SECTIONAL TRANSACTIONS.— D. 369 



and .1. hcviijata; Turritella communis is avoided by both. A Paludestrina- 

 Cardium-jMacoma community in the littoral zone of the Dovey Estuary is also 

 under investigation : plaice caught over this region contained Cardium edtde. 

 Curves indicate the period of growth and rate of growth of various forms, 

 and fluctuations in the frequency of their occurrsnce in successive years. In 

 the cockle the fluctuations are p.-irticukily striking, and an attempt is made 

 to throw some light upon them. 



((') Dr. Joseph Pearson. — The Growtli-rate of Phcwiia Placenta. 



The account was bated on a considerable mass of data from Ceylon waters, 

 and was a summary of twelve years' work. Illustrative curves dealing with 

 linear growth and with weight were exhibited. 



7. Dr. Joseph Pearson exhibited diagrams showing a remarkable series 

 of seasonal changes in the salinity of Lalce Tamblegam, a large marine 

 area opening by a narrow entrance from the harbour si Trincomalee, 

 Ceylon. 



8. Inspection of Eesearch Vessels. — The members of the Section 

 inspected the reseaiTh vessels A-isiting Hull during the meeting — 

 namely, the Danish Government vessel Dana, the Scottish Explorer, 

 the George Bligh of the English Ministry of Agriculture and Fisheries, 

 the Salpa from the Marine Biological Association at Plymouth, and the 

 Evadne from Cullercoats. 



Friday, September 8, 



9. Presidential Address by Dr. E. J. Allen, F.R.S., on The 



Progression of Life in the Sea. (See p. 79.) 



10. Discussion on The Sea Fisheries. (a) Opener: Mr. J. A. 

 Robertson, J. P., O.B.E., on Fluctuations in the Fisheries. 



There have always been apprehensions that the stock of trawl fish was 

 diminishing- through over-fishing. Since 1853 a variety of Commissions have 

 investigated the matter, Acts of Parliament have been passed and repealed, 

 but no authoritative finds have been reached. The present paper suggests 

 that rather than there being a progressive diminishing of the stock of fish due 

 to fishing operations, there are upward and dov/nward fluctuations about a 

 mean which are of more importance than are human agencies due to such 

 factors as temperature and food supply. An increase in the intensity of fishing 

 may lower the mean about which the fluctuations occur, but the degree of 

 lowering will not be material. An example is given of what is believed to be 

 a case of a Huctuation clue to natural agencies. 'Hake had not been recorded 

 in any abundance on the Morecambe Bay grounds before 1899, but in that 

 year large hauls were made by a few boats, which secured still greater catches 

 in 1900; but in 1901 very few were caught, and by 1905 they had entirely 

 disappeared and have not reappeared since. In this case there was no question 

 of the gradual depletion of a regularly fished ground. Again, the fishing trade 

 had made plans to deal with considerably increased catches in the North Sea, 

 which it was anticipated would follow the rest period of the War. It was 

 calculated that in 1920, when the trawling fleet had ^ct hack to its full strength, 

 catches would be double the pre-War maximum, l.-at the quantity L-vnded was 

 actually less than a third of what was anticipated. The main obstacle to the 

 solution of this difficult problem is the lack of reliable statistics. The present 

 method of collecting them is nnti'ustworthy. At Cilrimsby , for example, erroneous 

 statistics were known to be given to the Ministry's collectors, so that trade 

 grants might be preserved, and so in conclusion a strong plea is made for co- 

 pperation bgtwpen the Ministry and the industry for the drawing rip of a new 



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