Crevalle jack, continued 



Temperature - Juveniles and Adults: Juveniles and 

 adults have been collected over a temperature range 

 of 1 5.0 to 38.0°C (Gunter 1 945, Gunter and Hall 1 963, 

 Franks 1 970, Roessler 1 970, Perret et al. 1 971 , Wang 

 and Raney 1971, Christmas and Waller 1973, Perret 

 and Caillouet 1974, Juneau 1975, Tarver and Savoie 

 1 976, Barret et al. 1 978). The lower lethal temperature 

 limit for juveniles is around 7.4-1 0.0°C (Hoff 1971, 

 Gilmore et al. 1978). Their apparent preference is 

 25.0-29.9°C (Perret et al. 1971). Adults are most 

 common in temperatures of 18 to 33.6°C (Gunter 

 1945, Johnson 1978). 



Salinity - Larvae: Larvae have been recorded in salini- 

 ties of 35.2 to 36.7%o (Johnson 1978). 



Salinity - Juveniles and Adults: Both adults and juve- 

 niles are considered euryhaline and have been found 

 in waters with salinities ranging from 0.0 to 60.0%o 

 (Gunter 1 942, Gunter 1 945, Reid 1 955, Gunter 1 956, 

 Simmons 1 957, Gunter and Hall 1 963, Gunter and Hall 

 1 965, Dugas 1 970, Franks 1 970, Roessler 1 970, Perret 

 et al. 1971, Swingle 1971, Wang and Raney 1971, 

 Dahlberg 1972, Christmas and Waller 1973, Perret 

 and Caillouet 1974, Swingle and Bland 1974, Juneau 

 1 975, Tarver and Savoie 1 976, Barrett et al. 1 978). In 

 one study, fish 30 to 285 mm in total length (TL) were 

 mostly caught in salinities above 30.0%o (Gunter 1 945). 

 In another study, the majority of fish ranging from 20 to 

 180 mm TL with an average size of 60 mm TL were 

 collected from 1 0.0 to 1 9.9%, (Perret et al. 1 971 ). 



Dissolved Oxygen: Juveniles have been collected in 

 waters with a dissolved oxygen (DO) range of 4.0 to 7.5 

 parts per million (ppm) (Barrett et al. 1978). 



Movements and Migrations : Little is known about move- 

 ments and migrations of this species, but they probably 

 involve a complex pattern of spawning and develop- 

 mental migrations, and temperature induced move- 

 ments. Adults migrate offshore to spawn, but a con- 

 certed migration is improbable due to the extended 

 spawning season (Gunter 1945, Berry 1959, Moe 

 1972, Johnson 1978, NOAA 1985). Larvae are asso- 

 ciated with the northern movements of the Gulf Stream 

 (Berry 1959). Early juveniles, 21-55 mm standard 

 length (SL), migrate inshore. Juveniles enter bays and 

 estuaries from the Gulf when the water temperature is 

 above 20.0°C, and they have reached 90 to 285 mm TL 

 in size (Gunter 1945, Benson 1982). They probably 

 migrate south or move into warmer, offshore waters 

 during colder months (Berry 1959). In Florida, the 

 crevalle jack has been observed in shallow water at all 

 times of the year except during winter months (Reid 

 1 954). Juveniles and adults have been recorded along 

 the Atlantic coast and in the Gulf of Mexico from April 

 through November. However, they are most common 



in coastal waters of the Gulf from June to October 

 (Joseph 1 952, Joseph and Yerger 1 956, Bass and Hitt 

 1978). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe. 



Spawning : Spawning evidently occurs over the outer 

 shelf in oceanic waters greaterthan 40 m in depth (Ditty 

 pers. comm.), and probably to the south of the Florida 

 Straits (Berry 1 959, Hoese 1 965, Fahay 1 975, Benson 

 1 982). The spawning season in the western Atlantic is 

 thought to be March to September (Berry 1959). 



Fecundity : Actual fecundity is unknown. In one study, 

 the ovaries of a 520 mm TL female with well developed 

 eggs were 1 1 by 60 mm (Beebe and Tee- Van 1 928). 



Growth and Development 



Egg Size and Embryonic Development , and Age and 

 Size of Larvae : The actual spawning locations of 

 crevalle jack are not well known, and little is known 

 about the development of eggs and larvae (Berry 1 959, 

 Johnson 1978). 



Juvenile Size Range : Metamorphosis to the juvenile 

 stage occurs around 12 mm SL (Ditty pers. comm.). 

 The growth rate is reported to increase after juveniles 

 reach a length of 50 mm (Nichols 1937, Johnson 

 1 978). Age and size at sexual maturity remain uncer- 

 tain. Males with developed testes have been collected 

 when 540 to 690 mm SL in size (Berry 1 959), and a 406 

 mm SL female was recorded as having well developed 

 eggs (Beebe and Tee-Van 1928). 



Age and Size of Adults : Specific maximum sizes forthis 

 species are uncertain. Lengths of 1010 mm TL and 

 weights up to 25 kg have been documented, but 

 unsubstantiated reports have recorded fish measuring 

 more than 1 50 cm TL and weighing 32 kg (Berry 1 959, 

 Fischer 1 978, Shipp 1 986). Adult females are typically 

 larger than males of a given age (Berry 1959). 



Food and Feeding 



Trophic Mode : This species is a diurnal carnivore, 

 apparently preying on small schooling fish of the coastal 

 zone (Hildebrand and Schroeder 1928, Saloman and 

 Naughton 1984). 



Food Items : This species has been observed in Florida 

 feeding wildly along shorelines on larval fishes consist- 

 ing mostly of ladyfish, anchovies, and cyprinodonts 

 (Tabb and Manning 1961). Small jacks have been 

 found to prey mostly on a variety of clupeids, while 

 medium size fish usually ate clupeids and spa rids, and 



218 



