O. G. Dely szerk.: Vertebrata Hungarica 7/1-2. (Budapest, 1965)

Tóth, J. ; Rácz, B.: A new method of marking fish with a plastic (PVC) opercular tag 1-8. o.

would assure the marking of a great amount of fiah in a short time, and also the more sensitive species would tolerate their handling concomitant in the marking process; 2. The marking process and the tag itself should not cause any injuries which would eventually result in the death of the fish, at the same time assuring the retention of the tag. A practical consideration was the inexpensive, eventually home-made, production of the mark. Ever since the first attempts at marking fish /ATKINS, 1885/, countless variations of processes have been worked out. A bibliography is given by G-. A. ROUNSEFELL and J.L. KASK /1945/,their discussion by G.A. ROUNSEFELL and W.H. EVERHART /1953/, in the fundamental work on methodics. In essentials, one might distinguish three basic types of individual marking techniques: the marking of the body surface by electrical branding or by chemical compounds; indications by external markings; and the introduction of a mark within the body itself. For our purposes - mainly the simple and quick execution of the marking process - we could consider only the external attaching of the given mark. Of the many attaching methods /to the rays of the dorsal fin, the dorsal muscle, the operculum, etc./, the most meritorious seemed to be R.A. MCKENZIE'

s process /194-8/, who affixed his fish-tag, made of celluloid, by sticking it between the operculum and the preoperculum. In the elaboration of our marking method, we selected,as a starting-point, that of the above author. However, the celluloid tag was not found to be suitable for every species of fish, and its attachment failed to be lasting in every case. Hence we have attempted to make certain alterations in the method which would, besides adhering to the eminently selected site of attachment, prevent injuries or deformations of the operculum caused by the tag, and thereby its subsequent loss.