Harvesting of Laminaria digitata
This information has been largely abstracted from Arzel (1996).
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).