EMBRYONIC DEVELOPMENT OF ATLANTIC MENHADEN, BREVOORTIA 

 TYRANNUS. AND A FISH EMBRYO AGE ESTIMATION METHOD 



Steven P. P^rraro* 



ABSTRACT 



Eggs of Atlantic menhaden, Brevoortia tyrannus, were artificially fertilized and embryos were reared 

 in the laboratory at 12 temperature-salinity combinations (temperature: 10', 15", 20", and 25" C; 

 salinity: 10, 20, 30%o). Salinity between 10 and 30%o had no significant effect on embryonic mortality 

 and no noticeable efTect on rate of development. Temperature had a significant effect on embryonic 

 mortality and rate of development. Embryonic mortality was significantly greater at 10° C than at 15°, 

 20°, and 25 " C, and significantly greater before than aft«r blastopore closure at 15°, 20°, and 25° C. The 

 temperature coefficient for embryonic development of B. tyrannus from fertilization to hatching at 

 temperatures between 10° and 25° C is 3.89, 



Age of S. tyrannus embryos can be estimated by the regression of age on developmental stages when 

 incubated at constant temperature. 



The Atlantic menhaden, Brevoortia tyrannus, is 

 an important commerical and forage fish of the 

 east coast of North America (geographic range: 

 lat. 27°-46° N). Atlantic menhaden spawn in Con- 

 tinental Shelf waters and in bays and estuaries in 

 the northern part of its range during a northward 

 spring and southward fall-winter migration 

 (Reintjes 1961, 1969; Higham and Nicholson 1964; 

 Kendall and Reintjes 1975; Chapoton^). Brevoor- 

 tia tyrannus embryos were first described by 

 Kuntz and Radcliffe ( 1917), and B. tyrannus em- 

 bryos captured at sea have been reared in the 

 laboratory by Reintjes (1968) and Hettler (1970), 

 but rearing conditions were not well controlled 

 and details on development were not published. 

 Rapid growth and low natural survival charac- 

 terize the early life history of many marine fishes. 

 Presented in this paper are results of a laboratory 

 experiment to determine effects of temperatures 

 between 10° and 25" C and salinities between 10 

 and 30'Kio on survival and development rates of 

 B. tyrannus embryos. Also presented is a useful 

 method for estimating fish embryo age from em- 

 pirical relations between embryo age, stage of de- 

 velopment, and temperature. This fish embryo age 

 estimation method is simple and has broader prac- 

 tical applications than other methods. It was de- 



'Department of Ecology and Evolution. State University of 

 New York at Stony Brook, Stony Brook, NY 11794. 



^R. B. Chapoton. 1972 On the distribution of Atlantic 

 menhaden eggs, larvae, and adults. Unpubl. manuscr.. 69 p. 

 Atlantic Estuarine Fisheries Center, National Marine Fisheries 

 Service, NOAA, Beaufort, NC 28516. 



veloped for use in ichthyoplankton research to 

 identify cohorts, construct embryonic stage life 

 tables, and back calculate the time of day of 

 spawning. 



MATERIALS AND METHODS 



Adult Atlantic menhaden were captured by gill 

 nets off the Shoreham Power Plant, Long Island, 

 N.Y., at 2300 h on 14 June 1973 (lat. 40°58' N, 

 long. 72°52' W; water temperature 20.5" C; sahn- 

 ity 23.5"/oo). Eggs from a sexually mature female B. 

 tyrannus were artificially fertilized on shipboard 

 with milt from five adult males. Fertilized eggs 

 were carried in four 1 1 glass jars in an insulated 

 box to the laboratory at the Marine Sciences Re- 

 search Center, State University of New York at 

 Stony Brook, N.Y. 



Laboratory rearing experiments were two- 

 factor, 4x3 (temperature x salinity) factorial 

 designs with two replicates per treatment. 

 Twenty-five embryos were transferred to each cul- 

 ture dish containing 85 ml water with salinities 

 10, 20, or 30%o, and temperature 20° C. Distilled 

 water or artificial sea salts were added to filtered 

 seawater to produce the desired salinities, and 

 loose fitting plastic covers on the culture dishes 

 reduced evaporation. Culture dishes with embryos 

 were placed in thermostatically controlled con- 

 stant temperature Hotpoint (#535)^ incubators 



•^Reference to trade names does not imply endorsement by the 

 State University of New York at Stony Brook, or the National 

 Marine Fisheries Service. NOAA. 



Manuscript accepted Mav 1979. 



FISHERY BULLETIN VOL 77, NO 4.1980 



943 



