3 



J. O. BOKLEY 



\i. Ill iliis mutliDil ilic iiKuk used in 1) was applied at tiic base of tlic mid-dorsal fin. 



!•". This was method C with a vulcanite button substituted for a bone one. 



It may be of interest to e.xaminc the success which attended these methods. The 

 methods 1* and C may be treated as one: it may be taken as a coincidence that each of 

 the two recoveries from method F had a bad wound at the label. The following table 

 gives the results. Feeble or moribund fish are excluded. 



Recaptures after 6 months are not numerous. Eight fish out of 202 marked by 

 methods A, C and F and still untaken 6 months after marking were caught during their 

 second six months of liberty, and one fish marked by method D out of 37 untaken 

 after the same interval was returned fifteen, and one thirteen months after liberation. 



From the above remarks it will be seen that all the methods used were somewhat 

 unsatisfactory, since their labels appear either to have become detached a few months 

 after marking, . or possibly in some cases to have fatally injured the fish. As far as 

 the small figures concerned can show, no method used has a very marked superiority 

 over the others: and an examination of the records of fish recorded as having bad or 

 sore wounds under the label leads to much the same result. There is however, one 

 consideration much in favour of the use of methods which like A and C mark the body 

 of the fish, not the head, which is due to the number of fish returned from the fish-curers. These 

 cod are generally headless and of course are useless for most of the purposes of the 

 experiments, but they are at least available for ascertaining the proportion caught; 

 and a body-mark on the fish gives it this last chance of usefulness which a head-mark 

 would probably fail to do. 



The number returned within six months constitutes 12-9 % of the healthy fish set 

 at hberty. Of the 91 cod marked on the Dogger Bank 15 ■4% were returned during 

 the same period, a lower figure than the corresponding one for plaice; in the years re- 

 presented in the experiments 316 plaice of 25 cm. or more in length were transplanted 

 to the Dogger Bank, and within six months of liberation 21-5 % had been returned. 

 Smaller plaice are omitted in the above comparison as they are less likely to attract 

 the notice of fishermen than either larger plaice or cod. The smaller proportion of cod 

 returned is probably partly due to the difficulty of eflTectively marking cod, and may be 

 partly also the effect of fishermen being less actively on the look out for marked cod 

 than for marked plaice, with which they are now familiar. 



Migration. The chief conclusion to which examination of the chart leads is that 

 of the fish of whose recovery full particulars are available none travelled very far and all 

 appear to have stayed in localities of much the same character as those in which they 

 were first caught. Drs. Hjort and Petersen in their review of the results (obtained by 

 the end of 1904) in the International Fisheries Investigations write «The German re- 

 presentative statistics and the English and Scotch investigations of the North Sea banks, 



