MARINE BIOLOGICAL STATION AT PORT ERIN. 53 



" We all believe that most of our common food-fishes at 

 some stage of life feed upon plankton, but those who have 

 looked into sea-fisheries questions know that there is a great 

 want of actual observations connecting the occurrence of some 

 planktonic organism in quantity with the presence of a 

 particular fish. Consequently the following record may be of 

 interest to both marine biologists and fisheries experts. 



" We are out on a scientific fisheries cruise, and in addition 

 to members of my own family, two well-known naturalists, 

 Professor Newstead and Mr. Alfred 0. Walker, are with us on 

 the yacht, and we have just had what we all regard as a 

 satisfactory demonstration of the connection between a large 

 shoal of mackerel and the occurrence of Calanus finmarchicus 

 in unusual quantity. 



" 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, on looking closely, I found to be caused by large Cope- 

 poda close to the surface. 



" About twenty years ago I sent a 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. 



