596 



Fishery Bulletin 100(3) 



78° 76° 74° 72° 70° 68° 66° 64° 



36°- 



Figure 3 



Survey strata used in the Northeast Fisheries Science Center research bottom trawl surveys for the region from Cape 

 Hatteras, NC, to Nova Scotia, Canada. 



the late 1960s was followed by a low abundance from 1971 

 to 1985. After 1985, abundance indices increased steadily 

 to values that were 2-3 times larger ( 1993, 1996-981 than 

 those at the beginning of the time series (Fig. 4A). Atlantic 

 herring abundance was six times higher during 1992-98 

 than during 1968-75. 



Herring spawn between mid-September and mid-Octo- 

 ber, and the timing is dependent on location and year The 

 NEFSC autumn research survey is usually conducted just 

 after the spawning season for Atlantic herring, but this 

 survey is a useful indicator of the abundance of spawners 

 in the various component areas. Herring abundance in the 

 autumn surveys was low (range 2.5-17.7 million fish) dur- 

 ing 1963-67, very low from 1968-1986 (range 0.0-4.4 mil- 

 lion fish), and much higher since 1987 (range 45.6-604.2 

 million fish) (Fig. 4B). 



The herring complex occupied a consistently wider latitu- 

 dinal range in the spring during the late 1980s and 1990s 

 than in prior years. The complex was centered between 

 39°-41°N latitude during 1968-70 and then gradually 



shifted northwards (Fig. 5A). During 1982-84, the median 

 latitude of the complex had moved north to 42° (north of 

 Cape Cod); by 1984, the distribution of the stock complex 

 was confined between 40°30'-44°10'N latitude, about a 50% 

 decrease in latitudinal range as compared to 1968 (Fig. 5A). 

 As abundance increased in the late 1980s, the center of the 

 spring distribution of Atlantic herring moved southwards 

 and the range extended; since 1989 the medial latitudinal 

 position of the complex has remained at 41°N (Fig. 5A) 



Major shifts in the longitudinal position of the com- 

 plex have also occurred. During 1968-70, herring were 

 generally west of 70°W longitude (Fig. 5B). Subsequently 

 (through 1986) the complex shifted farther to the east. 

 As abundance increased, in the late 1980s, the longitudi- 

 nal center of the complex moved westward remaining at 

 about 70°W longitude during 1989-98. During this time 

 period, the east-west extent of the complex expanded 

 greatly (Fig. 5B). 



The median, interquartile range, and overall range in. 

 latitude of the herring complex in autumn is character- 



