534 



Fishery Bulletin 98(3) 



By the time YOY C. hippos reach shelf habitats during 

 autumn, we postulate that they are of adequate size to con- 

 tinue south to subtropical latitudes. For example, YOY C. 



0.20 



fc 0,10 



= 0.05 



0.08 1 



0.04 



A (All months combined) 



2 3 4 5 6 7 



stratum number 



10 11 12 



O 



0-02- 



000 



B (Strata 1-7 only) 



Month! 



Figure 4 



Variations in abundance of Caranx hippos from late June to 

 early November: (A) Geometric mean abundance by sampling 

 strata and year; (B I geometric mean abundance by month and 

 year All samples were collected with a 30.5-m seine and sym- 

 bols denoting sampling year ( 1986-199.3) in both A and B are 

 the same. See Figure 1 for reference strata. 



to 



.a ^ 



(3~ 



6.0 



1.5 



1.0 



0-5 



0.0 

 -150- 



,125- 



! 75- 

 i 50- 



^o Great Soutti Bay, NY 

 ^ '^ Haverstraw Bay. NY 

 Jamaica Bay, NY 

 Souttiern New Jersey 



B 



 -J * 



OD o 



25- 



Jun 1 



 m" ^f. 



Off "a 



Jul 1 



Aug 1 



Sep 1 



Oct 1 



Nov 1 



Figure 5 



(A) Geometric mean abundance of Caranx hippos plotted for each 

 sampling day during 1988 (seine-net collections only) for four estu- 

 arine systems in the New York and New Jersey region. (B) Mean 

 length of C. hippos plotted for each sampling day during 1988 (same 

 symbols used to denote each embayment as in A). Sampling gears 

 differ between bays: Great South Bay— 30.5-m seine, Haverstraw 

 Bay— 61-m seine, Jamaica Bay — 61-m seine, and two southern New 

 Jersey areas — 30..5-m seine plus lengths from weir samples. 



hippos are as large as "summer-spawned" YOY P. sal tu- 

 trix; McBride et al. (1993) concluded the latter migrate 

 from temperate nursery grounds to subtropical overwin- 

 tering habitats at sizes of 10-15 cm FL. Moreover, sev- 

 eral fish species have been tagged in temperate waters 

 and recaptured in subtropical waters at sizes similar to 

 those of C. hippos in autumn, including Atlantic croaker, 

 Micropogonias undulatus (Pearson, 1932; Haven, 1959); 

 spot, Leiostomus xanthiirus (Pearson, 1932); weakfish, 

 Cynoscion regalis (Nesbit, 1954); Atlantic thread her- 

 ring, Opisthonema oglinum (Pristas and Cheek, 1973); 

 bluefish, P. saltatrix (Lund and Maltezos, 1970); and 

 Atlantic menhaden, Brevoortia tyrannus (Kroger and 

 Guthrie, 1973). We reject the hypothesis that YOY C. 

 hippos migrate offshore to the shelf edge, because they 

 are distributed close to shore (<38 m) during autumn 

 and they are not collected in winter or spring sampling 

 out to 366 m depths by the National Marine Fisheries 

 Service's trawling program. We similarly reject the 

 hypothesis that the YOY C. hippos observed in coastal 

 habitats during autumn have moved inshore from "off- 

 shore" nursery grounds. This cohort was not evident in 

 summer trawl samples and such a hypothesis would 

 require an alternative life history tactic for using shelf 

 habitats as nurseries — a tactic that up until now has 

 not been reported for this species. 



Direct evidence (e.g. mark-recapture) of successful 

 migrations by marine fishes is rare, and the migration 

 patterns of many species are inferred from seasonal 

 changes in distribution (Leggett, 1977), as we have done 

 in our study. In addition, we have examined growth rates 

 and sizes to link the seasonal changes in geographic 

 distribution to the YOY cohort. The above evidence indi- 

 rectly links some YOY C. hippos that have dispersed to 

 temperate estuaries back to suitable overwinter- 

 ing habitats and suggests that these individuals 

 retain "membership" in the spawning population 

 isensu Sinclair, 1988 ). We do not, however, assume 

 that all individuals leave temperate estuaries 

 before hypothermal conditions can develop, nor 

 that all individuals sun'ive an autumn migration 

 to subtropical latitudes. The relative importance of 

 temperate estuaries over subtropical estuaries for 

 YOY C. hippos depends on the relative contribu- 

 tion to future spawning by individuals dispersed 

 to each biogeographic region, but this contribu- 

 tion can not be calculated without further study. 



Cape Hatteras represents a major faunal (and 

 floral) break along the U.S. east coast (Pielou, 

 1979; Briggs, 1996), but the larvae of many spe- 

 cies that spawn in coastal habitats, particularly 

 of those that broadcast their eggs into the water 

 column and have moderate-to-long planktonic 

 lai-val durations, are capable of being transported 

 around this geographic barrier ( e.g. Curran, 1989 ). 

 Among these species, we postulate that there is 

 a subset of species that have juvenile traits that 

 allow them to exploit nursery habitats in both 

 biogeographic provinces, and an additional subset 

 of species for which some individuals can return 



