ficulty in distinguishing one band from another. 



Observations on the timing of annual band deposi- 

 tion in this study agree well with our previouswesults 

 (Peterson et al. 1983). The 6 August-3 September 

 period in 1980 consistently fell within the season of 

 annual band deposition and near the end of the band 

 at all five new study sites. P\irthermore, the annual 

 band was still being formed or had just been com- 

 pleted in all clams collected 24 August-3 September 

 1982. The banding of M. mercenaria in North 

 Carolina appears to be a summertime event in con- 

 trast to the winter banding in northeastern popula- 

 tions (Barker 1964; Pannella and MacClintock 1968; 

 Rhoads and Pannella 1970; Clark and Lutz 1982). 



The only clams that failed to deposit two additional 

 annual bands in the 24 mo of this study were taken 

 from the North River locals. This is also the only 

 group that deviated in the timing of final band 

 deposition relative to the 1982 collection date Most 

 of these clams had just initiated their 1982 bands 

 at the time of collection in contrast to those from 

 all other sites where 1982 band depositon was either 

 far advanced or even terminated. This difference be- 

 tween sites is probably a consequence of the 3-4 wk 

 earlier date of collection at North River (Tkble 2). 

 Despite an identical, early collection date, the Back 

 Sound clams transplanted to North River exhibited 

 a pattern of band deposition in 1982 that more close- 

 ly resembled the other four sites than did the North 

 River local clams. This difference provides our only 

 suggestion of an effect of clam origin, but we have 

 no explanation for the possible effect and do not con- 

 sider it a serious cause to doubt the consistency of 

 annual band deposition in North Carolina's M. 

 mercenaria. 



The tests of consistency of annual band deposition 

 across habitats in a local estuarine system provide 

 an additional source of confidence in the accuracy 

 of using internal banding patterns to age M. 

 mercenaria in the Cape Lookout region of North 

 Carolina. Concern over the lack of such controlled 

 tests had earlier prompted Clark (1974), Gould 

 (1979), and Jones (1981) to question the widespread 

 assumption of regular periodicity in repeating shell 

 features. Our demonstration of consistency in annual 

 banding across local habitats should remove any 

 doubts about the general applicability of using an- 

 nual bands to age M. mercenaria in the Cape Look- 

 out region of North Carolina. The variation in line 

 deposition patterns which has been shown across 

 habitats for Protothaca staminea (Peterson and Am- 

 brose 1985) and among individuals within habitat for 

 P. staminea and Chione fluctifraga (Hughes and 

 Clausen 1980) does not exist for M mercenaria near 



Cape Lookout. Our results will not only enable inver- 

 tebrate fisheries biologists to use growth bands with 

 confidence to age North Carolina's M. mercenaria 

 but also should stimulate further research on under- 

 standing the environmental causes of variation in 

 bivalve shell deposition patterns. 



Acknowledgments 



K. Bowers, M. E. Colby S. R. Fegley C. Furman, 

 C. Groat, S. A. Hughes, K. C. Pierce, G. W. Safrit, 

 Jr., S. Smith, N. T Sterman, and J. Tbcker provided 

 field and laboratory assistance V. Page drafted and 

 H. Page photographed Figure 1, adapted from Beal 

 (1983). Reviews by S. R. Fegley W. Sutherland, and 

 M. C. Watzin improved the paper. This study was 

 sponsored by the Office of Sea Grant, NOAA, U.S. 

 Department of Commerce, under grant No. 

 NA81AA-D-00026, North Carolina Department of 

 Administration. 



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