Density-dependent and inter-specific interactions affecting European eel settlement in freshwater habitats
- 251 Downloads
Identifying the factors influencing the settlement of European eel (Anguilla anguilla) juveniles in continental habitats is crucial to designing effective management and conservation measures for this endangered species. A long-term data series (1993–2008) of European eel and European catfish (Silurus glanis) abundance in a freshwater canal of the Camargue water system (southern France), along with parallel data on water salinity and glass eel abundance in the adjacent Vaccarès lagoon, was analysed to identify the possible causes of decline in eel abundance observed in the canal during the last two decades. A model including glass eel recruitment and catfish abundance as covariates explained 78% of the observed variation in eel settlement success. Results suggest that (1) salinity does not play a significant role in determining the fraction of eels moving from the brackish lagoon to the canal; (2) density dependence affects settlement success, possibly through a reduction of juvenile survival in the adjacent lagoon; and (3) catfish abundance is negatively correlated with eel settlement. We discuss this latter point in terms of possible predation of catfish upon eels and/or inter-specific competition between the two species.
KeywordsAnguilla anguilla Interspecific competition Invasive species Population dynamics Silurus glanis
The authors thank two anonymous referees and M. Gatto for valuable suggestions, and J. P. Lewin for the language revision of the manuscript. The authors are particularly grateful to the National Natural Reserve of the Camargue for providing salinity data, and to P. Chauvelon for providing data on air temperature. This study was supported by the Fondation Sansouire (Tour du Valat, France), and the Italian Ministry of Research (PRIN project # 2006054928 and Interlink project # II04CE49G8). D.B. is a post-doctoral researcher funded by project MARE 2008/11 Lot 2: ‘Pilot projects to estimate potential and actual escapement of silver eel’ supported by the European Commission.
- Andrello, M., D. Bevacqua, G. Maes & G. A. De Leo. An integrated genetic-demographic model to unravel the origin of genetic structure in European eel (Anguilla anguilla L.). Evolutionary Applications. doi: 10.1111/j.1752-4571.2010.00167.x.
- Copp, G. H., J. R. Britton, J. Cucherousset, E. Garcia-Berthou, R. Kirk, E. Peeler & S. Stakenas, 2009. Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges. Fish and Fisheries 10: 252–282.CrossRefGoogle Scholar
- Council Regulation (EC) No 1100/2007 of 18 September 2007 establishing measures for the recovery of the stock of European eel.Google Scholar
- Gualtieri, M., M. Mecatti & F. Diodato, 2006. Growth of European catfish (Silurus glanis L.) in Florence province (Central Italy) and management proposals. Journal of Freshwater Biology (Quaderni ETP) 34: 287–291.Google Scholar
- Herrmann, G., 1967. Die Aalwirtschaft im Lande Schleswig-Holstein. Archiv für Fischereiwissenschaft 18(Suppl.1): 405–424.Google Scholar
- Larsen, K., 1961. Fish populations in small Danish streams. Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie 14: 769–772.Google Scholar
- Moriarty, C. & W. Dekker, 1997. Management of the European eel. Fisheries Bulletin 15: 1–110.Google Scholar
- Puzzi, C. M., A. Bellani, S. Trasforini, M. Bardazzi & A. Casoni, 2006. Results of a systematic action of control of the Wels catfish (Silurus glanis L.) conducted in the Ticino River and in the middle reach of the Po River (Northern Italy). Journal of Freshwater Biology (Quaderni ETP) 34: 83–88.Google Scholar
- Roche, H., A. Buet, O. Jonot & F. Ramade, 2000. Organochlorine residues in european eel (Anguilla anguilla), crucian carp (Carassius carassius) and catfish (Ictalurus nebulosus) from Vaccarčs lagoon (French National Nature Reserve of Camargue) – effects on some physiological parameters. Aquatic toxicology 48: 443–459.PubMedCrossRefGoogle Scholar
- Tesch, F. W., 2003. The Eel. Blackwell Science, Oxford: 408 pp.Google Scholar