Lead poisoning of waterfowl in Spain: conservation efforts, trend of prevalences and implications on game meat safety

Abstract

The prevalence of lead (Pb) shot ingestion in waterfowl hunted in Spanish wetlands around the Mediterranean coast during the 1990s was as high as 30-39 % in mallard (Anas platyrhynchos), 69 % in common pochard (Aythya ferina) and 74 % in northern pintail (Anas acuta). Lead shot use was banned in protected wetlands in Spain in 2001, however, this was not fully implemented in the Ebro delta until 2003. Here, we show results for four hunting seasons (2007-2011) where shot wintering waterfowl (n = 503) from this wetland were monitored. The type of embedded shot present in hunted birds was studied by X-ray and dissection. The prevalence of Pb shot ingestion was studied by gizzard examination. Ban compliance was relatively low in 2007-08, i.e., 26.9 % of birds had embedded Pb shot, 10.6 % had Pb and steel shot, 48.8 % had steel shot, and 13.8 % had no shot. After these results were produced, the ban was reinforced and compliance subsequently increased with less than 5% of birds with only Pb shot. However, 22.9% of harvested birds contained embedded Pb and steel shot in 2010-11. The prevalence of Pb shot ingestion in mallards in 2007-08 (28.6%) was comparable to the pre-ban prevalence (30.2 %), but, it was significantly higher than in subsequent seasons (in 2008-09: 5.1 %; in 2009-10: 13.8 %; in 2010-11: 13.5%). In the last year of the study, a significant proportion of birds still had embedded Pb shot and/or ingested Pb shot in their gizzards. This may be because the ban was not implemented in unprotected rice fields, where the majority of ducks often feed. By extending the ban to all waterfowl hunting (not only that undertaken in protected wetlands) the risk of Pb poisoning in waterfowl can be greatly reduced. Game meat Pb levels were above maximum residue levels according to EU regulation for livestock meat in birds that had ingested Pb shot and birds killed with Pb ammunition. A significant reduction in game meat Pb levels was observed with the implementation of the use of steel shot.