Internal Micro-tag Systems for Marking Juvenile Reef Fishes

Both intrinsic and extrinsic identification systems are commonly used to distinguish fish in biological and ecological studies. Easily recognizable variations in intrinsic factors are limited, constraining experimental parameters. Application of extrinsic marking systems enables validation of biocenosis assumptions and expands experimental parameters, especially relating to species, habitat configuration, and spatial and temporal scales. Fish tags are successful extrinsic identification systems that are seldom used to mark juvenile or small-sized reef fishes, usually due to physical incompatibility between the size of the fish and external tags. The binary-coded wire tag (CWT), alpha-numeric-coded Visible Implant (VI) tag, and Visible Implant Fluorescent (VIF) filament tag, are bio-compatible internal micro-tags that were tested in this study for applications in marking juvenile temperate reef fishes. Three tests of CWT resulted in 100% retention at 330d, 310d, and 68d, for Sehastes caurinus, S. maliger, S. auriculatus, and S. emphaeus (36–94 mm TL at tagging). Retention of VI tags varied with tag location and species; retention was 100% at 160 d in Ophiodon elongatus (152–190 mm TL at tagging), 85% at 330 d in S. emphaeus, and 0–7% and 9% at 245 d and 59 d, respectively, in two tests with the four species of Sebastes. Retention of VIF tags was 93% at 132 d in S. caurinus and S. maliger (30–62 mm TL at tagging). VIF tags in juvenile Sebastes spp. released on an artificial reef were visually recovered in situ up to 258 d during strip transects using ultra-violet underwater lights.