606 



Fishery Bulletin 100(3) 



Abundance 1995 

 . 1-25 

 . 26-50 



• 51-100 



• 101-500 

 5004- 



44' 



42° 



40° 



38° 



36° 



76° 74° 72° 70° 68° 



Figure 10 (continued) 



66° 



64° 



11). The recovery in the Gulf of Maine started in 1984 and 

 continued through to 1998 (Fig. 1 lA). The largest overall in- 

 crease in abundance has occurred in the Nantucket Shoals 

 region (range 28.8-398.3 million fish) (Fig. IIB). Similarly, 

 after a long hiatus from 1963-1986, this stock component 

 increased considerably during 1987-98. The Georges Bank 

 component was the last to recover, with significant increas- 

 es in abundance beginning in 1992 (Fig. IIC). 



Discussion 



Atlantic herring are currently abundant in the Gulf of 

 Maine-Georges Bank region as evidenced by research 

 survey results and recent stock assessments (NEFSC^). 

 This resource was heavily exploited during 1961-76 by 

 distant-water fishing vessels with catches that were not 

 sustainable, resulting in the collapse of the Georges Bank 

 component in 1977. The causes of this collapse have been 

 ascribed to excessive fishing mortality and concentration 

 of effort on spawning areas (Anthony and Waring, 1980). 

 ICNAF routinely set total allowable catches (TACs) in 

 excess of scientific recommendations and these TACs were 

 often exceeded (Anthony and Waring, 1980). Spawning con- 

 centrations were heavily fished, and egg and larval produc- 

 tion declined steadily, followed by the complete absence of 

 larvae on Georges Bank for an entire decade (Anthony and 

 Waring, 1980; Lough et al., 1985; Smith and Morse, 1993). 

 Full recovery of the Atlantic herring resource has re- 

 quired almost two decades (NEFSC^). Spawning area 

 closures and restrictions in the Gulf of Maine beginning 



in the 1980s may have been influential, but the relative 

 impact of these indirect measures cannot be assessed (Ste- 

 venson^). During 1978-94 there were almost no offshore 

 landings and abundance and biomass for the GB compo- 

 nent improved steadily (NEFSC-). 



The distribution range of the herring complex was greatly 

 reduced after each of the three stock components were heav- 

 ily fished; the extent of the spring distribution was much 

 reduced by the early 1980s and autumn spawning activity 

 was confined to the western Gulf of Maine. The relative en- 

 counter rate in both research surveys, as measured by the 

 proportion of tows with herring, also declined during this 

 period. As the complex began to recover, its range extended 

 and the proportion of survey tows with herring increased 

 dramatically. The complex was more widely dispersed by the 

 mid 1990s with the recovery of all three components to, or 

 above, historic abundance and biomass (NEFSC-). 



Murawski (1993) found that temperature is a very im- 

 portant factor in determining the distribution of pelagic 

 fishes, particularly Atlantic herring. Herring appear to 

 have maintained a preferred thermal regime despite el- 

 evated and variable overall shelf temperatures in spring 

 and autumn, and large changes in abundance. The ±5°C 

 median spring temperature for 1968-94 from our study 

 is in agreement with the average of 4.8°C from Murawski 

 (1993). After the complex recovered, the median spring 

 bottom temperature increased slightly to about 6°, prob- 

 ably indicative of the much broader range of the complex. 

 Murawski ( 1993) calculated an autumn average of 8.5° for 

 Atlantic herring and the median from the current study 

 was 7-8°. This autumn preference reflects the distribu- 



