DISTRIBUTION AND GENERAL NOTES ON THE SPECIES 363 



movements find a close parallel in those of its near relative Poronotus (Stromateus) triacanthus (Peck) 

 on the north-eastern seaboard of the United States. This 'butterfish' finds its optimum from New 

 Jersey to Chesapeake, and its shoreward congregations in summer may be even more pronounced 

 than those of the Patagonian species, for pound nets are the main means of capture. Near the northern 

 limit of the butterfish, considerable quantities are trawled in Massachusetts ; and in more southerly 

 waters off North Carolina, where it was previously only known from the summer inshore fishery, 



•400H 



•350- 



1-300- 



^ l'250- 



i-zoo- 



M50 



DECEMBER j JANUARY | FEBRUARY | MARCH 



Fig. 45. Stromateus maculatus: seasonal variation in ponderal index, and corresponding mean lengths. 



small quantities have been trawled offshore in winter (Pearson, 1932, Table 2, p. 18). Thus the 

 butterfish compares with our spotted pomfret not only in shoaling shorewards in summer, as so many 

 useful fishes do, but also in being trawlable near the colder limits of its geographical range, and in 

 wide dispersal to warmer and deeper waters in winter. 



A first step in further efforts to elucidate the bionomics of Stromateus maculatus was to test the 

 seasonal variation in ponderal indices for indications of the spawning season. Weight data were 

 available only from a limited period during the third survey, and average K for either sex, plotted at 

 mean dates, yielded the values joined by the heavy lines in Fig. 45. 



