Did the sea grapes just move?

A ‘vineyard’ of  Caulerpa lentillifera.

A ‘vineyard’ of Caulerpa lentillifera.

In general, seaweed shouldn’t move. Sway? Sure, but crawl? Slither? No, no. Yet there, inside the tank of sea grapes (Caulpera lentillifera), a green, globular, mass was climbing the glass. This looked like sea grapes … but the factor of motility had my biology senses tingling.

 We’ve been testing a range of different culture conditions for Caulerpa lentillifera – a green seaweed, the last several months. Caulerpa, or sea grapes is not yet a widely-farmed seaweed, but we believe that it could have great culinary appeal. This “vegan caviar” pops in your mouth, with a burst of ocean flavor. The thallus (or ‘leaf’, if you will) of sea grapes is a cluster of small, green vesicles, called ramuli, that look like tiny grapes.

Our  Sacroproteus  friend out of camouflage looks more like a pokemon.

Our Sacroproteus friend out of camouflage looks more like a pokemon.

 What we observed in our tank was akin to watching a bunch of grapes slinking down a trellis. A closer examination revealed a slug-like body beneath the bunch of greenery, and two antennae probing the waters as it slithered forward. Known to science as Sacoproteus smaragdinus, these sea slugs appear similar to nudibranchs, such as the famous “Spanish dancer”, but are only distantly related. The Sacoproteus genus was named after the Greek sea god, Proteus, who could change his shape at will. What an apt name for such a clever algae mimic!

 As a gastropod (“stomach-foot” in Latin), our S. smaragdinus literally walks all over its lunch. Most of the species of Sacoproteus seek out just a single Caulerpa species. The slugs sniff out their beloved sea grapes by perching on their sluggy haunches and waving their bodies through the water, hoping a wafting scent of Caulerpa leads them to the vineyard. Each species of slug has a uniquely-shaped tooth adapted to pierce the ‘bubble’ of its preferred species of sea grape.Once they’ve located their lunch/lounge, their special tooth pokes the grape, sucks it dry and stores the green pigments in their bulbous backs as the perfect disguise.

A conspicuous view of the  Sacroproteus sp.  slug. Photo Credit: Pam Madden

A conspicuous view of the Sacroproteus sp. slug. Photo Credit: Pam Madden

 Larval Sacoproteus are planktonic, and drift through the oceans with the currents, until they sense the Caulerpa species of their choice. This can then trigger metamorphosis, and they settle down to a more sedentary life. We suspect that this is probably how this slug “showed up” in our tank; by drifting in through our seawater intake line.

 Keeping tabs on our new-found friend is challenging; it’s more like “newly-lost”. Peering through a tank full of green bubble-algae is like one long, losing game of hide and seek, with a slug that Nicholas Paul (an expert on seaweed and algae at Australia’s University of the Sunshine Coast) says, “may be the best example of an animal masquerading as a plant that we have.”

One  Caulerpa,  two  Caulerpa,  three  Caulerpa—wait…  Photo credit: Pam Madden

One Caulerpa, two Caulerpa, three Caulerpa—wait… Photo credit: Pam Madden

More: Would you like further reading? See the National Geographic article: “Stunning new sea slug species looks just like seaweed”

Save a tuna, eat a vegetarian

Seafood has a smaller carbon footprint than any other animal protein (Nijdam et al, 2012).  But just like every other kind of meat, the higher the trophic level, the higher the energy input to make it.  

For seafood, low trophic level typically means filter-feeding bivalves, such as oysters, or forage fish, such as sardines or mackerel.  Most consumers will agree that an ahi fillet is more desirable than a plate of mussels or jellyfish.  But what if you could have a hearty, satisfying fillet – sashimi-grade for the poke-lovers – that was also an herbivore?  Enter Kyphosidae.  At Kampachi Farms we have been working with Kyphosus vaigiensis, an herbivorous reef-fish with a longstanding presence in Hawaiian cuisine.

Kyphosid  from local Kona waters; a commonly fished for species, popular as poke. He ded.

Kyphosid from local Kona waters; a commonly fished for species, popular as poke. He ded.

This fish is known as enenue or nenue in Hawaiian (rudderfish or sea chubs in Not Hawaiian), and in some regions was regarded as a prized reef fish, reserved for ali’i (royalty) only (Ulukua, 2019).  Nenue are found in abundant schools around Hawaii; 2-3-kilogram fish are common, while state records exceed 4.5 Kg. One of the traditional preparations for nenue was poke – a staple of native Hawaiian food, originally consisting of raw reef fish, sea salt, limu (seaweed), and kukui nuts.  Poke recently exploded onto the mainland United States fast-food scene; it can be found at myriad stand-alone poke counters as well as at the likes of Red Lobster and The Cheesecake Factory (Dixon, 2016).  While Hawaiian poke was traditionally made of a variety of fish, including nenue, the versions in vogue now are based almost exclusively on tuna or salmon, two high-trophic predators.

Nenue have a number of advantages as a candidate for aquaculture.  Our research at Kampachi Farms thus far has found that adult nenue spawn readily in captivity.  Larvae are exceptionally hardy in preliminary hatchery efforts. Our colleague Syd Kraul at Pacific Planktonics recently raised a final total of 200 baby nenuitos from a small sample of our captive-spawns, in an extensive ‘green-water’ culture system. We are planning larger-scale runs in our research hatchery in the near future.  Nenue also have ctenoid scales, with a rough texture and row of tiny teeth at the edge; this armor dramatically aids in ectoparasite resistance. 

Their most interesting feature, however, is their guts.[1]  Nenue have a unique digestive system that allows them to graze on macroalgae.  They subsist on seaweeds by using fermentation in the gut to break down the complex carbohydrates of limu.  Several rounds of grow-out trials with juveniles have shown that they can thrive on diets based on aquatic plant material as well as corn and wheat.  Herbivory precludes the need for wild-caught forage fish – reducing the overall ecological footprint – and perhaps renders them better suited to small-scale fish farming in less-developed countries. 

Hand-model displaying juvenile  Kyphosus vaigiensis , also known at this stage as  nenuito .

Hand-model displaying juvenile Kyphosus vaigiensis, also known at this stage as nenuito.

26 day-old  Kyphosus vaigiensis  learning their numbers.

26 day-old Kyphosus vaigiensis learning their numbers.

Between ready acclimation to captivity, routine marine fish larval rearing, parasite resistance, and a broad plant-based diet, this fish has all the trappings of success in sustainable aquaculture.  And it yields poke-quality meat to boot!

At Kampachi Farms we believe that seafood is healthier for people and healthier for the planet, compared to other types of meat.  But one should always strive for improvement: we can improve seafood sustainability by diversifying what we eat and prioritizing low-trophic species in this diversification.  Legions of researchers are pursuing plant-based and alternative proteins that can suitably nourish those carnivorous fish the market so demands – a noble pursuit, yet an admittedly roundabout way to produce ‘low trophic’ species.  The more direct way, the simpler way, is to culture natural marine herbivores.  Not all marine herbivores are suited for the dinner table. And market favorites – such as ahi, snappers, and our King Kampachi – are all beautiful food fish in their own right.  However, if even a fraction of the restaurants selling salmon and ahi poke bowls today also offered nenue grown on herbivorous diets, the seas would be that much better for it.

A flippin’ cute  nenuito  !

A flippin’ cute nenuito !


Dixon, Vince. 2016. Data Dive: Tracking the Poke Trend. www.eater.com.  Citing FourSquare.

National Oceanic and Atmospheric Administration. 2018. American seafood industry steadily increases its footprint. www.noaa.gov.

Ulukua: The Hawaiian Electronic Library. 2019.  Native use of fish in Hawaii.  Mok. 2 Descriptive list of Hawaiian fishes (‘Ao’ao 56-163).


In-text links to…




[1] Stay tuned for future blog posts about our imminent research on the kyphosid gut microbiome and its potential application to biofuel production.

Hooked on Aquaculture: Interview with Kampachi Farms’ Interns

From left to right: Travis Burroughs (intern), Julien Stevens (internship coordinator), and C.J. Chao (intern).

From left to right: Travis Burroughs (intern), Julien Stevens (internship coordinator), and C.J. Chao (intern).

As the Internship coordinator at Kampachi Farms, I regularly field emails and calls from marine scientists in training, and aspiring fish farmers. I myself started out at Kampachi Farms as an intern, and I’m a firm believer in the opportunities that volunteering can provide. It’s a great way to gain aquaculture experience, and to get to know an organization without having to commit yourself for the long term.  But often potential aquaculture interns have a romanticized notion about what their role might be.  To clarify what the role is all about I’ve asked our two summer interns, C.J. and Travis, to answer a few questions.

Can you tell us a bit about yourself and why you wanted to intern at Kampachi Farms?

C.J. Chao: I’m a senior at Boston University studying Environmental Policy and Analysis. I came to Kampachi Farms because of my great interest in aquaculture, which stems from my love of the ocean. I look at aquaculture as a possible sustainable substitute for depleting wild fisheries and want to be involved in an industry that is new, progressive and exciting. I’m originally from San Francisco but grew up in the suburb of Marin. I’m a certified master scuba diver and also maintained saltwater aquariums as a kid. These two hobbies fostered my interest in the aquaculture field.

Travis Burroughs: I’m from Larkspur, California, and am a senior at the University of Denver studying sustainability and marketing. My interest in aquaculture was sparked by my lifetime of fishing, which first led me to an internship at Monterey Abalone Company last summer. I had a fantastic experience there and with my love of fish, I wanted to gain work experience with a company that focuses on environmentally responsible fish farming.

What sort of work did you do during your internship at Kampachi Farms?

Travis: The internship was both full of routine experience and novel challenges, depending on research needs. These routine tasks included: feeding fish, observing behavior, scrubbing tanks, maintaining the filter systems through back flushing and cleaning filters, and tidying up the site. We also helped to move 20 tons of gravel to level the site for new broodstock tanks for our kampachi.

CJ: Each day Travis and I would complete necessary husbandry tasks, including feeding fish and cleaning tanks.  We also assisted with ongoing experiments, including a feed trial using an experimental soy-based feed, and testing the viability of growing algae in the open ocean for human, animal feed, and biofuel purposes.

What did you learn from your internship?

CJ: Kampachi Farm’s research team offered me a wide ranging and in-depth look into research-oriented aquaculture. During my internship I was able to work with many farmable marine species, including Seriola rivoliana (also known as Kampachi or Yellowtail Amberjack), Giant Pacific Grouper, Nenue (Grey Chub) and several species of algae.

Travis:  While at the Kampachi Farms R&D facility in Kona we were given a first-hand look into fish husbandry at the different life stages. We were lucky enough to be on site during a feed trial, where over 700 fingerling kampachi that had been spawned and hatched out on site, were being grown out on different sustainable feed options. We began feed trials with fish ranging in size from 14-40 grams, which involved weighing, measuring, and tagging each individual fish and then putting them into marked tanks. The goal of the feed trial was to compare different feeds and see which one produced the best FCR and overall fish health. The data collected on-site could then be used in future commercial use with Kampachi Farm’s King Kampachi in La Paz Mexico.

Some of the Kampachi Farms research team with C.J. and Travis on their last day.

Some of the Kampachi Farms research team with C.J. and Travis on their last day.

 A few considerations to keep in mind for potential interns: All of our research work in Kona is grant-funded, and so we are presently unable to pay interns for their time. Any internship would therefore need to be on a pro-bono basis. Feel free to get creative in your self-funding options; we have had students find outside funding from their University or regional STEM internship programs. Interns are required to provide their own housing and transport to Kona, and must also have reliable ground transportation when here on the island (public transport in Kona is virtually non-existent).

We love hosting passionate aquaculture interns when our research schedule allows it. If you are interested, please contact our team to learn more about our internship program. You can also stay up to date with our current research projects here.

Seaweed to the Rescue: Foods, Feeds, and Fuel


Macroalgae, or seaweeds, have been around for a very, very long time; fossil evidence of a red macroalga has been dated between 1 and 1.6 billion years ago (1). Seaweeds must be doing well for themselves, if they’ve survived this long! It’s this realization that has catalyzed phycological research ranging from nutrition, skin care, pharmaceuticals, and more recently, in aquaculture, alternative fuel sources, and carbon sequestration strategies (2-6). Seaweed is even being experimented with as an alternative to plastic packaging (7). Macroalgae have been overlooked by most of the world for far too long, but all of this is now changing, and rapidly. Although seaweed is not a new research topic, significant efforts and investments are being made to further explore its potential.

               Before all of this, though, seaweed has been a consistent source of food. The farming of macroalgae is thought to have originated in Japan between the 17th and 19th centuries (8); harnessing the value of seaweed mariculture with no need for using arable land, freshwater, or artificial nutrients, all while introducing a way to help absorb excess nutrients or carbon from the ocean.

Seaweed farming at Nusa Lembongan, Bali. ©  Jean-Marie Hullot

Seaweed farming at Nusa Lembongan, Bali. © Jean-Marie Hullot

               Macroalgae mariculture is a huge commercial operation in Southeast Asian countries like Japan, China, Korea, and the Philippines. The west is slowly catching on. In Hawaiʻi, seaweed has been utilized for hundreds of years. We have over 500 species of seaweeds here in the islands, and our edible macroalgae, or limu, are savored in local cuisine. As the most remote archipelago in the world, there is a lot of ocean to go around—and this ocean is deep. On the west side of the Big Island (Hawaiʻi Island), the water depth plummets to 6,000 ft. (1,829 m), a mere three miles (4.8 km) offshore. West Hawaiʻi’s Natural Energy Lab of Hawaiʻi Authority (NELHA) supplies a consistent source of seawater pumped from two locations: surface seawater (SSW) from 69 ft. (21 m) and deep sea water (DSW) from 2,211 ft. (674 m). With a broad selection of native algal species, access to NELHA’s DSW and SSW on tap, Hawaiʻi is an ideal location to research mariculture opportunities. Our Blue Fields Project is designed to do just that. Funded by the Department of Energy’s MARINER Program (Macroalgae Research Inspiring Novel Energy Resources), the Blue Fields project proposes to test a single-point mooring array for high-yield macroalgae culture (9).

               The two major challenges for offshore macroalgae culture in Hawaiʻi are species selection and offshore nutrient delivery. Very little research has been done into the culture of Hawaiʻi’s native species, and as a result there is limited knowledge of their growth requirements. There are demonstrable (and demonstrated) risks with introducing non-native algal species, which may compete with native ones (10). We will therefore only be using native species in our growth trials. Tropical surface waters are also nutrient poor, which explains their clear blue color.  However, Hawaiʻi’s bathymetry (the steep offshore slope of the islands) means that nutrient rich DSW is readily available, and we plan on testing this as a means to stimulate macroalgae growth.

               Before the Blue Fields offshore array becomes a reality, a series of land-based trials at our Kona research facility will establish which species may be best to grow, and what they need to thrive. In the coming months we will grow our limu with various mixes of deep seawater and surface seawater, and with different timed pulses of nutrients to determine the needs for scalable production. Our partners at Makai Ocean Engineering, are designing a wave-driven upwelling system to lift DSW nutrients to the offshore array. Once we have selected our target species, the team will finalize designs for a pilot-scale single-point mooring, long-line macroalgae array that harnesses wave, current and wind energy for nutrient delivery and harvesting. We also envisage testing a human-operated prototype algal harvester, with the long-term goal of it being a fully autonomous, reliable, high-yield cutting mechanism (think underwater ROV lawn mower). Through a competitive selection process, Blue Fields may eventually be deployed as a demonstration system offshore in West Hawaiʻi. The resulting biomass will be available for human consumption, as a source for feedstuffs for fish (see our nenue blog) or for cattle, and as material for testing as biofuels.

Seeded lines of  Ulva .

Seeded lines of Ulva.

We’re only just at the beginning. There’s a lot of work to be done and there is so much that’s still the subject of lively discussion. But that’s what research is about: asking, “What if?”. There is no single answer to all of our environmental challenges. However, seaweed offers a lot of potential to be a key player as we look for ways to feed humanity, mitigate ocean acidification and nutrient ‘dead zones’, and move towards alternative fuel sources.

Learn more about Research at Kampachi Farms







  1. Bengston, S., Sallstedt, S., Whitehouse, M. (2017) Three-dimensional preservation of cellular and subcellular structures suggests 1.6 billion-year-old crown-group red algae. PLoS Biol., 15(3): e2000735. Available at: http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2000735 [Accessed June 18].

  2. Shannon, E., Abu-Ghannam, N. (2016) Antibacterial derivatives of marine algae: an overview of pharmacological mechanisms and applications. Mar. Drugs., 14(81): doi: 10.3390/md14040081.Available at: https://arrow.dit.ie/cgi/viewcontent.cgi?article=1237&context=schfsehart [Accessed June 18].

  3. Mohamed, S., Hasim, S.N., Rahman, H.A. (2012) Seaweeds: a sustainable functional food for complementary and alternative therapy. Trends Food Sci. Technol. 23(2), pp. 83–96.

  4. The use of algae in fish feeds as alternatives to fishmeal (2013) The fish site [online] Available at: https://thefishsite.com/articles/the-use-of-algae-in-fish-feeds-as-alternatives-to-fishmeal [Accessed June 2018].

  5. Bach, Q., Sillero M. S., Tran, K., Skjermo, J. (2014) Fast hydrothermal liquefaction of a Norwegian macro-alga: screening tests. Algal Res. 6(Part B), pp. 271-276.

  6. How growing sea plants can help slow ocean acidification (2016) Yale Environment 360 [online] Available at: https://e360.yale.edu/features/kelp_seagrass_slow_ocean_acidification_netarts [Accessed June 2018].

  7. Eco-friendly packaging concept made from seaweed wins Lexus Design Award 2016 (2016) De Zeen [online] Available at: https://www.dezeen.com/2016/04/19/eco-friendly-packaging-concept-agar-plasticity-seaweed-wins-lexus-design-award-milan-deisgn-week/ [Accessed June 2018].

  8. Chopin, T., Sawhney, M. (2009) Seaweeds and their mariculture. Encyclopedia of Ocean Sciences (2nd Ed. ), pp. 317-326.

  9. Single point mooring array for macroalgae (2018) ARPA-E Department of Energy [online] Available at: https://arpa-e.energy.gov/?q=slick-sheet-project/single-point-mooring-array-macroalgae [Accessed June 2018].

  10. Huisman, J.M., Abbott, I.A., Smith, C.M. (2007) Hawaiian Reef Plants. University of Hawaiʻi Sea Grant College Program: Honolulu, HI.