Aquaculture

Connections to The Blue Economy

Aquaculture is an enormous topic that has many components adjacent to kelp restoration. Aquaculture is the inclusive term for all commercial fish, shellfish, and seaweed farms either ocean or land-based. Mariculture is a subset term referring to open-ocean cultivation of kelp or shellfish. Connecting kelp restoration efforts to a non-extractive ocean food economy is a huge motivation for funders and supporters of kelp recovery efforts.

Urchin Ranching is one of the most promising aquaculture experiment relative to bull kelp restoration. The impoverished, zombie, purple urchins pulled out of kelp restoration sites are fed kelp or kelp pellets and fattened up in aerated tanks (usually stacked inside a container) until their uni (gonads) are bright, fleshy orange. This uni is in demand by high-end chefs and the Japanese market. Red urchins have been a valuable fishery for years, but now efforts are growing to use the market—what might be called ‘The Blue Economy’—to incentivize these purple (or green if farther north) urchin farms. Most are still in the early days, but local efforts are emerging adjacent to the areas where urchin harvesting are trying to clear space for new bull kelp growth. Well-known chefs in Northern California are creating fantastic menus with this locally ranched purple urchin uni. Noyo Center for Marine Science in Fort Bragg California and groups at Port Orford, Oregon are beginning their urchin ranching projects. Open source information for urchin ranch start-ups is being generated by California Sea Grant. The market is there. Land-based abalone farms are following suit, to fill the market gap left by the disappearance of the recreational abalone fishery.

Abalone restoration — Abalone are grazers that can be beneficial to kelp as opposed to chomping it down to nothing. In Puget Sound, abalone restoration is in the spirit of rebuilding the kelp forests ecologies there, where urchin are not the issue but warming water, kelp crabs, and pollution largely from stormwater runoff has caused enormous decline in kelp forests. These conditions cause a build-up of microalgal growth on kelp blades restricting the kelp’s ability to photosynthesize. Gentle grazers such as abalone can clean off this layer of muck, allowing bull kelp to grow more efficiently. The Puget Sound Restoration Fund is at the forefront of developing holistic approaches to kelp forest recovery, by not only developing bull kelp nurseries and outplanting projects but also focusing on oyster and abalone recovery sites.

Bull Kelp Farming is extremely niche compared to the enormous amount of seaweed farmed in China, Indonesia, and South Korea; the seaweeds farmed in Asia comprise two of the top three aquaculture species worldwide by metric ton (the third is whiteleg shrimp). Even in the US commercial kelp farming world, bull kelp is a tiny player with only a few active bull kelp farms in Alaska and BC. All of these are relatively experimental.

In 1991 John E. Merrill and David M. Gillingham wrote the Bull Kelp Cultivation Handbook to detail the process of cultivating large bull kelp sporophytes (mature bull kelp) from sori patches collected from wild specimens. Their readers, they thought, were those interested in the commercial production of bull kelp. The book has extensive chapters on seed stock and production methods but also sections titled: Bull Kelp Market Analysis and The Economics of Bull Kelp Farming. Bull kelp, however, has continually defied efforts to make it a commercial commodity. It has always been part of indigenous foodways, but never found a commercial market similar to sugar kelp (Sacharrina latissima) or ribbon kelp (Alaria marginata). Barnacle Foods, located in the bull kelp-rich area of Southeast Alaska, is, however, the one company that has broken this trend and made successful bull kelp products such as hot sauce, salsa, and other condiments. Barnacle Foods has become an advocate and driver for learning how to farm bull kelp to better understand the wild organism, and in turn to better support bull kelp if it is in decline. They have issued an updated Bull Kelp Farming Guidelines Handbook, which is not too dissimilar from its 1991 predecessor. In the 32 years between these publications, the commercial prospects of bull kelp have not grown much beyond the Barnacle Foods product line. The only bull kelp farm in California, in Humboldt Bay, was only funded for a year and is abandoning bull kelp for Alaria, or ribbon kelp, a species more amenable to commercial food pathways. As a result the most recent 2023 “bull kelp cultivation handbook” is full of phrases such as “challenges to overcome,” “needs to be tested experimentally,” “mechanism is poorly understood”,  “has little testing”, and “this is an area of active research.”

This is perhaps what makes bull kelp both alluring and mysterious. We know how essential it is for ocean health and biodiversity but it does not necessarily conform to our market-driven systems; its unique shape and manner is stymieing even the most tried and true kelp farmers. It grows on its own, wild terms.

But there is a reason to farm bull kelp: restoration and knowledge learned. The majority of US commercial kelp farms, most of which are in either Alaska or Maine, farm sugar kelp or Saccharina latissima. Similar to the technique described in the 1991 Handbook, twine wrapped around a plastic tube is dipped into a sporulated solution [see Bull Kelp Cultivation Diagram], and thus inoculated with kelp spores which quickly evolve into gametophytes which fertilize in a seedling nursery (a square tank of seawater with controlled light and temperature) to produce baby sporophytes or kelp. The spools of twine, fuzzy with tiny kelp, are then deployed, unspooled, onto a larger rope that is set out at a certain height below the surface in an array of ropes, buoys, and anchors. Sugar kelp is fleshy and sweet, negatively buoyant, and grows downward on these lines starting in mid-winter. The ropes laden with long fleshy sugar kelp are harvested in early spring, having grown quickly using the power of sunlight and the nutrients of the surrounding ocean, with no freshwater or fertilizer inputs.

But growing bull kelp like sugar kelp is “like trying to grow tomatoes like you would kale,” says Matt Kern of Barnacle Foods who is establishing a bull kelp farm in SE Alaska, to better understand what techniques are best for this particular species…. Nereocystis luetkeana. The positive buoyancy of bull kelp means the lines need to be deeper, closer to the ocean bottom than sugar kelp lines. Line depth, spacing and density of spores, water temperature, and ocean dynamics of the location will all be factors in the bull kelp’s growth. Trying to make farmed kelp grow like wild kelp has proven to be a challenge. Bull kelp’s unique relationship to each of these elements is still trying to be understood; each farm is an opportunity to study and learn. This is also why it is so important to share experimental farm designs and growth data. Even the kind of twine and rope used will affect outcomes. The scuttlebutt is that there is a particular, expensive Korean twine that is the best for baby kelp to hold onto and entwine their holdfasts around. We can’t be sure what will be the game changer to help the kelp!