PLANKTON OP THE GULP OF MAINE 259 



In the western basin the number per square meter rose from none on February 23 

 (station 20049) to 5,550 on March 24 (station 20087), and then declined again to only 

 200 per square meter on April 18 (station 20015). It is probable, however, that this 

 decline was local, one haul hitting and the other missing a shoal, for a few miles to 

 the eastward. The interval from March 2 (station 20052) to April 17 (station 20114) 

 saw the number of M. lucens increase from 1,250 per square meter to 3,000. In- 

 creases were likewise registered in the southeastern part of the basin, in the eastern 

 and northern channels, and over the eastern part of Georges Bank from March to 

 April. In the year 1915 the average number of M. lucens at 4 stations in the inner 

 part of the gulf was about 8,000 in May, but one very rich catch, at the rate of about 

 26,000 per square meter off the Isles of Shoals (station 10278), was chiefly responsible 

 for this large figure. 



In 1920 the vernal augmentation of M. lucens was apparent earliest in the season 

 over a belt extending west-east across the gulf from the Massachusetts Bay-Cape 

 Elizabeth region to the southeastern part of the basin; but no general change of 

 this sort can have taken place in the northeastern part of the gulf generally until a 

 month or more later, because all the early spring catches were decidedly scanty there 

 (at the most 550 per square meter) , and in most instances the March figure was some- 

 what larger than the April count. Neither did the numbers of M. lucens taken in the 

 southwestern part of the basin and over the western end of Georges Bank in that 

 year show any change sufficient to be classed as seasonal, some of the later catches 

 being the larger, some the smaller. Off the southeastern slope of Georges Bank there 

 was an apparent falling off in the numbers of M. lucens from March 12 (stations 

 20067 to 20069) to April 16 (station 20109), but a high frequency (2,360 per square 

 meter) on the east slope of the bank on the 16th (station 20108) makes it likely that 

 the apparent seasonal drop actually reflected nothing more significant than a streaki- 

 ness in the distribution of the species. However this may be, our failure to find M. 

 lucens at the stations outside the slope of Georges Bank in July, 1914 (stations 10218, 

 10220), argues against the idea that this region is the site of a vernal augmentation 

 such as takes place in the inner part of the gulf. 



An average of about 3,300 per square meter at 14 stations in the inner part of the 

 gulf for August, 1913, ranging from 600 to 9,000 at the individual stations (Bigelow, 

 1915, p. 286), does not indicate any notable alteration in the numerical strength of 

 the stock of this species during the summer. One August station for 1915 (10304, 

 eastern side of basin) was unusually productive of M. lucens, the vertical haul taking 

 it at the rate of about 23,000 per square meter, but probably the net chanced to pass 

 through a local shoal of these little crustaceans on this occasion. 



In 1915, which may or may not have been a typical year, some multiplication of 

 M. lucens seems to have taken place from August to October, for though the dif- 

 ferences between the numbers taken are not large they are consistent. Thus none 

 at all were taken in a vertical tow off Gloucester or in the basin off Cape Ann on 

 August 31 (stations 10306 and 10307), but the stations in the coastal zone between 

 Cape Cod and Cape Elizabeth (stations 10319, 10320, and 10321) gave an average of 

 about 2,400 per square meter on September 20 to 29. On October 1 to 4 three 

 stations along the same zone (stations 10323, 10324, and 10325) gave an average of 



