N = 226 

 STANDARD LENGTH=24MM. 



Menhaden Biology- 

 James Y. Christmas, Jr. 

 Gulf Coast Research Laboratory, Dr, Gordon Gunter, Director 

 (Contract No. 14-19-008-9335) 



Field work during the year was linaited to (1) the collection of Gulf 

 menhaden, Brevoortia patronus, juveniles throughout the summer months 

 and adults during the spawning season; and (2) the observation of larval and 

 postlarval movement patterns in the Mississippi area. A few sinall menhaden 

 were caught in plankton samples late in November. Specimens were found in 

 Mississippi Sound in December. Although greater numbers of individuals 

 were tciken in January, schools of postlarval menhaden were not evident in 

 Mississippi estuaries until late February. 



Life history studies Reduc- 



tion of plankton samples yielded 

 106 vials of fish larvae thought 

 to be menhaden and approxi- 

 mately 110 samples of fish eggs. 

 Although spawning menhaden 

 have not been observed, their 

 eggs have been tentatively iden- 

 tified by comparison with eggs 

 from nearly mature ovaries. 

 Round eggs in various stages of 

 development found in plankton 

 tows and thought to be menhaden 

 eggs have a diameter of approxi- 

 mately 1.2 mm. The yolk sphere 

 is 0.8-0.9 mm. in diameter and 

 contains a single oil globule 0.13- 

 0. 15 mm. across. The egg mem- 

 brane is very thin and clear. Em- 

 bryos with 12-14 somites extend 

 about two-thirds of the distance 

 around the yolk sphere. Num- 

 erous small black- chromato- 

 phores are evident along the 

 dorsal surface and extend lat- 

 erally in the anterior region of 

 embryos that have reached a 

 length of 2. 3-2. 4 mm. 

 Morphometric characters of approximately 2, 300 young menhaden 

 in the transformation stage were measured. These specimens were taken from 

 samples obtained in 1958, 1959, and I960. Using material from the 1958 sam- 

 ples, the accompanying figure illustrates the changing body depth- standard 

 length ratio as the species progresses through this stage. 



Additional information concerning time and length of spa-wning, growth, 

 seasonal movements, natural enemies, and parasites is being incorporated into 

 a final report on menhaden life history. 



Jl 



J 



Body depth as percent of standard length, 

 to show change in body proportions of the 

 Gulf menhaden during transition from 

 postlarval to juvenile stages. 



33 



