<b>Evaluation of different external marking positions in juveniles of tilapia <em>Oreochromis niloticus</em> (Cichlidae)</b> - DOI: 10.4025/actascianimsci.v25i2.2001

Abstract

The effect of marking techniques on the development of tilapia juveniles, Oreochromis niloticus L. (Cichlidae) and their efficiency were evaluated. By means of a n. 9 needle, a flexible synthetic string (0.20mm) containing synthetic colored beads was fixed on the fish muscle in three positions: anterior part of the dorsal fin (D), insertion muscle of the dorsal (C) and ventral (V) fins. One hundred and twenty specimens, weight 11.5g and length 8.2cm, were marked and distributed into two net tanks, with stocking density of 30 fish.m-3. Sixty fish were stocked in each tank (three groups marked D, C and V, and one control group with no mark at all, SM), with 15 specimens per treatment. Results show that after 60 days C position was the most efficient; 5 specimens lost D marking, 2 lost C marking and 3 V marking, in each tank. Mean performance rates ranged from 40.8 to 55.7g; highest rates were those from marked ones (p<0.05). There was no difference in rates within the four groups for SM and D juveniles. Since marking technique did not cause any negative effect on the development of juveniles, it may be recommended for use.