— 17 — LATER STACKS: PLEURONECTIDS 



Food and Age — The food of the first bottom stages (Helgoland and Dune) — May 

 to November — consists chiefly of Crustacea and shows a seasonal variation asfoUows : — 



Date. Food. 



May Small Polychaeta and Crustacea {Harpacticids'). 



June Same. 



July 5th A small Mollusc found for first time. 



July 31st Cunia rathkei appeared for the first time and was never absent 



from then onwards in the smaller fish. 



August 1 I th Amphipods as well as above. 



August 18th Also Crab larvae (Megalopae). 



November 2nd. ... Mysidae. 



In 2 year plaice molluscs appeared in fair quantity for the first time. 



From 3rd. year onwards the Mollusca become most important. His observations 

 show that Molhcsca are the chief food of the plaice, more so than in any other fish in 

 the North Sea, the species especially favoured being Nucula, Corbiila, Syndosmya, 

 Mactra, whilst the species of the other groups are Pectinaria and Antphiura. 



These conclusions corroborate those of Todd so far as they go, but he omits Solen, 

 Tellina and Douax from his list of favoured species, probably from restricted observa- 

 tion. These species were found in large quantities by Todd. Solen is one of the chief 

 species found in plaice-food on the Dogger, whilst Donax and Tellina are both excee- 

 dingly common in the Flemish Bight — Leman to Brown Ridges. 



In the 3rd. year and onwards differences in food were found which may be due to 

 the larger fish eating larger animals. 



He draws the further conclusion that large plaice (40- 60 cm.) eat more Brachyura 

 and Pagurus than smaller citing one or two single examples. 



He summarises the food of plaice as follows: — 1st. bottom stages — species of 

 small Crustacea, at first Harpacticids, later more Cuma. 



From 3rd. year Mollusca form the chief food whilst at 40 cm. the fish eat more 

 large Crustacea than previously. Polychaeta occur at all stages, ophiurids from 3 years 

 onwards. 



Food and Food grounds— There are considerable differences in food from 

 different localities, and two examples are given of comparison between the species found 

 in the dredge and those found in the stomachs showing that the food depends on the 

 nature of the bottom fauna. 



In some regions, small condguous areas may be quite different in food supply, while 

 in other parts of the sea, we may have large uniform areas. As an example, the Dogger 

 Bank is given, and contrasted with another large uniform area — the South Mud Bank, 

 its contiguous neighbour to the North East. 



It is shown that stomach contents do not give a true sample of the bottom fauna, 

 but only a biassed one, the bias being always in a particular direction i. e. towards the 

 smaller animals. 



The opinion is expressed that plaice have no definite predilections but eat all bottom 

 animals and that the composition of the food depends first, on what it can perceive with 

 its sense organs, and second, what it is able, from physical considerations, to devour. 



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