lO 



THE SCIENTIFIC AND ECONOMIC ASPECTS 



birds (gannets, gulls, etc.) gave an impression that the fish 

 were more densely shoaling than they ultimately transpired to 

 be, but catches of 5,000 down distributed amongst nearly forty 

 vessels fishing over an area extending from Rame Head to 

 Looe, enclosing practically the whole of Whitesand Bay, 

 showed that the fish were swimming in that particular type 

 of open order which, so it is generally stated by fishermen, 

 is characteristic of a winter shoal. Measurements of 100 fish 

 from the tip of the snout to the curve of the tail showed a 

 length variation from 18 to 24 centimetres. 



Plankton samples taken on the position where the nets 

 were shot showed a large variety of species, the amount of 

 phytoplankton being in preponderance over zooplankton. The 

 former was chiefly composed of diatoms, Rhizosolenia 

 sioltefothii being very plentiful, whilst the animal matter was 

 represented largely by the Copepods Pseudocalanus elongatus 

 and C entro pages typiciis, together with Ohelia nigra, Sagitta 

 hipunctata, Oikopleitra dioica, etc. 



Examination of a series of stomachs showed a food condi- 

 tion very similar to that to be observed at times in early spring 

 mackerel from the Western area, viz., a coherent mass of 

 material of a greenish colour, which upon critical examination 

 proved to consist of large numbers of OikopleMra dioica, 

 Sagitta bipunctata, and occasional Copepods — Pseudocalanus 

 elo7zgattts, Corycaeus anglicns, C eniropages typicus, etc. — 

 together with a large quantity of diatomaceous matter, and the 

 " house " of Oiko pleura. 



It has been mentioned that the Medusa Obelia nigra 

 occurred in the plankton samples, its abundance causing con- 

 siderable " briming in the water along the fleet of nets, a 

 fact which caused the fishermen to consider a large catch 

 improbable. It is an important consideration therefore to 

 note that although particular search was made for the 

 manubrium of the species in the stomach material, no evidence 

 whatever of the existence of a single example was forthcom- 

 ing. Another matter of interest lay in the very high proportion 

 of Oikopleura in the stomach samples in comparison with that 

 observed in the plankton. Generally speaking, however, the 

 species identified in the stomachs were common to those of the 



