OVERHOLTZ and TYLER: DEMERSAL FISH ASSEMBLAGES 



SLOPE AND CANYON 

 200 r 



150 



100 



50 



1 •_! 1 a^^-S • 



200 



150 



100 



50, 



INTERMEDIATE 





 200 r 



150 



100 



50 



_l L. 



SHALLOW 



_1 I 



200 r 



150 



100 



50 



GULF OF MAINE DEEP 







_i I I I 



I 



^ 

 5 



60 r 



50 



40 



30 



20 



10 



_l_ 



_i_ 



_l_ 



60 



62 64 66 



68 70 72 

 YEAR 



74 



76 78 80 



63 66 69 72 73 78 



TIME 



Figure 7— Unstandardized effort data in thousands of days fish- 

 ed for the Georges Bank demersal fishery, all countries, for 1961-79, 

 expressed as 3-yr moving means. 



same trends as in the former case, but represented 

 more of the catch on a percent weight basis in the 

 later years of the fall time series (Fig. 8C). Gulf 

 Stream flounder was actually one of the more im- 

 portant species numerically during the mid-years of 

 the series (Fig. 8D). The same general trend for red 

 and silver hake, and the other species is apparent 

 in the percent by numbers data (Fig. 8D). 



The shallow assemblage was much more diverse 

 than the Slope and Canyon assemblage. The major 

 species of importance were Atlantic cod, winter 

 skate, longhorn sculpin, little skate, yellowtail 

 flounder, and haddock. Mean catch per tow in the 

 fall time series declined dramatically from 202 kg 

 in 1963 to 22 kg in 1972 and subsequently rose to 

 99 kg in 1978 or about one-half the 1963 value (Fig. 

 6). Winter flounder, longhorn sculpin, and winter 

 skate appear to have remained fairly constant in 

 abundance over the spring time period, while Atlan- 

 tic cod, windowpane flounder, and little skate 

 displayed an increasing trend in biomass (Fig. 9A). 

 Yellowtail flounder and haddock showed declining 

 mean catches over this interval. The fall time series, 

 since it is longer, clarifies some of the observed 

 spring trends. Cod and winter flounder CPUE re- 

 mained relatively stable over the fall period, while 

 windowpane flounder, winter skate, and little skate 

 appear to have increased from 1972 onward (Fig. 



Figure 6.— Mean catch per tow (kg) from NEFC Georges Bank 

 bottom trawl surveys for autumn 1963-78 for the five assemblages. 

 Dashed line indicates a 3-yr moving mean of the plotted data points. 



513 



