WILKENS and LEWIS: YOUNG ATLANTIC MENHADEN 



TEMPORAL DISTRIBUTION 



Larval menhaden entered the White Oak River 

 from November until early May. Two peaks of 

 abundance occurred each year, one in November 

 and December and the second and major peak in 

 February and March (Figure 2). 



Figure 2. — The mean biweekly abundance indexes at 

 Swansboro Bridge in 1967-68 (solid line) and 1968-69 

 (dashed line). 



The entrance of large numbers of larvae in 

 February and March probably resulted from the 

 migratory schools of menhaden that spawned off 

 the North Carolina coast during the winter. 

 Higham and Nicholson (1964) found that during 

 November and December most of the females in 

 the landings were nearly ripe. Reintjes (1969) 

 reported finding hundreds of thousands of de- 

 veloping menhaden eggs off the North Carolina 

 coast in December 1966. 



Those larvae that entered the estuary during 

 November and December were probably the 



1969 



Figure 3. — The relative abundance of larval (solid line) , 

 prejuvenile (dashed line) , and juvenile menhaden (dotted 

 line) in the White Oak River estuary. (The larval in- 

 dexes are from the bridge, and the prejuvenile and juve- 

 nile indexes are from the upstream zone where the fresh 

 and salt water mix. Larval and prejuvenile indexes are 

 biweekly means, but the juvenile index is a monthly mean 

 plotted on the day the sample was obtained.) 



progeny of fish that either had inhabited North 

 Carolina waters in the summer or had moved 

 into North Carolina waters from other areas in 

 early autumn. 



Prejuvenile menhaden were first caught in 

 March and became abundant in late March and 

 A])ril (Figure 3). After the peak in April the 

 number of prejuveniles decreased, and by the 

 beginning of May most had transformed into 

 juveniles. 



Juvenile menhaden, collected in relatively low 

 numbers from May until September, occurred 

 with maximum abundance in late May and June. 

 As young menhaden got above 45 mm fork length 

 during the summer of 1968, we caught fewer 

 fish during the day. To determine if illumina- 

 tion was a factor that resulted in greater net 

 avoidance by juvenile menhaden, we scheduled 

 a series of day-night sampling trips. We col- 

 lected larger samples of menhaden during night- 

 time tows, which indicated that some fish were 

 able to avoid our net during the day. Fish from 

 day and night tows were similar in length. In 

 addition, we caught more menhaden on overcast 

 or moonless nights than on clear, moonlight 

 nights. As a result of our findings in 1968, we 

 sampled for juveniles in 1969 only at night in 

 order to increase our sampling efficiency. 



785 



