SEA-FISHERIES LABORATORY. 297 



shown that Microcalanus pusillus appeared in the 

 deep water, in mid-channel, to the South-west of 

 the Isle of Man in large numbers in the late summer of 

 '07, and spread late in August and early in September 

 up to the surface (September 11th) and into the shallow 

 waters, until by September 21st it had entered Port Erin 

 Bay and seemed to be generally distributed. It remained 

 in evidence until the end of the year. This was inter- 

 preted in the Report as being possibly an instance of the 

 invasion of the district by a non-indigenous species. 

 Microcalanus does not appear in the '06 or earlier records. 

 It was only described by Sars in '03, and its distribution 

 was then limited to a few deep-water localities in Norway. 

 It has since been found off the N.W. coast of Scotland, 

 and (doubtfully) from the West of Ireland. It does not 

 appear to be recorded from the English Channel. If the 

 species was a new immigrant in the autumn of '07, it 

 apparently neither left again nor died out, as we find it 

 persisting throughout the winter in Port Erin Bay. 

 Altogether it appeared in 59 gatherings between August 

 24th and December 23rd, '07. In the '08 series of 

 gatherings, Microcalanus appears first on January 8th in 

 the Bay. In April it usually occurs only in the Hensen 

 and Nansen closing nets fishing in the zone from 20 up to 

 10 faths. In autumn likewise (August 5th to September 

 14th) it occurs only in the Hensen and Nansen closing 

 nets and in the weighted open tow-net which worked in 

 from 10 to 5 faths. The species was present in 49 

 gatherings during '08, extending from January 8th to 

 September 14th. 



In '09, Microcalanus is present 123 times in all, and 

 occurs in the records for every month except July, October 

 and November. Outside the Bay it is usually confined to 

 the Hensen, Nansen and weighted nets. It occurs, how- 



