The Canadian province of Nova Scotia does not allow mechanical cutting of rockweed in part because of the threat of habitat damage1. Annapolis Basin, St. Mary’s Bay, and Lobster Bay [NS] showed signs of overharvesting rockweed as recently as 2006. (Ref)
How does a mechanical cutter work?
"A reciprocating cutter blade cuts a 2.4 m swath; shoots are picked up by a conveyor belt and moved into a 1.4 t capacity storage bay." (Ref)
How much rockweed can a mechanical cutter take per day?
Mechanical cutters are capable of removing up to 50 tons of rockweed a day (Nova Scotia Department of Fisheries).
1"[Nova Scotia] rejects any mechanical harvest method similar to those used in NS in the past, arguing that this would reduce employment and could produce a negative habitat impact." (Ref)
After reaching the factory, the rockweed is shoveled onto a conveyor belt, then the rockweed is ground up using an old meat grinder, and this is likely where any remains of snails and rocks are removed. Next, the rockweed is turned into slurry.
"The still-dripping seaweed [rockweed cut in Maine] is then loaded on conveyor belts, where the snails, periwinkles, and other creatures on it are shaken loose and disposed of." ~ from a 2005 article in Spa Finder