Overholtz and Friedland: Recovery of the Gulf of Maine Georges Bank complex 



597 



1968 1974 1980 1986 1992 1998 



Y 700 

 I 600 - 



500 - 



400 - 



300 



200 



100 h 



B 



0^*S*M»^ 



1963 1970 



1977 1984 

 Year 



1991 1998 



Figure 4 



Abundance indices (swept area, millions offish) of Atlantic 

 herring from (A) spring bottom trawl surveys during 1968- 

 98 and IB) autumn bottom trawl surveys during 1963-98. 



ized by rapid changes and a general movement to the 

 north during 1963-75 (Fig. 6A). During 1963-64, the stock 

 complex was centered around 42°, moved a full degree to 

 the south by 1967, and then shifted north to almost 43° by 

 1975. Survey abundance was so low during 1976-81 that 

 any trends in median latitude were obscured (Fig. 6A). As 

 the stock recovered, median latitude became stable, rang- 

 ing between about 42°00' and 42°30'. 



The median longitude of the complex hovered around 

 68°15'-68°45' during 1963-72, then shifted to the west of 

 69° during 1973-86 (Fig. 6B). When recovery began, the 

 median longitude of the complex moved slightly to the 

 east of 69°, stabilized between 69°30' and 69°50' during 



2000 



2000 



Figure 5 



Median (notch), interquartile range, whiskers (±1.5 times 

 the absolute value of the interquartile range), values out- 

 side the whiskers ( * ), and far outside the whiskers (o) of the 

 (A) latitude and (B) longitude of positive catches of Atlan- 

 tic herring from the spring NEFSC bottom trawl survey 

 during 1968-98. 



1991-95, and moved farther east during 1996-98 to about 

 68°35'(Fig. 6B), 



Since 1968, median bottom water temperatures for the 

 entire continental shelf during spring have fluctuated 

 between 5° and 7.5°C, with individual bottom locations 

 ranging between 1° and 14°C and a few values falling out- 

 side this range (NMFS^). Herring maintained their pref- 



•'' NMFS (National Marine Fisheries Service). 2001. Unpubl. 

 data. Northeast Fisheries Science Center, Woods Hole, MA 

 02543. 



