of Diatoms and cotepoda in The utisit sea. 



117 



Calanids has gone, and there are now no signs of mackerel feeding in the 

 bay. In fact, the change has been noticeable for some days in the seas 

 outside, and we have not been getting lately the large plankton catches 

 that were usual in the latter half of July. On July 14th a haul of the 

 large surface tow-net, in the open sea off Ardnamurchan, gave such a huge 

 catch of Calanus (about 1000 c.c.) that we promptly took a second similar 

 haul, and had it cooked as a sort of potted ' shrimp ' confection for tea 

 (sampled by ten persons, including the crew, who were much interested to 

 try this new edible 'fish') ; while on August 11th a haul of the same 

 net, taken at the same spot, gave only a small catch of some 15 c.c, 

 containing very few Calanids, along with the usual scanty summer 

 zooplankton." .... 



The importance of Calanus as a food for migratory pelagic fishes such 

 as the mackerel cannot be doubted (see fig. 14). 



PSEUDOCALANUS. 



P seudocalanus elongatus (Boeck) is widely distributed in the North Atlantic 

 ami is present in the Irish Sea throughout the year (fig. 15). It reaches its 

 lowest level in January and February, and has its maximum in late summer 

 and autumn (June to October in our records, generally September or October). 



Flo. 10, — Fseudocalanus elongatus, from a photo-micrograph by A. Scott. ' 



This Copepod comes next alter Oithona as the second most abundant 

 species in the Irish Sea, its average per haul over the ten years being 4583. 



Some of the most important records are : — (15,200 on May 20th, 1912 ; 

 91,960 on October 21st, 1912 ; 08,120 on June 21th, 191)'. ; 60,000 on May 

 5th, 1916 ; 59,600 on September 25th, 19H ; 58,200 on October 31st, 1912 ; 

 54,350 on July 31st, 1911 ; and many other records between 35,000 and 

 50,000 in these same months. 



