Efficacy of PIT tags and an autonomous antenna system to study the juvenile life stage of an estuarine-dependent fish

Many marine fishes use spatially distinct habitats as juveniles and adults. Determining which juvenile habitats are most important to sustaining adult populations (i.e., which habitats are nurseries) has proven difficult, in part due to challenges in estimating survival of juveniles in putative nursery habitats. Recent technological advances have made large-scale tagging efforts a viable approach to estimating survival of juvenile fishes by increasing recapture rates and enabling the use of individual-identification tags. These techniques, using Passive Integrated Transponder (PIT) tags and autonomous antenna detection systems (antenna), have been successfully applied in freshwater environments. This paper reports the adaptation of these techniques to estuarine mangrove creeks (salinity: 2-28 parts per thousand) for research of the juvenile life stage on an estuarine-dependent marine fish, Centropomus undecimalis. Retention rate of PIT tags in juveniles > 120 mm standard length was 100%, with no mortality. The antenna detection field covered 48% of the creek water column, and the antenna was experimentally determined to detect approximately 67% of tagged fish that swam through. Overall recapture rate of tagged fish by the antenna was > 40%. This recapture rate is higher than the sparse data typical of traditional tag-recapture studies. A time-dependent Jolly-Seber model was fit to the data, providing estimates of capture probability (0.8) and weekly apparent survival (0.41) that will be invaluable in comparing juvenile habitats of different quality (e.g., natural versus anthropogenically degraded). This research demonstrates the viability of this approach to fish research in estuarine habitats.