LIFE+ LIMNOPIRINEUS: CONSERVATION OF AQUATIC HABITATS AND SPECIES IN HIGH MOUNTAINS OF THE PYRENEES LIFE+ LIMNOPIRINEUS: CONSERVATION OF AQUATIC HABITATS AND SPECIES IN HIGH MOUNTAINS OF THE PYRENEES COORDINATION Empar Carrillo Josep Maria Ninot Teresa Buchaca Marc Ventura GRAPHIC DESIGN creativadisseny.cat PRINT GoPrinters ISBN 978-84-18199-17-2 Coordination: Associated beneficiaries: Co-financier: ~ Lake Delluí Nord ~ Removal of introduced fish as a restoration 06 measure in high mountain lakes POU-ROVIRA et. al Changes in lakes after the reduction of fish 28 densities BUCHACA et. al Rapid recovery of amphibian populations 42 in eight high mountain lakes linked to the eradication of exotic fish MIRÓ et. al Alterations and changes that affect the 54 conservation of the biodiversity of Estanho de Vilac (Aran Valley) CARRILLO et. al The Trescuro mire system: how sharp environ- 72 mental gradients and climatic events constrain the local distribution of plant community types COLOMER et. al Habitats of Community Interest in the mires of Aigüestortes and Alt Pallars: distribution, 84 impacts and threats PÉREZ-HAASE et. al Evaluation of the perception of high mountain aquatic ecosystems by visitors and nearby 100 residents of the National Park ROMAGOSA et. al Conservation status of the Pyrenean sculpin 108 (Cottus hispaniolensis) in the Aran Valley ROCASPANA et. al Recovery of mires at the reservoir of font 114 grossa, Espot NINOT et. al ~ Lake Naorte ~ REMOVAL OF INTRODUCED FISH AS A RESTORATION MEASURE IN HIGH MOUNTAIN LAKES Quim POU-ROVIRA (1), Eloi CRUSET (1), Blanca FONT (1), Ismael JURADO (1), Meritxell CASES (1), Teresa BUCHACA (2), Ibor SABÁS (2), Alexandre MIRÓ (2), Victor OSORIO (2), MARIÀNGELS PUIG (2) & MARC VENTURA (2) 1. Sorelló, estudis al medi aquàtic. Parc Científic de la UdG, 17300, Girona, Catalonia, Spain. 2. Integrative Freshwater Ecology group, Centre for Advanced Studies of Blanes (CEAB-CSIC). Accés Cala St. Francesc, 14, 17300, Blanes, Catalonia, Spain. — • — ABSTRACT two most widespread species in the Pyrenean high moun- tain lakes are the common trout (Salmo trutta) and the Among the objectives of the LIFE+ LimnoPirineus minnow (Phoxinus sp). Other species introduced in the project (2014-2019) was the ecological restoration of lakes of the southern Pyrenean slope, but less widespread eight Pyrenean lakes, and the recovery or improvement of than common trout and minnow, are brook trout (Salveli- populations of various species of community interest in nus fontinalis) and rainbow trout (Oncorhynchus mykiss) these lakes, through the eradication or intensive control (Aparicio et al., 2016, SI-EXOAQUA, 2019, SIBIC, 2019). of up to four species of introduced fish. In most of the Currently, between 35% and 85% of the Pyrenees lakes lakes, the operational objective was eradication, while in are occupied by fish, depending on the valley (Miró & only one of them the objective was simply to carry out Ventura, 2013; 2015). It seems clear that the motivation intensive control to reach at least a 75% reduction of the for the introduction of salmonids has always been their initial population. At the end of 2019, these objectives value as target species of traditional fishing in the past were fully achieved for five of the lakes, while in the and sport fishing in modern times. However, in the case three remaining lakes, they are close to being achieved of minnow, its introduction began later, probably from probably before the end of 2020. Fish extraction methods the 70s of the twentieth century, when its use as live bait were conducted based on the combination of up to three and forage fish was increased. main catch techniques; nets, traps and electrofishing. It The effects of the introduction of fish in alpine lakes has shown that the eradication of fish is feasible in many originally free of ichthyofauna range from the removal of high mountain lakes, through sufficient investment in other wildlife species, both invertebrates and vertebrates, material and human resources, and with proper planning to radical changes in the structure and dynamics of the of operations. When eradication is not feasible, intensive lake ecosystem, even ultimately affecting the ecological control through a sustainable effort over time is also an status, or the quality and visual appearance of water (Bu- alternative to consider in the medium term. chaca et al., 2016; Knapp, 2005; Knapp et al., 2015; Max- well et al., 2011; Miró et al., 2018; Reissing et al., 2006; Tiberti & Von Hardenberg, 2012; Ventura et al., 2017). Along with the broad evidence of the impact caused by introduced species on the original biodiversity, both locally and regionally, there is also a broad consensus that the best measure to avoid or minimise these impacts is prevention and monitoring to avoid new introductions, | 2019 be they deliberate or involuntary (Wittenberg et al., INTRODUCTION 2001; García-Berthou et al., 2005; Simberloff et al., 2013). Alongside this, it is recognised that the active manage- he high mountain lakes of the Pyrenees are ment of populations of native species already established, isolated from the rivers of the main valleys by whether to eliminate them or at least to contain them or LIFE+LIMNOPIRINEUS hydrographic barriers that have prevented nat- mitigate their effects, is almost always technically unfea- ural colonisation by the fish (Pechlaner, 1984). sible or economically unattainable, despite the fact that Despite this, especially during the twentieth in some situations actions can be planned with certain Tcentury and linked to the practice of sport fishing, fish chances of success. In this sense, it is pertinent to concen- report technical have been introduced to the point that many lakes cur- trate action efforts on isolated populations of introduced rently maintain stable fish populations (Miró, 2011). The species, as is the case for the Pyrenean lakes, even more 7 POU-ROVIRA et. al so where a high potential for ecological recovery is com- was more diverse. The five lakes in the national park bined with a high conservation interest due to unique- contained salmonid, while two of these also contained ness or the biogeographical value of the habitats or native minnow. species potentially present. For organisation purposes, and mainly due to the Outside Europe, numerous projects or programmes capacity of workforces specifically intended for the task for the active management of exotic fish species have been of fish extraction, the start of operations in each lake carried out, either to eradicate established populations or was staggered. By way of exception, at Lake Closell fish to initiate stable intensive control programmes, especially elimination work began in 2013, in the context of a in North America (per ex. Tyus I Saunders, 2000; Hill & previous experimental project to begin evaluating the Cichra, 2005), but also in other areas such as Australia, most appropriate possibilities and methods to deal with New Zealand or South Africa (per ex. Lintermans, 2000; the eradication of minnow in high mountain lakes. These Thomas et al., 2006). Among these, it is worth mention- tests continued during 2014, within the framework of a ing the programmes conducted in the high mountains of parallel project, and extended to other lakes not selected North America, in the Rocky Mountain Range, with an within the LLP (Pou-Rovira, 2015c). Finally, in 2015 the extensive history of successful experiences. definitive work began at 4 of the initially planned lakes, In Europe, on the other hand, the history of active leaving the start at the three other lakes for 2016 and 2017 management of exotic fish species is still rare, although (Table 1). they are gradually increasing (per ex. Britton et al., 2009, When planning operations to eliminate fish nuclei Campos et al., 2013). But in the specific case of high or other aquatic fauna in inland bodies of water, there mountains, known projects are very scarce, although are several methodological options of value. These often successful (Tiberti, 2018). Despite this, so far they include strategies based on the temporary desiccation have focused mainly on salmonids, and only very occa- of the body of water, or alternatively on the use of sionally on small cyprinids such as minnow. ichthyocides, especially rotenone or its derivatives In this context, the LIFE+ LimnoPirineus project (Finlayson, 2010). Although very effective, desiccation (LIFE + Natura LIFE13 NAT/ES/001210) included is feasible in very few situations. Regarding the use of actions to eliminate exotic fish nuclei in a selection of ichthyocides, this represents a management tool with mountain lakes in the Alt Pirineu Natural Park (APNP) great practical potential, but unfortunately it still has and the Aigüestortes and Estany de Sant Maurici numerous limitations, both at the operational and legal National Park (AESMNP). The conservation objectives levels. Consequently, the LLP project concentrated efforts directly linked to these actions were 1) the restoration on a strategy based on the planning of intensive fishing of their structural quality and ecological function, 2) the campaigns, i.e. a massive and persistent fish catch until recovery of lake populations of threatened amphibians the established operational objectives were reached. In (Rana temporaria, Alytes obstetricans, Euproctus asper fact, there are numerous precedents for fish elimination and Lissotriton helveticus) for the improvement of its local projects through the application of intensive specimen metapopulations, and 3) the improvement of populations capture only (per ex. Bio et al., 2008; Pou et al., 2013; of various threatened mammals (Galemys pyrenaicus, Pou- Rovira, 2013; Pou- Rovira, 2017), among which, Lutra lutra, Rhinolophus hipposideros and Plecotus it is worth noting here the projects for the removal of macrobullaris) within these protected natural spaces. salmonid nuclei introduced in high mountain lakes (Bosch et al., 2019; Tiberti et al., 2018; Knapp & Matthews, 1998). These projects have constituted a reference base for the planning of similar operations set of salmònid METHODS removal forth by the LLP.