HOUDE: ABUNDANCE AND POTENTIAL YIELD OF ROUND HERRING 



TEMPERATURE 



SALINITY 



FIGURE 7. — Percent cumulative frequency dis- 

 tribution of 1971-74 stations where round her- 

 ring eggs occurred in relation to surface tem- 

 peratures (A) and to surface salinity (C), and 

 =£5.0-mm SL larvae occurred in relation 

 to surface temperature (B) and surface salinity 

 (D). 



100 



90 



80 



70- 



60- 



50- 



>- 40 

 U 



" 50 



^ 100 



X 



3 9 ° 



* 80 



£ 70 

 Q. 



60 - 



50- 



40- 



30 



20 



10 



Etrumeus teres 

 eggs 



Etrumeus teres 

 larvae -5mm 



-T 1 r- 



Etrumeus teres 

 larvae '5mm 



100 



'-•') 



80 



70 



t'i 

 50 

 40 



SO 

 20 



10 



IB I 



34 51- 35 01- 35 51- 3601- 



34 75 35 25 35 75 36 25 



SALINITY CLASS (%.) 



36 51- 

 36 75 



73, 94.7% of the egg occurrences were in that salin- 

 ity range. There were seven egg occurrences at 

 less than 35.50%o surface salinity on cruise IS 

 7320 (November 1973). This cruise influenced the 

 cumulative frequency distribution of egg occur- 

 rences in relation to salinity (Figure 7) over all 

 years. Data for the entire 1973-74 spawning sea- 

 son were not available to compare occurrence of 

 eggs in relation to salinity with 1971-72 and 

 1972-73 data; but, the frequency distribution ap- 

 parently would have been shifted to lower 

 salinities in that year, reflecting low surface 

 salinities that prevailed in the eastern Gulf in fall 

 1973. 



Egg and Larvae Abundance in 

 Relation to Zooplankton 



There was no apparent relationship between 

 zooplankton volumes and round herring egg or 

 larvae abundance. Zooplankton volumes (cubic 

 centimeters/1,000 m 3 strained) were determined 

 at each station for cruises in 1972 through 1974. 

 Round herring egg abundance and larvae abun- 

 dance were examined in relation to zooplankton 

 volume for stations included in those cruises but 

 the correlations were not significant. 



Fecundity and Maturity 



A total of 71 adult round herring was examined, 



of which 39 were males and 32 were females. 

 Based on this sample, the sex ratio did not differ 

 significantly from 1:1 (x 2 = 0.69; 0.25<P<0.50). 

 Sixty-five specimens, from 93 to 165 mm SL, were 

 collected in the Gulf of Mexico in August and 

 November 1974. The 59 specimens more than 100 

 mm SL were maturing or near ripe. Six additional 

 females, from 157 to 160 mm SL, that were col- 

 lected in June 1973 off the east coast of Florida 

 (lat. 30°20'N) were examined. Those six specimens 

 were spent, the ovaries containing only small, 

 clear, nucleated oocytes. 



Ripening females usually have two modes of 

 yolked oocytes (but occasionally only one), which 

 apparently are both spawned during a single 

 spawning season. Planktonic eggs were collected 

 only from November through May. The spawning 

 season extends from approximately 15 October to 

 31 May in the eastern Gulf of Mexico. 



The fecundities of eight near-ripe females, 130- 

 165 mm SL, were estimated, based on yolked oo- 

 cytes present in ovaries (Table 3). Fecundities 

 ranged from 7,446 to 19,699 and increased with 

 size of the females. Relative fecundity (ova per 

 gram body weight) ranged from 150 to 428 ova/g, 

 the mean being 296.5 ova/g (S* = 33.7 ova/g). 

 There was no apparent relationship between rela- 

 tive fecundity and either length or weight of 

 females. The mean relative fecundity estimate, 

 296.5 ova/g, was used in subsequent adult biomass 

 determinations. If all yolked oocytes were not 



75 



