OF THE CORNISH PH.CHARD FISHERY. 



21 



week in June of the present year. The tow-nettings taken in 

 August did not show the species other than in comparative 

 scarcity at any of the stations. It is fair to suppose therefore 

 that the shoal of Ajzomalocera and Calamis observed by Mr. 

 Matthias Dunn formed a later immigration into the coastal 

 waters. 



In a paper upon the mackerel,"^ previously referred to, 

 mention is made of certain types of w^ater described by the 

 fishermen as being of a " yellow," " blue " or " green " colour. 

 We already possess sufficient evidence in the form of stomach 

 material taken from mackerel caught in " yellow " w^ater to 

 show that this colour is probably due entirely to the presence 

 of a vast shoal of Calanoids, not necessarily of one species, 

 congregated at the surface. Mr. Dunn's observation appears 

 to throw some light upon the two other types of water, which 

 are considered by fishermen to offer attraction to drift fishes," 

 for if we may rely upon the evidence afforded by a single 

 sample, it would appear probable that a green or blue colour 

 is imparted to the surface of the water under varying conditions 

 of light by the presence of a dense shoal of Anomalocera, 

 which, it is well known, is of a vivid emerald hue. The sug- 

 gestion of yellow referred to in the above letter might possibly 

 have been due to segregated shoals of Calanus. 



The most important consideration, however, afforded by 

 these Mounts Bay observations generally is that there is some 

 ground for supposing that w^hilst phytoplankton remained 

 throughout the area in profusion, the fish were not attracted to 

 the coastal waters, whereas on the first advent of shoals of cer- 

 tain zooplankton organisms, which were undoubtedly of high 

 nutrient value, the fish began to arrive in their usual summer 

 haunts, and the fishery became productive. From which we 

 may presume that zooplankton forms " food of preference " 

 as far as the pilchard is concerned. 



Passing now to a consideration of the feeding habits of the 

 pilchard, it may be remarked that there is a certain amount of 



21 "Plankton Studies in relation to the Western Mackerel Fishery," p. 290. 



22 Id., p. 288. 



