2552 



108 



REPOIIT OX EXPERIMENTS AVITH MARKED 

 FISH DT RIXG THE YEAR 1904. 



]>y I AS. loilXSJOXK. 



A })i'eliiiiiiiaiy account of ilicsc cxpciiiucnls was 

 pivoii in the report for 1904,'" and tlio methods adopted 

 (whieh were those elaborated by the International Fishery 

 Investififation Staff) were explained. At the time when 

 this ijreliminary report was written, •»91 fishes had been 

 marked and liberated, but since then 404 other fish have 

 been dealt with. Many of the latter experiments are still 

 incomplete, inasmuch as sufHciiMit tinu^ has not yet 

 ela})sed to allow of the recapture of the fishes. It is only 

 w'ith regard to Experiments I. to X., which Avere made 

 before the end of March, 190-1, tliat any conclusioTis can 

 be drawn, and many more fish will doubtless be recaptuicd 

 from the later expeiimenfs. 



The first few batches of fish marked and liberated 

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

 time sufficient experience of the method to enable us to 

 UA'oid errors. Much difficulty, for instance, was 

 experienced in finding suitable labels. 'J'he first hundred 

 of these were obtained from the Marine liiologiral 

 Association, and were used in the hist Luce 13ay 

 experiments. Then 100 aluminium labels were tried, but 

 these proved to be most unsuitable. ^Fhe 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 

 again these were imperfect, inasmuch as the metal was 



* ll(,']iorl, l.aiicusliii'e Swi Fisheries Laboratury fur I'JOi, pp. 'Jl-'JI , 



