530 



Fishery Bulletin 98(3) 



rkm 90-100 



Newburgh  Beacon 

 Bridge 



5 rkm 76-90 



^iL Bear Mountain Bridge 



4 rkm 63-76 



3 rkm 55-63 



Haverstraw Bay 



2 rkm 39-55 



kilometers 



Figure 1 



Sampling strata (1-6) in the Hudson River region 

 where Caranx hippos was common. Haverstraw Bay 

 is within strata 2-4. Strata 7-12 (river kilometers 

 100-246) are not shown. Jamaica Bay is located just 

 east of the mouth of the Hudson River. 



Growth modeling and other statistical analyses were per- 

 formed by using SAS (SAS, 1990). 



Field sampling— Hudson River 



Recent data (1986-1993) were analyzed from an ongoing 

 ( since 1974 ) survey of the entire Hudson River ( Fig. 1 ). Fish 

 were collected during daylight over a 1-wk period every 

 other week between mid-June and mid-November During 

 each sampling week, a 30.5-m \ 2.4-m (max. mesh=10 mm) 

 beach seine was set in an arc from a boat at approximately 

 100 stations. Station locations were selected in a strati- 

 fied random design by using 12 strata between Manhattan 

 and Albany, New York (from river kilometer |rkm| 19 to 

 246). The length of each stratum varied from 8 to 44 km, 

 and typically 5-20 hauls were completed in each stratum 

 during each biweekly period. Mean abundance, by month 

 or stratum, was calculated from transformed values of the 

 number of fish in each seine haul (log^ In-nl]) and was 

 expressed as a geometric mean (antilogged mean values of 

 -1). Annual abundances were also calculated as geometric 

 means but only for data from August to September (when 

 C. hippos were consistently collected). 



Field sampling— Haverstraw and Jamaica bays 



Further analyses of the ecology of Caranx hippos in the 

 Hudson River were based on data from an independent 

 survey for the same 8-yr period ( 1986-1993) as the survey 

 of the entire river. This additional survey focused on two 

 subregions of the estuary: Haverstraw Bay and Jamaica 

 Bay. Haverstraw Bay corresponds to strata numbers 2-4 of 

 the Hudson River survey (Fig. 1); Jamaica Bay is a satellite 

 embaynient close to the mouth of the Hudson River 



Seining in Haverstraw Bay occurred biweekly from July 

 to November (see also McKown and Young, 1992). Typi- 

 cally, 25 stations were sampled during daylight over a 2-d 

 period; at each station, a single haul was made with a 

 61-m X 3-m beach seine (max. mesh=6.4 mm) set in an 

 arc from a boat. This seine was used similarly in Jamaica 

 Bay from May to November, but sampling frequency was 

 generally monthly and only 4—5 stations were sampled 

 each time. Temperature and salinity were measured with 

 a hand-held thermometer and refractometer from surface- 

 water samples after the net was hauled. Abundance of C. 

 hippos was calculated as above (i.e. by geometric means). 



Field sampling-the continental shelf 



To determine seasonal abundance of C. hippos above the 

 U.S. east coast continental shelf, we examined data col- 

 lected during 1972-1996 in the National Marine Fisheries 

 Service's bottom-trawling program. This program followed 

 a stratified random statistical design to survey fish stocks 

 of the continental shelf (9-366 m) from Cape Fear, North 

 Carolina, to Nova Scotia, Canada. Standard methods were 

 to tow a 24.4- or 30.5-m otter trawl ( 13-mm codend liner) for 

 30 min at randomly assigned stations within fixed strata 

 (strata were delimited largely by depth and latitude). All 

 samples combined covered all seasons, but sampling inten- 

 sity was greatest during spring (March-May) and autumn 

 (September-November), when about 350 stations were 

 sampled during each 6-8 wk period. Fish were measured to 

 the nearest cm. General survey design and its specific appli- 

 cations for other species can be found in many other studies 

 (e.g. Grosslein and Azarovitz, 1982; Despres-Patanjo et al.. 

 1988; McBride et al., 1998). 



Results 



Latitudinal comparisons 



Young-of-the-year C. hippos occurred in subtropical estu- 

 aries between North Carolina and Florida from June to 

 November and in temperate estuaries of New York and 

 New Jersey during July-November (Fig. 2). On average, 

 we observed only about one fish collected in three or more 

 seine hauls, and these arithmetic mean densities were the 

 same for temperate and subtropical estuaries (Fig. 3). 



At subtropical latitudes, individuals <4.0 cm FL were 

 present in all months, June-November (Fig. 2). Small indi- 

 viduals were also present for three months, July-Septem- 

 ber, at temperate latitudes. In both biogeographic regions. 



