FISHERY BULLETIN: VOL. 78, NO. 2 



Figure l. — Location of study site and 13 sampling stations in the Peconic Bays, Long Island, N.Y. 



from National Ocean Survey 1971, 1972, 1973) of 

 each collection were recorded. Since Peconic Bay 

 waters are well mixed (Hardy 1976), the surface 

 water temperatures were adequate indicators of 

 temperatures of the water column and the natural 

 incubation temperatures of recently spawned fish 

 eggs (see Discussion section). 



Over the 3-yr period more than 2,600 samples 

 were collected and processed. Plankton samples 

 were split into manageable subsamples and their 

 entire contents were viewed under a stereo- 

 microscope. Fish eggs were separated, identified to 

 species, staged (Table 1), and counted. Devel- 

 opmental stages in Table 1 are approximately 

 equal in duration when fish embryos are reared at 

 constant temperatures (Ferraro 1980). References 

 used for fish egg identification included: Kuntz 

 (1915), Kuntz and Radcliffe (1917), Hildebrand 

 and Cable (1930, 1934), Merriman and Sclar 

 (1952), Wheatland (1956), Richards (1959), Man- 

 sueti and Hardy (1967), Williams (1967), Austin 

 (1973), Berrien (1975), and Colton and Marak^. 



Estimates of time of day of spawning for each 

 species in a sample were determined by estimat- 

 ing the mean age of fish eggs <24 h old using 

 embryo age prediction equations for Atlantic 

 menhaden, Breuoortia tyrannus, in Ferraro 

 (1980), below: 



logioB = -0.193 + 17.193ri + 34.090 T^ 



-461.276 7-3 (1) 



stage 



Table l. — Fish embryo stages of development. 



Description 



1 Fertilized eggs prior to cell division to 8-cell stage 



2 Eight-cell stage to completion of blastodisc formation 



3 Blastodisc formation to germ nng V2 way around egg 



4 Germ ring Vz way around egg to just prior to blastopore closure 



5 Blastopore closure to tail bud beginning to separate from ttie 



yolk 



6 Tail bud free of yolk to caudal '/e of body free of the yolk 



7 Caudal Vs of body free of yolk to caudal 'Ath of body free of 



yolk 



8 Caudal 'Ath of body free of yolk to fin fold moderately wide and 



tail portion of embryo rotated out of embryonic axis and tail 

 approaching head 



9 Tip of tail approaching head to hatching 



and, 



where B = 



T = 



S = 



A = 



A =B (S -1) 



(2) 



development time (hours) per 



stage of development 

 temperature (in degrees Celsius) 

 stage of development (Table 1) 

 mean age (in hours) 



and subtracting these values from the time the 

 samples were collected in the field. (Field data on 

 differences in development stages of embryos from 

 consecutive day classes indicated that the B. 

 tyrannus embryo age equations introduced little 

 or no error when estimating embryo ages of <24 h 

 of most of the species in this study (see Results).) 



RESULTS 



3Colton,J.B.,Jr.,andR.R.Marak. 1969. Guide to identify- 

 ing the common planktonic fish eggs and larvae of Continental 

 Shelf waters. Cape Sable to Block Island. Bur. Commer. Fish. 

 Lab., Woods Hole, Mass., Lab. Ref No. 69-9, 43 p. 



Discrete day classes offish eggs of most species 

 were identified in the field samples. Fish eggs were 

 present in samples at distinct morphological 

 stages of development while other morphological 



456 



