J Appl Ichthyol. 2017;1–5. wileyonlinelibrary.com/journal/jai | 1 © 2017 Blackwell Verlag GmbH Received: 7 April 2017 | Accepted: 6 July 2017 DOI: 10.1111/jai.13447 ORIGINAL ARTICLE The use of live and frozen Artemia salina nauplii enriched with fluorochromes for mass-marking vendace Coregonus albula (L.) larvae K. Stańczak 1,2 | K. Mierzejewska 1 | J. Król 2 | P. Hliwa 2 1 Department of Fish Biology and Pisciculture, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland 2 Department of Ichthyology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland Correspondence Katarzyna Stańczak, Department of Fish Biology and Pisciculture, University of Warmia and Mazury in Olsztyn, Poland. Email: katarzyna.stanczak@uwm.edu.pl Funding information University of Warmia and Mazury in Olsztyn, Grant/Award Number: 18.610.001-300 and 18.610.003-300 Summary The aim of this study was to investigate the use of Artemia salina nauplii enriched with chosen fluorochromes for mass marking vendace Coregonus albula (L.) larvae. In the experiment, vendace larvae (6 DPH) were fed with live or frozen A. salina nauplii im- mersed in tetracycline hydrochloride (TC), calcein (Cal) or alizarin red S (ARS) for four subsequent days. More successful effects (marking otoliths) were obtained by feeding the fish with live nauplii enriched with fluorochromes, regardless of the dye type. The highest percentage of marked otoliths (100%) was recorded in the group fed with live nauplii immersed in TC. In the groups fed live or frozen nauplii enriched with Cal and ARS, a lower percentage of marked individuals (63.3%–73.7% and 56.7%–63.3%, respectively) were recorded. The survival rate of vendace larvae in particular groups oscillated between 93.7% and 95.7%. There were no significant differences in the total body length and body weight of the reared vendace larvae among different groups. In conclusion, for mass marking of vendace larvae using a feeding method, fish fed A. salinalive nauplii enriched with TC at a dose of 600 ppm is recommended for fishery practice. 1 | INTRODUCTION By the end of the 80s of XX century, the native coregonids (whitefish - Coregonus lavaretus L. and vendace - Coregonus albula L.) inhabited more than 50% of Polish lakes. Currently, in most of these reservoirs, whitefish and vendace no longer exist, and a drastic reduction in their population numbers is also observed. Accelerated eutrophication and sedimentation is the crucial cause of this situation, due to a decrease in the natural spawning effectiveness of native coregonids in dete- riorated habitats. Also, incorrect fishery management contributes to the decline of the population (Bnińska, 1998; Mamcarz & Skrzypczak, 2002). Maintaining stable populations of vendace requires systematic stocking actions with the use of material (specimens) reared under controlled conditions. Due to the long-term embryogenesis of this species, hatching often coincides with the ice cover on lakes. Stocking actions at times when available forms of zooplankton are lacking usu- ally are highly inefficient (Salojärvi & Ekholm, 1990; Taylor & Freeberg, 1984). They require rearing the coregonid larvae under controlled conditions until the appropriate food base arises in the environment. Support of natural populations with hatchery-reared fish requires the estimation of the effectiveness of such procedures. For this purpose, different methods of marking the stocking material are needed, which also facilitates the assessment of natural recruitment in particular pop- ulations (Eckmann, Czerkies, Helms, & Kleibs, 1998; Everhart, Eipper, & Youngs, 1975). Currently, the mass marking of fish with fluorochromes is based mainly on dye acquisition through immersion (Baer & Rösch, 2008; Hettler, 1984). However, the effectiveness of this type of marking pro- cedure is largely determined by water parameters (pH, temperature, hardness etc.) (Tsukamoto, 1985; Unfer & Pinter, 2013). Attempts to use the food as avector of fluorochromes have been undertaken to avoid difficulties caused by variable parameters of water and to find a new method of mass marking, which will be easier, less costly and safer, for both fish and the natural environment (Stańczak et al., 2015). In the beginning, those methods consisted of a few days of feeding the larvae