Consequences of dispersal of subtropically spawned crevalle jacks, Caranx hippos, to temperate estuaries

Caranx hippos spawn at subtropical and tropical latitudes, but some of thei r propagules are dispersed hundreds of kilometers north of Cape Hatteras in to temperate waters of the western North Atlantic. The effect that this nor thward dispersal pattern has upon the population depends on whether these j uveniles return south during autumn to overwinter or whether they become ex patriated from the spawning population and die from hypothermal winter cond itions at temperate latitudes. We evaluated whether repatriation was possib le by comparing C. hippos seasonal abundance and size-structure from New Yo rk to Florida. Young-of-the-year C. hippos occurred annually during summer and autumn but were uncommon in relation to other species in subtropical an d temperate estuaries. Sizes of C. hippos at temperate latitudes were as la rge as conspecifics at subtropical latitudes and juveniles of other species that are known to migrate during autumn from temperate nursery Pounds to s ubtropical latitudes. As C. hippos disappeared from estuaries of the middle Atlantic states in autumn. similar-size fish appeared on the inner contine ntal shelf. We postulate that at least some of the C. hippos observed migra ting from temperate estuaries during the autumn eventually ovenwinter at su btropical latitudes, where they can return to the spawning population. This is unusual, because individuals of many other species whose larvae are tra nsported north of Cape Hatteras do not appear to successfully migrate back to subtropical overwintering habitats. This life-history pattern, in which fish begin their first year in the Carolinian biogeographic province, are d ispersed to the Virginian province, and return to the Carolinian province b efore their first winter, has been demonstrated for only one other western North Atlantic finfish species: bluefish (Pomatomus saltatrix). A few other species are Likely to occupy and reproduce within such large-scale oceanog raphic systems because they have a combination of spawning, larval, and juv enile traits that is similar to that of P. saltatrix and C. hippos.