528 



Abstract.— Cora nx hippos spawn at 

 subtropical and tropical latitudes, but 

 some of their propagules are dispersed 

 hundreds of kilometers north of Cape 

 Hatteras into temperate waters of the 

 western North Atlantic. The effect that 

 this northward dispersal pattern has 

 upon the population depends on whether 

 these juveniles return south during 

 autumn to overwinter or whether they 

 become expatriated from the spawning 

 population and die from hypothermal 

 winter conditions at temperate lati- 

 tudes. We evaluated whether repatri- 

 ation was possible by comparing C. 

 hippos sea.sonal abundance and size- 

 structure from New York to Florida. 

 Young-of-the-year C. hippos occurred 

 annually during summer and autumn 

 but were uncommon in relation to other 

 species in subtropical and temperate 

 estuaries. Sizes of C hippos at temper- 

 ate latitudes were as large as conspecif- 

 ics at subtropical latitudes and juveniles 

 of other species that are known to 

 migrate during autumn from temper- 

 ate nursery grounds to subtropical lat- 

 itudes. As C. hippos disappeared from 

 estuaries of the middle Atlantic states 

 in autumn, similar-size fish appeared 

 on the inner continental shelf We pos- 

 tulate that at least some of the C. 

 hippos observed migi'ating from tem- 

 perate estuaries during the autumn 

 eventually overwinter at subtropical 

 latitudes, where they can return to the 

 spawning population. This is unusual, 

 because individuals of many other spe- 

 cies whose larvae are transported north 

 of Cape Hatteras do not appear to suc- 

 cessfully migrate back to subtropical 

 overwintering habitats. This life-history 

 pattern, in which fish begin their first 

 year in the Carolinian biogeographic 

 province, are dispersed to the Virgin- 

 ian province, and return to the Carolin- 

 ian province before their first winter, 

 has been demonstrated for only one 

 other western North Atlantic finfish 

 species; bluefish iPomatomiis saltatrix). 

 A few other species are likely to occupy 

 and reproduce within such large-scale 

 oceanographic systems because they 

 have a combination of spawning, larval, 

 and juvenile traits that is similar to 

 that of P. saltatrix and C hippos. 



Consequences of dispersal of subtropically 

 spawned crevalle jacks^ Caranx hippos, 

 to temperate estuaries* 



Richard S. McBride 



Rutgers University Marine Field Station 



Institute ol Marine and Coastal Sciences 



800 Great Bay Boulevard 



Tuckerton, New Jersey 08087 



Present address; Florida Marine Research Institute 

 100 Eighth Avenue Southeast 

 St Petersburg, Florida 33701-5095 



E-mail address nchard mcbndeia fwc state fl us 



Kim A. McKown 



New York State Department of Conservation 



205 Belle Meade Road 



East Setauket, New York 11733 



Manu.script accepted If) December 1999. 

 Fish. Bull. 98: 528-538 12000). 



In the western North Atlantic, many 

 species spawn at tropical and subtropi- 

 cal latitudes, and their lai^vae are dis- 

 persed to temperate and even boreal 

 regions (e.g. Gill, 1904; Markle et al., 

 1979; Curran, 1989). This transport of 

 larvae occurs in association with the 

 Gulf Stream (Wroblewski and Cheney, 

 1984; Hare and Cowen, 1991, 1996) and 

 disperses propagules from the Carolin- 

 ian to the Virginian biogeographic prov- 

 ince (Briggs, 1974, 1996). This process, 

 which involves the entrainment of eggs 

 and larvae into oceanographic currents 

 and the dispersal of propagules to vari- 

 ous water masses, is understood for only 

 a few species and may vary consider- 

 ably between species. Perhaps the most 

 famous example is that of catadromous 

 freshwater eels iAnguilla anguilla and 

 A. rostrafa), which spawn in the Sar- 

 gasso Sea and whose larvae are trans- 

 ported to coastal nurseries in North 

 America and Europe (McCIeave et al., 

 1987). Larval A. rostrata drift for up 

 to one year (Kleckner and McCIeave, 

 1985) through gyres in the southwest- 

 ern Sargasso Sea, the Antilles Current, 

 and the Florida Current and its Gulf 

 Stream extension before moving into 

 coastal waters (McCIeave, 1993). In the 

 case of a wrasse, Xyrichtys novacula, 

 northward transport across hundreds 

 of kilometers occurs in as little as eight 

 days, and cross-shelf transport in the 



northern portion of the Carolinian prov- 

 ince is aided by interactions between 

 western-edge, warm-core eddies and the 

 Gulf Stream itself (Hare and Cowen, 

 1991). Similar northward transport in 

 association with the Gulf Stream occurs 

 for "spring-spawned" bluefish, Poma- 

 tomus saltatrix. except that for this 

 species dispersal time is longer — about 

 2 months (McBride and Conover, 

 1991) — and its juveniles may actively 

 swim out of the Gulf Stream system 

 ( Hare and Cowen, 1996 ). Although some 

 species are transported annually in this 

 manner (e.g. Pornatomus), others are 

 transported less regularly iXyrichtys. 

 Bothus, Syacium), and still other spe- 

 cies do not move between slope and shelf 

 water masses (Cowen et al., 1993). 



Those individuals dispersed across 

 biogeographic boundaries become expa- 

 triated, in terms of passing on their 

 genes if they do not return to spawning 

 grounds to reproduce. Anguilla species 

 remain in coastal habitats for several 

 years before migrating back to the Sar- 

 gasso Sea (Tesch, 1977). but many spe- 

 cies that spawn at subtropical latitudes 

 are physiologically incapable of over- 

 wintering at temperate latitudes. To our 

 knowledge, only P. saltatrix spawns at 



Contribution 2000-06 of the Institute of 

 Marine and Coastal Sciences. Rutgers Uni- 

 vcrisitv, Tuckei'ton, New Jer.sev 08087. 



