European grayling populations have declined significantly in their central range, prompting numerous stocking programs with reared fish that did not bring desirable population prosperity. This study evaluated the effectiveness of stocking long-reared grayling brood fish before their spawning period. It focused on monitoring the presence of juveniles coming from their natural spawn in the stream and on recapture rates and growth parameters of stocked fish to estimate their adaptability in a natural river environment. The results revealed that the recapture rate of the stocked brood fish was notably low, with significant increases only in length growth but a decreases in condition factor, suggesting poor adaptability in the wild. The limited number of young-of-year grayling from natural spawning further indicated low reproductive success. These results highlight the inadequacies of this stocking approach to strengthen the wild grayling population. We suggest alternative strategies, such as using younger stock and implementing protective measures like catch-and-release, which may improve conservation efforts and enhance the success of grayling stocking programs.

Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses University of South Bohemia in České Budějovice Vodňany Czech Republic

See more in PubMed

Araki, H. , Becky, C. , & Michael, S. B. (2007). Genetic effects of captive breeding cause a rapid, cumulative fitness decline in the wild. Science, 318, 100–103. 10.1126/science.1145621 PubMed DOI

Auer, S. , Hayes, D. S. , Führer, S. , Zeiringer, B. , & Schmutz, S. (2023). Effects of cold and warm thermopeaking on drift and stranding of juvenile European grayling ( DOI

Avramović, M. , Turek, J. , Lepič, P. , Szmyt, M. , Pastejřík, J. , & Randák, T. (2024). Can stocking with advanced European grayling fry strengthen its populations in the wild? Acta Ichthyologica et Piscatoria, 54, 165–176. 10.3897/aiep.54.124289 DOI

Avramović, M. , Turek, J. , Tomčala, A. , Mráz, J. , Bláha, M. , Let, M. , Szmyt, M. , & Randák, T. (2024). Assessing the acclimatisation to the wild of stocked European graylings DOI

Ayllón, D. , Blasco Hernanz, S. , Nicola, G. G. , Elvira, B. , & Almodóvar, A. (2025). Mediterranean brown trout catch‐and‐release recreational fisheries might not be sustainable under concurrent climate warming and hydrological change. Hydrobiologia, 852, 659–672. 10.1007/s10750-024-05713-0 DOI

Bardonnet, A. , & Gaudin, P. (1990). Diel pattern of emergence in grayling ( DOI

Carlstein, M. (1997). Effects of rearing technique and fish size on post‐stocking feeding, growth and survival of European grayling, DOI

Carraro, L. , Bertuzzo, E. , Mari, L. , Fontes, I. , Hartikainen, H. , Strepparava, N. , Schmidt‐Posthaus, H. , Wahli, T. , Jokela, J. , Gatto, M. , & Rinaldo, A. (2017). Integrated field, laboratory, and theoretical study of PKD spread in a Swiss Prealpine river. Proceedings of the National Academy of Sciences, 114, 11992–11997. 10.1073/pnas.1713691114 PubMed DOI PMC

Cooke, S. J. , Twardek, W. M. , Reid, A. J. , Lennox, R. J. , Danylchuk, S. C. , Brownscombe, J. W. , Bower, S. D. , Arlinghaus, R. , Hyder, K. , & Danylchuk, A. J. (2019). Searching for responsible and sustainable recreational fisheries in the Anthropocene. Journal of Fish Biology, 94(6), 845–856. 10.1111/jfb.13935 PubMed DOI

Cowx, I. G. (1994). Stocking strategies. Fisheries Management and Ecology, 1, 15–30. 10.1111/j.1365-2400.1994.tb00003.x DOI

Czerniawski, R. , Domagala, J. , Krepski, T. , & Pilecka‐Rapacz, M. (2015). The effect of the live diet given to hatchery‐reared fry of the European grayling (

Dahl, J. (1962). Studies on the biology of Danish stream fishes. 1. The food of grayling (

Degerman, E. , Näslund, I. , & Sers, B. (2000). Stream habitat use and diet of juvenile (0+) brown trout and grayling in sympatry. Ecology of Freshwater Fish, 9, 191–201. 10.1111/j.1600-0633.2000.eff090401.x DOI

Einum, S. , & Fleming, I. A. (2001). Implications of stocking: Ecological interactions between wild and released salmonids. Nordic Journal of Freshwater Research, 75, 56–70.

Fraser, D. J. , Weir, L. K. , Bernatchez, L. , Hansen, M. M. , & Taylor, E. B. (2011). Extent and scale of local adaptation in salmonid fishes: Review and meta‐analysis. Heredity, 106, 404–420. 10.1038/hdy.2010.167 PubMed DOI PMC

Hauer, C. , Unfer, G. , Tritthart, M. , & Habersack, H. (2011). Effects of stream channel morphology, transport processes and effective discharge on salmonid spawning habitats. Earth Surface Processes and Landforms, 36, 672–685. 10.1002/esp.2087 DOI

Horká, P. , Horký, P. , Randák, T. , Turek, J. , Rylková, K. , & Slavík, O. (2015). Radio‐telemetry shows differences in the behaviour of wild and hatchery‐reared European grayling PubMed DOI

Hunt, T. L. , & Jones, P. (2018). Informing the great fish stocking debate: An Australian case study. Reviews in Fisheries Science & Aquaculture, 26, 275–308. 10.1080/23308249.2017.1407916 DOI

Jepsen, N. , Ravn, H. D. , & Pedersen, S. (2018). Change of foraging behavior of cormorants and the effect on river fish. Hydrobiologia, 820, 189–199. 10.1007/s10750-018-3656-2 DOI

Lyach, R. , & Remr, J. (2019). The effect of a large‐scale fishing restriction on angling harvest: A case study of grayling ( DOI

Okamura, B. , Hartikainen, H. , Schmidt‐Posthaus, H. E. I. K. E. , & Wahli, T. (2011). Life cycle complexity, environmental change, and the emerging status of salmonid proliferative kidney disease. Freshwater Biology, 56(4), 735–753. 10.1111/j.1365-2427.2010.02405.x DOI

Persat, H. , Mattersdorfer, K. , Charlat, S. , Schenekar, T. , & Weiss, S. (2016). Genetic integrity of the European grayling (

Riley, W. D. , & Pawson, M. G. (2010). Habitat use by DOI

Romakkaniemi, A. (2008). Conservation of Atlantic Salmon by Supplementary Stocking of Juvenile Fish. PhD thesis (University of Helsinki). https://helda.helsinki.fi/items/a8a459f0-07b7-4bf1-b293-98fec040df61

Schmutz, S. , & Moog, O. (2018). Dams: Ecological impacts and management. In Schmutz S. & Sendzimir J. (Eds.), Riverine ecosystem management: Science for governing towards a sustainable future (pp. 111–127). Springer International Publishing. 10.1007/978-3-319-73250-3_6 DOI

Simonović, P. , Tošić, A. , Škraba, D. , Mrdak, D. , Grujić, S. , & Nikolić, V. (2014). Effects of stocking with brood fish to manage resident stream dwelling brown trout DOI

Thorfve, S. (2002). Impacts of in‐stream sacclimatisation on post‐stocking behaviour of European grayling in a Swedish stream. Fisheries Management and Ecology, 9(5), 253–260. 10.1046/j.1365-2400.2002.00305.x DOI

Thorfve, S. , & Carlstein, M. (1998). Post‐stocking behaviour of hatchery‐reared European grayling ( DOI

Turek, J. , Horký, P. , Zlábek, V. , Velíšek, J. , Slavík, O. , & Randák, T. (2012). Recapture and condition of pond‐reared, and hatchery‐reared 1+ European grayling stocked in addition to wild conspecifics in a small river. Knowledge and Management of Aquatic Ecosystems, 405, 10. 10.1051/kmae/2012016 DOI

Turek, J. , Randák, T. , Horký, P. , Zlábek, V. , Velíšek, J. , Slavík, O. , & Hanák, R. (2010). Post‐release growth and dispersal of pond and hatchery‐reared European grayling PubMed DOI

Turek, J. , Žlábek, V. , Velíšek, J. , Lepič, P. , Červený, D. , & Randák, T. (2018). Influence of geographic origin on post‐stocking survival and condition of European grayling ( DOI

Vincenzi, S. , Crivelli, A. J. , Jesensek, D. , & De Leo, G. A. (2012). Translocation of stream‐dwelling salmonids in headwaters: Insights from a 15‐year reintroduction experience. Reviews in Fish Biology and Fisheries, 22, 437–455. 10.1007/s11160-011-9235-5 DOI