444 Memoir Sears Foundat'tofi for Marine Research 



I a. 



lb. 



Key to Species of Dorosoma Known from Brackish or Salt Water 



Mouth terminal; ventral edge of upper jaw smooth; fewer than 50 scales in lateral 

 series, regularly arranged; anal rays 17—27, usually 20—25; prepelvic scutes 14— 

 17 (rare); vertebrae 40—45. fetenense (Giinther) 1866, p. 448. 



Mouth subterminal or inferior; ventral edge of upper jaw with pronounced notch 

 (except in young); more than 50 scales in lateral series, irregularly arranged; 

 anal rays 25—36, usually 29—35, where sympatric with D.fetenense\ prepelvic 

 scutes 17—20; vertebrae 48-51. cepedianum (LeSueur) 18 18, below. 



Dorosoma cepedianum (LeSueur) 1818 



Gizzard Shad, Eastern Gizzard Shad 



Figure i i 6 



Study Material. Seventy-four specimens, 78—247 mm SL, for body proportions, 

 51—200 for meristic data except as otherwise stated, from various parts of its range, 

 Canada to Mexico. 



Distinctive Characters. The comparatively small scales, 52—70 in lateral series 

 and 36-45 around the body, a higher vertebral count (48-51, usually 50), the longer 

 anal fin and greater number of rays (25—36), and preponderantly 18 + 12 ventral scutes, 

 distinguish D. cepedianum from its sympatric relative D. petenense. Another relative, 

 Opisthonema oglinum, may be separated from D. cepedianum by features listed in the 

 generic account under Remarks (p. 443). 



Description. Proportional dimensions in per cent of standard length and head 

 length, with all measurements "stepped off" with a pair of precision dividers; based 

 on Study Material, specimens 78-247 mm SL; counts based on 51—200 specimens, 

 the number of specimens counted being given in parentheses. 



Body: depth 2.3—3.1 in SL. 



Caudal peduncle: length 2.4—3.5 ^""^ 



depth 2.45—3.4 in hi. 

 Head: length 3.0-3.9 in SL; width 1.8- 



2.5 in hi. 

 Snout: length 5.0-6.0 in hi. 

 Eye: length 3.3-5.4 in hi. 

 Interorbital: bony width 3.3-4.5 in hi. 

 Upper jaw: length 3.5-4.2 in hi. 

 Mandible: length 2.6—3.3 '" hi. 

 Dorsal fin: base 1.85—2.6 in hi; length of 



filament 3.1-6.5 in SL, 0.8—2.0 



in hi. 

 Caudal fin: length of lower lobe 0.7— i.i 



in hi, typically longer than anal 



base (rarely subequal). 

 Anal fin: length of base 3.2—3.9 in SL, 



0.75-1.25 in hi. 

 Pelvic fin: length 2.0—2.5 in hi. 

 Pectoral fin: length i.i 5-1.45 in hi. 

 Distances: predorsal 1.85—2.05; prepelvic 



2.0—2.35; anal origin to caudal 



base 2.4-2.8, all in SL. 



Scales: lateral series 52—70, av. 61.06 

 (67), the first scale counted being 

 the first above uppermost corner of 

 gill opening; between dorsal and 



