Atlantic croaker, continued 



Temperature - Juveniles and Adults: The Atlantic 

 croaker has been collected from 0.4° to 35.5°C in the 

 Gulf of Mexico (Miller 1 964, Parker 1 971 , Warren and 

 Sutter 1 982). Juveniles are generally more tolerant of 

 low temperatures (0.4°-38°C) than adults (5°-35.5°C) 

 (Parker 1971, Wagner 1973, Pineda 1975, Rogers 

 1 979, Ward and Armstrong 1 980, Benson 1 982). Pref- 

 erred temperatures for juveniles range from 6° to 20° C, 

 and they grow well between 12.8° and 28.4° C. In 

 Mississippi waters, adults were found in highest num- 

 bers at <30° C (Christmas and Waller 1 973). They are 

 rarely found below 10° C in Texas waters (Parker 

 1971). Lethal minimum and maximum temperatures 

 are 0.6° and 38° C for juveniles and 3.3° and 36° C for 

 adults (Parker 1971, Ward and Armstrong 1980). 



Salinity - Eggs and Larvae: Eggs and larvae are found 

 in euhaline waters. In the Gulf of Mexico, larvae have 

 been found in salinities ranging from 1 5 to 36%o (Cowan 

 1 985, Cowan and Shaw 1 988), but in the Chesapeake 

 Bay area, they are found from <1 to 21 %o (Ward and 

 Armstrong 1980). 



Salinity - Juveniles and Adults: Atlantic croaker are 

 euryhaline, having been collected from to 40%o and 

 rarely at 75%o (Simmons 1 957, Parker 1 971 , Wang and 

 Raney 1 971 , Warren and Sutter 1 982, Darovec 1 983, 

 Lassuy 1983). Juvenile croaker have been taken in 

 salinities of 0.0 to 36.7%o (Miller 1964, Parker 1971, 

 Wagner 1 973, Rogers 1 979). In Texas and Louisiana 

 bays, they have been found to be most abundant at 

 <1 5%o (Gunter 1 945, Wang and Raney 1 971 , Wagner 

 1973, Ward and Armstrong 1980), but they appear to 

 be relatively abundant from 10%o to 20%o in Alabama 

 and Mississippi (Swingle 1971, Etzold and Christmas 

 1979). Juveniles are reportedly more tolerant of low 

 salinities than adults (Gunter 1975). Adults are col- 

 lected in waters with salinities that range from to 70%o 

 (Simmons 1957, Ward and Armstrong 1980). In Mis- 

 sissippi, adults were most abundant in waters with 

 salinities of 15 to 19.9%o (Christmas and Waller 1973, 

 Ward and Armstrong 1980). 



Dissolved Oxygen (DO): Dissolved oxygen (DO) re- 

 quirements are not well known, but the presence of this 

 species in poorly oxygenated canals indicates a toler- 

 ance for low DO (Lassuy 1983). Juveniles are found in 

 waters with a dissolved oxygen content of 5.7 to 8.6 

 parts per million (ppm) (Hoese et al. 1 968). Captures 

 at DO concentrations from 1 through 13 ppm have 

 been reported with most occurring between 8 and 13 

 ppm (Marotz 1984). 



Turbidity: Densities of Atlantic croaker have been 

 noted as more abundant in areas of high waterturbidity 

 possibly as the result of increased food availability and 

 predator protection due to lower visibility (Lassuy 1 983). 



Migrations and Movements : Adults have seasonal 

 inshore and offshore migrations, although some ap- 

 pear to remain in offshore waters (55 to 1 1 8 m) all year 

 (Perry 1970). Adults move up bays and estuaries in 

 spring, randomly in summer, and seaward and south- 

 erly in fall. Larvae are carried by longshore currents 

 into nearshore areas where tidal flow transports them 

 into estuarine areas (Cowan and Shaw 1 988). Larval 

 recruitment into estuaries occurs from October to May, 

 peaking between November and February (Wagner 

 1973, Marotz 1984). As they mature into juveniles, 

 they move up into headwater areas. After spending 6- 

 8 months in the estuary, offshore emigration begins in 

 late March or early April at about 50 mm standard 

 length (SL) or larger and continues until November 

 (Kelley 1 965, Perry 1 970, Wagner 1 973, Yakupzack et 

 al. 1977, Rogers 1979, Marotz 1984). Emigration is 

 probably governed by cues from fluctuations in envi- 

 ronmental conditions in the nursery area (e.g. tides, 

 temperature, salinity, day length, etc.), and is not just a 

 function of fish size (Clairain 1974, Yakupzack et al. 

 1977). 



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 

 development is oviparous. 



Spawning : Spawning in the Gulf of Mexico has been 

 reported from September through May, with a peak in 

 October, specifically around mid-October, and possi- 

 bly November (Sabins and Truesdale 1 974, White and 

 Chittenden 1 976, Allshouse 1 983, Marotz 1 984). Based 

 on the presence of larval croaker in the northern Gulf 

 of Mexico, it can be inferred that spawning occurs 

 September through April, with a peak from October 

 through January (Ditty 1 986, Ditty et al. 1 988). Based 

 on larval growth information, the spawning season off 

 western Louisiana is probably limited to November- 

 January, with very little spawning occurring after Janu- 

 ary (Cowan 1988). Most spawning probably takes 

 place in the nearshore Gulf of Mexico near island 

 passes (Sabins and Truesdale 1974, Lassuy 1983, 

 Sogardetal. 1987). 



Fecundity : Sheridan et al. (1 984) found fecundities for 

 Gulf of Mexico fish ranged from 27,000 eggs for 136 

 mm SL to 1 ,075,000 for a 31 8 mm SL specimen. Fish 

 collected from Cape Hatteras, North Carolina north- 

 ward were reported to have a fecundity range of 

 100,800 to 1,742,000 for fish 196 to 390 mm total 

 length (TL) (Morse 1980). 



Growth and Development 



Egg Size and Embryonic Development : Eggs are spheri- 

 cal, and sizes range from 0.49 to 0.58 mm (Wang and 



279 



