A Comparison of Injectable Fluorescent Marks in Two Genera of Darters: Effects on Mortality and Retention Rates

Visible implant elastomer (VIE) and injectable photonic dye (IPD), two types of injectable fluorescent marks, have shown promise in previous applications in fish; however, neither has been extensively tested on darters.  We marked a species from each of two genera of darters (Percina and Etheostoma) in a laboratory experiment to determine 1) the influence of VIE and IPD marks on survival, and 2) the influence of mark type, mark color, and body location on mark retention.  Short-term (≤80d) survival was similar between marked and control specimens for both species.  Long-term (240d), however, the survival rate for IPD-marked P. roanoka was significantly lower than that for controls (50 vs. 80%).  In P. roanoka, retention rate for IPD was significantly lower than that for VIE (80 vs. 94%) by day 80 of the experiment, and retention varied extensively among locations.  In E. podostemone, retention was similar for VIE and IPD (79 vs. 83%) through day 240.  Overall, VIE was a superior mark in one species, but performed similarly to IPD in another.  Because of inter- and intra-specific variability in mark performance, we recommend a pilot marking study before initiating field use of injectable marks in an untested species.