Seaweed Harvest Survey
Kelp beds and intertidal algae habitats are highly productive areas providing protection, an abundant source of oxygen and a rich source of food for many species, including our own. Marine macroalgaes (commonly called seaweeds) have been harvested around the world for centuries for both human consumption and industrial products. In Washington State, seaweeds are only harvested recreationally; harvesters are required to have a permit and adhere to a 10 lbs wet-weight limit. The ecological impacts of seaweed harvesting are mostly unknown and the potential impacts on the ecosystem are poorly understood. The PTMSC decided to look at the issue of seaweed harvesting and conducted a three-year study to evaluate some of the effects associated with recreational seaweed harvesting.
Two beaches were selected for the study, North Beach County Park where recreational seaweed harvesting is common practice, and Kinzie Beach in Fort Worden State Park which was closed to harvest during the study period. The primary target species collected by harvesters was wing kelp (Alaria marginata), so the study focused on this species. During the study an estimated 200 to 300 harvesters per year (primarily women) removed between 2,000 and 4,000 pounds of Alaria from North Beach County Park, with at least half the harvesters having visible licenses. Compliance with the 10 lbs wet-weight per person harvest limit improved significantly over the three year study, probably due to the presense of the research teams. As one would expect, the most readily accessible Alaria in the higher intertidal region was removed first. Harvest efforts in 1996 and 1997 reduced the Alaria per cent cover from over 50% to about 15%.
This three-year study just began to answer our many questions about seaweed harvesting, but much remains to be determined before we can understand what effect harvest has on the intertidal flora and fauna of our rocky shores.