Bluefish, continued 



Salinity - Eggs: In one laboratory study, eggs fertilized 

 in vitro were successfully incubated in a salinity of 

 32.5%o until hatching (Deuel et al. 1966). Eggs in the 

 wild occur from 26.6 to 34.9%o, but are found most often 

 in 30%o or greater (Norcross et al. 1974). 



Salinity - Larvae: In one study of 1 8 specimens, larval 

 bluefish were reported in the Gulf of Mexico over a 

 salinity range of 35.7 to 36.6%o (Barger et al. 1978). 

 Ditty and Shaw (1 995) collected 70 larval bluefish in the 

 northern Gulf of Mexico at a mean salinity of 33.0%o, 

 with a range of 26.7 to 36.3%o. They have been 

 collected in salinities as high as 38%o in the Atlantic 

 Ocean (Kendall and Walford 1979). 



Salinity - Juveniles: Juveniles have been recorded 

 over a salinity range of 8.0 to 36.2%> in the Gulf of 

 Mexico (Gunter 1 945, Pullen 1 962, Perret et al. 1 971 , 

 Wang and Raney 1971, Franks et al. 1972, Hardy 

 1978). 



Salinity - Adults: Salinity preference for adults seems to 

 be 26.6 to 34.9%<= (Benson 1982), but they exhibit an 

 overall range of 7.0-36.5%o, with only rare occurrences 

 above 35%o (Simmons 1 957, Deuel et al. 1 966, Franks 

 etal. 1972, Hardy 1978). 



Movements and Migrations : Larval bluefish in the 

 northern Gulf of Mexico are reported to reach peak 

 abundance in April, and November-December (Ditty et 

 al. 1988). Young of the year bluefish move inshore 

 sometime during their first growing season, and some 

 are found in estuaries and their tributaries (Norcross et 

 al. 1 974, Hardy 1 978, Benson 1 982). Age class fish 

 arrive in Texas coastal waters during late November 

 when they are 48-56 mm standard length (SL) (Hoese 

 1 965), and some evidently enter bay systems (Gunter 

 1945, Pullen 1962, Perret et al. 1971, Benson 1982). 

 Adults are caught off the Texas coast primarily from 

 April to September, with peaks in July and August, and 

 appear to be entirely absent during December and 

 January (Springer and Pirson 1959). Adults move 

 seasonally in groups loosely collected into aggregates 

 that can be 6 to 8 km long (Hardy 1 978). They generally 

 move north in spring and summer, and south in fall and 

 winter (Moe 1 972, Wilk 1 977). In the Gulf of Mexico, 

 they remain offshore during much of the year, moving 

 inshore during the summer in Louisiana, late summer 

 and fall in Mississippi, and fall in Florida and the 

 northwestern Gulf. Florida bluefish remain inshore 

 until spring, with large numbers still found off southern 

 Florida in March and some present throughout the year 

 (Springer and Woodburn 1960, Deuel et al. 1966, 

 Perry 1970, Hoese 1977). Seasonal migrations ap- 

 pear to be linked to water temperature and possibly 

 photoperiod (Lund and Maltezos 1970, Olla and 

 Studholme 1971). In the Atlantic, fall migration ap- 



pears to be triggered when temperatures fall to 13 to 

 1 5°C. In this area, fall migration is believed to go in two 

 directions (Lund and Maltezos 1970): juveniles are 

 essentially shore fish and move southward along the 

 coast staying with the warmer water and will enter inner 

 bays, whereas adults are pelagic and move offshore to 

 find warmer water in which to overwinter (Lund and 

 Maltezos 1970). Movements between offshore and 

 inshore waters are irregular and may be a response to 

 wind induced changes in water temperature (Reid 

 1954, Lund and Maltezos 1970). Migrating bluefish 

 have been reported to enter public beach waters and 

 nip at swimmers (de Sylva 1976, IGFA 1991). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic), but hermaphroditism has not 

 been examined. Fertilization is external by broadcast 

 of milt and roe, and no accessory organs are present 

 (Wilk 1977). 



Spawning : The bluefish is an offshore ocean spawner 

 (Lippson and Moran 1 974). Gulf of Mexico populations 

 appear to spawn over the continental shelf, as they do 

 in the Atlantic off the eastern U.S. (Moe 1 972, Lippson 

 and Moran 1974, Norcross et al. 1974, Barger et al. 

 1978). The spawning period varies depending on 

 location. Spawning in the northern Gulf of Mexico may 

 be bimodal, occurring in both spring and fall. Fall 

 spawning occurs from late September through early 

 November (Hildebrand 1957, Barger et al. 1978, 

 Finucane et al. 1980). Spring spawning is known to 

 occur in waters off the Louisiana coast (Barger et al. 

 1978). Spawning locations may be associated with 

 hydrologically dynamic areas, such as the estuarine/ 

 oceanic frontal zone of the Mississippi River plume 

 (Ditty and Shaw 1995). It has been inferred, but not 

 consistently demonstrated, that such frontal zones 

 offer a nutritional advantage to larval fish. In the 

 Atlantic on the U.S. east coast, spawning is reported in 

 the spring 55 to 148 km offshore in salinities of 25.6 to 

 32.5%o, and water temperatures of 1 4 to 25.6°C (Deuel 

 et al. 1 966, Norcross et al. 1 974, Hardy 1 978). In this 

 area, optimal temperature and salinity for spawning 

 were 25.6°C and 31 %«, and little spawning was re- 

 ported at 18°C and 31.7%o, and 20.5°C and 26.6%o. 

 The majority of spawning in the Chesapeake Bay area 

 is reported to occur at temperatures above 22°C and 

 surface salinities of 31 %o or greater (Deuel et al. 1 966, 

 Norcross et al. 1974). 



Fecundity : The number of eggs produced is a function 

 of size and age (Wilk 1977). In Atlantic waters of the 

 U.S. east coast, a 528 mm female contained about 

 900,000 maturing eggs while a 585 mm female con- 

 tained about 1,100,000 eggs. 



206 



