Photo Credit: Tamsen Peeples
Bull Kelp Mariculture
Even though bull kelp can be naturally found throughout the southern Alaskan coastline, there are only 4 areas where bull kelp is currently farmed: Kodiak, Cordova, Juneau, and Sitka. Bull kelp is unique among kelps due to the fact that its stipe, in addition to its blades, is extremely palatable for human consumption and can be used for a variety of products such as pickles, salsa, and other foods. Currently, majority of the bull kelp on the market is sourced from wild harvest, but with permit-based supply limitations and climate change threats to the persistence of bull kelp forests, farmers and producers are actively working to develop bull kelp farming techniques to source this desirable species.
One of the main approaches to growing bull kelp in Alaska is the use of the catenary system. Catenary systems are characterized by 2 or more “catenary lines” stretched between buoys and anchors to provide the frame for the kelp farm. The grow lines are then strung between the catenary lines at a set depth where they are left to grow. However, due to the unique morphology of bull kelp (i.e. hollow stipe, highly buoyant), traditional kelp farm catenary arrays have experienced a number of challenges in producing a desirable product. The extreme buoyancy of bull kelp means it is relatively difficult to keep at depth as it grows larger, so countering that buoyancy with extra weight or tension creates transportation, ergonomic, and engineering challenges. It is critical for bull kelp to stay submerged for at least some amount of time every day in order to prevent bleaching, sunburn, frostbite, or other degradation of the blades.
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Other bull kelp farming challenges include seed security, site selection, contamination biofouling, line spacing and kelp density control to prevent tangling, and methods for processing such a large species.
Photo Credit: Barnacle Foods