Fishes of the Western North Atlantic 2 9 



Subgenera. There have been several attempts to subdivide the genus Acipenser as 

 defined by Linnaeus in 1758. The preferences of earlier authors may be judged from 

 the Generic Synonyms. Among contemporary authors, Berg {11 : 66), for instance, favors 

 three subgenera: Lioniscus Heckel and Fitzinger for A. nudiventris, Gladostomus Holly 

 for A. stellatus, and Acipenser s. str. for the rest. On the other hand, Antoniu (5: 317, 

 3 1 8) has grouped Black-Sea Sturgeon in two subgenera: Euacipenser Antonm, comprising 

 A. ruthenus and A. nudiventris, and Acipenser Linnaeus, embracing A. sturio, A. gUlden- 

 stddti, and A. stellatus. We believe that in the future any subdivision of the genus 

 Acipenser should be based on meristic and anatomical characters; this is not possible 

 yet because the anatomy of the Pacific species is completely unknown and that of 

 Atlantic species has not been sufficiently studied. 



Size. Among Acipenser species, the range in size is wide. The largest species 

 is A. transmontanus, with occasional individuals weighing up to 1,800 pounds {21: 

 74), as in the case of one taken about 60 years ago at Mission, British Columbia; 

 the smallest is no doubt A. brevirostris, about nine pounds (p. 38). The species of 

 Huso are much larger. Berg {11: 61) has mentioned the capture of a female H. huso 

 in the Volga in 1924 that weighed 2,707 pounds (1,228 kg). A still larger specimen, 

 weighing 6,614 pounds (3,000 kg), was taken in 1827. Females grow much larger 

 than males. 



Span of Life. The species of Acipenser and Huso may have a longer life span than 

 most fishes. For instance, through study of cross sections of the pectoral bony ray, 

 an A. sturio 230 cm long was found to be 25 years old (20: 61). The age of a Huso 

 dauricus, 500 cm long and weighing 1,600 pounds (655 kg), was estimated to be be- 

 tween 50 and 55 years (60: 199). Further information is given in the accounts of the 

 western North Atlantic species. 



Age in Sturgeons has been studied by two methods, one employing cross sections 

 of the pectoral ossified ray, the other otoliths." 



Breeding Habits and Sex. Sturgeons breed for the first time at a much more ad- 

 vanced age than most other fishes, and apparently the small species are more precocious 

 than the large. For instance, the relatively small A. ruthenus from the Volga may mature 

 at four years (jJ: 75) and A. brevirostris from the Hudson River at five years (J5: 

 82-83). On the other hand, such a large species as A. oxyrhynchus reaches maturity 

 in IO-I2 years. According to Y{zrkx\&?,s,,^^ A. fulvescens irom Lake Nipissing, Ontario, 

 spawns for the first time at 22 years of age.^^ 



Apart from the period when they are sexually mature, there is practically no 

 exterior distinction between the sexes. The cow Sturgeons, when full of ripe eggs, 

 have a greatly swollen abdomen with rather thin walls, and the mature males have a 

 more elongated appearance, with the walls of the abdominal cavity much thicker. 



11. For schematic drawings of otoliths of A. oxyrhynchus and bre'virostris, see Greeley {35: 81); and {01 ful'v-e 

 scens, see Harkness {38: 16-19). Harkness {38: 13-42) and Greeley {35) used otoliths for determination of age 

 while Classen (20) and other European investigators based their findings on cross sections of the pectoral 

 bony ray. 



12. For a review of the rate of growth and of the age at spawning of different species, see Classen (20). 



