COLTON: TEMPERATURE TRENDS AND GROUNDFISH DISTRIBUTION 



The catches of haddock were confined to the 

 area east of Nantucket Shoals (long70°W). The 

 general distribution pattern was similar during 

 all years with the exception that in 1956 (the 

 warmest year) the southern limit of occurrence 

 of haddock was north of its position during the 

 other years. For the most part, the variations 

 in abundance and distribution of haddock be- 

 tween years appear to be related to changes in 

 age composition of the catch due to the predom- 

 inance of certain year classes. For example, 

 the catches during 1964 and 1965 consisted prin- 

 cipally of 1- and 2-year-old fish of the strong 

 1963 year class (Grosslein, 1969). In general, 

 these young haddock inhabit shoaler water than 

 do older haddock (Colton, 1955). 



Although there were marked fluctuations in 

 the abundance of yellowtail flounder between 

 years, there was little change in the general dis- 

 tribution pattern. In all years yellowtail were 

 found in relatively shoal water (<100 m) both 

 to the east and west of Cape Cod. With the pos- 

 sible exception of 1956, the distribution of yel- 

 lowtail extended considerably beyond the west- 

 ern limit of the sampling area. The bulk of the 

 catch was made south of lat 42 °N, although small 

 concentrations occurred off the tip of Cape Cod 

 and on Browns Bank. The greater abundance 

 of yellowtail in later years appears to be due to 

 a succession of strong year classes and not to 

 a major shift in distribution (Lux, 1969). 



The main concentrations of butterfish oc- 

 curred on western Georges Bank and Nantucket 

 Shoals and off" southern New England and Long 

 Island. As in the case of the yellowtail, the 

 distribution of butterfish extended beyond the 

 western limit of the sampling area. In 1956 and 

 1961 only, appreciable numbers of butterfish 

 were caught north of lat 42 °N. In these years 

 butterfish occurred just east of Cape Cod, in the 

 Stellwagen Bank area, and in scattered concen- 

 trations within the Gulf of Maine. Butterfish 

 were least abundant in 1966. In this, the coldest 

 year, few fish were taken east of Nantucket 

 Shoals. 



JULY-AUGUST DISTRIBUTION 



The distribution of American plaice, haddock, 



yellowtail flounder, and butterfish during July- 

 August 1950, 1963, 1964, and 1965 is shown in 

 Figures 9 and 10, 



The area of occurrence of plaice extended 

 farther south and west with succeeding years 

 and decreasing temperatures. The catches of 

 haddock were confined for the most part to the 

 area east of Nantucket Shoals, and there was 

 little change in distribution between years. The 

 similarity of the distribution patterns of had- 

 dock during July-August and October-Novem- 

 ber 1964 and 1965 indicates limited seasonal 

 movement. Little change was evident in the 

 general distribution patterns of yellowtail be- 

 tween years. As in the case of the haddock, the 

 similarity of the distribution patterns during 

 July-August and October-November 1964 and 

 1965 indicates little seasonal movement. There 

 were no marked diflferences in the distribution 

 of butterfish in these years, although butterfish 

 were least abundant on Georges Bank in 1965, 

 and 1950 was the only year in which appreciable 

 numbers were taken in Cape Cod Bay. In con- 

 trast to October-November, the distribution of 

 butterfish during July-August 1964 and 1965 

 was confined within the western limits of the 

 sampling area. 



SEASONAL DISTRIBUTION 



Of the four species considered in this paper, 

 only the American plaice and the butterfish 

 showed any appreciable change in distribution 

 coincident with the downward trend in temper- 

 ature. During both summer and fall there was 

 an extension of the southern and western limits 

 of the area of occurrence of plaice and a con- 

 traction of the northern and eastern limits of 

 the area of occurrence of butterfish. Data ob- 

 tained on cruises made during January-Febru- 

 ary 1964 and 1966, together with data collected 

 during July-August and October-November 1964 

 and 1965 (Figures 11 and 12), give evidence of 

 the seasonal distribution of these two species. 



Although there were no extensive seasonal 

 changes in the distribution of plaice, the south- 

 westerly extent of the distribution boundaries 

 tended to be greatest during January-February 

 and least during October-November (Figure 



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