ABUNDANCE AND DISTRIBUTION OF YOUNG ATLANTIC MENHADEN, 

 Brevoortia tyratinus, IN THE WHITE OAK RIVER ESTUARY, 



NORTH CAROLINA 



E. Peter H. Wilkens' and Robert M. Lewis- 



ABSTRACT 



The effect of salinity, temperature, tide, turliidity, and illumination on the distribution of larval, preju- 

 venile, and juvenile menhaden in an estuary was investigated. Most menhaden larvae entered the estuary 

 in March after the water had warmed to about 10° C, and moved upstream to the low-salinity-freshwater 

 zone where they transformed into juveniles. More larvae were caught in the lower estuary on flood tide. 

 After transformation to juveniles they were caught in schools throughout the estuary. Turbidity and 

 illumination did not affect the distribution of menhaden, but illumination affected catchability, since 

 more menhaden were collected during night tows. 



In this study we investigrated the effects of tem- 

 perature, salinity, and light on the distribution 

 and abundance of larval, prejuvenile, and juve- 

 nile menhaden in a single estuary, the White Oak 

 River in North Carolina. As the strength of 

 individual year classes of Atlantic menhaden 

 fluctuates widely, we were interested in deter- 

 mining what effect these environmental factors 

 had on menhaden during their first year in an 

 estuary. This information could be helpful in 

 assessing and predicting the strength of indi- 

 vidual year classes. Estimates of the strength 

 of individual year classes before they enter the 

 fishery would be valuable to the commercial 

 fishery. A single estuary was selected so that 

 a better understanding of these variables could 

 be achieved before being applied to a coastwise 

 fishery. 



Atlantic menhaden, found along the eastern 

 coasts of the United States and Canada from 

 Nova Scotia to southern Florida (Hildebrand, 

 1964; Reintjes, 1964), spawn in almost every 

 month in some part of their range (Higham and 

 Nicholson, 1964). Menhaden are spawned in 



' National Marine Fisheries Service, Southeast Fish- 

 ery Center, Miami, Fla. 33149; formerly National 

 Marine Fisheries Service, Center for Estuarine and 

 Menhaden Research, Beaufort, N.C. 



" National Marine Fisheries Service, Center for Estu- 

 arine and Menhaden Research, Beaufort, N.C. 28516. 



Manuscript accepted May 1971. 



FISHERY BULLETIN: VOL. SO, NO. 4. 



the ocean and enter an estuar.y as larvae. Once 

 strong enough to swim against the tidal currents, 

 they move ujistream towards fresh water (Lewis 

 and Mann, 1971) where they transform into ju- 

 veniles. They remain in the estuary for their 

 first growing season, gradually moving down- 

 stream in the summer and reaching the lower 

 estuary or open sea by autumn (June and 

 Chamberlin, 1959; Massmann, Ladd, and Mc- 

 Cutcheon, 1954). 



STUDY AREA, SAMPLING LOCATIONS, 

 PROCEDURES, AND NETS 



The White Oak River estuary is a bar-built 

 estuary (Pritchard, 1967) which drains forest 

 lands in the upstream part and salt marshes in 

 the downstream part (North Carolina State 

 Board of Health. 1954) . The Intracoastal Water- 

 way crosses the mouth of the estuary near Bogue 

 Inlet. 



We selected this estuary because: (1) We 

 knew from preliminary sampling that larval 

 menhaden entered the lowei- section from the 

 ocean in the winter and early spring and that 

 juveniles occurred in the upper section in the 

 summer; (2) its small size (28sqkm) permitted 

 ample sampling coverage; and (3) its proximity 

 to the Beaufort laboratory made frequent sam- 

 pling easy. 



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