Shellfish Dredging Pushes a Flexible Avian Top Predator out of a Marine Protected Area
2006
Dekinga, Anne, | Piersma, Theunis, | Gils, Jan A. van, | Spaans, Bernard, | Kraan, Casper,
There is a widespread concern about the direct and indirect effects of industrial fisheries; this concern is particularlypertinent for so-called ‘‘marine protected areas’’ (MPAs), which should be safeguarded by national and internationallaw. The intertidal flats of the Dutch Wadden Sea are a State Nature Monument and are protected under the Ramsarconvention and the European Union’s Habitat and Birds Directives. Until 2004, the Dutch government grantedpermission for ;75% of the intertidal flats to be exploited by mechanical dredgers for edible cockles (Cerastodermaedule). Here we show that dredged areas belonged to the limited area of intertidal flats that were of sufficient qualityfor red knots (Calidris canutus islandica), a long-distance migrant molluscivore specialist, to feed. Dredging led torelatively lower settlement rates of cockles and also reduced their quality (ratio of flesh to shell). From 1998 to 2002,red knots increased gizzard mass to compensate for a gradual loss in shellfish quality, but this compensation was notsufficient and led to decreases in local survival. Therefore, the gradual destruction of the necessary intertidal resourcesexplains both the loss of red knots from the Dutch Wadden Sea and the decline of the European wintering population.This study shows that MPAs that do not provide adequate protection from fishing may fail in their conservationobjectives.
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