Conservation and restoration of the Allis shad in the Gironde and Rhine watersheds

PROJECT DESCRIPTION

BACKGROUND

The Allis shad (Alosa alosa) population in the Gironde watershed in France was the most important population in Europe until the beginning of the 21st Century, with annual catches of several hundred tonnes of fish. Since 2006 there has been a marked decline in the return rates of mature shads to rivers for reproduction, the reasons for which are still not well understood. In 2008, a moratorium on Allis shad fishing was established in the Gironde watershed. One hundred years ago, the Allis shad population in the Rhine watershed in Germany was the most important shad population in its northern distribution range with fish catches of several hundred tonnes/year. Within 30 years this population had collapsed. Reintroduction efforts were started in 2007 as part of the LIFE project (LIFE06 NAT/D/000005).

OBJECTIVES

The key objective of the LIFE+ Alosa alosa project was to reintroduce Allis shad to the Rhine watershed in Germany. In a unique European approach, the project aimed to combine the conservation of the largest remaining Allis shad population in Europe in the Gironde watershed, with the reintroduction of Allis shad to the Rhine watershed. Other key project objectives were to transfer Allis shad aquaculture techniques from France to Germany and to develop techniques for an ex-situ stock. These are important conservation tools for diadromous (i.e. species that spend part of their lives in freshwater and part in saltwater) fish restoration and have been implemented in recovery plans for the European sturgeon and Atlantic salmon.

A pilot ex-situ facility was established in Germany, with mature, or nearly mature, fish expected by the end of the project. The idea was that development of these techniques would enable the project to remove fewer fish from French rivers and to include returning fish to the Rhine watershed in the ex-situ stock in the future. In addition, these techniques could be used in other European watersheds where Allis shad populations are endangered.

The following actions were planned:

Analysis of the potential bottlenecks for Allis shad in the Gironde watershed, river connectivity and reproduction success, and the improvement of the situation thanks to the results of these studies;

Re-defining the Allis shad fish pass design in Europe, in the light of the latest knowledge and improvements coming from US Shad fish passes. These improvements would be implemented to aid fish migration in the Garonne and Dordogne rivers;

Stocking of 1.5-2 million Allis shad larvae per year in the years 2011-15 resulting in a total number of 7.5-10 million shad larvae over the duration of the project;

Monitoring of the expected increase in the return rates of mature Allis shad in the Rhine watershed from 2013 onwards;

Development of the techniques for an Allis shad ex-situ stock in France and Germany and the installation of a pilot facility in Germany close to the Rhine; and

Transfer of knowledge of Allis shad aquaculture from France to Germany. Reintroduction programmes of the closely related American shad stock to show that around 250 Allis shad larvae are required in order to obtain one returning adult. Based on this premise, the project team expected 30 000-40 000 Allis shad, i.e. up to nine thousand in 2015.

RESULTS

The key objective of the project, i.e. the reintroduction of the Allis shad into the Rhine system in Germany, was successfully achieved. In 2015 (the final year of the project) around 250 adult Allis shads were observed. (These were returning to the Rhine system from the North Sea.) This indicates, according to the LIFE team, that several thousands of adult Allis shad are returning annually to the Rhine system and is a clear sign of their success.

In total, some 6.2 million Allis shad larvae were produced and released into the river Rhine. Although this is less than the originally envisaged (around 7.5 m larvae) the scientists believe that the figure nevertheless signals a significant contribution to the long-term establishment of the Allis shad in the Rhine system.

The LIFE team has also increased knowledge about the reasons of the decline of the Allis shad population in south-western France: Detailed deficits of the fish pass facilities were detected and this initiated considerable efforts towards improving these fish passes. This also highlights an important positive leverage effect of the LIFE project. The development of an ex-situ stock, however, was not successful. The initial target was to achieve 50 premature or mature Allis shads in the German rearing facility by the end of the project. This was not achieved as unfortunately all fish died before reaching maturity. This failure is attributed to an electric blackout and a lack of continuous control at the rearing facility. Allis shad in a second ex-situ stock in France however have been proofed to reach maturity in 5 years of culture.

The main elements of success of the LIFE project are summarised as follows:

Thorough investigations of the fish migration through fish passes at weirs of the rivers Garonne and Dordogne resulted in actions to improve the pass through ability of these weirs;

A pilot facility for the rearing of Allis shads was established in Aßlar in Germany. As already stated, this did not, however, result in any mature Allis shads. However, during the project period, the knowledge of the long term rearing of Allis shad was significantly increased, mainly as a result of the intensive cooperation with the universities of Gießen and Koblenz-Landau;

A total of 6.2 million Allis shad larvae of were produced and released into the river Rhine; and

In October 2015 a scientific conference was organised by the project, which helped to disseminate the main findings and lessons learnt. More than 100 people from nine different countries attended the conference.

Finally, the project’s work meets requirements of several EU policy issues. Notably, these encompass the Habitats and Water Framework Directives and reflect EU fisheries policy, especially concerning measures to improve fish migration/ efficiency of fish passes.

Further information on the project can be found in the project's layman report and After-LIFE Conservation(see "Read more" section)."