YELLOWTAIL FLOUNDER OFF NEW ENGLAND 



217 



100 



29 30 31 32 33 34 35 36 37 38 39 40 

 LENGTH -CENTIMETERS 



Figure 23. — Relation of length to percent mature of 

 female yellowtail. 



Table 40. — Percentage of spent female yellowtail sampled 

 from the southern New England stock during the 1943 

 spawning season 



1 Included some unusually small samples. 

 100 r 



-APRIL- 



FIGURE 24. — Relation of date to percent spent in female 

 yellowtail from the southern New England stock in 

 1943. 



developed: (1) Ninety percent of the yellowtail 

 spawned between April 12 and June 26; (2) the 

 peak of spawning (the point of greater slope on a 

 sigmoid curve) and the day on which half of the 

 yellowtail spawned was May 20; (3) the period of 



heaviest spawning was from May 4 to June 4 dur- 

 ing which 50 percent of the females became spent. 



Distribution of Eggs and Larvae 



Because the yellowtail shares with the mackerel 

 the habit of spring spawning in the area between 

 Cape Cod and Chesapeake Bay as well as the 

 feature of pelagic eggs and larvae, we benefited 

 from the mackerel investigations conducted by 

 O. E. Sette (1943). The field work, from 1925 

 through 1932, included quantitative surveys of the 

 distribution of mackerel eggs and larvae, and on 

 these cruises large quantities of yellowtail eggs 

 and larvae were taken in the plankton nets. Sette 

 recalls that year after year the yellowtail seemed 

 to be one of the most abundant spring spawners 

 in the area. Quantitative data on yellowtail eggs 

 and larvae from two cruises in April and May 

 1929 and on larvae only from a series of cruises in 

 1932 are available for analysis. In both years, a 

 series of stations was established along section 

 lines across the Continental Shelf. The lines were 

 named after the nearest land feature and the sta- 

 tions were consecutively numbered seaward on 

 each line from I (fig. 25). 



Our task was eased by several reports that have 

 appeared. The 1932 survey, the only one to cover 

 adequately the range and spawning period of the 

 mackerel (Sette 1943), included estimates of the 

 mortality rates of the mackerel eggs and larvae 

 and of the total number of eggs spawned. Other 

 findings have been included in reports on the cycle 

 of temperature by Bigelow ( 1933 ) , the salinity by 

 Bigelow and Sears (1935), and a volumetric study 

 of the zooplankton by Bigelow and Sears (1939). 

 A detailed account of methods used in the 1932 

 survey is given in Sette (1943) and the complete 

 temperature and salinity observations for all 

 years are reported by Bigelow (1933). 



From our knowledge of the yellowtail spawn- 

 ing season, it appears that the period of the 

 mackerel surveys, May 2 to July 24, 1932, covered 

 the major part of the yellowtail spawning season 

 (p. 217) . Ninety percent of the yellowtail spawn- 

 ing off New Bedford in 1943 occurred between 

 April 12 and June 26, but eggs have been taken 

 from mid-March to September in various places 

 (see p. 216). We would expect spawning to occur 

 a little earlier in the warmer waters off New Jer- 

 sey and a little later in the colder waters of the 

 Gulf of Maine, north of Cape Cod. 



