172 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY^ 



AN EXAMINATION OF THE OBSERVATIONS 



MADE ON THE BLACKPOOL CLOSED GROUND 



DURING THE PERIOD 1892 TO 1906. 



(Plate IV.) 



By H. J. Buchanan Wollaston. 



The statistics for the Closed Ground off Blackpool 

 deal with 327 hauls made with shrimp-trawl, shank-net, 

 and fish-trawl. Table I. is an analysis of the hauls. In 

 three years, 1899, 1901, and 1902, no hauls were taken with 

 the shank-net. As our aim is to form some idea of the 

 variation in the number of young fish from month to 

 month, or year to year, it is obviously of little value to 

 consider the catches of the fish trawls, which have large 

 meshes and are constructed to avoid as much as possible 

 the capture of young fish. We have to resort then to 

 hauls taken with the shrimp-trawl and shank-net for 

 results. 



The numbers of hauls were found to be quite 

 insufficient to give useful results if taken monthly. They 

 have, therefore, been taken in seasons of three months 

 each, viz., January to March, April to June, July to 

 September, and October to December, as will be seen on 

 reference to Table I. 



The relation between the shrimp-net and shank-net 

 in catching power is shown in Table II. The results were 

 obtained by averaging groups of hauls taken with the 

 two kinds of net as far as possible on the same day and 

 under similar conditions. The averages of the values thus 

 obtained were then reduced to hourly catch, thus giving 

 a fairly reliable picture of the relation between the nets in 

 taking-power. The shank-net thus appears to be far 

 superior to the shrimp-trawl in avoiding the capture of 



