Abstract. -Atlantic menhaden 

 Brevoortia tyrannus and gulf men- 

 haden B. patronus expressed signifi- 

 cant differences in their early-life- 

 history traits under laboratory 

 conditions. Eggs of Atlantic menha- 

 den were larger and contained more 

 yolk. Their larvae were larger at 

 hatching, and contained more yolk. 

 A suite of developmental events (yolk 

 depletion, age at first feeding, and, 

 possibly, age at metamorphosis) was 

 achieved earlier in Atlantic menha- 

 den. The expression of these early- 

 life-history traits in each species may 

 reflect adaptations to the contrast- 

 ing environments that these species 

 occupy. 



A comparison of early-life-history 

 traits in Atlantic menhaden 

 Brevoortia tyrannus and gulf 

 menhaden B. patronus 



Allyn B. Powell 



Beaufort Laboratory, Southeast Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 Beaufort. North Carolina 28516-9722 



Manuscript accepted 4 November 1992. 

 Fishery Bulletin, U.S. 91:119-128 1 1993). 



Progeny size is a key life-history trait 

 that has evolved in response to the 

 predictability of the reproductive en- 

 vironment (Stearns 1976). The influ- 

 ence of progeny size on early-life- 

 history characteristics has received 

 considerable attention (Blaxter & 

 Hempel 1963; see reviews or sum- 

 maries by Miller et al. 1988, Hinckley 

 1990, Pepin 1991); however, compara- 

 tive early-life-history studies between 

 congeners are sparse and largely re- 

 stricted to salmonids (e.g., Beacham 

 & Murray 1990). A preliminary study 

 suggested differences between early 

 life histories of the Atlantic and gulf 

 menhadens (Powell & Phonlor 1986). 

 Here, a more extended and detailed 

 documentation of differences between 

 these menhadens is provided. 



Atlantic menhaden Brevoortia 

 tyrannus and gulf menhaden B. 

 patronus are morphologically-similar 

 allopatric clupeids. Both are school- 

 ing, filter-feeding clupeids that use 

 estuaries during their first year of 

 life. Individuals of Atlantic menha- 

 den range from Nova Scotia to 

 Florida and thus encounter variable 

 environmental conditions during 

 their lifetime. The distribution of At- 

 lantic menhaden is stratified by age 

 and size, with older and larger fish 

 ranging further north (Nicholson 

 1971). Spawning is protracted and 

 occurs throughout its range, in in- 

 shore waters during summer and 

 early fall in Long Island Sound and 



New England. From Long Island to 

 Chesapeake Bay, spawning occurs off- 

 shore during October-December and 

 March-May (Higham & Nicholson 

 1964). 



Gulf menhaden, in contrast, are re- 

 stricted to the Gulf of Mexico, dis- 

 tributed from Cape Sable, FL to Vera 

 Cruz, Mexico (Reintjes 1969). Spawn- 

 ing occurs October through March in 

 nearshore and offshore coastal wa- 

 ters (Christmas & Waller 1975). 



The specific objective of this study 

 was an interspecific comparison of 

 egg size, yolk volume, and the char- 

 acteristics they may influence: size- 

 at-hatching, first-feeding and meta- 

 morphosis, resistance to starvation, 

 development (yolk and oil depletion, 

 age-at-first-feeding), growth, and 

 mouth size. In addition, for Atlantic 

 menhaden, relationship between egg 

 size and latitude of capture was 

 evaluated. 



Methods and materials 



Spawning and rearing 



Adult gulf menhaden ( 179-201 mmTL) 

 were captured by cast net in 

 Pensacola Bay, FL in the fall of 1983- 

 85 and transported to Beaufort, NC 

 (methods followed Hettler 1983). 

 Adult Atlantic menhaden (204- 

 212 mmTL) were collected from com- 

 mercial purse seines in Core Sound, 



I 19 



