V^od-u)arking experiments have been conducted from the SS "Huxley" at intervals 

 during the past four years. Unfortunately the condition of trawl-caught cod is seldom 

 so good as to furnish any reasonable hope of the fish surviving if returned to the sea ; for 

 this reason although the number of occasions on which cod were marked and liberated 

 is 48, the total number of fish treated has only reached 252. In examining the accom- 

 panying chart, which has been drawn up to illustrate the result of these experiments, 

 the small number of fish liberated must be born in mind; at many of the libei'ation 

 points one fish only was liberated, and the maximum number for an experiment is 40. 

 The small number of fish charted as recaptured is thus no indication of a low proportion 

 of cod returned. The area in which the experiments were made consists of the Dogger 

 Bank, and the sea to the south-west of it and some 60 miles beyond its western border. 

 Some cod were also marked between Lat. 52° and 53° N. and west of 3° E. 



Method. Cod intended for marking were, on hauling the trawl, immediately 

 placed m tanks previously put in readiness and furnished with a constant circulation of 

 sea-water. If apparently healthy they were taken out, measured (the measurement being 

 made to the centre of the posterior margin of the tail fin), marked, and returned to 

 the tank; if after some time still free from any evidence of injury, they were thrown 

 overboard. Various methods of marking were tried. In the detailed~account of the ex- 

 periments these are designated by the letters A— F; these letters have the following 

 significance ; 



A. A bone button was fitted with a silver wire as in the Danish and British method 

 of plaice marking, the wire being prevented from passing right through the button by a 

 loop at its end. A hole was then pierced just behind the base of the second dorsal fin, 

 the silver wire passed through until the button rested against the cod, a numbered brass 

 disc (a plaice label) was threaded on the wire, and the wire turned down to keep the 

 disc in place. To allow for the growth of the cod, the label and button were not made 

 to fit very closely to the back of the cod. Method A is thus a common plaice marking 

 method, applied to the cod. 



B. The same marks or labels, wire, and buttons were used, but they were applied 

 to the gill cover. The button was inside the gill cover, the brass disc without. 



C. This is identical with A except in the position of the label, which was placed at 

 the base of the mid-dorsal fin. 



D. In this, a black vulcanite stud identical with the Helgoland plaice-label was used. 

 It was forced through the gill cover from within, the flat disc only remaining inside the 

 gill chamber. 



