OF DIATOMS AND COPEPODA IN THE IRISH SEA. 193 
from the yacht at various localities in the deep lochs on the west coast of 
Scotland large hauls of Calanus by means of vertical hauls when no 
specimens were obtained at the surface. In fact this Copepod seems to be 
permanently present in the deeper waters of these lochs. 
Tn addition to these deep water specimens of Calanus we find on occasions, 
on the west coast of Scotland, large swarms on the surface, which may be 
the result of invasions from the ocean, and there is a considerable amount of 
evidence that such swarms are the cause of local mackerel fisheries. 
Some years ago (1909) Dr. E. J. Allen and Mr. G. E. Bullen published * 
some interesting work, from the Plymouth Marine Laboratory, demonstrating 
the connection between mackerel and Calanus and sunshine in the English 
Channel; and Farranf states that in the spring fishery: on the West of 
Ireland the food of the mackerel is mainly composed of Calanus. In the 
summer of 1913 we had an experience at Tobermory, in Mull, which I shall 
quote from two letters written from the yacht at the time, and published in 
* Nature." 
* S.Y. ‘Runa,’ Tobermory, July 12th, 1913. 
“ On arriving in this bay last night we found that the local boats had been 
catching abundance of mackerel close to. We bought some for supper (good 
fish for a halfpenny each), and on dissection found that the stomachs of all 
of them were crammed full of fresh-looking Calanus (the individual Copepods 
being for the most part distinct and perfect), along with a few immature 
Nyctiphanes and larval Decapods. Professor Newstead and my daughter 
then noticed, while fishing over the side of the yacht, about 8 p.m., that the 
gulls in the bay were feeding in groups around patches of agitated water 
evidently caused by shoals of fish. On rowing out to these we saw distinctly 
the mackerel, large and small, darting about in great numbers in the clear 
water, and we also noticed every here and there on the smooth surface of the 
water—it was a beautifully calm evening—innumerable small whirls or 
circular marks which, looking closely, I found to be caused by large Copepoda 
close to the surface. 
“ About twenty years ago I senta note to ‘ Nature,’ from the yacht * Argo,’ 
in regard to large Copepoda (I think it was Anomalocera on that occasion, and 
the locality was further north, off Skye), splashing on the surface so as to 
give the appearance of fine rain; and this present occurrence at once 
reminded me of the former occasion, but here the Copepod was Calanus 
inmarchicus of large size and in extraordinary abundance. They could be 
clearly seen with the eye on leaning over the side of the boat, a small glass 
collecting jar dipped at random into the water brought out twenty to thirty 
specimens at each dip, and a coarse grit-gauze tow-net of about 30 em. in 
diameter caught about 20 cubic centimetres of the Copepoda in five minutes. 
* Journ. Mar. Biol. Assoc. vol. viii. (1909) pp. 394-406. 
T Conseil Internat. Bull. Trimestr. 1902-8, Planktonique, p. 89. 
TURN 
