for clupeid species that spawn in South Florida 

 marine waters. 



Developing embryos resembled those described 

 and photographically illustrated by Reintjes 

 (1962). On our preserved specimens, tiny 

 melanophores were present only on the dorsal 

 surface of the developing embryo. The yolk mass 

 was segmented, but this was observed with 

 difficulty in preserved material. No pigment was 

 observed on the yolk sac or oil globule of our 

 preserved eggs. 



Spawning by yellowfin menhaden in Biscayne 

 Bay occurred at least between November and 

 February. Spawning by this species has not been 

 reported previously in Biscayne Bay, but eggs 

 were common during 1971-73. We do not know the 

 time of day at which spawning took place or the 

 total incubation time at 22° to 26°C. Hettler 

 (1970b) collected planktonic eggs of yellowfin 

 menhaden in the Indian River and observed that 

 they spawned at dusk. Reintjes (1962) reported 

 hatching in 46 h at 19°C. Since we have collected 

 embryos only in a single stage of development 

 when temperatures were above 22°C, incubation 

 time might be 24 h or less at these temperatures. 

 Eggs were collected between 0900 and 1400 h; 

 hatching in our aquaria was complete before 

 2400 h. 



Description of Larvae 



Body Shape and Growth 



Larvae were about 3.0 mm SL at hatching. They 

 averaged 4.2 mm SL at 20 h after hatching (Figure 

 2A) when the body axis had straightened. During 

 the first 2 days after hatching they were similar to 

 yellowfin menhaden larvae described by Reintjes 

 (1962). Larvae resemble those of other clupeid 

 fishes. They are elongate, rod-shaped larvae after 

 the yolk has been absorbed. At transformation 

 they become deeper bodied and more laterally 

 compressed. Proportional measurements of larvae 

 in relation to standard length are summarized in 

 Table 4. 



Most larvae did not grow in length from the 1st 

 until the 4th day after hatching at 26°C. Growth 

 was rapid from the 4th until the 10th day (Figure 

 1), averaging about 0.80 mm/day. Growth was 

 slower and more variable on subsequent days, but 

 averaged about 0.45 mm /day from the 4th until 

 the 20th day after hatching. Our 36.2-mm 

 specimen was preserved 102 days after hatching, 



18 



15- 



ol2 



z 



o 



z 

 .< 



in 



3- 



»»*, 



10 



15 



20 25 30 



DAYS AFTER HATCHING 



35 



40 



45 



Figure l.-Growth of laboratory-reared larvae of Brevoartia 



smithi. 



but growth rate of juveniles was almost certainly 

 lower than might be expected under better feed- 

 ing conditions because we did not maintain a 

 careful feeding schedule after larvae transformed 

 to the juvenile stage. Several juveniles from 50 to 

 60 mm were preserved when the experiments were 

 terminated at 235 days after hatching. At 20°C, 

 Hettler (1970a) reported growth rates of about 

 0.27 mm /day for yellowfin menhaden larvae that 

 he reared for 27 days. The four smallest larvae that 

 we preserved on the 4th and 5th days after 

 hatching were smaller than larvae preserved on 

 previous days (Figure 1). It is probable that those 

 larvae had not begun to feed and that they were 

 starving at the time of preservation. 



Yolk Absorption and Gut Differentiation 



The yolk sac is broadly ellipsoid in newly 

 hatched larvae with the oil globule located ven- 

 trally and just posterior to the middle of the yolk 

 mass (Figure 2A; see also Reintjes 1962). The yolk 

 was nearly absorbed in specimens preserved 1 day 

 after hatching (Figure 2B). All visible yolk 

 remains, including the oil globule, had disappeared 

 by 60 h after hatching at 26°C. Many larvae were 

 observed to begin feeding before all of the yolk 

 had been absorbed. At that time the gut was a 

 straight tube, but within 24 h (at about 5.0 to 5.5 

 mm SL) it had developed into distinct fore and 

 hind sections, the latter characterized by the 

 bands of muscle common to all clupeid larvae. 



Preanus Length 



Preanus length averaged 82 to 84% SL from 

 hatching until larvae were 15.0 mm SL (Table 4). 



664 



