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Fishery Bulletin 88(2), 1990 



further south to Virginia (37°N). Later Richards (1982), 

 for no stated reason, reported a more Hmited distribu- 

 tion for A. dubius, with no individuals found further 

 south than the Scotian Shelf. Winters and Dalley (1988) 

 also reported A. dubius as ranging no further south 

 than Georges Bank. 



Restricting the southern limit of the range for A. 

 dubius to Georges Bank creates several problems, in 

 particular the explanation of a southern offshore, high- 

 meristic form. Richards et al. (1963), Richards (1982), 

 and Winters and Dalley (1988) recognized two popula- 

 tions of A. americanus in southern waters: one an in- 

 shore low-meristic form, and the other an offshore, 

 intermediate- to high-meristic form. This conclusion 

 seems to stem from Perlmutter's (1940) recognition of 

 two offshore populations, one occurring north and one 

 south of Cape Cod, which were designated as subspe- 

 cies of A. fobitinus. In those studies (Richards et al. 

 1963, Richards 1982, Winters and Dalley 1988), A. 

 americanus was probably chosen for the species name 

 for southern offshore specimens because meristic 

 values (vertebrae, dorsal and anal fin rays) were more 

 similar to the counts they found for /I. americanus than 

 for northern A. dubius. However, all of these studies 

 reported and accepted the existence of a north-south 

 and/or an inshore-offshore cline for at least one (but 

 not always the same) species. Furthermore, the off- 

 shore A. americanus occupied the habitat commonly 

 inhabited by A. dubius. Also, the morphometric 

 description given by Winters and Dalley (1988) for their 

 southern offshore A. americanus was the same as that 

 for their .4. dubius. Meristic differences between in- 

 shore and oHshore Am modyfes in southern waters are 

 consistent with a hypothesis of two distinct sympa- 

 tric— but not necessarily syntopic— species, A. ameri- 

 canus and A. dubius, occurring in these waters. Addi- 

 tionally, meristic variation between northern and 

 southern offshore forms supports the hypothesis of 

 geographic intraspecific variation for A. duhi)is. The 

 data are not consistent with a hypothesis recognizing 

 only A. americanus in the southern region. 



Misconceptions regarding species designations of 

 western North Atlantic Ammodytes are further com- 

 pounded by the tendency of some authors (Richards 

 et al. 1963, Winters and Dalley 1988) to create three 

 groups— a low, intermediate, and high meristic group- 

 within their data sets to explain the variation, instead 

 of recognizing geographic variation in the offshore 

 species. Recognizing three groups results in consider- 

 able overlap between groups, thus adding to the diffi- 

 culty of identifying species. Modal analysis (only for 

 vertebrae; Winters and Dalley 1988) in some cases 

 seems to identify modes that are not immediately 

 obvious in the accompanying figures or data. The ac- 

 curacy of identifying groups within collections, let alone 



individuals, is questionable using this method. The 

 number of components and first estimates of the modes 

 and standard deviation must be specified first. Addi- 

 tionally, as Winters and Dalley (1988) point out, the 

 reported high standard error for certain modes in- 

 dicates that these means are estimated poorly. 



To eliminate confusion or guesswork surrounding 

 identification of individuals of Ammodytes, it was 

 necessary to devise an objective method of identifica- 

 tion. PCA achieves this goal since this method iden- 

 tifies patterns of variation between individuals without 

 regard to the groups represented. PCA scores were 

 utilized as a tool to summarize the data and to verify 

 the usefulness of these meristic characters. A plot of 

 the component scores of 332 individuals clearly showed 

 two groups (Fig. 4). Further testing showed that these 

 groups represent the two species. Thus, the two species 

 can be separated using meristic characters instead of 

 morphometric ratios of questionable validity (i.e., 

 length-weight; see Scott 1972) with little overlap. 



Furthermore, by designating a component score 

 boundary between the two groups, the two species are 

 clearly defined and meristic variation can be delimited 

 for each of the two species. This is particularly impor- 

 tant for individuals with intermediate counts, especially 

 those occurring in collections containing both species. 

 These individuals were the hardest to identify, but 

 defined limits for plicae, vertebral, and dorsal ray 

 counts made identifications easier. 



To support our data analysis, a comparison with 

 Perlmutter's 1940 data was made (Table 7; in the pres- 

 ent study. Northern = Labrador and Quebec-Nova 

 Scotia, Southern = Maine-Massachusetts and New 

 York-North Carolina). The Perlmutter (1940) data 

 were utilized because the data collected and geographic 

 locations were similar. Designations of north-south as 

 well as inshore-offshore locations were given also. 

 Means for meristic data were surprisingly similar 

 between the two studies. 



Perlmutter (1940) recognized north-south and in- 

 shore-offshore clines in his data, yet misinterpreted 

 these results. He designated several subspecies within 

 a single worldwide polytypic form instead of recogniz- 

 ing geographic variation within two parapatric species. 

 Evidence for recognition of two species is that both 

 species have been collected in sympatry in coastal 

 waters, particularly in the Newfoundland area. It has 

 been postulated that /I. dubius spawns inshore along 

 the Newfoundland coast (Dalley and Winters 1987). 

 The continued occurrence of high meristic individuals 

 inshore suggests that these species are reproductive- 

 ly isolated (Winters and Dalley 1988). Our data provide 

 additional support for recognition of two parapatric 

 species since there tend to be ecological differences 

 between the species, in particular, habitat preference. 



