EVALUATION OF CODED WIRE TAGS FOR MARKING FINGERLING GOLDEN PERCH, MACQUARIA AMBIGUA (PERCICHTHYIDAE), AND SILVER PERCH, BIDYANUS BIDYANUS (TERAPONIDAE)

Trials were conducted to evaluate coded wire tags for marking hatchery -produced golden perch and silver perch fingerlings prior to their rel ease into the wild. Two size classes of fish were tagged:'small' fish were 21-39 mm in total length and 'large' fish were 50-71 mm in total length. Tags were implanted into either the cheek muscle or the snout. Tagging rates were 200-548 fish h-(1). Although tag retention in larg e cheek-tagged golden and silver perch was 100% after 30 days, rearing fish to this size was not practical. Retention rates for small cheek- tagged golden perch (94%) and silver perch (100%), the usual size of f ingerlings when released to the wild, were considered to be sufficient for a tagging programme. Retention of tags in the snout was poor; onl y 6% of golden perch and 48% of silver perch retained tags after 30 da ys. Most cheek-implanted tags that were shed by fish during long-term tag-retention trials were lost in the first four months. With the exce ption of silver perch in one trial, which were infested by Ichthyophth irius multifiliis, survival of tagged fish was 95-100% after 30 days. Factors affecting tag retention and survival of tagged fish, including fish size, tagging site and operator experience, are discussed. The r esults indicate that coded wire tags are a potential means of marking golden and silver perch fingerlings prior to stocking. Their use will assist fisheries managers in the assessment of the contribution of sto cking programmes to commercial and recreational fisheries.