SEA-FISHERIES LABORATORY, 



279 



Before the middle of June the plankton begins to increase 

 in quantity again, and this is seen to be due to zoo- 

 plankton, which now predominates over the phyto- 

 plankton. In fact the Diatom maximum is followed by 

 the appearance of Dinonagellates, and then of Copepoda, 

 Sagitta and Medusae, although the increase in one or all 

 of these may be due to the normal life-history of the 

 organisms and so, perhaps, be quite independent of the 

 previous Diatom maximum. 



A remarkable swarm of Lamellibranch larvae (pro- 

 bably Pecten opercularis) was encountered outside the 

 Bay, mainly at Stat. Ill, on April 5th. A few Lamelli- 

 branch larvae are always present throughout the year. 

 On March 31st they reach 1,000, and in the first days of 

 April the numbers increase to two or three thousand per 

 haul, and then on April 5th there is a sudden increase to 

 form the maximum of 117,000 in the fine surface net at 

 Stat. Ill ; but other large hauls were taken also that day, 

 as the following table shows : — 



Surf. Surf. Surf. Surf. Hensen. Nansen. Weight. 



Coarse, fine. Old. Otter. 



Stat. I. 10,000 111,000 19,520 58,800 5,520 1,600 59,000 



Stat. III. 30,000 117,000 24,000 86,000 1,600 2,350 110,000 



The numbers remain high for the next two or three 

 days. On the 6th one haul gave 70,000, and on the 7th 

 the largest haul was 55,000. After that the numbers 

 rapidly fell to 1,000 in June, and with occasional rather 

 higher records (6,000 on October 18th), died away to end 

 the year as it began with a few hundreds and tens. There 

 was no such swarm of Molluscan larvae in either of the 

 previous years. In '08 the highest number was 7,500; 

 and in '07, 2,500. 



