FISHERY BULLETIN: VOL. 86, NO. 2 



low (11 nauplii/L). The same pattern was ob- 

 served off Cape San Bias (Fig. 2d); there was no 

 marked vertical heterogeneity, and the maxi- 

 mum and average concentrations were low, 14 

 and 12 nauplii/L. In contrast, nauplii at stations 

 near the 50 m isobath in the region near the Mis- 

 sissippi River delta typically showed marked ver- 

 tical heterogeneity in abundance. At station IV-2 

 (Fig. 2b), the maximum concentration was 187 

 nauplii/L and the minimum was 24 nauplii/L. At 

 station II- 1, II-2, and II-3 in the Mississippi River 

 delta region (Fig. 2c) naupliar abundances were 

 also vertically heterogenous, although concentra- 



tions were lower than at Station IV-2. In general, 

 based on all our vertical profiles (most not 

 shown), regions influenced by the Mississippi 

 River can contain high concentrations of nauplii 

 in the surface layer, while subsurface concentra- 

 tions are similar to concentrations in the other 2 

 regions. 



Vertical structure in the distribution of nauplii 

 appears to be related to physical structure. At the 

 stations off the coasts of Texas and Florida (Fig. 

 2a, 2d), temperture and salinity were essentially 

 vertically homogenous (Fig. 3a, 3d) whereas off 

 the Mississippi River delta temperature and 



20%. 24 28 



32 36 



24%. 28 

 16*0 18 



Figure 3. — The vertical distribution of temperature (•) and salinity (x) at the stations represented in Figure 2. 



324 



