PROJECT DESCRIPTION
BACKGROUND
The apron (Zingel asper) is a small, nocturnal bottom-dwelling fish listed in Annex II of the Habitats Directive. It only occurs in the Rhône river basin. It is about 15 to 20 cm in size and thrives in clear, oxygen-rich waters with clean gravel bottoms. The apron's behaviour is sedentary and territorial. At daytime, it remains hidden among riverbed stones and is almost invisible due to its excellent camouflage. At the onset of the 20th century the apron could be found throughout the entire Rhône catchment, i.e. over a length of 1 700 km. At present, its distribution only covers 380 km at most and the total population is estimated between 2 000 and 4 000 individuals, divided into various genetically isolated sub-populations. The main reason for its decline is the impact of hydraulic engineering works such as dams and weirs. These are effectively impassable barriers to the aprons and isolate sub-populations from each other. River pollution and flow changes due to water pumping for agricultural purposes have also led to a severe degradation of the apron's habitat. A first three-year LIFE-Nature project (1998-2001) for the apron considerably improved knowledge of its ecological requirements; it also conducted a feasibility study for rearing this species for re-introduction purposes and developed a long-term conservation strategy.
OBJECTIVES
The general aim of this second LIFE project on Zingel asper was to implement the measures proposed in the ‘Guidelines for Management and Conservation of the Apron’, which was produced by the first LIFE project. There were three main operative objectives: 1) improve the genetic exchange and increase population size through the construction of fish passes at impassable dams (13 fish passes suitable for the apron are planned); 2) determine the feasibility of re-introducing the species through trials in several test sites, using both hatchery and wild-born fish; 3) improving knowledge on populations by field surveys to find unknown populations and to estimate the size of known populations and the extent of adequate habitat.
RESULTS
The actions implemented during the project lifetime yielded very good results, even though the project’s longer-term objectives are not yet fully evaluated.
Following extensive annual surveys carried out in the French watercourses of the Rhône catchment area (a total of 296 km were surveyed on foot at night!), the knowledge of the species was significantly improved and the geographic limits of the apron populations were identified. Its presence is now estimated at 11% of the presumed historic river length (about 240 km).
To meet the objective of improving the intra-population genetic mixing and opening up large parts of the river basin to natural recolonisation, four actions were undertaken:
- Identification of the different types of obstacles/barriers along the rivers separating the sub-populations, and the designing of fish passes that have hydraulic characteristics suited to the species' swimming abilities;
- Proposals and detailed plans for fish passes for 17 obstacles/barriers along the Loue, Durance and Ardèche rivers;
- Fitting five weirs with fish passes suitable for the apron (for one of these an artificial river by-passing the weir was installed instead of a more classical fish pass);
- Drafting a guidance document ‘Fish passes suitable for the apron: design and feedback from experience’ (this can be downloaded form the "read more" section below).
The effectiveness of these fish passes is not yet fully evaluated as they are only recently finished, but the first monitoring results are very encouraging.
To overcome the threat of extinction, reintroduction tests were undertaken in 2006, 2008 and 2009. A total of 1,700 apron were released into the Drôme River. The first inventories showed good survival two years later, but it is too early to know if they successfully reproduce in the wild (which is the indicator of the long-term success of this action). These reintroductions could not have taken place if the Besançon Museum had not succeeded in enabling, for the first time, captive reproduction of the apron. This result is very significant because it secures a long-term future for this endangered species.
An apron ‘observatory’ was set-up: 21 stations were monitored to measure the population size and different environmental parameters. However, factors limiting the distribution of the species could not be clearly identified from the data obtained. The water managers are nevertheless very satisfied with the observatory and the information obtained has already influenced management plans.
Finally, a significant information campaign was organised to make the apron better known to the general public. Leaflets, brochures and high-quality documents were widely distributed. Three permanent exhibitions showing live apron and interactive computers were established in the Rhone basin territory. More than 6 000 children were reached during school activities.
In conclusion, the apron remains a species in critical danger of extinction. Yet the measures implemented during this LIFE project have made a significant contribution to its long-term conservation. The continuation of the project seems ensured: ten additional weirs will be equipped with fish passes suitable for the apron in the next few years, completing the work already made to reconnect the different sub-populations and to open a much larger part of the river basin to natural recolonisation. Furthermore, a National Action Plan for the species is nearly finalised and is expected to coordinate the continuation of the work initiated by these two successive and successful LIFE projects.
Further information on the project can be found in the project's layman report (see "Read more" section).