184 



Fishery Bulletin 90(1). 1992 



(Table 1). Adequate numbers of 

 larvae allowed growth compari- 

 sons of larvae collected on the 

 Cape San Bias transect in De- 

 cember 1980 and larvae collected 

 on the Mississippi Delta and Gal- 

 veston Bay transects in Febru- 

 ary 1981. 



Larvae were measured to the 

 nearest 0.1mm (NL before and 

 SL after the formation of hypu- 

 ral plates). Guts were dissected 

 and all gut contents were ex- 

 cised, identified, and measured. 

 Percent similarity (Schoener 

 1970) was used to compare the 

 diets of larval round herring 

 and gulf menhaden from single 

 collections. 



Sagittal otoliths were removed 

 from larvae, cleaned in distilled 

 water, and mounted on glass 

 microscope slides with clear acry- 

 lic resin; no griding or sectioning 

 was necessary to resolve daily 

 growth increments. Otoliths of 

 round herring were semi-opaque 

 and similar to those of gulf men- 

 haden. Presumed daily incre- 

 ments were clearly discernable 

 as bipartite structures consisting 

 of adjoining incremental and 

 discontinuous zones (Campana 

 and Neilson 1985). 



In describing the growth of 

 larval round herring, we did not 

 experimentally verify that their 

 first otolith increment appeared 

 5 days after hatching or that sub- 

 sequent increments were added 

 daily as Warlen (1988) has done 

 for gulf menhaden. We assumed 

 that initial and subsequent incre- 

 ment deposition in round herring 

 was similar to gulf menhaden. 

 This assumption is justified, in 

 part, by similarities in the period 

 of some key developmental 

 events. Incubation takes 36 

 hours at 20.5°C for round her- 

 ring (O'Toole and King 1974), 

 and 40-42 hours at 19-20°C for 

 gulf menhaden (Hettler 1984). 

 Complete adsorption of the yolk 

 occurs in 4 days for round her- 



