Researcher(s)
- Alex Montana, Marine Science, University of Delaware
Faculty Mentor(s)
- Ed Hale, School of Marine Science and Policy, University of Delaware
Abstract
Passive Integrated Transponder (PIT) tags are inexpensive and widely used to re-identify fish. To be detected, the tags must cross an electromagnetic field generated by an antenna with a limited (< 1 m) detection radius. PIT tag antenna detections have been observed to degrade with salinity, but this relationship has yet to be quantified. Antennas installed in estuaries, where salinity changes with tide and season, will have fluctuating detection fields. A living shoreline was recently installed in the estuarine Delaware Bay to reduce erosion. ReefBalls, small concrete domes with holes meant to attenuate wave energy and provide habitat, are a central feature. Determining which organisms use this habitat is necessary to demonstrating the installation’s benefits. A ReefBall is also small enough to be monitored by a single PIT tag antenna. An antenna was thus constructed and tested in the laboratory to investigate the relationship between detection volume and salinity. A model was fit to the data to predict detection volume given salinity and tidal height. Detection volume decreased with salinity, with a significant difference between water at 0 psu and 28 psu (p < 0.01). Replicates with different tag orientations (horizontal/vertical) had different detection volumes, so data were merged to determine the full detection boundary. A Weibull model was the best fit for the data. The antenna was installed at the living shoreline on 7/23/2026. 80 fishes were PIT tagged between 6/9/2026 and 8/2/2026. Preliminary detections include three individuals between 7/23/2026 and 8/2/2026: a black sea bass (Centropristis striata) for a cumulative 02’49.0”, an oyster toadfish (Opsanus tau) for 20’21.0”, and an American eel (Anguilla rostrata) for 0.4”. Standardizing detection volume with changing environmental conditions will improve living shoreline monitoring, justifying further artificial habitats and fisheries conservation.