THE OCCURRENCE OF SPOT, 

 LEIOSTOMUS XANTHURUS, AND 



ATLANTIC CROAKER, 



MICROPOGONIAS UNDULATUS, 



LARVAE IN ONSLOW BAY AND 



NEWPORT RIVER ESTUARY, 



NORTH CAROLINA 1 



Past studies indicate that spot, Leiostomus xan- 

 thurus, and Atlantic croaker, Micropogonias un- 

 dulatus, spawn offshore in autumn and probably in 

 winter (Hildebrand and Schroeder 1928; Hildebrand 

 and Cable 1930; Dawson 1958). Peak spawning 

 times and specific spawning areas have been 

 deduced from sightings of large numbers of recently 

 spawned larvae at specific locations nearshore or 

 offshore. Weinstein et al. (1980) reported on the up- 

 stream distribution of postlarval spot and Atlantic 

 croaker within the Cape Fear River estuary, N.C., 

 above a steam electric power plant. 



Extensive studies have been conducted in the Cape 

 Fear River estuary 2 in the southern portion of Onslow 

 Bay. Some of these studies dealt with recruitment of 

 sciaenids into the Cape Fear River estuary. However, 

 the hydrographic conditions of this estuary 3 are 

 markedly different from those of other estuaries 

 along the North Carolina coast and from most other 

 estuaries along the east coast of the United States; 

 therefore, any comparisons made with the Cape Fear 

 findings will result in some differences. 



In our current study which extended from October 

 1972 through April 1974, ichthyoplankton was sys- 

 tematically sampled monthly in northern Onslow 

 Bay and Newport River estuary, N.C. The goal of the 

 study was to determine the abundance and distribu- 

 tion of Atlantic menhaden, Brevoortia tyrannus, lar- 

 vae (Nelson 4 ), but spot and Atlantic croaker larvae 

 were also caught in large numbers. Our study is based 

 on the findings from these sciaenid samples. We pre- 

 sent data on the occurrence, size, and abundance of 

 spot and Atlantic croaker larvae from offshore to in- 

 shore and relate these findings to spawning time and 

 area, as well as timing and duration of recruitment of 



these larvae into the Newport River estuary. Little 

 has been previously published concerning the re- 

 cruitment of larvae of these two species into es- 

 tuaries, particularly in North Carolina waters. 



Methods 



Larval fish were collected monthly aboard the RV 

 Onslow Bay by towing paired 60 cm bongo plankton 

 nets of 0.333 and 0.505 mm mesh. Oblique tows were 

 conducted from surface to near bottom at each sta- 

 tion at a speed of 2.8 km/h (1.5 kn). Minimum dura- 

 tion of tows was 5 min, and the number of oblique 

 tows (normally 2-4) made at each station depended 

 on the water depth. This procedure was followed to 

 insure similarity of water volumes sampled at each 

 station. Bongo nets were weighted with a 45.4 kg (100- 

 lb) lead weight, and depth of tow was recorded with a 

 bathy kymograph attached just above the bongo nets. 

 Flow rates were estimated from torpedo-shaped digi- 

 tal flowmeters (made by General Oceanics, Inc., 

 Miami, Fla. 5 ) that were placed in the center of the 

 mouth of each bongo net. A calibration factor, based 

 on the length of tow, was determined for each flow- 

 meter; average volume of water strained, per station 

 per month, ranged from 63.3 to 78.1 m 3 . 



Collection stations were grouped among three 

 areas: Offshore, inshore, and estuarine. The two 

 ocean areas were each divided into three zones, while 

 the estuarine area was considered one zone (Fig. 1). 

 The approximate distances from shore, depths of 

 water, and number of stations for each zone are de- 

 scribed in Table 1. 



The number and location of stations varied between 

 the 1972-73 and the 1973-74 sampling periods. 

 Nineteen stations were sampled each month, except 

 April, from October 1972 to September 1973. In Oc- 

 tober 1973, three inshore stations, two in zone 1 and 

 one in zone 2, and all offshore stations in zone 4 were 

 deleted, and three stations in zone 6 were added, 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



'Contribution No. 83-20B, Southeast Fisheries Center Beaufort 

 Laboratory, National Marine Fisheries Service, NOAA, Beaufort, 

 NC 28516. 



^Brunswick Steam Electric Plant, Cape Fear Studies, Sections 1- 

 10. Reports to Carolina Power and Light Co., Raleigh, N.C, January 

 1980, 428 p. 



'Brunswick Steam Electric Plant, Cape Fear Studies. Ocean larval 

 fish, November 1976-1978. Environmental Technology Section, 

 Vol. V, 1979. Report to Carolina Power and Light Co., Raleigh, 

 N.C, 305 p. 



4 Nelson, W. R. 1977. Onslow Bay studies. Unpubl. manuscr., 64 

 p. Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service, NOAA, Beaufort, N.C. 



TABLE 1. — Number, offshore distance, and depth of collection 

 stations in Zones 0-6, Onslow Bay and Newport River estuary, N. 

 C, 1972-73 and 1973-74. 



FISHERY BULLETIN: VOL. 81, NO. 2, 1983. 



405 



