Publication Abstract

Clam cultivation: Localised environmental effects. Results of an experiment in the River Exe, Devon (1991-1995)

B.E. Spencer

A clam growing experiment was set up on the intertidal shore of the River Exe to measure whether any localised changes might occur to the animal and plant communities and to the sediment composition. The experiment showed that plots covered with netting encouraged the proliferation of certain sediment-feeding worm species, a small increase in the organic content of the sediment and in one component of particle sediment size. These changes occurred irrespective of whether or not clams were present in the plots. Changes were partly influenced by the presence of a green alga which grew on the nets and by periwinkles which fed on the alga. These changes were recorded soon after planting the clams and remained throughout the cultivation cycle until harvesting took place 21/2 years later. The immediate effects of harvesting by hand-raking caused a reduction of invertebrate species in the sediment by 50% and suction harvesting a reduction of >90%. Trenches formed by suction harvesting were infilled naturally within 3-4 months, but invertebrate community recovery was slow over winter reaching normality in the summer, 6 months after harvesting.

Reference:

B.E. Spencer, 1996. Clam cultivation: Localised environmental effects. Results of an experiment in the River Exe, Devon (1991-1995). Handout, CEFAS Lowestoft, 10pp