140 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
increased. But that indicates nothing more than this—that 
fishing has become much more profitable since 1914; that 
there is an mcreasmg demand, and therefore better prices, 
and that fishermen have found it pays better to abandon 
other methods of working in favour of these lucrative ones, 
or else to trawl more often than they did in pre-war times. 
—$—__—__—_—_—. 
These (prelimmary) observations show that there has 
been a very marked natural periodicity in the productivity 
of the plaice fisheries durmg the term of years 1892-1917. 
Maximum succeeds minimum, and minimum succeeds maximum 
with regularity, so far as the data go. It will be interesting 
to find whether this periodicity is maintained in future years, 
and it is very important that these experimental trawlmgs 
in the Mersey Estuary should be continued by the same 
methods, and with the same care and intelligence as that 
displayed by Captain Eccles. 
As for the artificial change in conditions resulting from 
the circumstances of war, this has not affected, in the least, 
the natural periodicity noted here—at least, there is no evidence, 
- go far, that it has done so. , 
