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



607 



90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 







1963 1970 1977 1984 1991 1998 



W^ 



«*» t«..,i 



400 



I 300 



E 



0) 



o 



I 200 



2 100 



B 



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1963 1970 1977 1984 1991 1998 



150 



100- 



50- 



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1963 1970 1977 1984 

 Year 



1991 1998 



Figure 11 



Abundance (swept area, millions of fish) of 

 Atlantic herring from (A) the Gulf of Maine, (B) 

 Nantucket Shoals, and (C) Georges Bank from 

 autumn bottom trawl surveys during 1963-98. 



Several independent sources of information suggest 

 that the recovery of this stock occurred in a stepwise 

 manner with the Gulf of Maine component recovering 

 first, followed by the Nantucket Shoals component, and 

 finally the Georges Bank component. The autumn bottom 

 trawl survey data showed an improved trend in the Gulf of 

 Maine in 1984, the Nantucket Shoals component in 1987, 

 and Georges Bank in 1992. Larval surveys conducted dur- 

 ing 1971-90 showed a progression of larval abundance 

 from the Cape Cod Bay-Stellwagen Bank area in 1976-84, 

 to Nantucket Shoals in 1985-87, and on Georges Bank 

 in 1988-90 (Smith and Morse, 1993). Larval distribution 

 data suggested that larvae from Jeffreys Ledge spawners 

 were probably transported to Nantucket Shoals and that 

 in subsequent years larvae from these areas were trans- 

 ported or adults moved to western Georges Bank and 

 finally eastern Georges Bank (Smith and Morse, 1993). 

 The general pattern of water circulation in the region 

 (McGillicuddy et. al, 1988) also favors this hypothesis for 

 the recovery. 



Smith and Morse (1993) suggested that the larval sur- 

 vey data support the hypothesis that a recolonization of 

 Atlantic herring occurred on Nantucket Shoals and Georg- 

 es Bank. The data from their study showed a chronological 

 pattern in larval abundance and distribution, beginning 

 in the Gulf of Maine and progressing toward the Nantuck- 

 et shoals region and finally to Georges Bank. In contrast, 

 Stephenson and Kornfield (1990) asserted that the reap- 

 pearance of herring on Georges Bank was more related 

 to a resurgence of low numbers of stock-specific endemic 

 fish. The autumn NMFS bottom trawl survey data tend to 

 support the conclusions of Smith and Morse ( 1993) in both 

 direction and timing. Survey indices show a progressive 

 recovery in herring abundance from the Gulf of Maine to 

 Nantucket Shoals, and finally to Georges Bank. 



Significant changes in stock distribution, shifts in cen- 

 ters of primary abundance, and regional declines or disap- 

 pearance of historically important spawning contingents 

 are evident from the data. Autumn indices show that 

 the stock component in the Gulf of Maine reached very 

 low abundances during 1973-83 and that the Nantucket 

 Shoals and Georges Bank components were nearly, if not 

 actually, extirpated. Recovery times for these two compo- 

 nents of the stock were relatively long — on the order of 

 10-15 years. Without a local supply of larvae, recovery was 

 delayed considerably. Recovery was probably contingent 

 on a supply of larval herring from the Gulf of Maine that 

 eventually recolonized the offshore areas. Spawning re- 

 strictions along the coast of Maine and on Jeffreys Ledge 

 in the 1980s may also have contributed to the recovery of 

 Gulf of Maine component, thereby setting in motion the 

 recovery of the entire stock complex. 



tion of postspawning fish in the cooler waters of the Gulf 

 of Maine and Northern Georges Bank. Although thermal 

 conditions play a major role in the zoogeography of fishes, 

 the influence of abundance was probably overwhelming in 

 producing the recovery of the historic range in distribution 

 observed in the Atlantic herring complex. 



Acknowledgments 



We thank the dedicated personnel from the Northeast 

 Fisheries Science Center and the many volunteers who 

 worked tirelessly to collect the bottom trawl survey data 

 during 1963-98. 



