Black drum, continued 



Habitat 



Ty pe: Eggs are marine to estuarine. Larvae are 

 marine, occurring over the inner continental shelf 

 (Cowan 1985, Peters and McMichael 1990), to estua- 

 rine. Juveniles are marine to riverine. Adults are 

 marine to estuarine occurring primarily in inshore neretic 

 waters just outside the ocean littoral zone and in 

 estuaries (Richards 1 973). Juveniles and young adults 

 prefer estuarine habitats, but older adults (>4 yrs.) 

 move to nearshore Gulf waters (Sutter et al.1986, 

 Leardetal. 1993). 



Substrate : Black drum juveniles prefer unvegetated 

 muddy bottoms in marsh habitats. Adults are found 

 over unvegetated sand, mud and oyster/worm reefs 

 (Pearson 1929, Mok and Gilmore 1983, Cornelius 

 1 984, Peters and McMichael 1 990). Adult black drum 

 have been collected over heavily vegetated seagrass 

 beds during summer fish kill events in Florida Bay 

 (Schmidt 1993). 



Physical/Chemical Characteristics : 

 Temperature - Eggs and Larvae: Eggs and larvae 

 successfully develop at 1 8° to 20°C (Garza et al. 1 978, 

 Johnson 1 978). Larvae have been collected at over a 

 temperature range of 1 1 ° to 22°C (Cowan 1 985, Peters 

 and McMichael 1990). 



Temperature - Juveniles and Adults: Adults and juve- 

 niles are eurythermal. They have been found in water 

 temperatures ranging from 3° to 35°C (Wang and 

 Raney 1971, Mcllwain 1978). Sharp decreases in 

 water temperature cause movements to deeper water, 

 and mass mortalities result when conditions remain 

 adverse for long periods of time (Cowan 1985). 



Salinity - Eggs and Larvae: Laboratory spawned eggs 

 hatched successfully at 8.8 to 34.0%o, with highest 

 survival occurring at 23 to 34%o (Garza et al. 1978). 

 Larvae have been collected at to 36%o (Cowan 1 985, 

 Peters and McMichael 1990). 



Salinity - Juveniles and Adults: Adults and juveniles are 

 euryhaline (Gunter 1942, Gunter 1956). They are 

 found from to 80% o and are common at 9 to 26%o 

 (Simmons and Breuer 1 962, Mcllwain 1 978). In hyper- 

 saline waters at the upper end of this salinity range,'f ish 

 can be blinded and have body lesions (Simmons and 

 Breurer 1962). In Florida, juveniles 16 to 90 mm SL 

 occur most often in low to moderate salinities while 

 large juveniles are mainly found in moderate to high 

 salinities (Peters and McMichael 1990). 



Migrations and Movements 



Larvae and small young move into upper estuarine 

 areas and tidal creeks to low salinity nursery areas 

 during flood tides (Wang and Kernehan 1979). Juve- 



niles move out of creeks and secondary bays at about 

 100 mm SL (Peters and McMichael 1990). As they 

 reach 1 50-200 mm SL they move into the open waters 

 of river mouths, bays, passes, and the nearshore Gulf. 

 Mature individuals often remain in bays until nearly ripe 

 before migrating to passes to spawn. After spawning, 

 they quickly return to their preferred bay habitat 

 (Simmons and Breuer 1 962). In fish less than 4 years 

 old, there is little interbay and bay-Gulf movement 

 throughout the year (Osburn and Matlock 1 984). There 

 is little intra-bay movement except for the spawning 

 migration, and during adverse conditions such as 

 temperature extremes and/or insufficient food. Black 

 drum move constantly in their search for food, and 

 these movements within a bay system can be consid- 

 erable if food is not abundant (Simmons and Breuer 

 1962, Osburn and Matlock 1984, Bryant et al. 1989). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Mature adults are known to 

 form spawning aggregations. Fertilization is external, 

 by broadcast of milt and roe into the water column. 

 Development is oviparous. 



Spawning : Black drum exhibit group-synchronous 

 maturation of oocytes and multiple, or batch spawning 

 (Peters and McMichael 1990, Nieland and Wilson 

 1993). Mature fish spawn near passes, in open bays 

 and channels, and nearshore waters of the northern 

 Gulf of Mexico (Simmons and Breuer 1962, Mok and 

 Gilmore 1983, Peters and McMichael 1990, Fitzhugh 

 et al. 1993, Ditty pers. comm.). Depth of spawning 

 appears to be around 20 to 27 m (Ross et al. 1983, 

 Cody et al. 1 985). Ripe individuals are usually present 

 from November until May. Peak spawning occurs from 

 January to mid-April with a secondary peak sometimes 

 reported in Texas during early fall (Pearson 1929, 

 Simmons and Breuer 1 962, Allshouse 1 983, Cornelius 

 1 984, Murphy and Taylor 1 989, Peters and McMichael 

 1990, Nieland and Wilson 1993). Saucier and Baltz 

 (1993) reported that black drum form "drumming" ag- 

 gregations in estuarine waters of Louisiana from 

 January to April, at salinities from 10 to 27%o, and 

 temperatures from 1 5 to 24°C, from 6pm to 1 0pm, and 

 that spawning sites were primarily located in deep, 

 moving water in passes between barrier islands. Based 

 on the presence of larval black drum in the northern 

 Gulf of Mexico, it can be inferred that spawning occurs 

 December through May, with a peak from February 

 through April (Ditty etal. 1988). Spawning peaks occur 

 during the period of rising water temperatures in the 

 spring (Peters and McMichael 1990). Tides may also 

 influence the amount of spawning activity or successful 

 recruitment. Laboratory spawning has been achieved 

 at 21 °C and 28-31 % (Garza et al. 1977). 



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