Report on the Life Project 00NAT/E/7331: “Conservation of the Eurepan Mink ( Mustela lutreola ) In La Rioja (Spain)”

Global Analysis of the aims and out comes of the project.

Here we will make a global analysis of the extent to which the aims and expected outcomes of the project have been met in the main actions carried out, and also the need to continue with these actions in the future.

A) To prevent the American mink (Mustela vison) from establishing itself in the region.

A.1.- Action: Annual trapping campaigns have been used to control possible specimens of American mink from the neighbouring provinces of Alava and Burgos managing to reach rivers at the western end of La Rioja in which the European mink live.

A.2.- Outcomes: Thanks to these campaigns, the establishment of this invasive species has been prevented to date in La Rioja, by capturing and removing various randomly scattered specimens (5 animals), in the upper reaches of the Najerilla river and the western stretch of the River Ebro in the Rioja Alta (Upper Rioja). Even though the latest samples (2004) have returned negative finds, there is always the possibility of new scattered specimens arriving here in the future.

A.3.- Future actions: Three lines of future action are proposed with regard to controlling American mink in the territory of La Rioja:

In the Upper Najerilla, sampling of traces of their presence must continue over the next few years, with the purpose of detecting the presence of possible specimens of American mink. If these are detected, trapping will be used to remove them from the natural surroundings. In the western reaches of the River Ebro, systematic annual sampling of traces and trapping must continue, since this route of penetration could continue to be a permanent threat. In the remaining areas which are potentially suitable for the establishment of American mink (upper reaches of the Oja, the Tirón), it is not regarded as necessary to take any further control measures other than surveillance, as at present these routes of penetration are regarded as dormant.

Tracking has been shown to be a valid control method of this invasive species in La Rioja, so long as the number of specimens entering from bordering areas continues to be low. Therefore, the future success of these actions must go hand in hand with the intensity of the eradication campaigns which are being carried out in the exporting areas of American mink (Burgos and Alava). In this sense, it is necessary to promote, as far as possible, the continuation of intensive, ongoing trapping activities in these “frontier territories”, while they test out more effective control methods aimed at larger, highly dense populations.

The existence of a fur farm breeding American mink in the town of San Adrián (Navarra) presents a risk for the European mink populations established in the nearby rivers Ebro, Cidacos and Aga, both from the point of view of specimens escaping and getting into the natural environment, and that of the transmission of diseases. To reduce this, it is recommended that incentives should be offered, wherever possible, for the definitive closing of this farm in the neighbouring province of Navarra.

B) Monitoring Programme of populations of European mink.

B.1.- Action: During the period 2001-2004, a campaign of intensive monitoring of European mink has been carried out in the lower reaches of the Najerilla river (17 km.), the western section of the River Ebro (70 km.) and the Tirón river (30 km.).

B.2.-Outcomes: 61 European mink were caught: 28 of these were radio tagged in the Ebro and Najerilla rivers for an average of 11 months/animal. This monitoring has provided a lot of detailed information about the biology, ecology and state of conservation of these populations.

During the study period, the trend observed has been a stable population in the lower reaches of the Najerilla and Tirón rivers (medium-high density: 5-6 specimens/10 km., in an ideal habitat) and a decline in the western section of the Ebro (low density: 2 specimens/10 km., in a below ideal habitat), with a slight upward curve in the last year after the decrease suffered in the previous years. Some of the conservation problems observed are related to: 1) the deterioration of the habitat, as a result of a change in the path of the river to reduce the effects of flooding, 2) a shortage of females, their high mortality rate and low fertility, and 3) the significant incidence of ADV is some populations.

B.3.- Future actions: The conservation of the European mink, in the Areas of Monitoring La Rioja and its surrounding area, depends on trying to stop the occurrence of the recessive factors which have been identified and, simultaneously, on getting more information on the processes which have a negative influence on these populations.To achieve these two objectives we recommend the development of the following lines of action:

    • It is necessary to protect the most favourable habitats for the presence of this species at all costs, particularly in the stretches of river where there is a denser concentration of population, specifically in the presence ofsignificant numbers of females (lower reaches of the Najerilla and Tirón rivers).
    • We recommend the continuation of the campaign to control the American mink in the rivers of the western end of La Rioja, in particular in the course of the Ebro in the Upper Rioja.
    • In the medium term, it is necessary to monitor (through radio tagging) specimens in the lower reaches of the Najerilla and Tirón rivers, with special attention to the evolution of these populations (mortality rate, success in reproduction, dispersion of young animals), to the impact of diseases (ADV) and to the state of conservation of the habitat.

The results obtained in the aspects related to the use of the space and use of the medium by radio-tagged European mink over the last four years (2001-2004) have a direct effect on the conservation measures to be applied to this species. Among others we would especially mention the following:

    • The large size of the areas of activity used by the European mink in La Riojaand, in particular, the vast extension of the river banks that the males frequently follow, involve a high level of vulnerability for the population exposed to hazards which can cause death (roads, hydroelectric power stations, populated areas, etc.).
    • In addition, this need for large areas of space determines the conservation of the river banks as continuous natural biological corridors (also including river banks in towns) and the establishment of protected areas, since the presence in these of a significant number of specimens involves very long stretches of river.
    • The most important areas for the conservation of the species are those areas where there are females, often very localised spots, as in the case of the lower reaches of the Najerilla, the Tirón and the Ebro, in which they are very fond of the islands. These therefore require special protection. Similarly we would highlight the small marshy areas (very scarce in this territory: La Grajera, loop of Gimileo, etc.), in which the high availability of resources makes for a significant presence of females, as zones with very good quality conditions for reproduction.

In the same way, the different results obtained from monitoring the radio-tagged European mink with regard to the types of micro- and macro habitats chosen tell us a lot about which sectors of the space have to be protected and specially encouraged. These are small rivers and irrigation channels with slow running water, with a lot of plant cover of scrub and reeds on the banks and shoreline, as well as the wetlands (lakes and ponds).

C) Regular checking programme of the European mink population.

C.1.- Action: During 2002 and 2004 campaigns were run to check the state of the European mink populations in the whole of the Autonomous Community of La Rioja with emphasis on the evolution of the population, the detection of diseases due to pathological processes, checking the level of pollutants and the genetic condition of the population.

C.2.- Outcomes: It was estimated that 99 and 88 adult specimens existed respectively for each year, with the number in recession since 2000.During the period of monitoring, there was a sharp upturn in the populations of the Ebro and Alhama rivers, although in this latter case, the absolute figures are less significant, and a decrease in the other rivers in the region (Tirón, Oja, Najerilla, Iregua andCidacos). The reasons for this general decline is unknown, but there could be severalacting in conjunction. Some of the problems observed are connected to the deterioration in the habitat and the scarcity of numbers of the female population.

The studies of the health of the populations carried out within these campaigns detected a high level of the Aleutian Disease virus in mink (ADV) which was present in 27% of the European mink analysed, although its real occurrence in the population is not known.

In addition, a study was made to characterise the genetic make-up of these populations and this has found a high degree of uniformity among the mink of La Rioja and those from the rest of the regions with a presence in Western Europe (the Spain-France nucleus). The consequence of this monomorphism still has to bedetermined. Research has been made to determine specific European mink micro-satellites through sequencing 99 positive clones, 15 sequences suitable for designing feeders and 9 micro-satellites which can already be used in studies of genetic characterisation.

C.3.- Future actions: It is necessary to continue with regular checks of the European mink population with specific campaigns to be run on a biannual basis. Monitoring the populations should cover the whole of the area in which the species is present, with a similar impetus and intensity to that employed in the Life project. Emphasis should be placed on those populations in which a recessive trend has been noted or where the area of regular presence has shrunk, as in the case of the middle and upper reaches of the rivers Oja, Najerilla and Iregua.

With regard to the detection of diseases caused by pathological processes, it is necessary to remain alert with regard to the evolution of the percentage of prevalence with regard to ADV observed among European mink populations and to try and ensure the Aleutian disease virus does not reach the Iregua, the only river currently free of the disease.

The results obtained from the detection of genetic micro-satellites till December 2004 form part of an ongoing project for developing molecular markers and their application in various populations of European mink, in which the Zoology Laboratoryof the Pharmacy Faculty of the University of the Basque Country is going to continue to be working. Currently, the selection of marking of the primers is continuing, as well as the pursuit of good enlargements of the micro-satellites obtained. Part of this research will be carried out in collaboration with Dr J. Michaux in Montpellier, France, where subsequently the genotype of the European mink populations will be established. For this, samples of minks from both research groups will be shared. An average of 30 individuals from each population will be studied, whose data will then be analysed statistically to determine the genetic flux between populations, the genetic diversity and variability, the possible bottleneck effects, loss of heterozygosity, changes in the distribution of the allele frequency and other genetic parameters of interest. The conclusions gleaned from this analysis will be of great practical value for the conservation and management of this endangered species.

As future applications of the marker molecules developed during this period, we can point to some of great importance for the management and conservation of the European mink:

    • To find the Evolutionarily Significant Units (ESUs) by determining whether the French and Iberian populations are different lines, or whether they must be regarded as a single population, as well as the genetic divergence between the two with respect to the population in Russia and Rumania.
    • To select the most suitable populations from which to take animals for breeding in captivity, maintaining an appropriate genetic variability by avoiding as far as possible the creation of a decline due to endogamy.
    • To make genetic checks of the breeding in captivity programmes, as well as monitoring the reproductive success of freed animals and the spread of their offspring.
    • To avoid a cross breeding between genetically distinct populations unless absolutely necessary.
    • To reinforce local populations which so require them with individuals from other neighbouring localities through appropriate redistribution.
    • To facilitate the genetic flux between isolated populations.
    • To combat problems of endogamy in populations with little genetic polymorphism, through exchanges between those populations which so require.
    • To determine the levels of hybridization between European mink and polecats, as well as the fertility of possible hybrids.


D) Conservation of the habitat: the waterways and natural riverbank vegetation.

In this area, major progress has been made thanks to the measures taken.

D.1a. Action: Proposal for the Enlargement of the Red Natura 2000 network.

D.1b.- Outcomes: After the proposal of the inclusion as LICs of the following areas considered as of high natural value: “Sierras of la Demanda, Urbión, Cebollera and Cameros” (LIC: ES2300001), “Crags and outcrops of the rivers Iregua, Leza and Jubera” (LIC: ES2300004) and “Thickets and Riverbanks of the Ebro” (LIC: ES2300006), we should mention the enlargement of the latter space in 2004 by 879 has. Corresponding to a stretch of 57 kms. All the increased stretches of riverbank form part of the area of distribution of the European mink.

D.1c.- Future actions: When all the proposed spaces form an integral part of the Red Natura 2000 network, administrative, regulatory and management measures necessary must put in place to ensure a favourable state of conservation of the habitats which responds to the ecological needs of this species. In addition, during the first months of 2005, with the approval of the Government Council, the new proposal for the enlargement of the LIC “Thickets and Riverbanks of the Ebro” will be finalised with the inclusion of some stretches of the river Ebro as it passes through the towns of Aldeanueva de Ebro, Calahorra and Rincón de Soto (241has).

D.2a.- Action: Work in waterways and drafting of reports.

D.2B.- Outcomes: As the project was being implemented various legal and administrative measures have been taken to preserve the habitat by drafting reports regarding the review of regional projects to correct the riverbanks and to carry out work on hydraulic infrastructures, and for the regulation of the ecological water courses.

Nevertheless, problems were encountered in relation to emergency work carried out. Intervention has taken place in many rivers in La Rioja to reconstruct water courses and to replace the shorelines of the banks damaged by the heavy flooding between the 25 February and 1 March and from 5 to 7 May, 2003.

Of the 1,500 Km. Of the waterways network in La Rioja, taking the main rivers and their tributaries, the length of the water course affected was 60.815 kms. (4%), with the river Najerilla and its tributaries the most affected with 28.22 kilometres.

Details of actions taken:

  1. Removal of sediment on riverbeds.
  2. Repair of eroded banks through the accumulation of deposits.
  3. Protection with a breakwater in specific points.
  4. Clearance, pruning and felling of vegetation causing a barrage effect.

D.2C.- Future actions: Subsequently, with immediate effect (Spring 2004) the Ebro water Authority and the Government of La Rioja replanted vegetation in 12.76 kms. of water courses scattered throughout La Rioja, with an investment of 416,700 €, as a first stage in the most ambitious intervention that the regional government has undertaken in the restoration of the vegetation of the river bank of the stretches and rivers damaged over a length of 58.12 kms. And a total investment of 1,291,350.60 €.

Coordination meetings have been held with the Water Authority to set a calendar for these restoration measures and a financial schedule which will make possible the execution, with priority given to the areas of interest for the conservation of the European mink and those stretches included in the Red Natura 2.000 network.

Furthermore, in order to ensure emergency works in swollen rivers and flooding situations are carried out in a proper way with regard to the aims of the conservation of the European mink the need has been established for the river basin body to request authorisation from the Environmental Department of the A.C. of La Rioja and for there to be greater involvement in the works management by environmental specialists.

D.3a.-Action: Actions on the shore and on riverbanks.

D.3b.- Outcomes: Among the grants that the Government of La Rioja gives to encourage poplar plantations in farming areas, it has been made obligatory for landowners who want to plant poplars and whose land borders with water courses to leave a gap of at least 5 m unplanted so that the natural vegetation of the riverbank can grow spontaneously. This measure is giving very positive results for the consolidation of a greater width of margin between river and crops.

Measures have also been taken for the regional government to purchase some land covered with natural thickets, such as the estate in the spot known as“El Susar”, within the Sotos del Ebro Nature Reserve in Alfaro (pLIC), with a surface area of 37 has. Similarly, and within this protected natural area, former poplar copses are being returned to a natural state of thickets (of willow, white poplar, ash and tamarisk) in the place known as El Hormiguero, with an approximate total area of52 Has.

D.3c.- Future actions: This line of action will continue, with the acquisition by the Autonomous Community of La Rioja of private property with natural thickets or poplar groves within the PLIC area of “Thickets and Riverbanks of theEbro”. On the basis of the experience of the pilot project for restoration of the habitat carried out on the banks of the river Ebro in Haro, gradually the poplar groves will be transformed into riverbank woodland with indigenous plants.

The condition for receiving grants imposed on poplar plantation owners will be continued, in order to conserve riverside vegetation, and the possibility of funding the plantation of this natural vegetation in the space bordering the poplar plantations and the rivers will be studied.

D.4a.- Action: Habitatrestoration project.

D.4b.- Outcomes: Habitat restoration measures have consisted in fostering a change of use in a wide band of riverbank (14 kms.) by transforming industrial poplar groves into strips of natural riverside vegetation. The area in which work has been undertaken, (banks of the Ebro in Haro) is a “Public Woodland” owned by the Government of La Rioja, located in an area of special interest for the conservation of the European mink (LIC ES2300006). This is a pioneering measure which could be extended to other areas inhabited by this endangered species, with very positive effects for encouraging its habitat in the medium and long term.

Industrial poplar plantations have been felled and annual regrowth controlled. Indigenous trees have been planted using “mild” techniques over 13.18 Has. and the shore has been pegged for 8.5 kms. Reinforcement planting and maintenance work has been undertaken in the plantations each year. A dirt path has been created for 2.7 kms. next to the riverbank, so as to facilitate public access and use.

During the execution of the restoration project, a difficulty has arisen over the construction and functioning of a small electricity generating plant in Labastida (Alava) planned since 1995, which due to an excessive superelevation of the dam due to construction deficiencies, has led to flooding of the banks over a longer stretch than originally forecast. It was therefore necessary to relocate some of the planned plantations. Action is being taken with the developer and the water authority to find a solution to this problem.

D.4c.- Future actions: The replanting measures will continue with the elimination of annual regrowth of the former poplar stumps, as well as through the clearing of herbaceous plant growth around the trees planted and the replacement of errors in repopulation work. The experience gained from this pilot project will be used for carrying out similar ones in other areas.

D.5a.- Action: Treatment of waste water.

D.5b.- Outcomes: Throughout the LIFE project, a big effort has been made to invest in waste water treatment plants which were previously pumped directly into rivers, thereby improving water quality, with a total investment over the period of 105 million euros, with virtually all the cohesion funds being devoted to this purpose.

D.5.c.- Future actions: This line of work will continue with the aim of meeting requirements of community directives on water treatment, with special emphasis on those rivers and wetlands included in protected natural spaces.

E) Contribution to raising public awareness about the species and its plight.

E.1a.- Action: Preparation of educational and informative materials.

E.1b.- Outcomes: The excellent coordination between all the Autonomous Communities that benefit from LIFE funds which are involved in protecting this species has contributed to the creation of jointly produced educational materials and their subsequent dissemination. In this action both the general public and social sectors and those public and private bodies more involved in the conservation of the species have been taken into account (angling associations, riverbank dwellers, water authorities, etc).

E.1c.- Future actions: This action needs to be the basic support measure for all the other actions related to the conservation of the European mink and research into this species. In the European Mink Recovery Plan for la Rioja, one of the aims is to raise awareness and knowledge in society regarding the conservation problems of the mink, including the design of teaching and general information materials, educational packs aimed at children and young people and the organisation of training courses. .

E.2a.- Action: Organization of an International Conference on the conservation of the European mink.

E.2b.- Outcomes: In November 2003 the International Conference on the Conservation of the European Mink was held in Logroño, and in October 2004 we attended the Technical Workshops on the Conservation of the European mink and its Habitats in France, and these events have helped to bring together a large number of experts involved in the study and conservation of the species, setting up a network for exchanging experiences between managers and researchers.

E.2c.- Future actions: Shortly the Monographic Study from the Conference will be published, with scientific and technical articles based on the various papers presented during the Conference by the experts who attended. Subsequently, all those who attended will receive a copy and also research centres, university and departments of the various authorities involved.
Meetings of this kind should be held in the future on a regular basis, with the purpose of updating the existing technical knowledge at European and pan-European level and to advance in an understanding of the reasons for the extinction of this species and their solutions.