Management of invasive alien fish species in Lake ...

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In 2014-2015 for 76 days, electrofishing and trapping (with standard funnel traps; Fig. 2 a) campaigns were conducted to control invasive alien species. Length ...
Management of invasive alien fish species in Lake Caicedo Yuso-Arreo (Spain) Phillip J. Haubrock1,2*, Paride Balzani1, Alberto Criado3, Agustín P. Monteoliva3, José Augusto Monteoliva3, Tamara Santiago3, Alberto F. Inghilesi2 and Elena Tricarico1 1 2 3

Department of Biology, University of Florence, Via Romana 17, 50125 Florence, Italy NEMO, Nature and Environment Management Operators s.r.l., Piazza M. D’Azeglio 11, 50121 Florence, Italy Ecohydros, S. L. Pol. Ind. de Cros, Ed. 5, N. 8. 30600 · Maliaño (Spain).

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Introduction Lake Caicedo Yuso-Arreo (Fig. 1a, b) is a freshwater lake,, in Basque country (Spain) and situated over a saline chimney, leading to a high salinity. It is a protected area, being an important site for migratory birds and refuge to endemic species. Its native fish community is entirely composed by alien species like largemouth bass (Micropterus salmoides Lacépède, 1802), pumpkinseed (Lepomis gibbosus L., 1758) and common carp (Cyprinus carpio L., 1758). A dense population of red swamp crayfish (Procambarus clarkii Girard, 1852) is also present. Phragmites australis and Cladium mariscus (Fig. 1c) form the main vegetation around the lake. The alien species in the lake have caused several impacts, such as the extinction of all native species and a decrease in water bird abundances.

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Methods In 2014-2015 for 76 days, electrofishing and trapping (with standard funnel traps; Fig. 2 a) campaigns were conducted to control invasive alien species. Length and weight of sampled individuals were measured to assess the effects of control on the population, while gonads were extracted to evaluate the reproductive status of the populations. In 2017, a trapping and electrofishing survey was conducted to investigate the effect of previous control session. Diet of sampled specimens was analysed by means of stomach and stable isotopes analysis (SIA: δN13 and δC15). For SIA, muscle tissues from 15 individuals of all species and 5 leaf samples from P. australis were taken.

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Results In 2014-2015, 20,679 fish and 117,950 crayfish were removed, while in 2017 3760 fish and 47 crayfish. A decrease in Catch per Unit Effort (CPUE) index was observed from 2014 to 2015 for all species (Fig. 3), especially for C. carpio, except for an increase in 2015 in largemouth bass and pumpinkseed due to reproduction. Control activities affected population structure of all species (i.e. for M. salmoides only two size groups were found in 2015; Fig. 4). Stomach content analysis and SIA (Fig. 5 & 6) showed that sampled species were separated by isotope values and trophic position, with M. salmoides being a top predator and P. clarkii a primary consumer. Also, a strong link within North American species was observed and applied models indicated predation on macrozoobenthos by the common carp.

Fig. 3 Fig. 4 Conclusion The CPUE data indicated that control activities were successful, even if a stop in 2016 led to a partial recovery of all species. SIA shows strong interactions among species, especially the North American ones, this potentially being an obstacle to a complete eradication. Carp control was probably more successful due to the lack of interactions with other invasive species. The presented study highlights the importance of continuous control efforts of invasive alien species, indicating how difficult it could be eradication of invasive species with common life-histories and shared co-evolution in invaded species communities Acknowledgements

Phillip J. Haubrock Tel.: +39145399682; [email protected]

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska -Curie grant agreement No 642197.

We thank to Gonzalo Alonso, José Manuel Gómez, Ana Aja, and especially to David Corta and Ana Gracia for field work and support. Financial support was provided by the LIFE+ TREMEDAL Project (Inland wetlands of Northern Iberian Peninsula: Management and restoration of mires and wet environments. LIFE11 NAT/ES/000707, European Union) and more recently by the County Council of Araba (Technical Assistance for the Restoration of the Aquatic Ecosystem in the Lake Caicedo Yuso ZEC ES2110007 during Post LIFE TREMEDAL project). Thanks for promoting and supporting this work to URA (Ur Agentzia, the Basque Water Agency), HAZI (Foundation of the Basque Government for the rural, littoral and food development) and the Natural Heritage of County Council of Araba, particularly to Javier Pérez and Joseba Carreras. Funding was also provided by the Aquainvad-ED project (2020 Marie Sklodowska-Curie ITN-2014-ETN-642197).