Positional effects of passive integrated transponder tags on rejection, survival, and health biomarkers in pearlspot cichlid (Etroplus suratensis).

Abstract

Passive integrated transponder (PIT) tagging is essential in fisheries research to monitor fish growth, health, and migration, and facilitate selective breeding and aquaculture advancement. The study was conducted for 30 days to assess the effect of the PIT tag (12 mm × 2.1 mm) on juvenile Etroplus suratensis. The tagging study consisted of five treatments, viz., dorsal horizontal (DH), dorsal vertical (DV), peritoneal cavity via injection (PCI), peritoneal cavity via incision and manual insertion (PCM), and untagged control (UT) in triplicate. Fifteen circular containers containing 60 L of UV-sterilized water were stocked with 15 juveniles each, with an average weight of 10.60 ± 0.06 g and a total length of 67.75 ± 1.07 mm. Fish were given commercial floating feed with 38% crude protein thrice daily (9 am, 1 pm, and 5 pm). In the present study, the DV-tagged juveniles had the highest survival (95.55 ± 2.22%) with a low tag rejection rate (4.44 ± 2.22%) and a higher weight gain (5.10 ± 0.76 g), followed by the DH-tagged, which showed survival of 91.11 ± 2.22% with a tag rejection of 31.11 ± 2.22% and a weight gain of 4.36 ± 0.23 g. The serum biochemical and haematological parameters were substantially higher in tagged fish than in untagged fish. Histological examination of tagged fish revealed observable changes in myocytes compared with untagged fish. Analysis of growth, survivability, tag rejection rate, and histological interpretations indicate that DV tagging is the best practice for E. suratensis juveniles. This study highlighted the importance of optimizing PIT tagging procedures for E. suratensis and demonstrated that the insertion position significantly influences tag retention, survival, and stress parameters. The results enhance the acceptability of PIT tagging in pearlspot for aquaculture and stock assessment studies.