Fishes of the Western North Atlantic 4 1 



Canad., 7J, 1946: 43 (detail, acct. of shields and gill rakers, size); Nat. Canad., jS, 195 1 : 199 (detail. 



acct. of gill rakers for three w. Atlantic species). 

 Acipenser {Huso) lesueurii Valenciennes (Ms.) Dumeril, Hist. Nat. Poiss. 2, 1870: 166 (descr., New York).-* 

 Acipenser {Huso) rostellum Dumeril, Hist. Nat. Poiss., 2, 1870: 173 (descr., New York?).^* 

 Acipenser {Huso) sinus Valenciennes (ms.) Dumeril, Hist. Nat. Poiss., 2, 1870: 175 (descr., New York.').^* 



Acipenser fulvescens Rafinesque 18 17 

 Lake Sturgeotij^s Smoothback 

 Figures 7, 9 



Study Material. Over 800 specimens, 6—229 cm or 2.5—90 inches TL (5.7— 

 21 1 cm or 2.3—83 in. FL), from different sections of the St. Lawrence River, Quebec; 

 also odd specimens from Lake Ontario on both the Canadian and New York sides. 

 Specimens from a large number of interior waters not included. For details, see Vla- 

 dykov and Beaulieu (83: 18). 



Distinctive Characters. A. fulvescens., like A. irevirostris, is distinguishable from 

 A. oxyrhynchus by: the arrangement of its preanal shields in a single row, a mouth 

 not less than 66 '/o as wide as the interorbital width, the absence of a soft area 

 (fontanelle, p. 27) on the top of the head, and black viscera. From brevirostris it 

 differs in that its lateral shields are of the same color as the background. 



Description. Scutes in young specimens (up to 12 in. FL), in all rows, developed 

 even more strongly than in A. oxyrhynchus of corresponding sizes; progressively ab- 

 sorbed with age, beginning with the ventral rows, until they may be completely so, near 

 spawning time, especially in the ventral rows (hence the commercial name Smooth- 

 back); in 516 Quebec specimens, 9-17 (av. 13.4) dorsal shields, and in 242 specimens, 

 29—42 (av. 35.4) lateral shields; shields behind dorsal fin in a single row; elongated 

 fulcrum at base of lower caudal lobe never longer than base of anal fin. Dermal 

 OSSIFICATIONS minute, but the skin much tougher than in A. oxyrhynchus. 



Head longer in young than in larger individuals, on the average 24 "/p of FL in 

 specimens 40-70 cm FL. Snout in specimens less than 50 cm FL longer than post- 

 orbital distance, but shorter in older individuals. Interorbital width rather large, 

 varying; in 79 young specimens 8-36 cm FL, 2 1. 6-31. 8 "/o (av. 2 8''/o) of hi; in 143 

 older specimens 40-211 cm FL, 29-40''/o (av. 34''/o). Mouth large, its width (ex- 

 cluding lips) 66-93 "/o (^v. 77 "/o) of interorbital width. 



Gill rakers rather short and blunt, but numerous; 350 Quebec specimens above 

 8 inches FL with 25-40 (av. 33.1) rakers. 



25. The Dumeril holotypes of these three species are kept mounted in good condition at the Paris Museum National 

 d'Histoire Naturelle. They were examined in 1950 and identified as A. bre'virostris by Vladykov. A similar identi- 

 fication was made by Benin {12: 252). Jordan, et al. {4$: 34) quoted two more names given by Dumeril 

 {28: 164-168), based on locality only: microrhynchus (New York) and dekayi (New York). 



26. In Quebec, the French-speaking fishermen call the adults Esturgeon jaune or Camus, that is, short and flat 

 snout; the latter name was already in use at the end of the last century (55: 188). The young specimens are usually 

 named Escargot, or in certain sections (Nicolet) Charbonnier, on account of the black blotches (83: 32). On the 

 New York market, this species is often called the Smoothback. 



