Red drum, continued 



salinity (Yokel 1 966, Crocker et al. 1 983). Both groups 

 have been collected trom salinities ranging from to 

 45% , but only rarely at 50%o or above (Gunter 1945, 

 Simmons 1957, Simmons and Breuer 1962, Yokel 

 1 966, Franks 1 970, Perret et al. 1 971 , Christmas and 

 Waller 1973, Juneau 1975, Tarver and Savoie 1976, 

 Bonin 1 977, Swift et al. 1 977, Barret et al. 1 978, Ward 

 and Armstrong 1 980, Perret et al. 1 980, Crocker et al. 

 1981, Holt et al. 1981a, Daniels and Robinson 1986, 

 Loftus and Kushlan 1 987, Peters and McMichael 1 987). 

 Juveniles and adults appear to prefer salinities from 20 

 to 40%o with maximum growth for juveniles occurring at 

 35%o (Bonin 1977, Perret et al. 1980, Ward and 

 Armstrong 1 980, Crocker et al. 1 981 , Holt et al. 1 981 a, 

 Benson 1982, Peterson 1986). One report found the 

 greatest abundance of small juveniles (1 7-58 mm total 

 length (TL)) in salinities below 15%o (Gunter 1945). 

 Captive juveniles survived best at salinities of 1 .3%o or 

 greater (Miranda and Sonski 1985). 



Dissolved Oxygen: Fry can not survive low dissolved 

 oxygen (DO) concentrations of 0.6 to 1.8 parts per 

 million (ppm) (Overstreet 1983). Large juveniles have 

 been reported in waters with oxygen concentrations of 

 5.2 and 8.4 ppm (Barret et al. 1978). 



Other: The maximum ammonia (NH 3 ) concentration 

 allowing normal growth of larvae is 0.1 1 mg/l, but older 

 fish are able to tolerate higher concentrations (Holt and 

 Arnold 1983). 



Movements and Migrations : The red drum is relatively 

 non-migratory with no major coastwise movements, 

 but does have broad random movements, loosely 

 coordinated temperature induced migrations, and 

 strong offshore or deep water spawning migrations 

 (Simmons and Breuer 1962, Moe 1972, Adkins et al. 

 1979, Perret et al. 1980, Ward and Armstrong 1980, 

 Osburn et al. 1 982). Larger fish (>750 mm) appear to 

 move greater distances than smaller fish (Bryant et al. 

 1989). Tagging studies have shown little intra-bay 

 movement or bay-Gulf travel except, perhaps, for short 

 periods, and a few infrequent individuals with some 

 extensive movement (Simmons and Breuer 1962, 

 Beaumariage 1 969, Pafford 1 981 , Osburn et al. 1 982, 

 Bryant et al. 1989). These studies also indicated that 

 fish tagged in the Gulf of Mexico tended to stay there 

 (Simmons and Hoese 1959, Simmons and Breuer 

 1 962). Eggs, larvae, and early juveniles are carried by 

 tides and currents in late fall into the shallow estuaries 

 and bays with peaks occurring in October. Larvae tend 

 to move through barrier island passes in mid-channel 

 surface waters with the tidal current (King 1 971 , Bass 

 and Avault 1 975, Holt et al. 1 981 a, Benson 1 982). Fish 

 move from bay shores farther into the estuary to quiet 

 back water areas as they grow, eventually occupying 

 secondary bays considerable distances from their origi- 



nal point of entry (Yokel 1 966, Perret et al. 1 980, Peters 

 and McMichael 1987). Young drum will leave these 

 shallow areas when about 40 to 1 20 mm TL and move 

 into primary bays and somewhat deeper waters (>1 .8 

 m). This movement may be accelerated by cold 

 temperatures (Pearson 1928, Yokel 1966, Osburn et 

 al. 1982, Peters and McMichael 1987). Movement of 

 sub-adults (<3 years) in bays appears limited with 

 schools remaining in a single locale for several months 

 (Osburn et al. 1 982). Most of their movements appar- 

 ently consist of responses to temperature and salinity, 

 and foraging which can be considerable even if these 

 fish remain within a small general area (Pafford 1981, 

 Overstreet 1983). As juveniles approach 200 mm TL 

 during their first spring, they may remain in deep water 

 areas of bays or congregate near passes usually in 

 large aggregations (Simmons and Hoese 1 959, Peters 

 and McMichael 1987). Sub-adults may remain in the 

 bays throughout the year, but older fish (>2) move into 

 the open Gulf in fall and winter, and possibly during late 

 summer (Perry 1970, Perret et al. 1980, Hein and 

 Shepard 1 986a, Matlock 1 987, Beckman et al. 1 988). 

 This seasonal movement is a general, gradual one with 

 fish disappearing offshore presumably to spawn 

 (Pearson 1928, Benson 1982). Class I juveniles leav- 

 ing bay systems in the fall probably reenter with older 

 juveniles the following spring in a more contracted 

 migration (Pearson 1928, Ward and Armstrong 1980, 

 Benson 1982). Migrating fish may use salinity gradi- 

 ents as predictive cues for directed movements from 

 estuarine to oceanic habitats and back (Owens et al. 

 1 982). Results from recent studies suggest large fish 

 in offshore waters may have a more extensive migra- 

 tion over time than was previously thought. These 

 movements may be due to the abundance of specific 

 food items, causing the red drum to continually migrate 

 in a relatively consistent pattern in order to optimize 

 feeding in specific rich and different areas on a sea- 

 sonal basis (Overstreet and Heard 1 978, Pafford 1 981 , 

 Overstreet 1983). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe into the water column, and 

 egg development is oviparous. Mature adults probably 

 form spawning aggregations (Johnson and Funicelli 

 1991). Red drum are multiple batch spawnwers, with 

 group-synchronous oocyte maturation (Wilson and 

 Nieland 1994). 



Spawning : The spawning season typically lasts from 

 summer through early winter, but its onset and duration 

 vary with photoperiod, water temperature, and possi- 

 bly other factors (Holt et al. 1981a, Overstreet 1983). 

 Spawning can start as early as August in some parts of 

 the study area, but it usually begins in September and 



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