NOTE Hare and Govoni: Larval fish transport and vertical distributions on the southeast US continental shelf 



729 



Cape Hatteras 



16 



35 



34 



A 1986 

  1989 

 • 1991 



33 



77 

 Longitude °W 



75 



Figure 1 



(A) Map of the east coast of the United States rotated 18° counter-clockwise. The 

 spatial extent of the northeast and southeast United States continental shelves 

 is indicated by each rectangle. The area of panel B is shown as a trapezoid. (B) 

 The northern portion of the southeast United States continental shelf showing 

 the coastline, the 10-m, 20-m, 30-m 40-m, 50-m, and 100-m isobaths. The three 

 prominent capes are identified and locations of stations sampled in this study 

 are shown. 



Material and methods 



Data collection 



Larval fish were collected every six hours (0600, 1200, 

 1800, and 2400) at an offshore and an inshore station 

 during three winters: 21-26 February 1986, 26 January- 

 1 February 1989, and 5-7 February 1991 (Fig. IB). 

 Offshore stations were located on approximately the 

 50-m isobath, and inshore stations were located on 

 approximately the 35-m isobath. In 1986, offshore and 

 onshore stations were occupied for 102 and 48 h, respec- 

 tively. Collections were taken horizontally at 1, 18, and 

 32 m at the offshore station and 1, 13, and 25 m at the 

 inshore station with a 60-cm opening-closing bongo net 

 (Weibe and Benfield, 2003) with 333-^m mesh and a 

 1-m 2 Tucker trawl ( Weibe and Benfield, 2003 ) with 202-f<m 

 mesh. In 1989, offshore and inshore stations were occu- 

 pied for 78 and 72 hours, respectively. Collections were 

 taken horizontally at 1, 22, and 45 m at the offshore 

 station and 1. 13, and 30 m at the inshore station with 

 a 1-m 2 Tucker trawl with 333-,um mesh. In 1991, offshore 

 and inshore stations were occupied for 24 and 30 h, 

 respectively. Collections were made with 1-m 2 MOC- 

 NESS (Wiebe et al., 1976) with 333-jim mesh. Oblique 

 samples were collected within 5-m intervals from 35 m 



to the surface at the offshore station and from 30 m to 

 the surface at the inshore station. The mid-point of each 

 depth stratum was used as the depth of the collection. In 

 1986 and 1989, volume of water filtered was measured 

 with a flowmeter (General Oceanics model 2030, Miami, 

 FL) with a standard rotor. In 1991, volume filtered was 

 measured with a flowmeter provided with the MOC- 

 NESS (BESS, Falmouth, MA). 



Larval fish were sorted from collections and identified 

 to the lowest taxon possible. The larvae of selected taxa 

 were counted: Bothus spp., Etropus spp. (not including 

 E. crossotus). E. teres, Paralichthys spp., P. triacanthus, 

 S. papillosum and X. novaeula. Counts of B. tyrannus. 

 L. xanthurus, and M. undulatus were obtained from 

 Govoni and Pietrafesa (1994) and Govoni and Spach 

 (1999). Larval concentrations were calculated for each 

 depth stratum (number of larvae/100 m 3 ). 



Comparisons of larval vertical distributions 



Center of mass calculations are frequently used for com- 

 parison offish larval depth distributions (e.g., Brodeur 

 and Rugen, 1994), but Pearre (1979) raised valid criti- 

 cisms of this approach; for example a uniform distribu- 

 tion still has a mean depth. To obviate these criticisms, 

 larval depth distributions of each taxon were compared 



