987. 



167 



