66 



Fishery Bulletin 98(1 



3) sea-surface salinity, dissolved oxygen, and nitrate 

 concentrations taken along with neuston collections 

 (Mathews and Pashuk, 1986); 4 1 records of the Na- 

 tional Oceanographic Data Center; and 5) records of 

 U.S. Coast Guard visual observations from aircraft. 

 The width of the frontal zone, and consequently the 

 area occupied by frontal zone water, was determined 

 as three times the standard deviation of the mean 

 course of the front, i.e. ±10 nautical miles ( 18.5 km) of 

 the estimated location of the frontal axis (Olson et al., 

 1983). 



Forty-seven collections taken from 22 to 24 June 

 1984 with a 1.0 X 0.5 m neuston net wdth 909-]am mesh 



\ 



\. 



Figure 1 



Nominal station.s occupied by the Marine Resources Monitoring Assessment 

 and Prediction Program from 1973 to 1980; each station was occupied at least 

 once, some more than once. 



towed for 10 min at 5.6 km/h in the Gulf Stream 

 and within its western frontal zone between Cape Ca- 

 naveral and Cape Hatteras (CF8406) afforded an ex- 

 amination of coarse scale differences in occurrence of 

 swordfish larvae within the frontal zone and in the 

 body of the Gulf Stream. Six collections were taken 

 during night, the remainder during the day. Larvae 

 were preserved in 5% formalin. A sea-surface temper- 

 ature plot, generated from composite AVHRR images 

 of SST compiled on 20 June 1984 (Fig. 2), in conjunc- 

 tion vrith continuous temperature and salinity values 

 from a hull-mounted thermosalinometer, was used to 

 determine the position of the Gulf Stream and its 

 frontal zone and to classify these collections to 

 water mass. 



One hundred and fifty-six collections 

 ( CH8807 ), taken from 13 to 24 September 1988 

 with a 2.0 x 1.0 m neuston net with 947-pm 

 mesh along six cross-shelf and cross-slope tran- 

 sects (encompassed by 31°30.4N/080°16.5W, 

 30°45.0N/078°411.5W, 32 24°30.0N/076°19.5W, 

 and 33"16.0N/077'54.0W), afforded examina- 

 tion of coarse- and fine-scale distribution of 

 larval swordfish within and about the Gulf 

 Stream frontal zone (Fig. 3). Neuston nets 

 were towed for 10 min at 5.6 km/h. Ten sta- 

 tions were occupied along each transect (60 

 stations); 96 additional neuston collections 

 were taken within the Gulf Stream or within 

 its frontal zone. The 60 collections along tran- 

 sects were 18.5 km apart, whereas 94 of the 

 additional 96 collections within the frontal 

 zone or body of the Gulf Stream were clus- 

 tered in groups of four to ten, with collections 

 about 1 km apart. Surface salinity, two-dimen- 

 sional sections of isotherms derived from XBT 

 casts taken at each station along transects, 

 and AVHRR images of SST were used to clas- 

 sify collections. 



Six neuston collections taken on 31 May 

 1997 (CH9703) with a 2.0 x 1.0 m neuston net 

 with 947-pm mesh within the Gulf Stream 

 frontal zone in an area encompassed by 

 33°52.94'N/076°23.89'W,33=52.30'N/076°24.77'W, 

 and 33°52.92N/076°22.27W afforded exami- 

 nation of fine-scale distribution of lan'al sword- 

 fish within the Gulf Stream frontal zone (Fig. 

 4). Nets were towed for 10 min at 5.6 km/h, 

 twice in the Gulf Stream frontal zone, and 

 twice each on the shelf and Gulf Stream sides 

 of the front. Larvae were preserved in 959^ 

 ethanol. Sea-surface temperature from a hull- 

 mounted thermister in conjunction with XBT 

 profiles and AVHRR images of SST were used 

 to classify collections. 



