153 



Abstract.— Atlantic sturgeon ^Aapcnscr 

 oxynnchtis) are a large anadromous 

 fish which is especially vulnerable to 

 overharvesting owing to its late age of 

 maturity and low rate of reproduction. 

 Age determination methods and growth 

 rates are poorly described for this spe- 

 cies. Pectoral-fin spine sections and sag- 

 ittal otolith sections were examined to 

 determine whether one of these struc- 

 tures would be u.seful in estimating the 

 age and growth of Atlantic sturgeon. 

 Otoliths have been difficult to collect, 

 process, and interpret. Interpretation 

 of annuli in sectioned pectoral spines 

 has proven to be an unbiased method 

 for aging juvenile and adult Hudson 

 River Atlantic sturgeon. Marginal incre- 

 ment analysis has indicated an annual 

 cycle of annulus deposition. Microchem- 

 ical analysis with an electron micro- 

 probe of the periphery of fin spines has 

 shown seasonal patterns of calcium and 

 phosphorus concentrations related to 

 the translucent and opaque zones of the 

 annuli. Formation of yearly annuli was 

 verified in 4-year-old laboratory-reared 

 sturgeon. \'on BertalanflTy growth models 

 (based upon fin-spine interpretations) 

 were fitted for the Hudson River popu- 

 lation. Models predicted a more rapid 

 growth rate for males than for females 

 (females: K=0.07, L„=251 cm; males: 

 A'=0.25,Z,. = 180cm). Females, however, 

 attained a greater maximum age 1 42 yr I 

 and size (TL=277 cm). We believe that 

 exploitation has had a large but unquan- 

 tifiable bias on gi'owth estimates for 

 male and female Atlantic sturgeon. As 

 the Hudson River population recovers, 

 age structure and growth rate estimates 

 should be refined to predict population 

 recovery rates more accurately in the 

 absence of a directed fishery. 



Age determination and growth of 

 Hudson River Atlantic sturgeon, 

 Aa'penser oxyrinchus* 



Jill T. Stevenson 

 David H. Secor 



Center lor Environmental Science 



Chesapeake Biological Laboratory 



University ol Maryland 



PO Box 38 



Solomons, Maryland 20688-0038 



Present address (lor J Stevenson): Highly Migratory Species Management Division, F/SFl 



National Marine Fishenes Service 



1315 East-West Highway 



Silver Spring, MD 20910 

 Email address (for J Stevenson) jill stevenson(g'noaa gov 



Manu-script accepted 13 January 1999. 

 Fish. Bull. 97: 153-166 ( 1999). " 



Atlantic sturgeon iAcipeiiser oxyrin- 

 chus) are a large anadromous fish 

 that ranges the East Coast of North 

 America and spawns in rivers from 

 Florida to Canada. Population levels 

 throughout the range of the species 

 declined appreciably in the late 19th 

 century owing to increased harvest 

 of sturgeon for caviar following the 

 Civil War (Murawski and Pacheco, 

 1977; Secor and Waldman, in press). 

 Overfishing and deterioration of 

 habitat, predominantly the blockage 

 of spawning runs, have contributed 

 to the extirpation of several Atlantic 

 sturgeon populations (Taub, 1990; 

 Waldman and Wirgin' ). The life his- 

 tory strategy of the anadromous 

 Atlantic sturgeon indicates that age 

 structure and vital rates are espe- 

 cially critical to conservation . Atlan- 

 tic sturgeon exhibit high maximum 

 age, late maturation (females 14-17, 

 males 10-12; Van Eenennaam et 

 al., 1996), and probable low mor- 

 tality rates; growth, however, is 

 rapid. These traits, as well as low rel- 

 ative fecundity and less-than-annual 

 spawning frequency, make sturgeon 

 especially susceptible to overexploi- 

 tation (Boreman, 1997). Therefore, 

 models of Atlantic sturgeon popula- 

 tion dynamics may be expected to be 

 sensitive to biases in estimated vital 

 rates and reproductive schedules. 



Atlantic sturgeon growth rates have 

 been estimated in several studies, 

 but results are divergent (Table 1). 

 Poorly validated techniques have 

 been employed to estimate age; and 

 rates of growth, reproduction, and 

 mortality have not been developed 

 sufficiently to support resource man- 

 agement models (Taub, 1990). 



Studies of acipenserid age have 

 employed annuli in calcified struc- 

 tures including scutes, pectoral-fin 

 spines, otoliths, operculi, and other 

 skeletal parts ( Harkness, 1923; Gree- 

 ley, 1937; Brennan and Cailliet, 1989, 

 1991; Guenette et al., 1992; Rien and 

 Beamesderfer, 1994). The term "fin 

 ray," previously used to describe the 

 leading ( primary) ray of the pectoral 

 fin supporting element, was revised 

 by Feindeis ( 1997 ) because this ele- 

 ment becomes fully ensheathed with 

 dermal bone early in ontogeny, and 

 therefore should be termed a spine. 

 Pectoral-fin spine sections have been 

 preferred for aging because annuli 

 in sections can be consistently inter- 

 preted, and fin spines are easily col- 



' Contribution 3272 of the University of 

 Maryland Center for Environmental Sci- 

 ence, Solomons, MD 20688-0038. 

 Waldman, J. R., and I. I, Wirgin. 1998. 

 Status and restoration options for Atlantic 

 sturgeon in North America. ICES Coun- 

 cil Meeting/T 16. 



