Ditty et al.: A redescription of Chaetodipterus faber larvae 



269 



shoreward from 83 to 26 m; larvae may, therefore, 

 primarily inhabit coastal waters. This shoreward 



LONGITUDE 



Figure 4 



Distribution of Atlantic spadefish larvae (Chaetodipterus 

 faber) in the northern Gulf of Mexico by month. Months are 

 combined across years ( 1982-1986, and August 1988). Not all 

 months sampled each year. Plus ( + ) signs are total stations 

 sampled and squares are positive catch stations. Distribution 

 of stations are for both bongo and neuston net tows. 



shift in median station depth was reinforced by dis- 

 tribution of larvae in bongo net tows and by distri- 

 bution of larvae during June and July (Fig. 

 4, Table 4). About 86% of all Atlantic spade- 

 fish larvae collected in bongo net tows (rc=128) 

 were from waters <25 m deep. In addition, 

 distribution of larvae during June and July 

 was shoreward of that during August. Simi- 

 larly, 51% of all stations where larvae were 

 collected (i.e. 41 of 81) were inside 25 m; 64% 

 were inside 50 m. Only 14% of positive catch 

 stations were located beyond the 100 m 

 isobath; most of these stations were near the 

 Mississippi River delta, an area with a nar- 

 row shelf and rapidly increasing water 

 depths. 



Discussion 



Our observations on the morphological devel- 

 opment of Atlantic spadefish larvae generally 

 agree with Hildebrand and Cable (1938). 

 These authors, however, do not discuss pig- 

 ment on the roof of the mouth. The presence 

 of a single, median patch of pigment on the 

 roof of the mouth is helpful in identifying 

 early Atlantic spadefish larvae before the 

 supraoccipital crest is clearly visible. 

 Hildebrand and Cable (1938) do not discuss 

 small spines or ridges along the circumorbital 

 bones (i.e. supraorbital, suborbitals, and 

 dermosphenotic) or tabular bone (Fig. 2) but 

 do illustrate serrate ridges above the eye and 

 in the pterotic region (Hildebrand and Cable, 

 1938, their Figs. 26 and 27). Spination on the 

 circumorbital bones has generally been found 

 only in those larval percoids with cranial or- 

 namentation (Johnson, 1984). Most of these 

 larval percoids also have other specializa- 

 tions, such as spinous scales and an elongate 

 spine at the angle of the preopercle, among 

 other characters (Johnson, 1984). Neither 

 Hildebrand and Cable (1938) nor Johnson 

 (1984) mention the supracleithral spines we 

 found on Atlantic spadefish larvae (Fig. 2) and 

 in larvae of Pacific spadefish, Chaetodipterus 

 zonatus (Martinez-Pecero et al., 1990). The 

 "short, hair-like spines on the upper surface 

 of the head" noted by Hildebrand and Cable 

 (1938) on 9.0-mm Atlantic spadefish larvae 

 may be the same spines we found scattered 

 over the frontal and occipital bones (Fig. 3). 

 These frontal and occipital spines are difficult 

 to see under a dissecting microscope because 



