Development of a Calcein Marking Technique for Juvenile Mulloway Argyrosomus japonicusto Be Used in Stock Enhancement Programs

Mulloway (also known as Japanese Meagre) Argyrosomus japonicusis an important recreational species targeted by anglers across southern Australia. This marine-spawned species recruits into estuaries as juveniles; however, there is some evidence for potential recruitment limitation arising from variable freshwater flows, which are characteristic of temperate Australian estuaries. Consequently, juvenile Mulloway are being stocked in a number of estuarine systems, and a suitable marking technique is required to distinguish stocked individuals from wild fish upon recapture. Calcein is widely used to mark the otoliths of freshwater fish species, yet there is little evidence of its suitability to mark marine species. We evaluated the suitability of calcein as a marking method using a combination of immersion times (6, 12, and 24 h) and calcein concentrations (0 [control], 100, 150, and 200 mg/L). Mulloway otoliths were found to autofluoresce at the same wavelengths as calcein, but despite this, a combination of the longest immersion time and highest concentration (24 h and 200 mg/L) produced marks that were significantly stronger than unmarked control otoliths. Assuming the intensity of calcein marks does not decline over time, such a combination would be suitable for marking Mulloway for release into marine waters and may be suitable for other marine species. Received May 15, 2016; accepted October 23, 2016 Published online January 12, 2017