KENDALL and REINTJES: DISTRIBUTION OF ATLANTIC MENHADEN EGGS AND LARVAE 



73* 



ATLANTIC MENHADEN LARVAE 

 CRUISE D-65-4 

 DEC. 3-15, 1965 



34 76* 



graphically with observed surface temperatures 

 and salinities. Surface observations were thought 

 adequate since most larvae were collected when 

 hydrographic conditions were nearly uniform with 

 depth and menhaden larvae were scarce below the 

 thermocline. Mean temperatures and salinities 

 within the sampling depth range were also com- 

 pared with catches and showed patterns similar to 

 those discussed here. 



Observed surface temperatures varied from -1° 

 to 28°C (Figure 12). At each of nine whole-degree 

 intervals between 6° and 19°C, more than 30 sta- 

 tions were occupied. More than 40 stations were 

 occupied at 10° and 14°C. Menhaden occurred at 

 stations when temperatures were between 0° and 

 25° C. The curve of positive stations (those where 

 menhaden were taken) was similar in shape and 

 range to that of total stations. The numbers of 

 larvae taken at each temperature were plotted on 

 a log scale. This plot was slightly skewed to the 

 right, with modal catch at 18°C. Catches of over 

 100 larvae were made at temperatures from 9.3° to 

 20.5°C, with most between 15.8° and 18.5° C. 



Surface salinity varied from 23 to 38''/oo, with a 

 mode at 31o/oo (Figure 13). Positive stations oc- 

 curred over the entire range of salinities, with a 

 mode at 30"/oo. The larval catch curve, on a log 

 scale, is similar in shape to the total station curve, 

 with a mode at 31"/oo. At stations with salinities 

 between 30 and 36«/oo, a total of at least 200 larvae 

 were taken within each part-per- thousand inter- 

 val. 



Diel- Vertical Comparisons of Larval Catches 



Comparisons were made of the catches of larvae 

 in shallow and deep tows made during night and 

 day. These comparisons are on the basis of the 

 volume of water sampled, which was assumed to be 

 constant among the tows. The use of parametric 

 statistics was precluded by the highly nonnormal 

 catch frequency curve (Figure 3). Of the 172 tows 

 with menhaden larvae, 48 contained only 1 larva, 

 and 11 tows contained more than 100 larvae. Of the 

 11 tows with more than 100 larvae, 7 were taken in 

 shallow tows during daylight. Altogether 

 menhaden occurred in 85 daylight tows and 87 

 nighttime tows (Table 3). The distribution of 

 catches was not significantly different with time 

 of day (chi-square test; P > 0.50). Day and night 



Figure 8.-Distribution and abundance of menhaden larvae in 

 the December 1965 cruise. 



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