Influence of intraperitoneal implantation of 12 mm PIT on the welfare of juvenile brown trout (Salmo trutta)

The influence of the implantation of 12 mm passive integrated transponders (PIT) tags on juvenile brown trout (fork length approximately 19 cm) for 28 days after tagging was analyzed. The fish were divided into three groups: control, sham (injected with a syringe without PIT tag insertion), PIT tagged. Biological data were collected on days 0 (initial sample), 7, 14, and 28 of the experiment. Growth performance, feeding effectiveness, PIT retention, implantation wound healing, and hematological, biochemical blood plasma (stress indicators, nutritional status), and phagocytic activity indicators were analyzed. On day 28, the implantation wounds were fully healed, and PIT retention was 97.5%. The treatment did not influence growth performance, feeding effectiveness, survival, or the majority of hematological indexes. After day 7, significant changes were noted in plasma cortisol levels (PIT and sham groups), white blood cell counts (all groups), hemoglobin levels, and dif-ferential leukocyte counts (PIT group), and cidal ability after day 14 (PIT and sham groups). After day 28, the physiological indicators in the control, sham, and PIT groups did not differ significantly. These results should be taken into consideration when stocking natural streams with juvenile brown trout tagged with PITs, e.g., the period that tagged fish are held prior to stocking.

Automated summary

The influence of implanting 12 mm PIT tags on juvenile brown trout was analyzed for 28 days. The study found that the implantation wounds fully healed and the PIT retention rate was 97.5% after 28 days. Furthermore, the tags did not affect growth performance, feeding effectiveness, or survival. However, significant changes were observed in cortisol levels, white blood cell counts, hemoglobin levels, and cidal ability after tagging, although these indicators returned to normal after 28 days.