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TRANSACTIONS I.I YKKPOOI. It l()L()(. K A I. SOCIETY 



REPORT OX EXPERIMENTS WITH MARKED 

 FISH DURING THE YEAR 1904. 



By Tas. Johnstone. 



A preliminary account of these experiments was 

 given in the report for 1904,* and the methods adopted 

 (which were those elaborated by the International Fishery 

 Investigation Staff) were explained. At the time when 

 this preliminary report was written, 391 fishes had been 

 marked and liberated, but since then 464 other fish have 

 been dealt with. Many of the latter experiments are still 

 incomplete, inasmuch as sufficient time has not yet 

 elapsed to allow of the recapture of the fishes. It is only 

 with regard to Experiments I. to X., which were made 

 before the end of March, 1905, that any conclusions can 

 be drawn, and many more fish will doubtless be recaptured 

 from the later experiments. 



The first few batches of fish marked and liberated 

 were to some extent experimental, as we had not at that 

 time sufficient experience of the method to enable us to 

 avoid errors. Much difficulty, for instance, was 

 experienced in finding suitable labels. The first hundred 

 of these were obtained from the Marine Biological 

 Association, and were used in the first Luce Bay 

 experiments. Then 100 aluminium labels were tried, but 

 these proved to be most unsuitable. The colour of the 

 metal and its lightness induced us to try it, but we soon 

 found that the corrosion caused by electrolytic action 

 between the label and the silver wire was very rapid, and 

 only a small percentage of these was returned. Then 

 some hundreds of thin brass labels were obtained, but 

 a^ain these were impelled, inasmuch as the metal was 

 • Report Lancashire Sen Fisheries Laboratory for L904, pp. 91-9T. 



