﻿REVIEW OF GENUS DOROSOMA — MILLER 405 



U. S. N. M. No. 133098 and U. M. M. Z. No. 144575: 113 young to adult, 

 73 to 134 mm. long, from Rfo Yecorato about 7 miles northeast of Guasave, 

 Sinaloa. 



U. M. M. Z. No. 143185: 2 specimens from a tributary of Rfo Sinaloa, 

 about 6 miles northeast of Guasave, Sinaloa. 



U. S. N, M. No. 129951: 10 half-grown, 74 to 91 mm. long, from Rio de 

 Mocorito, about three-fourths of a mile from Guamuchil, Sinaloa. 



Range. — Known so far only from southern Sonora (Rio Yaqui) to 

 southern Sinaloa (Rio Piaxtla), Mexico. 



CHANGES WITH GROWTH 



A detailed study of changes with growth in Dorosoma has not been 

 attempted, principally because many of the stages of development are 

 lacking in the material at hand. The data obtained, however, are 

 sufficient to indicate some of the changes that take place with age in 

 gizzard shads. This phase of the study was limited almost exclusively 

 to the three southern species: anale, chavesi, and smithi. 



The following changes with age m the relative position or in the 

 relative size of certain structures are indicated by tables 7, 10, and 11 

 as the normal growth pattern for the southern species: (1) The pelvic 

 and anal fins move forward; (2) the head becomes shorter and less 

 deep; (3) the eye becomes smaller and the snout shorter (as best ex- 

 pressed in the measurement "snout+eye"); and (4) the mandible 

 and the upper jaw becomxC much shorter as the young fish attains 

 maturity. That this general pattern of development is to be expected 

 also in D. cepedianum is indicated by measurements (not recorded 

 here) of a young specimen (27.5 mm., standard length) and of an adult 

 (102 mm.) from Mississippi (U. S. N. M. No. 129325). The differ- 

 ences in their measurements agree with the changes described above. 

 An examination of table 1 in Hubbs and Miller (1941, p. 235) demon- 

 strates further agreement of the growth pattern of cepedianum with 

 that of the other species. 



The growth of the dorsal filament requires special mention because 

 the pattern of development is not uniform in the four species of 

 Dorosoma. In cepedianum, anale, and smithi this structure is very 

 small in young fish but increases in length with age, at least up to a 

 certain size range. What the limits of this range may be is undeter- 

 minable from the material examined and is only hinted at by the 

 resultant data. For example, in table 10 the structure is seen to 

 grow relatively longer in D. anale from a young fish 28 mm. long to 

 specimens ranging from 116 to 165 mm. long.® Specimens varymg 

 between 171 and 190 mm. show little change in the relative length of 

 the filament, and in a single fish approximately 256 mm. long this 



' Values of 300 or over in the table fall generally between these standard lengths, 105 mm. being the 

 maximum. 



