Blue runner, continued 



20.4°-29.4°C (Johnson 1978). Adults inhabit areas 

 where the temperature ranges from 20.0-30.8°C. 



Salinity: The blue runner inhabits polyhaline to euhaline 

 areas depending on life stage. Offshore spawning 

 suggests that eggs occupy areas of marine salinities. 

 Newly hatched larvae occur in salinities of 25.0-36.2% o 

 (Shaw and Drullinger 1990). Larvae occupy salinities 

 ranging from 24.8-37.7%o, with most larvae found be- 

 low 33%o (Shaw and Drullinger 1990). Juveniles are 

 taken in 35.2-36.0% o , and adults inhabit areas ranging 

 from 26.0 to 36.2%o (Johnson 1978). 



Migrations and Movements : In the Caribbean Sea and 

 Atlantic Ocean, larval and early juvenile blue runner 

 are carried to the Florida coast and then northward by 

 the Antilles Current and Gulf Stream, respectively. 

 Juveniles 80-140 mm in length may migrate to inshore 

 waters of the Atlantic coast or move eastward with the 

 currents (Berry 1 959, Dooley 1 972). Adults and juve- 

 niles favor the northern Gulf of Mexico during warm 

 months (Berry 1959). Adults and larger fish migrate 

 southward or move offshore during colder months 

 (Decemberto June) (Berry 1 959, Johnson 1 978, NOAA 

 1985). Adults probably migrate offshore during the 

 spawning season to reproduce (Goodwin and Finucane 

 1985). 



Reproduction 



Mode : This species has separate male and female 

 sexes (gonochoristic). Fertilization is external, by 

 broadcast of milt and roe. 



Spawning : Based on the collection of larvae in the Gulf 

 of Mexico, spawning occurs from January to August in 

 offshore waters, but some evidence indicates spawn- 

 ing may occur throughout the year in some areas of the 

 Gulf (Goodwin and Finucane 1985). Along the south- 

 east Atlantic coast of the United States, spawning 

 occurs from early April to early September (Berry 

 1959). The greatest period of activity occurs during 

 June, July, and August (Goodwin and Finucane 1 985). 

 Larvae are most abundant in the Gulf Stream mid-June 

 to mid-August (McKenney et al. 1958, Berry 1959, 

 Johnson 1978, Ditty et al. 1988), but are captured 

 throughout the year in some areas of the Gulf (Goodwin 

 and Finucane 1985). Spawning location, based on 

 occurrence of larvae, is offshore and occurs in water 

 depths >40m (Ditty pers. comm., Shaw and Drullinger 

 1990). 



Fecundity : Reported fecundity varies from 41 ,000 ova 

 in a 288 g fish to 1,546,000 ova in a 1,076 g fish. 

 Goodwin and Finucane (1985) have developed curvi- 

 linear equations to estimate fecundity. 



Growth and Development 



Egg Size and Embryonic Development : Little informa- 

 tion is available on blue runner eggs, but the closely 

 related Caranx mate has clear, spherical, pelagic eggs 

 with a yolk diameter of 0.66±0.02 mm (Shaw and 

 Drullinger 1990). 



Age and Size of Larvae : Blue runner larvae are not well 

 known, but the larvae of the closely related Caranx 

 mate range 1 .32 to 1 .70 mm SL when they hatch, and 

 average length is 1.46 mm SL (Shaw and Drullinger 

 1990). 



Juvenile Size Range : Transformation to the juvenile 

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

 most noticeable changes in the structural development 

 of a blue runner occur in two stages. The first stage 

 happens between 8-12 mm and the second between 

 45-60 mm (McKenney et. al. 1958). Blue runner is a 

 fast growing species. Approximately 75% of their 

 maximum size is attained by age 3 to 4 years (Johnson 

 1978, Goodwin and Johnson 1986). 



Age and Size of Adults : Males mature by a length of 

 225 mm SL, but females do not mature until approxi- 

 mately 247 mm SL. The largest recorded blue runner 

 is 711 mm FL (Johnson 1978, Goodwin and Johnson 

 1986). Estimates of maximum weight approach 2.73 

 kg. The blue runner is a moderately long-lived species, 

 with a possible life span of up to 1 1 years. Goodwin and 

 Johnson (1 986) have developed a growth equation for 

 this species. 



Food and Feeding 



Trophic Mode : The blue runner is a carnivorous preda- 

 tor, feeding on fish, crustaceans, and other inverte- 

 brates (McKenney et al. 1958, NOAA 1985). Larval 

 and early juveniles are carnivorous planktivores ca- 

 pable of foraging throughout the water column. 



Food Items : 



Larvae forage almost entirely on cyclopoid copepods. 

 Juveniles also feed on calanoid copepods. At lengths 

 greater than 1 0.0 mm, juvenile blue runner eat amphi- 

 pods, larval fish, decapod larvae, ostracods, and fish 

 eggs; however, copepods remain the main diet con- 

 stituent (McKenney et al. 1958, Dooley 1972). Adults 

 feed throughout the water column on fishes, crusta- 

 ceans, and other invertebrates (NOAA 1985). 



Biological Interactions 



Predation : Juveniles are evidently preyed on by sur- 

 face-feeding shore birds such as terns (McKenney et 

 al. 1958). 



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