HOUDE: ABUNDANCE AND POTENTIAL YIELD OE SCALED SARDINE 



TABLE 4. — Annual spawning and biomass estimates for scaled sardines from the eastern Gulf of Mexico during 

 1971, 1972, and 1973 spawning seasons. Estimates are based on theSette and Ahlstrom (1948) technique. Details 

 of the estimating procedure are given in Houde (1977a). 



that few adult scaled sardines were killed, but 

 that they did not spawn during red tides or that 

 spawned eggs experienced high mortality. Failure 

 to spawn or unusual egg mortality could have 

 caused biomass to be underestimated in that year. 

 Effects on biomass estimates of area adjust- 

 ments for the four cruises that did not completely 

 cover the scaled sardine spawning area were im- 

 portant. Unadjusted biomass in 1971 was only 

 10,100 metric tons, 60.5% of the adjusted esti- 

 mate; in 1972 it was 85,964 metric tons, 58.0% 

 of the adjusted estimate. 



Method II 



Biomass estimates, using Simpson's (1959) 

 method in a modified form (Houde 1977a), were 

 calculated (Table 5). Mean biomass estimated for 

 the 3 yr was 146,595 metric tons. 



Most Probable Biomass 



Scaled sardines as small as 8.0 cm SL are ma- 

 ture (Martinez and Houde 1975), and estimates 

 of adult biomass from egg and larvae surveys 

 probably include most of the stock, juvenile 

 weights being relatively insignificant. Biomass 

 estimates ranged from 16,000 to nearly 400,000 

 metric tons and stock apparently increased from 

 1971 to 1973. The evidence from cruise CL7412 

 indicated that spawning increased nearer to shore 

 than measured at regular survey stations. This 

 suggests that biomasses were underestimated, 

 perhaps by as much as 30%. If so, then biomass 

 may have ranged from 23,000 to 571,000 metric 

 tons during 1971-73, the mean being 265,000 



TABLE 5. — Annual spawning and biomass estimates for scaled 

 sardines from the eastern Gulf of Mexico during 1971, 1972, 

 and 1973. Estimates are based on the method described by 

 Simpson (1959). 



Year 



Cruise 



Daily spawning Annual spawning 



estimate estimate Adult biomass 



(eggs x 10") (eggs x 10") (metric tons) 



1971 



1972 



1973 



42.981 



1 6,282 



245 940 93.168 



872000 330,334 



metric tons. Despite variability in estimates, it 

 is clear that the eastern Gulf scaled sardine 

 stock was less than 700,000 metric tons between 

 1971 and 1973, and it apparently was less than 

 100,000 metric tons in 1971. 



Comparison of Scaled Sardine Biomass 

 With That of Other Clupeids 



Biomass of scaled sardines in the eastern Gulf 

 of Mexico is similar to that reported for round 

 herring and thread herring (Houde 1977a, b). 

 Mean biomass of round herring was estimated to 

 be approximately 400,000 metric tons, mostly 

 distributed between the 30- and 200-m depth 

 contours, while thread herring mean biomass was 

 about 250,000 metric tons, much of it occurring 

 in the same areas as scaled sardine, although 



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