RICHARDS and KENDALL: DISTRIBUTION OF SAND LANCE LARVAE 



days of soaking in "Biz," the vertebrae of a 

 few specimens could be counted. 



RESULTS 



Appearance and 

 Meristic Character Counts 



According to pigmentation and general ap- 

 pearance, all sand lance larvae in these col- 

 lections are similar to those described by 

 Richards (1965) and listed as Ammodytes, 

 mari)ius by Macer (1967). In this group, Macer 

 included A. hexapterna and A. duhius of the 

 eastern coast of North America which Richards 

 et al. (1963) previously separated. 



The number of larvae examined varied among 

 three cruises; some larvae could not be used 

 because of net damage, and others were too 

 small to have developed fin rays or the total 

 complement of vertebrae. The mean, range, 

 and standard deviation of the meristic counts 

 are listed in Table 2 for specimens from each 

 cruise regardless of locality. Although a slight 

 increase in meristic counts was noticeable as 

 the season progressed, it was not significant. 



Table 2. — Meristic character counts of larval sand lances 

 from three cruises of the RV Dolphin, 1966. 



There was no evidence from pigment pat- 

 terns, meristic counts, or seasonal abundance 

 of these larvae that we had more than one 

 species of sand lance between December and 

 May south of Cape Cod, Mass. As Reay (1970) 



pointed out, the specific definitions of Ammo- 

 dytes in the northwest Atlantic are tenuous, 

 so it is presumptuous to be definite in naming 

 species. Variations in appearance and meristic 

 character counts of these postlarvae appeared 

 to be primarily due to the stage of development. 

 Rate of development fluctuates during the dif- 

 ferent months because of changes in the physi- 

 cal characteristics of the water at the time 

 of hatching and early growth. As shown pre- 

 viously by Richards (1965), individuals in 

 colder water take longer to develop dorsal and 

 anal fin rays and a full set of vertebrae. Speci- 

 mens collected in spring were more fully 

 developed than those of an equal length taken 

 in winter. 



Numbers of Postlarvae in 

 Night and Day Collections 



The time of day during which a particular 

 station was occupied varied between cruises; 

 therefore, the diel time factor must be con- 

 sidered before discussing geographical and 

 seasonal distribution of the sand lance larvae. 



The greater catch rate of night tows com- 

 pared to day tows is apparent from Table 3, 

 in which all night collections are separated 

 from all day collections (including dawn and 

 dusk) regardless of location. In general, there 

 was a higher percentage of positive tows at 

 night than during the day. Roughly 34% of the 

 night tows contained larvae, while only 23% 

 of the day tows were positive. When all tows 

 are considered, larvae were more consistently 

 taken at night throughout all the cruises. The 

 mean number of larvae at night dropped from 

 16/tow in winter to 5.1 and 5.6/tow in April 

 and May, respectively. During the following 

 spawning season, in December, the mean num- 

 ber of larvae per tow at night was just less 

 than 1. A daylight mean of 5.3 larvae/tow in 

 winter dropped to 1.9/tow in April and 0.1/ 

 tow in May. None were taken during the day 

 on the ci*uise of the following December. Thus, 

 a seasonal change in availability was evident 

 in both day and night tows and was due pri- 

 marily to dispersion, net avoidance, and mor- 

 tality. Further analysis of the diurnal distribu- 

 tion of the larvae is not warranted bv these 



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