ESR 28:175-186 (2015)  -  DOI: https://doi.org/10.3354/esr00692

Development of salinity tolerance in the endangered anadromous North Sea houting Coregonus oxyrinchus: implications for conservation measures

Lasse Fast Jensen1,*, Dennis Søndergård Thomsen2, Steffen S. Madsen3, Mads Ejbye-Ernst4, Søren Brandt Poulsen5, Jon C. Svendsen1,6 

1Fisheries and Maritime Museum, Tarphagevej 2, 6710 Esbjerg V, Denmark
2Ramboll Denmark, Englandsgade 25, 5000 Odense C, Denmark
3Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
4The Danish Nature Agency, Skovridervej 3, 6510 Gram, Denmark
5Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, 8000 Aarhus C, Denmark
6Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal
*Corresponding author:

ABSTRACT: The North Sea houting Coregonus oxyrinchus is an endangered anadromous salmonid belonging to the European lake whitefish complex. The last remaining indigenous population of North Sea houting is found in the River Vidaa, Denmark. Despite legislative protection and numerous stocking and habitat restoration programmes, including a € 13.4 million EU Life restoration project, populations are declining in most rivers in Denmark. Limited knowledge of the general biology of the species, in particular of the early life history stages and habitat requirements, is a serious impediment to management and conservation. In this study, we investigated larval and juvenile salinity tolerance, providing novel information on the early life stages of North Sea houting. Results revealed an ontogenetic differentiation in salinity tolerance when comparing newly hatched larvae, larvae at later developmental stages and juveniles expected to initiate migration to the Wadden Sea. At all developmental stages, larvae exhibited poor hyperosmotic tolerance, while juveniles performed significantly better. Larvae suffered from high mortality and loss of body water at salinities of 18 ppt and higher, while most juveniles survived 30 ppt at least when exposed to gradually increasing salinities. Our results suggest that larval North Sea houting experience very high mortality if carried directly into the Wadden Sea prematurely, highlighting the need for suitable habitat within rivers to retain larvae. Our study shows how different life stages respond differently to varying environmental conditions and emphasizes the need for understanding the physiological mechanisms to improve conservation of endangered species.


KEY WORDS: Anadromous · Conservation · Coregonus oxyrinchus · Habitat restoration · North Sea houting · Ontogeny · Osmoregulation · Salinity tolerance · Whitefish


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Cite this article as: Jensen LF, Thomsen DS, Madsen SS, Ejbye-Ernst M, Poulsen SB, Svendsen JC (2015) Development of salinity tolerance in the endangered anadromous North Sea houting Coregonus oxyrinchus: implications for conservation measures. Endang Species Res 28:175-186. https://doi.org/10.3354/esr00692

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