Relationships Between Changes in Habitat Conditions and Population Density of an Introduced Population of Signal Crayfish (Pacifastacus Leniusculus in a Fluvial System.

Abstract

After the disappearance of the native crayfish in many rivers in Biscay, Basque Country, Spain, the signal crayfish Pacifastacus leniusculus was introduced in the main fluvial stretches and several breeding populations have established. One of the most productive zones was the Cadagua River, where the population was established from 1989 (first introduction) to 1995. Starting from that year, a marked decrease in population was recorded downstream, and this fact is studied in relation to fluctuations in physical and chemical conditions caused by human perturbations in the fluvial corridor mainly caused by the construction of a road.

Cambios en las condiciones físicas, químicas y faunísticas de un sistema fluvial (río Oma, Bizkaia), y desaparición de una población de cangrejo autóctono (Austropotamobius pallipes): ¿causa y/o efecto?

“…Las intervenciones en cauce pueden ser también motivo de mortandades de cangrejos, lo que se ha constatado en otras zonas de la red fluvial de la provincia (Rallo et al, 1996;Rallo et al, 2001). En el caso del Oma, no tenemos constancia de que se realizara ninguna intervención ni en el cauce ni en zonas cercanas al río durante el periodo de estudio.…”

The future of the indigenous freshwater crayfishAustropotamobius italicusin Basque Country streams: Is it possible to survive being an inconvenient species?

“…Crayfish mass mortalities that could have been due to the crayfish plague were not detected, suggesting that other factors must have caused local extinctions. Indeed, habitat alteration was identified as the most likely cause for the disappearance of both native and non-native crayfish from Basque streams (Rallo et al, 2001(Rallo et al, , 2004. High vulnerability to crayfish plague, but also to habitat alteration, must therefore be regarded as important weaknesses of the native crayfish from the perspective of any SWOT analysis.…”

“…In contrast, small populations of the native white-clawed crayfish are found in the Basque Country only in brooks, small springs, and in headwaters of a limited number of streams (García-Arberas and Rallo, 2000). Although spread of the fungus Aphanomyces astaci is the main reason given to explain the disappearance of most native crayfishes from European waters (Diéguez-Uribeondo et al, 1997b;Söderhall and Cerenius, 1999), the decline of these species is also due to habitat loss and habitat degradation (Westman, 1985;Smith et al, 1996;Rallo et al, 2001;Souty-Grosset et al, 2006). Here we used SWOT analysis to evaluate the situation of the indigenous white-clawed crayfish A. italicus in the province of Biscay (Basque Country).…”