Black drum, continued 



Fecundity : In one study, average fecundity of 451 

 females was 1,090,000 eggs (Cornelius 1984). In 

 Louisiana, the estimated mean annual egg production 

 during three breeding seasons ranged from 31.05 to 

 41.69 million eggs (Nieland and Wilson 1993). Esti- 

 mated annual egg production by a 6.1 kg female could 

 be as high as 32 million eggs (Fitzhugh et al. 1 993), and 

 the maximum observed was 67.33 million in an 1 1 .51 

 kg female (age 19, 855 mm FL) (Nieland and Wilson 

 1 993). Spawning may occur as often as every 3 or 4 

 days during the breeding season, with an average 

 clutch size of 1 .6 million eggs over 20 spawns (Fitzhugh 

 et al. 1 993, Nieland and Wilson 1 993). Batch fecundity 

 increases with age and size, and no evidence of 

 spawning senescence has been observed. 



Growth and Development 



Egg Size and Embryonic Development : Reported egg 

 sizes are from 0.8 to 1 .1 mm in diameter, with a mean 

 of 0.9 mm (Ditty and Shaw 1994). Eggs have been 

 reported to hatch in 24 hours at 20°C (Joseph et al. 

 1964, Johnson 1978, Wang and Kernehan 1979). 



Age and Size of Larvae : Larvae are 1 .9 to 2.4 mm TL 

 at hatching (Joseph et al. 1 964, Johnson 1 978) and are 

 as large as 9.2 mm SL before becoming juveniles 

 (Peters and McMichael 1990). Larval growth rates 

 range from 0.2 mm/day to 0.9 mm/day. 



Age and Size of Adults : In Texas waters, Simmons and 

 Breuer (1 962) reported adults growing to 400-430 mm 

 SL by the end of the third year; beyond that tag returns 

 indicate a growth of 25 to 50 mm/year (Simmons and 

 Breuer 1962, Matlock 1990). There is a sharp de- 

 crease in growth rate at 4-5 years that may reflect a 

 reallocation of energy from growth to reproduction, 

 because black drum mature at approximately this age 

 (Beckman et al. 1990). This is a relatively long-lived 

 species. Based on size, some individuals may live as 

 long as 35 years (Benson 1982), while otolith studies 

 indicate some individuals may live up to 43 years in 

 Louisiana (Beckman et al. 1990) and 58 years in 

 Florida (Murphy and Taylor 1 989). Black drum are the 

 largest sciaenids in the southeastern United States 

 (Peters and McMichael 1 990), and they grow to be the 

 largest members of the family Sciaenidae (Fitzhugh et 

 al. 1 993). The average maximum total length typically 

 reached in Texas appears to be approximately 1 000 to 

 1200 mm (Matlock 1990). The largest recorded adult 

 weighed 66.3 kg (Cave 1 974). The average maximum 

 TL for black drum in the Gulf of Mexico appears to be 

 smallerthan that occurring in the colder waters north of 

 Cape Hatteras. This may be due to zoogeographic 

 variation in black drum population dynamics (Beckman 

 et al. 1 990, Matlock 1 990). Beckman et al. (1 990) have 

 developed Von Bertalanffy growth equations for this 

 species. 



Juvenile Size Range : Transformation to the juvenile 

 stage occurs at a total length of approximately 12 mm 

 (Ditty and Shaw 1 994). By 1 5 mm TL, juveniles attain 

 a general adult body shape (Johnson 1 978). Juveniles 

 growing from 35 to 150 mm SL average 0.9 mm/day, 

 and reach 1 40-1 80 mm standard length (SL) at the end 

 of the first year; 21 0-250 mm SL at 1 .5 years; and 290- 

 330 mm SL in two years (Simmons and Breuer 1962, 

 Peters and McMichael 1990). Ages and sizes at 

 maturity are similar for most U.S. locations with the 

 exception of Texas (Leard et al. 1993). In Texas, 

 studies indicate females reach maturity at 275-320 mm 

 total length (TL) when at the end of their second year 

 (Pearson 1929, Simmons and Breuer 1962). Florida 

 studies found males mature at sizes beginning at 450- 

 499 mm TL at age 4 or 5 years (Murphy and Taylor 

 1 989). Florida females mature when older and slightly 

 longer during their fifth or sixth year and between 650- 

 699 mm TL (Murphy and Taylor 1989). In Louisiana, 

 males and females are first mature at 600-640 mm FL 

 and most are age 5 or older (Fitzhugh et al. 1993, 

 Nieland and Wilson 1993). All males and females 

 studied whose lengths were greater than 640 mm FL 

 and 690 mm respectively were mature. The minimum 

 lengths for mature males and females were 552 mm FL 

 (age 3) and 628 mm FL (age 5), respectively. 



Foods and Feeding 



Trophic Mode : All free swimming life stages are car- 

 nivorous. Larvae feed on zooplankton in the water 

 column, while juveniles and adults are benthic feeders. 

 In shallow depths, their tails will stick out of the water at 

 times (flagging) while they feed in a vertical position 

 (Pearson 1929, Leard et al. 1993). Bottom feeding is 

 aided by the presence of a sensitive chin barbel for 

 finding food, and powerful pharyngeal teeth for crush- 

 ing molluscs and crabs (Simmons and Breuer 1962). 



Food Items : The major food organism groups in order 

 of importanceare molluscs (mostly bivalves), arthropods 

 (mostly decapod crustaceans), annelids, and fish 

 (Dugas 1 986, Leard et al. 1 993). Some sand and plant 

 material have also been found that were probably 

 ingested incidentally while feeding. Larvae feed on 

 zooplankton with copepods being the primary prey 

 item found in stomachs (Peters and McMichael 1 990). 

 The numeric and volumetric importance of copepods 

 declines with increasing fish size. They are rarely 

 found in 30-60 mm black drum and are not evident in 

 any fish >60 mm SL. Juveniles and adults feed on 

 benthic organisms. Small juveniles eat soft foods such 

 as small fish, polychaetes, bivalve siphon tops, and 

 crustaceans (Pearson 1929, Simmons and Breuer 

 1962, Martin 1979, Peters and McMichael 1990). In 

 larger juveniles, bivalve and gastropod molluscs are 



287 



