A DESCRIPTION OF YOUNG ATLANTIC MENHADEN, Brevoortia tyrannus, 

 IN THE WHITE OAK RIVER ESTUARY, NORTH CAROLINA 



Robert M. Lewis/ E. Peter H. Wilkens/ and Herbert R. Gordy^ 



ABSTRACT 



Atlantic menhaden exhibit three different stages — larva, prejuvenile, and juvenile — during their stay in 

 the estuary. For specimens collected from the White Oak River estuary, N.C., the length-weight rela- 

 tion was logg Y = -8^1104 + 3.6050 (log^ X) for larvae, log^ Y = -16.9638 + 6.3083 (log^ X) for 

 prejuveniles, and logg Y = —5.2298 + 3.1452 (logp X) for juveniles, where Y =: weight in mg and 

 A' = length in mm. Larvae and prejuveniles concentrated in the low salinity-freshwater zone upstream. 

 Juveniles tended to move downstream toward the higher salinity water. Condition factors of larvae and 

 prejuveniles increased toward the higher salinity zone. 



Atlantic menhaden spawn and hatch in coastal 

 oceanic waters from Maine to Florida. The 

 larvae enter estuaries where they transform in- 

 to juveniles near the freshwater zone. The re- 

 lation of young menhaden length and weight to 

 time, salinity, and location within an estuary 

 provides insight on the environmental require- 

 ments of menhaden during a critical phase in 

 their life cycle. We collected young menhaden 

 from a small estuary in North Carolina, from 

 March to September 1969 with a tidal net (Lewis 

 et al., 1970) to study changes in the length- 

 weight relation. 



The lower portion of the White Oak River 

 estuary (28 sq km) is shallow with depths from 

 to 3.0 m and distances from opposing shores 

 from 1 to 3 km. The intracoastal waterway 

 crosses the lower estuary and is maintained at 

 a depth of approximately 4 m. The upstream 

 portion narrows into a river up to 4.6 m deep. 

 During the study period we generally found that 

 the change from brackish to fresh water oc- 

 curred between 18 and 24 km upstream from 

 Bogue Inlet. The exact location of this low sa- 

 linity zone was influenced by tide, rainfall, and 

 direction and speed of the wind. The mean tidal 



^ National Marine Fisheries Service, Atlantic Coastal 

 Fisheries Center, Beaufort, NC 28516. 



" National Marine Fisheries Service, Southeast Fish- 

 eries Research Center, 75 Virginia Beach Drive. Miami, 

 FL 33149. 



Manuscript accepted August 1971. 



FISHERY BULLETIN: VOL. 70, NO. 1. 1972. 



range at Bogue Inlet is 2.2 ft (0.67 m) (U.S. 

 Coast and Geodetic Survey, 1970). At 21 km 

 upstream the average river flow is 14.7 cfs (0.42 

 mVsec) (North Carolina State Board of Health, 

 1954) . A map showing the location of the White 

 Oak River estuary is shown in Lewis and Mann 

 (1971). 



We selected 14 stations from Bogue Inlet to 

 34 km upstream (Wilkens and Lewis, 1971). 

 Stations ranged from 2 to 5 km apart and were 

 selected to be representative of the various sa- 

 linities encountered. We also sampled in fresh 

 water to determine how far menhaden move up- 

 stream. Salinity measurements were taken 

 within 1 m of the surface. During collections, 

 spot checks of salinity between the surface and 

 bottom indicated that in this shallow estuary 

 thorough mixing generally occurred. Diff"er- 

 ences between measurements at one location 

 were due to flooding and ebbing tides. 



Our menhaden collections ranged from 15 to 

 several thousand individuals. We measured and 

 weighed all fish to the nearest 0.5 mm total length 

 and 0.1 mg in collections containing less than 26 

 and subsampled the larger collections. Since 

 both length and weight variances in the sub- 

 samples were small, we considered our estimates 

 of length and weight to be reliable. Our mea- 

 surements of total length were based on the 

 greatest dimension between the most anteriorly 

 projecting part of the head and the farthest tip 



115 



