FISHERY BULLETIN: VOL. 75. NO. 3 



many thread herring also occurred farther off- 

 shore (Houde 1977b). In aggregate the three spe- 

 cies totalled approximately 850,000 metric tons. 

 The menhaden (Breuoortia spp.) resource appar- 

 ently is small in the survey area, since relatively 

 few eggs and larvae were collected (Houde et al. 

 1976). No estimate of Spanish sardine {Sardinella 

 spp.) biomass was obtained, but its eggs and lar- 

 vae were abundant (Houde et al. 1976). Its bio- 

 mass may be as great as that for thread herring, 

 i.e., 250,000 metric tons. If true, then aggregate 

 adult biomass of unfished clupeids exceeds 1 mil- 

 lion metric tons. The contention that large poten- 

 tial fisheries exist in the eastern Gulf of Mexico 

 is supported by the estimated biomasses. How- 

 ever, none of the individual species appears to 

 represent a resource as large as that of Gulf men- 

 haden, B. patronus, which presently yields about 

 500,000 metric tons annually to the northern Gulf 

 fishery. 



TABLE 6. — Range of potential yield estimates for eastern Gulf of 

 Mexico scaled sardines, based on biomass estimates in 1971, 

 1972, and 1973 by the Sette and Ahlstrom ( 1948) method. Yields 

 are predicted at three possible values of M, the natural mor- 

 tality coefficient. Biomass estimates were obtained from values 

 in Table 4. 



194,305 metric tons (Table 6). Based on mean bio- 

 mass estimates for 1971-73, potential yield was 

 between 46,132 and 92,264 metric tons. If scaled 

 sardines were evenly distributed over the 

 60 x 10 9 m 2 where they occur in the eastern Gulf, 

 harvestable annual yield, based on 1971-73 

 mean biomass, is 7.7 to 15.4 kg/ha. 



Concentration of Biomass 



Scaled sardine eggs and larvae occurred in most 

 of the 76 x 10 9 m 2 area between the coast and 

 30-m depth contour, except for approximately 15 

 to 20 x 10 9 m 2 in the northeastern part of the 

 survey area (Figure 1-). During the spawning 

 season, adult scaled sardines were assumed to 

 occur in 60 x 10 9 m 2 of the eastern Gulf. Concen- 

 tration of biomass, assuming an even distribution, 

 based on the annual biomass estimates from 

 Method I (Table 4) and their 0.95 confidence limits 

 were: 1971, to 9.4 kg/ha; 1972, to 54.5 kg/ha; 

 and 1973, 50.2 to 79.4 kg/ha. Mean biomass con- 

 centrations were: 1971, 2.8 kg/ha; 1972, 24.7 kg/ 

 ha; and 1973, 64.8 kg/ha. Estimated scaled sar- 

 dine biomasses under a hectare of sea surface are 

 similar to those of thread herring but less than 

 those of round herring (Houde 1977a, b). 



Potential Yield to a Fishery 



Estimates of annual yield varied greatly from 

 year to year, reflecting the biomass fluctuations 

 (Table 6). The estimator C max = XMB Q was used 

 to predict potential maximum sustainable yield 

 (Alverson and Pereyra 1969; Gulland 1971, 1972). 

 X is assumed to equal 0.5 and B is the virgin 

 biomass. M, the natural mortality coefficient, 

 was allowed to vary from 0.5 to 1.0, values that 

 are probable for scaled sardines. The range of 

 potential yields over the 3-yr period was 4,177 to 



Comparison of Potential Yield With 

 That of Other Clupeids 



Potential yield of scaled sardines is slightly less 

 than that estimated for thread herring and less 

 than that for round herring (Houde 1977a, b). 

 Using mean annual biomass estimates by Method 

 I, and the value 1.0 for M, potential maximum 

 sustainable yields are: scaled sardines — 92,264 

 metric tons; thread herring — 120,598 metric tons; 

 and round herring — 212,238 metric tons. Total 

 potential for the three species is 425,100 metric 

 tons. If Spanish sardines are as abundant as 

 thread herring, they could contribute another 

 120,000 metric tons raising the aggregate poten- 

 tial yield to 545,100 metric tons. 



Potential yields were estimated for adult stock. 

 If a significant biomass of harvestable juveniles 

 is present, they could contribute to the yield. For 

 scaled sardines, and probably round herring 

 (Houde 1977a), small size at first maturity makes 

 it unlikely that a significant, unestimated juve- 

 nile biomass is present, but the large size at first 

 maturity of thread herring (Prest 3 ) and Spanish 

 sardines (Varea Rivero 1967) indicates that a 

 significant unestimated biomass of juveniles may 

 be present. 



3 Prest, K. W., Jr. 1971. Fundamentals of sexual maturation, 

 spawning, and fecundity of thread herring {Opisthonema 

 oglinum ) in the eastern Gulf of Mexico. Unpubl. manuscr., Natl. 

 Mar. Fish. Serv., NOAA, St. Petersburg Beach, Fla. 



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