JOHNSON and LOESCH: MORPHOLOGY AND DEVELOPMENT OF AMERICAN SHAD 



taining the same range in total myomere number (Ta- 

 ble 2) . Jones et al. ( 1 978) did not report a decrease in 

 preanal myomeres with shortening of the gut; rather 

 they indicated an increase in the mean number of 

 preanal myomeres. The information presented by 

 Jones et al. (1978) is based on the work of Chambers 

 et al. (1976), which compares the means and ranges 

 of the preanal myomeres for larval clupeids. Findings 

 of this study and information reported in Mansueti 

 and Hardy (1967) are different from that reported by 

 Chambers et al. (1976). Difference in sample size 

 may explain the difference in results among the 

 studies. Larval A. sapidissima, cultured for this 

 study, exhibited a steady decrease in the PAL/SL 

 ratio and in the mean number of preanal myomeres. 

 These changes correspond with shortening of the gut 

 throughout the flexion stage of development. 



Ahlstrom (1968) proposed the use of dorsal fin posi- 

 tion (PDL), and the relative number of and difference 

 between predorsal myomeres and preanal myo- 

 meres, as an accurate method of identifying clupeid 

 larvae. Predorsal myomere counts and ranges report- 

 ed herein trace the anterior migration of the dorsal fin 

 during ontogeny. The morphometric data in Tables 1 

 and 2 fulfill the previous information gap in accurate 

 identification of larval A. sapidissima. 



The sequence of larval fin development and 

 developmental osteology of A. sapidissima has not 

 been extensively studied. Bigelow and Welsh (1925) 

 postulated that fin formation may be completed in A. 

 sapidissima by 20 mm SL. Nichols (1966) compared 

 the fin ray meristics of several populations of juvenile 

 A. sapidissima, and his results compare favorably 

 with this study in the number of fin rays in cultured A. 

 sapidissima larvae and juveniles. The mean counts 

 in this study of dorsal (19), anal (21), and pectoral (16) 

 fin rays on cultured larvae and juveniles agree with 

 the means and frequencies of meristic counts made 

 by Nichols (1966) on juvenileA. sapidissima from the 

 York River, Va. 



Leim (1924), Hildebrand (1963), and Jones et al. 

 (1978) discussed the ventral pigmentation pattern 

 seen from yolk absorption to about 13 mm SL. In- 

 deed, this is one of the most important characteris- 

 tics in identification of larval A. sapidissima. 

 Ahlstrom (1968), however, pointed out that clupeids 

 can be difficult to identify unless precaution is taken 

 to note the sequence of changes in the larva. This is 

 especially true with respect to pigmentation in larval 

 A. sapidissima. Leim (1924) and Jones et al. (1978) 

 noted that specimens from freshwater are more 

 heavily pigmented than those in brackish water. This 

 was confirmed in the present study by comparison of 

 field and cultured specimens of larval A. sapidissima. 



Pigmentation is heavier on the head and dorsal trunk 

 regions of freshwater cultured larvae than on native 

 brackish-water larvae. 



The sequence of pigmentation described herein for 

 A. sapidissima larvae can be used to identify A. 

 sapidissima of freshwater origin, because the culture 

 method utilized freshwater. The pattern of ventral 

 pigment described by Leim (1924) should be used 

 when identifying larvae in the 10-13 mm SL range 

 from samples collected in brackish water. There is a 

 large amount of variability in the distribution of 

 melanophores in freshwater-cultured larvae; there- 

 fore, special care should be taken when attempting to 

 identify and confirm larval A. sapidissima collected 

 in freshwater. Additionally, meristic characters 

 should be used in conjunction with pigmentation pat- 

 terns to fully confirm identification of A. sapidissima 

 from freshwater samples. 



Pigmentation patterns may be useful for separating 

 larval A. sapidissima from larval A. aestivalis and A. 

 pseudoharengus. Leim (1924) used the ventral 

 pigmentation pattern to separate A. sapidissima 

 from A. pseudoharengus. Chambers et al. (1976) 

 noted that the ventral pattern of pigmentation was 

 similar for A. aestivalis and A. pseudoharengus. Ven- 

 tral pigmentation patterns and size differences can 

 be used to distinguish these species when they are in 

 the early preflexion and postflexion stages of 

 development. When A. sapidissima is in the early- to 

 midflexion stage and A. aestivalis and A. pseudo- 

 harengus are in the mid- to late-flexion stage, mis- 

 identification can occur between these species. 

 Morphometries presented herein (Tables 1-5) and 

 the work of Chambers et al. (1976) could be used to 

 distinguish these species. Table 6 exhibits the 

 pigmentation characteristics that distinguish larval 

 A. sapidissima, A. aestivalis, andA. pseudoharengus. 

 Careful examination should be made of both the 

 pigmentation patterns (presented in Table 6) and 

 morphometric and meristic characteristics of each of 

 the three species to fully confirm the identification. 



ACKNOWLEDGMENTS 



There are a number of people to whom we would like 

 to offer thanks for their contributions to this study. 

 Jack Musick, Ken Sulak, Herb Austin, Bill Macln- 

 tyre, and Alan Blair (Manager, Harrison Lake 



National Fish Hatchery, U.S. Fish and Wildlife Ser- 

 vice) offered their advice and criticisms. Special 

 thanks also to John J. Govonii for his advice and 

 criticism of this study. John Gourley, John Zernes, 

 Jack Travelstead, and William Kriete helped in the 

 collection of juvenile samples on the Pamunkey 



337 



