Desenvolvimento de novo marcador visual externo para peixes e suas influências sobre desempenho e hematologia de Pacamã (Lophiosilurus alexandri)

Abstract

The purpose of this work was to produce and test a technology that allows the manufacture and application of an external visual fish tag, economically viable that presents a good retention rate without compromising the performance of the animals. Firstly, an external device was developed (BR1020170075770) containing a fish tag (obtained via laser cutting of PETG polymer sheets) and an applicator with needle, latch and holder. The technology developed was tested in Pacamã (Lophiosilurus alexandri) and two experiments were carried out. In the first one, the retention rate and the influence of the tag on the survival and weight gain of three size classes of L. alexandri: small (10.58 ± 0.63 cm and 14.50 ± 0.63 g), medium (11.71 ± 0.52 cm and 23.95 ± 1.76 g) and big (13.5 ± 0.60 cm and 31, 96 ± 3.50 g) for 90 days. Four replicates were used for each animal size, each replicate was composed of 25 animals, 15 animals with tag and 10 animals without tag. The retention rate of the tags was calculated every 30 days and the weight gain of the animals at the end of the 90 days. In the second experiment, the influence of the Tag on hematological parameters of juveniles (17.09 ± 1.02 cm and 64.28 ± 11.80 g) was verified after 5, 10 and 30 days of the tagging that were compared to non-juvenile animals tagged. In experiment 1, the survival rate was 100%. The tag presented a higher retention rate (P <0.05) for big animals, and at the end of 90 days the retention rate was: 46.66 ± 5.44% for the small, 63.31 ± 3.83% for the Medium and 84, 83 ± 8.34% for the big animals. Small animals with tag gained less weight (P <0.05) than small animals untagged. In Experiment 2, the mortality was of two fishes: one tagged and the other untagged. Hematocrit level was higher on the thirtieth day for tagged animals, while no difference was observed on the level of leukocytes, plasma protein, erythrocytes and corpuscular volume. We can conclude that the developed device presented limitations when applied in smalls L. alexandri, resulting in low retention rate and influence on the weight gain. However, it had a good retention rate and no influence on the weight gain of the big animals. We also observed the increasing of retention rate with the size of the animals. Among the hematological parameters studied the marker only influenced the hematocrit, which shows that the tag can be used without causing big influences in the physiology of the animals.