Decrease of the carrying capacity of the Oosterschelde estuary (SW Delta, NL) for bivalve filter feeders due to overgrazing?

Bivalve growth and condition are food limited, as shown by a negative correlation between average mussel meat content and bivalve filter feeder stock size in a certain year. The annual growth of cockles has decreased, and the fraction picoplankton is now up to 30% of total phytoplankton. Food limitation, high filtration capacity, picoplankton abundance, and only short-term bottom-up control of primary production by nutrient limitation, point to overgrazing as a cause of primary production decline. Further expansion of shellfish stocks may induce the risk of overexploitation.