Lyczkowski-Shultz and Steen. Diel vertical distribution of Saaenops ocellatus in northcentral Gulf of Mexico 



637 



A 



I 

 h- 



Q_ 



LJ 

 Q 



Figure 3 



Vertical profiles of temperature (°C, 

 solid line in each plot) and salinity (ppt, 

 dotted line in each plot) during after- 

 noon (left plot), night (center plot), and 

 morning (right plot) sampling periods 

 from cruises: (A) 84-9-1, (B) 84-9-2, 

 (C) 84-10-1, (D) 85-9-1, (E) 85-10. 



(Lyczkowski-Shultz et al. 1988). Results of these anal- 

 yses led to the separation of red drum larvae into three 

 size categories: <2mm, >2 to <4mm, and >4mm, 

 based on diet composition. Column A in Table 4, 

 "preferred" prey, is the combined observed density, 

 from field collections, of those taxa of calanoid and 

 cyclopoid copepods found to most uniquely describe the 

 diet of larvae of the size indicated by the mean lengths 

 listed in Table 3. Crustacean nauplii, column B in 

 Table 4, were the most ubiquitous prey found in red 

 drum larvae of all sizes, and column C is the density 

 of all potential prey items within the size range 

 63-230^, i.e., the total size range of prey found to be 

 ingested by red drum larvae. 



In only 6 of 15 vertical data sets did the depth of max- 

 imum abundance of larvae coincide with the depth of 

 maximum abundance of their prey. Of the 10 daytime 

 vertical data sets when red drum larvae were most like- 

 ly to be feeding (Lyczkowski-Shultz et al. 1988), the 

 depth of maximum abundance of red drum larvae coin- 

 cided with the depth of maximum abundance of their 

 prey in only three instances. In one of those instances, 

 the morning sampling period of cruise 84-10-1, red 

 drum larvae were equally abundant at the depths of 

 lowest and highest observed microzooplankton 

 densities. 



