Fish farming abandonment and pond use by ducks breeding in Sologne (Central France)

摘要

Fishpond complexes are important wetlands for waterfowl breeding in Europe. In France, extensive fish farming in several pond regions seems to be threatened by a massive abandonment of fish stocking and production due to low economic returns. This study investigated at pond level the consequences on duck breeding of the interruption of pond management by fish farmers in Sologne (Central France). We compared models (GLMs) with duck pair number or with the brood: pair ratio as dependent variables, including as explanatory variables an index of abundance in high or low littoral vegetation (descriptor of potential nesting cover), of willow Salix sp. stand development (descriptor of helophyte encroachment by wooden vegetation), physico-chemical characteristics of water and sediment, and a categorical variable for fish farming (ponds harvested every 1-3 years, not harvested for 4-10 years or for > 10 years). Regular fish farming best explained: (1) high duck pair abundance and (2) high brood: pair ratios provided that water transparency was > 40 cm. Our results seem to indicate that extensive fish farming, and therefore pond management by fish farmers, may contribute to enhance pond carrying capacity for breeding ducks.