272 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



different countries, but the most successful form of mark 

 seems to have been that first employed by the Dutch 

 investigators and elaborated later on by the English 

 section of the international fishery research organisation, 

 and adopted now by England, Sweden, Holland and Belgium. 



A photograph of a plaice bearing a mark is given 

 in PL II. 



This consists of a bone button and a numbered brass 

 label fixed to the body of the fish by means of a silver 

 wire. The wire is about one inch in length and is *85mm. 

 thick. A small loop is made at one end and is bent down 

 at right angles to the rest of the wire. A bone button 

 about f inch in diameter is threaded on this wire. A 

 narrow hole is pierced through the body of the fish (flat 

 fishes only) about midway between the head and the tail 

 and about 1cm. below the insertion of the dorsal fin. The 

 wire is then pushed through this hole so that the bone 

 button is on the blind side of the fish and the brass label 

 is then threaded on the wire so that it lies on the ocular 

 side. The free end of the wire is now bent into a small 

 closed loop with round-nosed pliers, and the loop is turned 

 down at right angles. In making these experiments the 

 fishes are caught by a wide meshed trawl net hauled for 

 an hour so as to catch comparatively few fishes, and not 

 to encumber and damage -them with a mass of invertebrate 

 and other debris. The fish suitable for marking are 

 rapidly picked out as soon as the net is hauled, and are at 

 once put into tanks through which a continual stream of 

 sea water circulates. After a few hours any injured or 

 obviously un healthy fish are picked out and rejected. 

 The others are marked. One man takes the fish from the 

 tank, measures it, calls out the size, and hands it to the 

 operator. Another man records the size of the fish and 

 the number of the label to be used, which he hands to the 



