No abstract

Any initiative aimed at the management of a threatened species needs a good knowledge of its environmental requirements. Aims of this study were to individuate suitable areas for the reintroduction of crayfish species belonging to the Austropotamobius pallipes complex and to evaluate the causes of the local extinction in Tuscany (Italy) of some populations. Between May 2003 and September 2004, we collected ecological data from 19 streams of 4 catchments, 9 watercourses where crayfish were present (WI) and 10 where they were present in the recent past and absent now (WO), and we compared them. Multivariate analyses were performed using chemico-physical and biotic parameters to examine the relationships between their values and the presence of crayfish. The results did not allow us to find significant differences between the two categories of streams, suggesting their suitability for crayfish reintroduction. Key-words:Austropotamobius pallipes complex, Extended Biotic Index (IBE), Fluvial Functionality Index (IFF), biotic and abiotic parameters. Bull. Fr. Pêche Piscic. (2006) 380-381 : 1095-1114 -1096 -hydrographiques différents, qui abritent actuellement des écrevisses (WI) ou qui en sont dépourvus depuis peu (WO). Des analyses multivariées ont été réalisées en prenant en compte à la fois les paramètres physico-chimiques et biotiques afin d'examiner les relations entre ces données et la présence du complexe Austropotamobius pallipes. Les résultats ne montrent pas de différence significative entre les deux catégories de ruisseaux ce qui traduirait l'aptitude des sites WO à accueillir des écrevisses. CARACTÉRISATION ÉCOLOGIQUE DE RUISSEAUX TOSCANS (ITALIE) POUR LA GESTION DE L'ÉCREVISSE MENACÉE AUSTROPOTAMOBIUS PALLIPES

ABSTRACT1. As part of the Austropotamobius pallipes species complex, the crayfish Austropotamobius italicus is a species of community interest whose preservation requires the designation of Special Areas of Conservation (SACs) (Annex II, EU Habitats Directive). This study aimed at (1) assessing the conservation status of this threatened indigenous species by stock assessment in Central Italy and (2) identifying some aspects of its elective habitat.2. Surveys were conducted in nine streams harbouring A. italicus (streams WI) and in 10 streams where crayfish populations became extinct at least 5 years before the study (streams WO).3. The results confirmed that A. italicus is a K-selected species, with a relatively slow growth rate (males: 0.34; females: 0.37) and a long life expectancy (males: 8.2 years, females: 7.8 years). The extant populations are healthy, showing balanced sex-ratios and well structured age-class compositions. Mortality is mainly due to fishing, which is illegal in Tuscany.4. Principal Components Analyses showed that the streams WI and WO differ in the abundance of allochthonous plant detritus but not in the taxonomic composition of their macroinvertebrate communities. Age classes were found to be spatially segregated, juveniles mainly using cobbles as substrates and adults seemingly avoiding them.5. The loss of the pristine riverine landscape seems to have been responsible, together with illegal fishing, for the local extinction of the species. As a consequence, retaining, enhancing, and restoring the habitat and its complexity are required for the preservation of A. italicus.6. The designation of SACs might help in this endeavour if accompanied by programmes aimed at publicizing the need for conservation of this species. Unfortunately, crayfish-focused projects supported by LIFE in Italy since 1992 (4%) and the SACs involved (1.4%) have been relatively few, despite the poor conservation status of this species and its well recognized ecological role.

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