Stevenson and Secor; Growth of Aapenser oxyrinchus 



163 



Males 



Females 



mean = 1 75 + 1 .30 cm 

 mode = 152 cm 



mean = 217 + 3.49 cm 

 mode= 2 1 8 cm 



nJ cm 



240 280 120 

 Total length (cm) 



160 



200 



240 



280 



B 



mean =17 + 0.278 yrs 

 mode= 1 6 years 



an = 23 + 0.913 yrs 

 mode= 19 years 



12 

 10 



8 



6 



41- 



2 







10 15 20 25 30 35 40 45 



5 10 15 20 25 30 35 40 45 



Age (years) 



Figure 8 



(A) Total length and (B) age of male and female Atlantic sturgeon caught in the Hudson 

 River gillnet fishery (1992-95). Sublegal fish (<152 cm) were a result of a minimum 

 dressed carcass length of 91 cm. Conversion from dressed length to total length may 

 have resulted in "undersized" fish. 



fishery (as evidenced by residual patterns), increas- 

 ing K and decreasing L„. 



Growth parameter estimates reported here for 

 females are consistent with another study of the same 

 population (Doroshov et al.'^) but do not agree with 

 an earlier study (with sexes combined) of the popu- 

 lation (Dovel and Berggren, 1983). Recent reduction 

 of the accumulated biomass by fishing, and resul- 

 tant age and size truncation of the population, would 

 cause lower apparent L _^ and higher K values than 

 in an unexploited population. Maximum length (L^) 

 determined for females was substantially smaller 

 than historical records of maximum size for this spe- 

 cies (427 cm; Murawski and Pacheco, 1977), which 

 may be a result of increased fishing pressure on the 



* Doroshov. S., J. Van Eenennaam, G. Moberg, and G. Waton. 

 1994. Reproductive conditions of the Atlantic Sturgeon ^Acipen- 

 ser oxyrinchus) stock in the Hudson River. Report for year two to 

 Hudson River Foundation. Animal Science Department, Uni- 

 versity of California, Davis, 65 p. 



largest (female) component of the population during 

 the past ten years. The historical longevity of females 

 in the Hudson River also probably exceeded our esti- 

 mate of 42 years; Magnin ( 1964) reported a 60-year- 

 old female in the St. Lawrence estuary. 



Because the largest male sampled ( 72 kg) was only 

 22 years of age, yet much smaller males were older 

 than 30 years, male longevity in the unexploited 

 population was also probably higher than in the pop- 

 ulation we sampled. Consideration of possible bias 

 in von Bertalanffy growth parameters should direct 

 managers to undertake sensitivity analyses in devel- 

 oping demographic-based stock assessments. Because 

 L„ and K are inversely related (Kimura, 1980), age 

 and size truncation would result in an over-estimated 

 K (a lower L^^ is approached more rapidly). 



We found L^ values that were relatively low com- 

 pared with estimates in previous studies of Hudson 

 River Atlantic sturgeons (Greeley, 1937; Dovel and 

 Berggren, 1983). These low values may indicate 



