Mass-Marking Otoliths of Larval and Juvenile Walleyes by Immersion in Oxytetracycline, Calcein, or Calcein Blue

Abstract

Immersion of larval and juvenile walleyes Stizostedion vitreum for 6 h in a 500-mg/L solution of oxytetracycline hydrochloride or Calcein resulted in fluorescent marks on 100% of the otoliths. Few marked fish (≤27.0%) were found after immersion in Calcein blue, Immersion of larvae at 15°C resulted in significantly higher mortality (57.7%) than at 10°C (20.9%). Mortality at 10°C was lowest for larvae immersed in oxytetracycline (9.0%) and greatest for those immersed in Calcein (41.6%). Juvenile mortality (1.3–32.7%) was correlated with high pond water temperatures during June (26.1°C) and August (32.2°C). All of the juveniles survived when immersed in any of the three chemicals in cases where pond water temperatures were less than 20°C at the time of collection.