Harvesting of Laminaria digitata

This information has been largely abstracted from Arzel (1996).

Brittany

Around the coasts of Brittany there is a long tradition of seaweed collection. Several species of seaweeds have been harvested on a commercial scale, larger or smaller, since the 1950s and form the basis of a series of flourishing industries. The collection of L. digitata around the coasts of Brittany has provided the French alginate industry with feedstock for the production of emulsifiants. The plants are collected from small boats using a device called a "scoubidou". This is a 2-3 m long steel bar with a spiral curved hook at the end which is lowered into the thickest part of the L. digitata forests and then twisted, gathering up the stipes like twisting spaghetti on a fork (D. Birkett, pers. obs.). The hook is then winched inboard and whole plants of L. digitata are ripped from the substratum, including blades, stipes and some holdfasts.

There is no literature available on the effects of this method of harvesting on the biodiversity and population structures of the kelp bed species. L. digitata plants rapidly re-colonise any gaps in the upper infralittoral which result from storm damage and are assumed to respond in a similar way to areas cleared by harvesting. The areas licensed for harvesting represent only a small proportion of the total habitat of L. digitata around Brittany, but the substratum area which is effectively cleared each year is not recorded, just the wet mass of the harvest. The complaints of local fishermen that crustacean catches are locally reduced in harvested areas have been dismissed as an example of the historical animosity between fishermen and seaweed harvesters (Dauvin, 1997).

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