Calcein and alizarin red S are safe and effective fluorochrome labels for marking Atlantic Sturgeon pectoral fin spines

Objective Fluorochrome markers are often used for in vivo studies investigating increment formation in calcified structures of fish (e.g., otoliths, bones, or scales) because they are rapidly incorporated and form a visible time stamp in the structures. Oxytetracycline is the most common fluorochrome marker used in fisheries studies, but due to concerns about antibiotic resistance, its use has been discouraged or restricted. We evaluated safety and efficacy of intramuscular injection of two alternative fluorochrome markers, calcein and alizarin red S (ARS), for marking pectoral fin spines in age-1, hatchery-raised Atlantic Sturgeon Acipenser oxyrinchus. Methods We injected 20 age-1 Atlantic Sturgeon for each of three calcein and ARS dosage treatments. Growth and survival of experimental fish were compared with those of fish injected with 0.9% sterile saline (procedural control) and fish that were not injected with anything. Half of the fish received an injection in late May at a tank water temperature of 23°C, and half were given an injection in mid-July at a tank water temperature of 29.5°C to simulate water temperatures in southeastern rivers during the sampling period. Fish growth and survival were monitored until early October, when small sections of the pectoral fin spine were collected to evaluate marking efficacy. Contingency tables were used to compare survival across treatments, and ANOVA was used to compare growth (length and weight). Results Survival was high (>97%) across the study period and did not differ among treatments; only one mortality was observed for each of the chemical and saline treatments, and one mortality was observed in fish that did not receive an injection. Marking was 100% effective for fish injected with calcein and 98% effective for fish injected with ARS. Growth did not differ across treatments. Conclusions Calcein and ARS are safe and effective fluorochrome markers for use in juvenile Atlantic Sturgeon. Because we found effective marking at all treatment levels, we recommend a calcein dosage of 5 mg/kg or the use of our low-dosage protocol for ARS.