Stevenson and Secor: Growth of Aapenser oxyrinchus 



161 



marginal annulus was completely formed in the fall 

 rather than in the spring. Ideally, marginal incre- 

 ment analysis should be performed on separate age 

 classes to ensure that annulus formation occurs for all 

 ages (Casselman, 1983). However, owing to the rela- 

 tive scarcity of older individuals and the unavailability 

 of fish in some seasons and because marginal incre- 

 ments are often difficult to discern in fin-spine sec- 

 tions taken from older individuals, age classes were 

 pooled in our study. Accuracy of age estimation at 

 older ages remains untenable. An attempt to validate 

 longevity estimates of Hudson River Atlantic sturgeon 

 using radiometric ->0Pb/'--^Ra dating was unsuccessful 

 (Burton et al., 1999). Recapture of hatchery-released 

 Atlantic sturgeon (Secor-) has provided an opportu- 

 nity to verify age determinations in older or mature 

 individuals. Fin spines taken from juvenile sturgeon 

 did not exhibit belts of annuli; such belts may provide 

 information about spawning behavior in females. 



^ Secor, D. H. 1998. Habitat utilization patterns of mid-Atlan- 

 tic Bight juvenile Atlantic sturgeon. Final report on project 

 1445-CT-09-0189 to National Biological Survey, 30 p. Ref. no. 

 [UMCES] CBL 98-019. lAvailable from David Secor, Chesa- 

 peake Biological Laboratory, 1 Williams St., Solomons. MD 

 20688-0038.1 



Chemical microanalysis of hard parts is a promis- 

 ing tool for age verification (Jones and Geen, 1977; 

 Casselman, 1983; Cailliet and Radtke, 1987). How- 

 ever, seasonal cycles were not consistently observed 

 in elemental chronologies of Atlantic sturgeon fin 

 spines. The technique assumes that the hard part is 

 a closed system, and there is no resorption or remod- 

 eling. Burton et al. (1999) using radiometric tracers, 

 found that Atlantic sturgeon fin spines appear to be 

 open systems. In our study, we may have observed a 

 corrupted seasonal signal. 



Growth 



Sexually dimorphic growth patterns in Atlantic stur- 

 geon may be a result of differential reproductive 

 schedules and migration patterns. The age-length 

 relationship shows substantial variability in both 

 males and females. Males mature earlier ( 12 yr) and 

 spawn annually. Females mature later at a much 

 larger size and are thought to spawn every 3-5 years 

 ( Smith, 1985 1. Lower growth rates and larger achieved 

 sizes are typical for large, long-lived fish that broad- 

 cast numerous offspring (Adams, 1980; Moreau, 1987; 

 Roff, 1988, Winemiller and Rose, 1992). 



