FISHERY BULLETIN: VOL. 75, NO. 3 



TABLE 2. — Abundance estimates of scaled sardine eggs for each 

 cruise. Estimates were obtained using equations (2) and (3) 

 (Houde 1977a) and are not corrected for duration of the egg 

 stage. 



Cruise 



Area represented 



by the cruise 



(m 2 x 10 9 ) 



Positive area 1 

 (m 2 x 10 9 ) 



Cruise 

 egg abundance 

 (eggs x 10'°) 



GE7101 

 8C7113and 



TI7114 

 GE7117 

 8C7120and 



TI7121 

 GE7127, 8B7132 



andTI7l31 

 8B7201 and 



GE7202 

 GE7208 

 GE7210 

 IS7205 

 IS7209 

 IS7303 

 IS7308 

 IS7311 

 IS7313 

 IS7320 

 CL7405 

 CL7412 



25.79 



120.48 

 101.10 



189 43 



72.99 



148.85 



124.88 



48.43 



104.59 



149 80 



14980 



151.42 



156.50 



153.18 



153 89 



52 00 



91.33 



0.77 



18.32 

 7.93 



13.41 



0.00 



0.00 



27.56 



15.60 



4.88 



0.00 



3.05 



43.38 



25.43 



40.79 



0.00 



5.84 



43.45 



0.18 



0.94 

 1.69 



1.57 



0.00 



0.00 

 2.51 



17.10 

 0.00 

 0.00 

 0.00 



21.77 



49 44 



10339 



0.00 



0.00 



45.93 



' Positive area is defined as the area representing stations where either eggs 

 or larvae of scaled sardines were collected. 



Newly fertilized eggs were collected only at night 

 in the Gulf of Mexico surveys and only advanced 

 embryos usually were present from midday to late 

 afternoon. Similar observations were made for 

 scaled sardine eggs collected near Miami and used 

 in laboratory rearing experiments (Houde and 

 Palko 1970; Houde et al. 1974). The estimated 

 peak spawning time is 2200 h. 



Egg abundance was underestimated on most 

 cruises because hatching time was less than 1 day. 

 All cruise abundances were adjusted by dividing 

 them by the estimated mean egg stage duration 

 (Table 3) before annual spawning estimates were 

 made. 



Adjusting Cruise Egg Abundance 

 Estimates for Area 



Some cruises did not completely cover the area 

 within the 30-m depth contour of the eastern Gulf 

 where scaled sardines spawned. Egg abundance 

 estimates for those cruises were adjusted by divid- 

 ing the cruise abundance estimate (Table 2) by 



TABLE 3. — Assigned egg stage durations of scaled sardine eggs 

 for each cruise in which they occurred, 1971-73. 



Cruise 



Egg stage duration 

 (days) 



Egg stage duration 

 Cruise (days) 



an adjustment factor, the proportion of the spawn- 

 ing area represented by the cruise. Egg abundance 

 estimates were adjusted for cruises GE7117, 

 8C7120-TI7121, GE7208, and GE7210. Area ad- 

 justment factors were: GE71 17— 0.394; 8C7120- 

 TI7121— 0.746; GE7208— 0.644; and GE7210— 

 0.574. Cruise IS7205, in which scaled sardine 

 larvae but no eggs were taken, also did not 

 encompass the entire spawning area. Larval 

 abundance estimates were adjusted for that cruise 

 by its area factor, 0.750. Cruise egg abundance 

 estimates from Table 2, after adjustment, were: 

 GE7117— 4.29 x 10 10 ; 8C7120-TI7121— 2.10 x 

 10 10 ; GE7208— 3.90 x 10 10 ; and GE7210— 29.79 

 x 10 10 . 



Annual Spawning and Biomass Estimates 

 Method I 



Estimates of total annual spawning by scaled 

 sardines were obtained after egg stage duration 

 and area factor corrections had been made on 

 daily spawning estimates using the Sette and 

 Ahlstrom ( 1948) method and procedures described 

 by Houde (1977a). They were: 44.106 x 10 11 eggs 

 in 1971, 391.357 x 10 11 eggs in 1972, and 

 1,025.834 x 10 11 eggs in 1973 (Table 4). No esti- 

 mate was obtained in 1974 because the entire 

 season was not surveyed, but the abundance of 

 eggs from cruise CL7412 (Table 2) suggested that 

 annual spawning was high in that year. 



Estimated biomasses increased from 16,708 

 metric tons in 1971 to 148,255 metric tons in 1972, 

 and to 388,610 metric tons in 1973 (Table 4). 

 Variance estimates for each year's spawning 

 (Table 4) were used to place 0.95 confidence inter- 

 vals on biomass estimates. These ranged from to 

 56,210 metric tons in 1971, to 327,130 metric 

 tons in 1972, and 300,965 to 476,271 metric tons 

 in 1973. The mean of the three annual biomass 

 estimates was 184,527 metric tons. The 1972 

 estimate may be unreliable because of poor area 

 coverage and curtailment of cruise GE7210 due 

 to a hurricane, but the low 1971 estimate probably 

 is accurate because area coverage was good on 

 cruises during the peak spawning period. 



A severe red tide in 1971 occurred during spring 

 and summer along the Florida coast of the Gulf of 

 Mexico (Steidinger and Ingle 1972), and it may 

 have caused a high mortality of adult scaled sar- 

 dines. Dead scaled sardines were observed in red 

 tide areas during cruise GE7 1 17. It is also possible 



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