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chin roe products, the Japanese government sup-ported basic and applied research on the feed-

ing habits, reproductive cycle, and environmen-tal requirements. Initial research led to additionaland ongoing studies of nutrition, environmen-tal control, culture systems, and control of thereproductive system (Imai 1978; Agatsuma1998).

Since 1970, approximately 55 prefecturalhatcheries have produced small sea urchins forcooperative units, which have collective rightsover local aquatic resources. The productionlaboratories are responsible for supplying sea

urchins to cooperative associations. The coop-erative associations manage the land-basednursery units and restocking programs in suit-able coastal habitats. The coastal areas are man-aged by predator removal, addition of algae,and sometimes habitat improvements, untilharvest, usually 2 to 5 years later. More recently,some cultured sea urchins are reared in cagesystems at high density and fed cultured sea-weed until they are large enough for market-ing (Mottet 1976, 1980; Doumenge 1990; T.

Horii, National Research Institute of FisheriesScience, Nagai, Japan, personal communica-tion). Large-scale aquaculture of sea urchinsto harvest size is not popular in Japan, and

most cultured sea urchins are released as ju-veniles (Table 2).

Japanese demand for sea urchin productsincreased dramatically during the 1980s anddomestic production was able to supply aboutone-half the consumer demand. This led torapid development and expansion of sea urchinfisheries in North and South America. Earlywarnings from fishermen and resource manag-ers warned of fishery declines. Aquaculture re-search was rapidly initiated in many countries.Sea urchin aquaculture in countries with fish-eries followed the same pattern as that seen in

Japan during the 1960s. Fishermen and scien-tists initially worked with sea urchins from thefishery populations and developed methodsand diets to enhance gonad production. Thesestudies included holding sea urchins in sus-pended cages or on the sea floor and transplant-ing urchins to habitats with more natural algalfood. Today, sea urchin aquaculture researchoften utilizes sea urchins collected from theocean in laboratory studies.

In Europe, there is also a long history of

sea urchins used as food. Sea urchins are eatenwhole and fresh in southern Europe, in contrastto the processed roe products popular in Japan.Sea urchins are sold through the fisheries sec-

Table 1.—Species, range, and countries where the species is cultured or where research projects are cur-rently in process.

Species Family Range Country

Anthocidaris crassipina Echinometridae mid-Honshu to Kyushu, South Japan Japan

Heterocentrotus pulcherrimus Strongylocentrotidae North Honshu to Kyushu, South Japan JapanPseudocentrotus depressus Toxopneustidae Tokoyo Bay to Kyushu, South Japan JapanStrongylocentrotus intermedius Strongylocentrotidae Tohoku to Hokkaido, North Japan,

Korea, China, Russia (Kamchatka) JapanS. nudus Strongylocentrotidae Sagami Bay to Hokkaido, North Japan,

Korea, China, Russia (Kamchatka) Japan Lytechinus variegatus Toxopneustidae Subtropical–Tropical Americas USA Loxechinus albus Echinidae South Peru, Chile ChileS. droebachiensis Strongylocentrotidae Circumpolar and south to Washington,

New Hampshire, and Norway USA, CanadaS. franciscanus Strongylocentrotidae Alaska to Baja California, East Pacific USA, CanadaS. purpuratus Strongylocentrotidae Alaska to Baja California, East Pacific USA Heliocidaris erythrogramma Echinometridae Australia Australia

Evechinus chloroticus Echinometridae New Zealand New ZealandTripneustes gratilla Toxopneustidae Indo-Pacific Japan, Taiwan,and Philippines

T. ventricosus Toxopneustidae Atlantic South America to Gulf of Mexico USAParacentrotus lividus Echinidae North Atlantic–Mediterranean France, Belgium,

Italy, Ireland,and Israel

Psammechinus miliaris Echinidae North Atlantic–Mediterranean (Norwayand Iceland to Morocco) Scotland

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tor network by auction. Cultured sea urchinscould be sold at a fixed price, which would re-quire management of harvesting, production,and shipping. Much of the European sea urchinsupply is not eaten locally and the diversity of regional preferences must be considered forindustry expansion (Birulés 1990).

South Americans, particularly in Chile,also enjoy fresh whole sea urchins. Chile cur-rently produces 50% of the world’s harvestedsea urchins with approximately 10% of the pro-duction consumed in Chile (Roa 2003). InNorth America, approximately 5–10% of pro-duction from California fisheries is sold do-mestically. These markets, though small, areexpanding. Most sea urchin roe, called uni in Japan, is sold at sushi bars as topping forcooked rice wrapped in seaweed. People seemto either love or hate the taste of uni, whichhas been described as “ocean bubble gum,” better than caviar, tastes like custard or a mildpate. It is not to everyone’s taste, but it is adelicacy and worth a try.

Countries now looking to sea urchin aquac-ulture for stock enhancement of depleted fish-eries include Canada, Chile, New Zealand, andthe United States. Sea urchin aquaculture inthese countries and others is repeating the pat-tern of the early Japanese research. Enhance-

ment of wild populations with supplementalfeeding, transplanting of sea urchins to favor-able habitat, and research scale hatcheries indi-cate aquaculture production of sea urchins is biologically possible, but the economics areunclear. Providing a consistent supply of a qual-ity product is essential for the sea urchin roemarket. The proper balance between identify-ing market potential, research priorities, and theeventual production of a consistent supply of asuperior product are among the criteria essen-tial for successful aquaculture of sea urchins.Some of these criteria have been met for sea ur-chins, but many remain to be explored.

Taxonomy and Anatomy

Sea urchins are members of the Phylum Echi-nodermata. Sea urchins are entirely marine andfree-living. Most edible sea urchins are adaptedfor life on hard, benthic surfaces and generallylive in areas with algal food available. They tendto live in shallow waters, usually from mid tolow intertidal zones to depths of about 50 m.

Commercially important sea urchins arespherical but slightly flattened and with mov-able spines. Each spine fits neatly into a socket joint in the shell and can be used to move verti-cally and horizontally. Tubular feet or podia are

Table 2.—Production of sea urchin seed for release and aquaculture in Japan for fiscal year April 1999 toMarch 2000 (data from T. Horii, National Research Institute of Fisheries Science, Nagai, Japan,). The numberof product organizations that cultured or cooperative fishery associations that released each species andareas where species were released are also shown. The number of seeds produced is the total for the yearand the number released is the actual amount released during this fiscal year. (org. = organizations, n.a. =

not applicable)Seed Seed

produced releasedProduction size (mm) # of # of seed size (mm) # seed # of # of

Species type mean range org. produced mean range released org. areas

Tripneustes

gratilla release 11 1–25 3 136,000 14 3–50 99,000 3 20 aquaculture n.a.

Pseudocentrotus

depressus release 16 3–29 11 9,460,000 12 3–30 3,739,000 79 25 aquaculture 8 3–17 2 152,000 n.a.

Heterocentrotus

pulcherrimus release 9 3–15 3 590,000 11 3–27 489,000 10 47 aquaculture 10 8–12 1 10,000 n.a.

Strongylocentrotus

intermedius release 11 2–49 28 64,985,000 12 2–106 57,895,000 94 486 aquaculture 8 3–22 2 6,696,000 n.a.

S. nudus release 18 6–46 10 6,718,000 18 7–50 7,120,000 11 302 aquaculture 11 6–31 3 366,000 n.a.

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found in rows alternating with the spines andhave well-developed suckers for attachment.Podia are also sensitive to chemicals and touch,absorb oxygen, catch drifting algae for food, and

keep the body clean. The spines are controlled by muscles and are used for protection, to cap-ture and hold food, and for locomotion. Healthysea urchins can right themselves using the spinesand podia. In between the spines and also at-tached to the calcified body wall or test, arepedicellaria, small, stalked, appendages used fordefense, capturing small prey or to clean the bodysurface.

The body is radically symmetrical. Exter-nally, sea urchins are extremely colorful due to

skin pigments and can be pale yellow, green,pink, purple, red, or black. Internally, the go-nads are also colorful due to carotenoid pig-ments and desirable gonad colors are yellowand orange. Undesirable gonad colors are white,tan, brown, black, or green.

The sea urchin body has an oral (bottom)and aboral (top) surface. The aboral surface con-tains the anal region where excretory productsand gametes are released and water vascularsystem is controlled (Figure 1).

The spherical body surface covered withmovable spines comprises 50% of the live seaurchin body weight. The oral surface includesthe mouth, which can be protruded, a peristomalmembrane allowing movement of the mouth,short spines, and podia. The mouth or “Aris-totle’s lantern,” named in honor of the Greeknaturalist and philosopher, is effective at tear-ing algae into manageable pieces. It is composedof five calcareous plates and teeth that are con-trolled by muscles. The mouth leads to the tu-

bular digestive system, which is intimately con-nected to the five gonads by mesenterial andhemal strands. Between the five gonads arestructures of the water vascular system. Whensea urchins are harvested, gonads must be 10–14% of the body weight for successful process-ing and marketing.

Reproduction in sea urchins is a complexprocess involving nutrient accumulation in thegonads, transfer of the accumulated nutrientsfrom nutritive cells to gametogenic cells, stor-

age of the gametes, and spawning either througha series of dribbling releases or a mass spawn-ing at one time (Pearse and Cameron 1991;Walker et al. 2001). Gonad production in edible

sea urchins progresses through reproductivestages that include gonads in the mature, spent,regenerating, growing, and premature condi-tion. Commercial harvest is optimal when thegonads are in the growing or premature stage.Gonads in this condition contain a majority of nongerminal, nutritive cells filled with glyco-gen, protein, and lipid. They are firm, have goodcolor and texture, and are large. Gonads are

equally large or larger during the mature phase, but moisture content is higher, the texture is verysoft, and the gonads tend to fall apart. Gonadsthat are spent or regenerating are too small, of-ten very dark, and are not marketable (Figure2a, 2b).

Aquaculture of sea urchins has developedpartly because the annual reproductive cyclelimits availability. The mature and growing sea-sons each last about 1 to 6 months, dependingon the species. Seawater temperature, food

availability, photoperiod, and sea urchin den-sity effect timing of the annual reproductivecycle. Gonad production in sea urchins is mea-sured by the gonad index. Throughout this pa-

Figure 1.—Internal and external anatomy of a seaurchin. Upper drawing shows external spine attach-ments, pedicellaria, and tube feet. The mouth andteeth (Aristotle’s lantern) and internal digestive sys-tem are shown in the lower drawing. The five go-nads of sea urchins can be seen in the upper draw-ing (from Mottet 1976).

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per, unless otherwise stated, gonad index isgiven as a percentage [(wet gonad weight/

whole animal live weight) × 100].Some innovative, intermediate forms of

aquaculture have been developed for sea urchinsto increase productivity of wild populations.

Intermediate Stages of

Aquaculture—TransplantingAdults and Collecting Juveniles

In Japan, reduction of fishery stocks resulted inactivities focused on maintaining sea urchinpopulations and increasing production frompopulations in less favorable areas. Transplantsof adult sea urchins were conducted under theassumption that some populations were lim-ited by the amount of food or habitat available.

Sea urchins from overgrazed areas devoid of algae were moved to areas with more food avail-able. These sea urchins were of poor qualitywith virtually no gonadal development and

could not be harvested as part of the commer-cial fishery. The transplanted sea urchins weremoved when the gonads were in the growingstage of their annual reproductive cycle. With

sufficient food, these urchins were harvested 3months later. In some cases, the transplanted seaurchins were fed fish or algae at the new site.The main species involved in transplants werePseudocentrotus depressus and Strongylocentrotus pulcherrimus in southern Japan and S. interme-dius and S. nudus in the north (Saito 1992a).Mortality was generally low, 1–2%, and as a re-sult many fishing areas depended heavily onthis method. Approximately 20 metric tons (mt)of sea urchins had been transplanted before 1969

(Takagi 1986). Transplanting of wild sea urchinsremains an important fishery management toolin Japan.

A field test to examine transplanting seaurchins was completed in California in 1997.Strongylocentrotus franciscanus measuring 25–70 mm in test diameter were transplanted froman area devoid of algae to dense kelp beds. Fish-ermen and scientists moved approximately34,000 urchins. The transplant site was 0.24 ha(0.6 acres) and had a standing population esti-

mated at 2,100. The area where the urchins werecollected was the same size and had about42,000 sea urchins. After 1 year at the new site,many sea urchins have grown to nearly 90 mm,the legal size for harvest. A conservative esti-mate of survival, not taking into considerationanimals that have moved from the study site, is60% of the original transplants. The transplantwas cost effective at US$3,500 or $0.10 per ur-chin and the high recapture rate was encourag-ing for the future of the California sea urchin

industry (Schroeter and Steele 1998).In Japan, the next intermediate phase was

collection of naturally set larvae. The first ex-perimental collection of larvae was completedin 1967 with P. depressus. Early larval collectorsused nylon threads for settlement. Other in-water and benthic larval collectors were devel-oped and included transparent polyvinyl chlo-ride (PVC) plates with a corrugated surface andenclosed gravel beds (Takagi 1986). After 8months, an average of 1,200 sea urchins mea-

suring 2 mm in test diameter was harvestedfrom the in-water collectors. The small urchinswere moved to suitable habitat or preparedgravel beds (Mottet 1980). Small urchins tended

Figure 2.—Adult red sea urchin Strongylocentrotus franciscanus with (a) low gonad index of 2% and (b)

with full gonads and a gonad index of 20%.

a

b

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to fall off the in-water collectors, and preda-tion was a problem in the benthic systems. Col-lection of natural seed in Hokkaido was notpursued due to fluctuation in the supply of

natural seed. Most cooperative associationscarried out some form of adult or juvenile trans-planting or collection between 1967 and 1984.Cultured sea urchin seed production began atthe national level in 1984.

In California, transplants of juvenile S. franciscanus with a mean size of 25 mm in testdiameter were completed between 1992 and 1998at four sites. Survival at two sites was greaterthan 50%, and at the other two sites, it was lessthan 10% after 1 year. Survival after 5 years was

between 6% and 11%. About half the survivorswere large enough for harvest. The work was notcontinued because there was no source of com-mercially available sea urchins for additionalstock enhancement (Dixon et al. 1998).

In Ireland, Paracentrotus lividus has beenfished for decades with minimal fishery man-agement. Transplanting of animals fromgrounds with poor growth rates to areas withmore food available is done with subcommer-cial size animals, 35–45 mm. In general, these

animals reach good market size and conditionafter 1 year. This type of work has been carriedout by fishermen with little data available, butanecdotal evidence shows small urchins (10mm) grow to 50+ mm in 2–2.5 years (Leighton1995). Natural seed collection trials based ontechniques used in Japan collected P. lividus andPsammechinus miliaris juveniles. The results wereencouraging but have not been continued(Moylan 1997).

The next phase of in-water sea urchin

aquaculture is feeding seaweed to animals en-closed in cages or on the sea floor. In Japan, theUnited States, Canada, Scotland, Ireland, andMexico, experimentation with this type of in-termediate culture has been completed but itis not used on a commercial basis. Enclosureson the sea floor near Southern California kelp beds were used to feed groups of S. purpuratusand S. franciscanus. Some groups were fed withkelp; Macrocystis pyrifera and others were unfed.Gonad production was significantly increased

in groups that received supplemental feeding(Leighton and Johnson 1992). This project wasexpensive and cumbersome. Gonad productioncan be enhanced quickly, but in California and

Mexico, ownership and environmental modifi-cations of the sea floor are not legal and associ-ated issues of multiple use of coastal areas havenot been addressed (Tegner 1989).

Development of

Sea Urchin Aquaculture

Sea urchin rearing developed in several loca-tions for a variety of reasons. In university labo-ratories, holding adult sea urchin broodstock,usually S. purpuratus, for embryology and toxi-cology research is widespread. The sea urchinembryo is important because of the ease of han-

dling and observing early development. Cul-turing a variety of sea urchin species for fisheryproduction enhancement has been practiced in Japan since 1968. More recently, aquaculture of sea urchins for food production is under intenseresearch in Canada, the United States, Mexico,Chile, Scotland, Belgium, France, Ireland, Nor-way, Israel, New Zealand, and Japan. Very re-cently, research projects have begun in Austra-lia, China, and the Philippines.

Japan

Extensive studies of naturally setting S. inter-medius larvae resulted in rearing the small ur-chins in land-based hatcheries until they werelarge enough for outplanting (Kawamura 1973).Aquaculture of sea urchins was first conducted

in the Yamaguchi Prefecture in 1968 with P.depressus and H. pulcherrimus and was soon fol-lowed by work with H. crassispina. During thesestudies, the phytoplankton Chaetocerous gracilis

was used successfully to feed the larvae. Thefirst cultured sea urchin seed of 10-mm test di-ameter were stocked in prepared gravel bedson the sea floor in 1974. Survival for the first yearwas between 65% and 75% (Takagi 1986).

In the early 1980s, projects were organizedat the Hokkaido Institute of Mariculture to de-velop techniques of mass seed production of S. intermedius under a 3-year plan. The national,prefectural, local governments and the localcooperative association contributed to the pro-

gram. Generally, the national governmentfunds about 50%, the prefectural governmentabout 25%, and the local government and co-operative association provide the remaining

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25%. There are regulations for administrationof the research station, hatchery, and nursery.Profits to the program come from sales of thesea urchin seed to fishermen and cooperative

associations that release them to fisherygrounds. Often the facility does not earn aprofit, but as long as the cooperative fisheryassociation earns a profit from fishery harvestor sales to fishermen, the government contin-ues to support the facility.

The Hokkaido Experimental Fish Stationand its associated sea urchin culture programhas been especially important since 1989 when Japanese fishery production dropped below20,000 mt. With foreign imports and low domes-

tic harvest, the national government policy con-tinues to support this program. Production of cultured sea urchin seed expanded rapidly. InHokkaido, 8 million S. intermedius and S. nudusseed were produced in 1986 and 30 million in1989. The 1989 sea urchin seed production was70% of the national total. The remainder of thesea urchin seed production was southern spe-cies (Saito 1992b). In 1989, there were 17 sea ur-chin hatcheries and 27 in 2000 with annual pro-duction of 100 million in the 10–20-mm size

range (Y. Agatsuma, Tohoku University, Aoba, Japan, personal communication)Some new sea urchin hatcheries were con-

structed, and some abalone hatcheries were con-verted to sea urchin culture. The objectives of the program were to collect wild broodstock,cultivate planktonic algae to feed the larvae, rearthe planktonic sea urchin larvae, and grow theurchins to a size suitable for release to appro-priate habitat.

The technique of mass seed production had

been developed at southern hatcheries prior tothe Hokkaido expansion. Broodstock are col-lected from the wild populations when they aremature. Broodstock management is not welldeveloped, but water temperature, food avail-ability, and photoperiod have been studied insouthern species. Reproductive developmentof Pseudocentrotus depressus and Hemicentrotus pul che rrimus (Yamamoto et al. 1988) and Anthocidaris crassispina (Sakairi et al. 1989) isdetermined by temperature, not photoperiod.

Spawn induction is done by removing themouthparts and inverting the sea urchins overa 300-mL beaker containing seawater filteredthrough 1-m mesh. The ova leave the urchin via

the gonoduct and gonopores and are collectedat the bottom of the beaker. Males are invertedover Petri dishes and the sperm is collected“dry” (that is without mixing in seawater). Fer-

tilization is done by mixing 1 mL of concentratedsperm with 50 mL of seawater and mixing thiswith the eggs from one female. After fertiliza-tion, the entire mixture is diluted to 5 L.

Fertilization is assessed every 30 min whenthe eggs are washed to remove excess sperm andprevent polyspermy. This continues for 2.5 h. Thefertilized eggs are then further diluted to 20 L,and the eggs are left undisturbed for 20 h or un-til the larvae hatch out. The hatched out larvaeor dipleurula do not increase in size until they

are able to feed, about 3 or 4 d later. The feedingpluteus shows complete gut development anda single pair of arms in early stages and four armsin later stages. The pluteus continues to add armsas the rudiment of the juvenile sea urchin devel-ops inside the larva. The echinoplutei is the fi-nal stage before settlement and metamorphosis.

Figure 3.—Larval stages of Strongylocentrotus purpuratus. (a) 3 d pluteus or nonfeeding larvae. (b)23 d echinopluetei larvae with rudiment of juvenilesea urchin visible.

a

b

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Larval development takes 3 to 4 weeks in thehatchery, depending on the seawater tempera-ture and species (Figure 3a, 3b).

Larvae are cultured in 600-L flow-through

tanks receiving 1-m filtered seawater and aregently aerated. The incoming water is introducedto larval rearing tanks from a header tank wheretemperature is maintained at 18°C. Five larvaltanks receive water from one header tank. Waterenters the larval tanks at the bottom and exitsthrough a centrally placed column with a meshof 50, 90, or 150 m, depending on the size andage of the larvae. Larval density is 1–2 larvae/mL. Batch culture of Chaetocerous gracilis are fedto the sea urchin larvae, providing 5,000 cells/

mL/d, initially, and 20,000 cells/mL when lar-vae reach the eight-arm + rudiment stage. Heteroshigma akashiwo are also fed to the larvae at500 cells/mL and 2,000 cells/mL at the begin-ning and end of larval rearing. Other algae thathave been tested, but are not widely used areDunaliella salina, Monochrysis lutheri, and Phaeocay-tylum tricornatum (Naidenko 1983). Water flow isalso increased during larval culture. Approxi-mately 60–68% survive the larval rearing process,and of these, 50% survive settlement and meta-

morphosis to become juveniles (Saito 1992b).Larvae are ready for settlement and meta-morphosis at the eight-arm echinoplutei stagewhen the rudiment is approximately 300–350m in diameter, depending on the species. An-other indicator of larval competence is the abil-ity to bend the arms, and podia may occasion-ally be seen protruding from the larvae. Settle-ment is induced using the single-celled Chlor-

ophyte Ulvella lens (Saito 1992b) or the diatomNavicula ramosissima (Ito et al. 1987) that have been

cultured on vinyl wavy plates. Ulvella lens is suc-cessfully mass cultured as food source for aba-lone, Haliotis spp., and sea urchins. It releasesspores that attach to surfaces on a permanent basis and serve as a food source. Ulvella lens re-duces the high costs of diatom culture for theearly nursery phase in sea urchin culture.

The plates with cultured U. lens or N.ramosissima are held in racks of 24 plates in 5-mrectangular tanks. The newly settled sea urchinsare held in these large tanks until they reach 5

mm in test diameter, approximately 3–4 monthslater. Sometimes soft algae such as Ulva lactucaare added to tanks where small urchins aresettled on the wavy plates (Figure 4a, 4b).

The next nursery phase is removal of thesmall urchins from the wavy plates and trans-ferring them to baskets (65 × 65 cm), which aresuspended in the 5-m tanks or in long-line sys-tems in the sea. The small sea urchins are thenfed kelp Laminaria japonica, the terrestrial knot-

weed Polygonum sachaliense, or a prepared dietuntil they reach 15–20 mm in test diameter about6 months later.

Sea urchin seed is released when they are15 mm or larger in test diameter and are ap-proximately 1 year old. If seed is held in land- based systems with heated water, 15 mm seedmay be released after 5 months of rearing. Theseeds are released by broadcasting them fromfishing vessels over suitable habitat. After 1 year,survival of the seed averages 40%. Predation is

usually minimal on seed 15 mm or larger aspredators are removed from the release sites(Miyamota et al. 1985). Cultured seed of S. in-termedius reached 40 mm and had a 37.8% sur-

Figure 4.—(a) JuvenileStrongylocentrotus intermedius

rearing tanks at the Shikabe hatchery in Japan,showing the wavy plate inserts. (b) close-up of young sea urchins on the wavy plates.

a

b

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vival (Omi 1987) compared to wild S. interme-dius, which took a minimum of 5 years to reach60 mm (Fuji 1967). Cultured seed of S. interme-dius grew faster than natural populations for the

first 14 months and then growth rate decreasedand was lower than native stock after 3 years(Agatsuma and Momma 1988). In recent years,sea urchin seeds have been produced for releaseto coastal areas with and without existing popu-lations and for culture to adult or market size.

In addition to research directly applicableto sea urchin culture, a wealth of research hasexamined aspects of sea urchin biology and ecol-ogy that are often used by current aquacultureresearchers. Key papers examine reproductive

cycles, energetics of growth and ecological rela-tionships (Fuji 1967), and population modeling,habitat requirements, and energy needs of seaurchin populations (Fuji and Kawamura 1970a,1970b). It is important to note that despite thishuge effort, Japanese fishery harvest has contin-ued to decline. Annual harvest for the last 10 yearshas been between 10 and 15 mt. The cause of thedecline is unknown, but reduced food availabil-ity, decreases in juvenile recruitment, and fish-ing pressure must play a role.

Europe

Europe is a valuable market for aquacultureproducts and sea urchins have been harvestedfor thousands of years from many nearshoreareas. Currently, no commercial aquacultureproduction of sea urchins occurs in Europe, butsea urchin research is at an exciting stage. As-pects of the biology and culture parameters of Paracentrotus lividus are well documented and

Psammechinus miliaris is under investigation.

France

In France, natural sea urchin fisheries collapsedin the 1970s (Southward and Southward 1975)leading to development of a recirculating seaurchin culture system (Le Gall 1990; Blin 1997;Grosjean et al. 1998).

Larval diets and culture were studied indetail by Fenaux et al. (1985a, 1995b). A small

scale flow-through larval rearing system wasdeveloped using a haptophycean flagellate, Hymenomonas carterae, as food. This successfulmethod is modeled after the Japanese larval

rearing system. Understanding larval develop-ment and response to food quantity and qual-ity contributed significantly to development of sea urchin culture systems in France (Fenaux et

al. 1988, 1994; Strathmann et al. 1992). Later work by Fenaux et al. (1994) showed P. lividus reaches16 mm after 1 year of culture on optimal dietscompared to 12.3 mm reported by Le Gall andBucaille (1989) in heated seawater. Both of thesegrowth rates compare well with fishery calcu-lations (Turon et al. 1995).

The recirculation system developed by LeGall and Bucaille (1989) has been used and re-fined to culture Paracentrotus lividus from fer-tilization to harvest. The system utilizes one

area for spawning, larval and algal cultures, anda separate rearing system for P. lividus fromsettlement and metamorphosis to adult market-size animals. Spawning is induced with potas-sium chloride (KCl); fertilization is checked af-ter 4 h at 20°C. Fertilized eggs are placed in 200-L tanks at a low density (250 larvae/L) for theduration of larval culture. Larvae are fedPhaeodactylum tricornatum once a day with 600mL of a 10 × 106 cells/mL concentration. Thelarval culture system is maintained on a 12/12

photoperiod with gentle mixing from aeration.When 80% of the larvae are ready to settle, theyare transferred to the pregrowth portion of therearing system. Transfers of larvae are doneusing 10-m screens to prevent larval arms fromentering the mesh and breaking.

The pregrowth area contains sieves with500-m screens. The early postmetamorphic stagelasts about 8 d when the young sea urchins donot feed. As the mouth and digestive system

reorganize, fresh Enteromorpha linza is fed to the

sea urchins. The sieves are cleaned weekly andthe animals are sorted and graded monthly.Animals larger than 5 mm are transferred to 1-mm sieves.

When P. lividus reach 10 mm in test diam-eter, they are cultured in baskets until they reachmarket size of 40 mm. Sea urchin growth in bas-kets submerged in shallow troughs takes ap-proximately 2.7–3.5 years. When the sea urchinsreach 40 mm, some are prepared for harvest bya 1- to 2-month period of starvation followed

by feeding of kelp, Laminaria digitata, or a pre-pared diet. The remaining adult P. lividus areconditioned for spawning. These individualsare held at 18–20°C and at either a 12/12 photo-

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period or in complete darkness. This systemprovides mature P. lividus year round. For com-plete description of this system, see Grosjeanet al. (1998) (Figure 5).

The success of this system is encouraging,and most likely, the research group will con-tinue to improve and refine it. This recirculat-ing system has also been tested in other areasof the world (Blin 1997; Fernadez 1998).

An important factor that may influencegrowth in the recirculating system is accumu-lation of ammonia, nitrate, or nitrite. Echinoidsexcrete urea. In an important study (Basuyauxand Mathieu 1999), the ammonia and nitratetolerance of P. lividus was measured in 20-L static

tanks with the test solutions changed daily.Weight gain was used to determine the effectsover 15 d. The safe ammonia level determinedfor P. lividus was 1 mg N-NH

3–4/L (or 0.045 mg

N-NH3/L) and a slight toxicity was found at 5

mg N-NH3–4/L (or 0.226 mg N-NH

3/L).

Behavior was used to test sublethal effectson four species of sea urchins to ammonia con-centrations between 12.5 and 100 mg NH

4Cl/

L (Lawrence et al. 2003). Tube feet were moresensitive than spines or the Aristotle’s lantern,

probably due to their higher permeability. Tube

feet functions include respiration, feeding, andlocomotion. A decrease in their activity wouldhave a deleterious effect on the capacity for go-nad production and may explain the reduced

growth in P. lividus found in Basuyaux andMathieu (1999).

Scotland

In Scotland, where no fisheries exist, Psam-menchinus miliaris has been identified as an ed-ible sea urchin with good potential for aquac-

ulture. Mass rearing of P. miliaris was success-ful using culture methods developed forParacentrotus lividus (Kelly et al. 2000). Larval

growth and survival was optimal usingDuniella tertiolecta and low larval-rearing den-sities of 1 larvae/mL.

Small (1-mm test diameter), culturedPsammenchinus miliaris grew equally well whenfed a prepared salmon diet or Ulva lactuca. Thesmall urchins grew to 8 mm in test diameter in6 months. Mortalities were 18.7% in the U.lactuca and 37.4% in the prepared diet treatment.Morphologically, P. miliaris fed U. lactuca hadlonger spines and a more flattened test com-

pared to those fed the prepared diet (Cook etal. 1998). High stocking density (four individu-als/L) compared to lower stocking density (twoindividuals/L) were significantly smaller after6 months. Mean initial size was 9-mm test di-ameter and final size was 14 and 15 mm for highand low stocking densities, respectively (Kelly2002). These studies of juvenile P. miliaris sug-gest more research is needed for diets that en-hance somatic growth of juvenile sea urchins.

Ireland

Culture research in Ireland since the decline of the fishery (Byrne 1990) has focused on larvaland early juvenile growth. The violet sea ur-

chin Paracentrotus lividus is spawned by peri-stomal injection of 0.5 M KCl. Flow-through andstatic culture systems were compared with sig-nificantly greater larval survival in the static (80–90%) compared to the flow-through (1%) sys-tems. Experiments testing various algae re-

sulted in a larval culture system using 500-L batch cultures that were fed a haptophyceanflagellate, Hymenomonas elongata. Larvae arestocked at 1 larvae/mL, and each tank is lightly

Figure 5. —European sea urchin culture system from

Grosjean et al. (1998). This completely enclosed andrecirculating system has been successful used to cul-ture several generations of the European sea urchinParacentrotus lividus.

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aerated with one air stone near the bottom of the tank. Temperature is maintained between21°C and 24°C. Seawater introduced to the lar-val rearing tanks is filtered to 10 m. Larval sea

urchins are fed H. elongata in excess daily orevery other day. Microalgae is fed at 5,000 cells/larvae during the four-arm stage, 8,000 cells/larvae for the six-arm stage, and 12,000 cells/larvae for the eight-arm stage. Larvae are re-moved from the culture tanks every 2 or 3 d,collected on 10-m sieves, and placed in a cleantank. Larvae are generally ready to settle in 14–16 d (Leighton 1995).

Norway

University research has focused on spawning,larval rearing, and gonad enhancement. Local broodstock of the green sea urchin S. droeb-achiensis are spawned and reared at 10°C. Lar-vae are fed supplemented Dunaliella tertiolectaand reared in a modified, flow-through systemfollowing the Japanese method. All work is cur-rently experimental (N. Hagen, Bodø Univer-sity, Bodø, Norway, personal communication)

Israel

Paracentrotus lividus has been culture for 4 yearsat the National Center for Mariculture in Eilat,Israel (M. Shipgel, National Center for Maricul-ture, Eilat, Israel, personal observation) Spawn-ing and larval rearing are done according toLeighton (1995) in winter months when ambi-ent seawater temperatures are 20–21°C. Settle-ment of competent larvae is done when the ru-diment is greater than 320 m in diameter and

the larvae are between 14 and 17 d old. Larvaeare settled on cultured benthic diatoms Naviculaspp. in 100-L tanks of 1 m diameter. A few daysafter settlement, cultured red alga Gracilariaconferta is added to the tanks. Young P. lividusquickly move onto the algae. About 1 weeklater, small amounts of cultured U. lactuca areadded also. Growth to 30-mm test diametertakes about 2 years.

Canada

Currently, there is one research laboratory at St.Andrews Biological Station, New Brunswick,working with larvae and one private sea urchin

hatchery in Canada Island—Scallops, Ltd., lo-cated in Parksville, British Columbia. The com-pany is entering commercial production. IslandScallops produced 750,000 small (5 mm) green

sea urchins S. droebachiensis in 2000 for aquac-ulture production and fishery enhancement anda smaller number of red sea urchins S. francis-canus. Expected production in 2001 is 3 millionS. droebachiensis and 750,000 S. franciscanus. Is-land Scallops is also working with S. droebach-iensis collected from wild population and con-ducting gonad enhancement studies (see Nutri-tion section).

At Island Scallops, larvae are reared in astatic system at four larvae/mL, with single

bubble aeration to maintain larval distributionin the water column. The size of the rudimentis used to determine the time of metamorpho-sis. Larvae are settled on polycarbonate platesheld in racks. Jaw formation occurs in about 4d. Ambient seawater is used during culture andranges between 9°C and 14°C. Large diameterpipe is cut longitudinally and used as a nurs-ery system (Y. Alabi, Island Scallops, Ltd.,Qualicum, Canada, personal communication).

The university research group, lead by Dr.

Shawn Robinson, is rearing S. droebachienis forlaboratory research and offshore field trials incommercial grow-out facilities. The researchgroup has already completed preliminary go-nad maturation studies and juvenile rearingmethods (Morgan 2000; S. Robinson, Depart-ment of Fisheries and Oceans, St. Andrews,Canada, personal communication).

De Jong-Westman et al. (1995a) examinedthe effects of adult diet on egg size and number, larval development, survival, and metamor-

phic success for S. droebachiensis. Adults wereconditioned for 9 months with eight experimen-tal diets: 1) Low protein: (LoPro < 10% protein);2) High protein: (Hi Pro > 20%); 3) LoPro + M(with mannitol 9.7%); 4) LoPro + A (with 9.75%algin); 5) Hi Pro +C (with 0.5% cholesterol); 6)Hi Pro + b (with 0.006% b -carotene); 7) HiPro C+ b (with 0.5% cholesterol and 0.006% b -caro-tene); and 8) Air dried kelp: Nereocystis luetkeana.

Spawn induction during the natural spawn-ing season (March) was conducted using 0.1

M acetylcholine through the peristomal mem- brane. Diet had no effect on egg size or fertili-zation rate. Egg energy content was lowest onLoPro and highest on HiPro with no difference

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in the other diets. Larval culture was completedfor diets 1, 2, 6, 7, and 8. Fertilization did notdiffer among the five diet treatments. Larvaldevelopment had no pattern, but larvae fed diet

7 formed the eight-arm stage 3 d earlier thanother treatments. Larvae from parents fed diet8 were abnormal, and developmental stagescould not be determined. Larval survival at thesix-arm stage was 92–95% on diets 1, 2, 6, and 7.Diet 8 had high mortality with 15% survival onday 20. Only larvae from diet 6 consistentlyshowed faster larval development from embry-onic stages. Larvae from diets 6 and 7 were also13–18% larger than those reared by McEdward(1986) from broodstock fed algae. Overall, this

study showed the diet of the adult may influ-ence the larvae and that larva like adults re-spond to their environment by changes in shape.

Other larval research in Canada has shownS. droebachiensis growth is most rapid at 14°C(Hart and Sheibling 1988); growth can be accu-rately compared measuring the oral arms(McEdward 1984); settlement with developedmicrobial films induced more settlement thanplates without films (Pearce et al. 1990).

Chile

Chile has a highly regulated aquaculture indus-try with over 13 species of fishes, algae, and in-vertebrates commercially cultured. The com-mercially important sea urchin Loxechinus albusis cultured on a research and development scaleat government (Instituto Fomento Pesquero atHuehue and Putemún) and university researchfacilities (Universidad Catolico del Norte,Universidad de Conceptión, Universidad

Andres Bello) and several private hatcheries(Fundacion Chile, Palo Colorado CultivosCosteras, and others) (Norambuena and Lemb-eye 2003). Of these facilities, government andprivate operations produce about 3 millionseed per year but have an estimated total seedproduction capacity of 18 million seed (Letelier2003) (Figure 6).

Loxechinus albus is successfully culturedusing established methods. Adults are inducedto spawn with 0.5 M KCl and reared in a labo-

ratory system to the eight-arm echinopluteistage. Metamorphosis was induced with bacte-rial films. Larvae are fed Dunaliella tertiolecta,Chateoceros gracilis, Isochrysis galbana, or a mixed

diet of both algal species in flow-through sys-tems. Seawater is filtered to 1 m and flow ratesare low; about one-third to two-thirds of thewater is exchanged in 24 h. Larvae fed the mixeddiet completed metamorphosis after 33 d at 10–12°C and after 20 d at 18–20°C. Larvae were

settled with benthic diatoms, Navicula spp.,Nitzchia spp., and Cocconeis spp., in 2-L, clear

plastic containers. Young L. albus reach 500–7,200 µ after 76 d (Gonzales et al. 1987; Bustosand Olave 2001).

Mass culture of newly settled L. albus is con-ducted in large rectangular tanks (5.2 × 1.3 ×0.65 m, 4,400 L) with fiberglass plates inoculatedwith pinnate diatoms. When sea urchins reach5 mm in test diameter, some are moved to sus-pended long-line and cage systems. Loxechinusalbus reaches commercial size, 50–55 mm, inabout 30 months. Chile has a patented prepared

diet used to feed L. albus during the long grow-out period (Bustos and Olave 2001).

Mexico

In 1994, the Universidad Autónoma de BajaCalifornia began research and production of juvenile S. franciscanus and S. purpuratus on anexperimental scale. The program started in re-sponse to declining fishery harvests. Approxi-mately 15,000 juveniles are produced each year.

The juvenile sea urchins are used for labora-tory research, cage culture grow-out research,and have been seeded to artificial reefs. Thewhite sea urchin Lytechinus pictus is cultured for

Figure 6. —Juvenile Loxenchinus albus at the Instituto

de Fomento Pesquero hatchery in Huehue, Chile.

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research on G-proteins and signal transduc-tion mechanisms between the sperm and egg(E. Carpizo, University of Hawaii, Honolulu,personal communication).

United States

Some important laboratory studies were com-pleted in relation to embryological studies of sea urchins in universities. Hinegardner (1969),who studied several species from the east andWest Coast of North America, comprehensivelydescribed sea urchin larval rearing and meta-morphosis (Figure 4). Cameron and Hine-gardner (1971) identified key factors that induce

sea urchin larval settlement.In California, the sea urchin fishery fundedaquaculture research for S. franciscanus at theUniversity of California Davis Bodega MarineLaboratory. The sea urchins produced from thesystem were used in stock enhancement experi-ments. Wild, adult broodstock were induced tospawn with 0.5 M KCl. Eggs were collected infiltered seawater and sperm was collected inchilled bowls without seawater. Eggs were fer-tilized using 1,000 sperm/egg. Fertilized eggs

were placed in 1,500 mL of 5-m filtered seawa-ter. Larvae were cultured at high densities, 5–7/mL, in a static system using 1,500-mL glasscontainers with stir paddles moving at 25–30rpm (revolutions per minute). Larvae were feda single-celled algae Rhodomonas lens at 60–10,000 cells/mL. Algae were cultured in heatsterilized (70°C) seawater and Prvaosoli-Guillard culture medium (Guillard 1975). Trans-ferred cultures took about 5 d to bloom to highenough densities for feeding (>500,000 cells/

mL) under grow lights at 22°C. Cultures werereared in 17-, 23-, and 100-L containers. Culturesattained peak densities of 1.25 million cells/mLaround day 10 and exhibited a dark red color.They were used until densities declined,around day 13.

Larval urchin survival was variable amongspawn cohorts and within each spawn. Bacte-rial contamination was initially a problem butwas controlled by rinsing larvae onto 10-mscreens and cleaning the jars daily with fresh-

water. Over time, larval survival averaged 61–66% at day 16 postfertilization and 32% on day22, 1 d prior to settlement.

Settlement of larvae varied and occurred

over 2 to 3 weeks with high rates of metamor-phosis, 60–90%. Newly settled S. franciscanuswere 0.40 mm ± 0.038 (mean ± SD) in test diam-eter. At settlement, juveniles lacked functional

jaws. When the jaws emerged, diatoms, red turf algae, and kelp Macrocystis pyrifera were placedin the settlement tanks. At 6 months of age, the juveniles averaged 10.0 ± 2.6 mm, at 9 months16.4 ± 5.4 mm. One year later, approximately1.7% survived from fertilized embryos. Survivalestimates, calculated from the end of the larvalrearing period (with 32% surviving) was 5.3%.The laboratory-cultured sea urchins were usedfor fishery enhancement experiments (Rogers-Bennett et al. 1994).

In New Hampshire and Maine, cultivationand growth studies with S. droebachiensis have been conducted for several years (Harris et al.2003). Sea urchins are produced for laboratoryresearch, stock enhancement, and sea ranching.Adult sea urchins are spawned with standardspawning and fertilization techniques (Hine-gardner 1969; Strathman 1987). Laboratory re-

search with S. droebachiensis testing several al-gal diets during larval rearing found Nano-chloropsis superior to Dunaliella tertiolecta and

Isochrysis galbana. Survival and settlement werelow compared to other studies, but the re-searchers plan to expand the culture research(Lake et al. 1998). Juveniles are settled in fiberglass tanks with microalgal films and grownto approximately 15 mm in test diameter. Nu-merous experiments indicate outplanting inwinter months is most successful as naturalpredators are less active (Harris and Chester1996).

Water flow in rearing containers is also im-

portant for sea urchin gonad growth. Feed in-gestion did not vary when S. droebachiensis wereheld in 350 mL/min compared to 219 mL/min, but somatic and gonad growth was greater inthe lower flow rate (Tollini et al. 1997).

Adult Lytechinus variegatus were fed a pre-pared diet for 10 months (George et al. 2000).Following spawn induction, egg size, and timeto metamorphosis showed the prepared dietsupported development similar to those fromfield populations.

Large-scale culture work with sea urchinsis in the initial stages in several universities inCanada, the United States, New Zealand, Nor-way, and Scotland. Undoubtedly, new culture

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systems will emerge as additional sea urchinspecies are cultured.

Nutrition

Studies of sea urchin nutrition using naturaland prepared diets and examination of the as-sociated somatic or gonadal growth have beenactive areas of research for the past century.Much of the earlier research resulted from in-terest in these extraordinary animals, and,more recently, nutritional research has over-lapped with fishery depletions and the mar-ket demand for sea urchin products. Somaticgrowth and annual gonadal growth patternscomplicate sea urchin nutrition. Somaticgrowth is slow after metamorphosis to about5 mm, rapid juvenile growth to about 15–30mm, and then slow growth in the adult stage.The annual reproductive cycle results in sea-sonal gonadal growth. These patterns suggestsea urchins may have different nutritional re-quirements during their life history as well asseasonal differences.

The normal food of edible sea urchins isalgae, but numerous studies have shown thatthey may also act as carnivores or scavengers.Sea urchins apparently feed continuously if food is available. Digestibility is generallyhigh (>80%) for organic matter, protein, energy,and soluble carbohydrates, but may be low forlipid and insoluble carbohydrates (about 50%)(Klinger et al. 1998; Lares 1999). Digestive pro-cesses include enzymes and gut bacterial com-munities that break down dietary components.Many questions remain regarding the transferof nutrients from the digestive system to thehemal system and gonads. The sea urchin di-gestive system and gonads respond to foodavailability by increasing or decreasing in size.Sea urchins may utilize nutrient reserves in any body tissue during starvation or may showrapid growth with high quality food available.There is no discrete nutrient storage site orsites of nutrient reserves in the digestive sys-tem, and the conspicuous gonads are believedto partly serve this function.

Excellent reviews of sea urchin nutritionfor wild populations can be found in Ander-son (1966), Lawrence (1975), and Lawrence andLane (1982). In this section, a review of juve-

nile and adult sea urchin nutrition studies us-ing both wild and cultured animals is pre-sented.

Gonad Growth andEnhancement Studies

Algal Diets

The scientific literature on ecological relation-ships between sea urchins and algae in the natu-ral environment is enormous. Here, I will re-view only those studies with objectives relevantto aquaculture.

The European edible sea urchin Para-centrotus lividus was fed 12 macroalgae ad libi-tum for a 6-month period to examine gonadalgrowth. Findings related food ingestion to go-

nadal growth where P. lividus, which digestedmore than 3 g of organic matter per day, showedgonadal growth. Above this food intake rate, thespecies of macroalgae did not have a signifi-cant effect on gonadal growth. Absorption rateswere strongly correlated with food preferences.The algae species included three red, six brown,and three green algae, all of which were domi-nant in the natural habitat of the P. lividus col-lected. The highest gonadal growth was found

on the Rhodophyte species Rissoella verruculosaand the lowest on the red algae Asparagopsisarmata and the brown algae Dilophus spiralis. Dif-ferences in ingestion rates were attributed toattraction factors and chemical defenses of thealgal species tested (Frantzis and Grémare 1992).

Two interesting studies have examined thefeasibility of out-of-season gonad enhancementof S. droebachiensis. One study was conductedin the laboratory and compared to naturalpopulations (Hagen 1998), and the second studywas conducted in cages held near the shore(Vadas et al. 2000). Both studies collected S.droebachiensis from barren ground habitat de-void of macroalgal species during the post-spawn or summer season. In the laboratory

study (Hagen 1998), S. droebachiensis were fedLaminaria hyperborea, L. digitata, L. saccharina, and Alaria esculenta and attained maximal gonad size before field populations. This study also exam-ined optimal size for gonad enhancement andfound S. droebachiensis of 50–60 mm in test di-ameter would provide aquaculturists with

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where they have access to uneaten salmon pel-lets (Kelly et al. 1998).

The Japanese red sea urchin Pseudocentrotusdepressus from two cultured populations were

fed the brown algae Eisenia bicyclis for 1 year.Field samples were compared to the laboratoryanimals, in which monthly subsamples mea-sured somatic growth, gonad index, and histo-logical analysis (Unuma et al. 1996). Laboratorypopulations maintained a higher gonad indexover the year with significantly less decreasefollowing spawning than field populations (5%vs. 2%). The laboratory group did not increasein gonad index as rapidly as the field popula-tion; however, gametogenesis was delayed

about 2 months and was sustained longer. Theauthors suggest environmental factors in thelaboratory study are probably responsible forthe differences between the two populations.From an aquaculture perspective, the sustainedmature condition of the gonads should beavoided. Shortening the mature period by con-trolling the environment or changes in the feedmay provide methods to maintain the imma-ture gonadal condition (Unuma et al. 1996).

Overall, algal diets successfully enhance sea

urchin gonadal growth. The main concerns arethe costs of natural algae, availability of algae,and possible negative impacts to the naturalenvironment. Comparison of algal and pre-pared diets was a natural follow up to testingalgal diets, and several studies have done this.

Comparison of Algal and Prepared Diets

Several published studies have compared go-nadal growth for sea urchins fed natural algal

diets and prepared diets. Seven prepared dietsand air-dried Nereocystis luetkeana were fed toadult S. droebachiensis (50–70 mm) collected froma population near Vancouver Island. The com-position of the diets is the same as those shownin the “Development of Aquaculture” (de Jong-Westman et al. 1995a) section. The experimentwas conducted from July 1991 to March 1992with subsamples taken from each treatmentevery 6 weeks. All of the HiPro diets and N.luetkeana had higher gonad indices than S.

droebachiensis fed the LoPro diets. It is impor-tant to note that gonad indices were calculatedas wet gonad mass/drained test mass × 100.Initial gonad indices were 15.9–17.8% and final

gonad indices were 32% and 39% for LoProand HiPro, respectively. There were no signifi-cant effects of diet on somatic growth, gonadlipid, or dry matter content.

Adult S. droebachiensis (40–60 mm) were col-lected by scuba diving and sorted into 15groups. Three agar-based diets were compared

to Laminaria longicruris in cages suspended froma long-line system. The sea urchins were fedapproximately 10 kg every 2 weeks over a 3-month period. Gonad production was greateston a prepared diet containing carrots, cabbage,soy meal, potato starch, seawater, and guar gumas a binder (Diet A). The other two diets con-tained the same ingredients with poultry meal

substituted for soy meal (Diet B) or raw potatoinstead of raw cabbage (Diet C). The initialsample and samples from the wild populationhad gonad indices of 4.3–4.9% at the beginningand end of the experiment. The prepared dietsshowed final gonad indices of 9.8% and 8.0%for prepared diets A and B and 7.5% for pre-pared diet C and L. longicruris. Similar to otherstudies, the prepared diets showed greater go-nad production than macroalgae but suggestthat refinement of prepared diets for improved

gonad production is essential for successful seaurchin aquaculture (Robinson and Colborne1997).

Between 1991 and 1994, several 4- to 5-weekstudies were completed with S. droebachiensisfed semimoist prepared diets or dried Laminarialongicrispus. Diets were formulated with algae,wheat gluten, starch, calcium phosphate, cal-cium carbonate, calcium sulfate, vitamins, cho-line chloride, and vitamin C into rubbery, sink-ing pellets. Sea urchins were collected by divers

and experiments conducted in laboratory tanksat densities of 40–50 g/L of seawater. Condi-tioning in January was inconclusive with sea-water temperatures below 6°C. Gonad indices between 11% and 12% from initial values of 3.4–6.4% were found in May, July, August, and Oc-tober trials for prepared and algal diets. Thesestudies again showed it is possible to increasethe gonad index in a relatively brief period(Motnikar et al. 1997).

Cultured Loxechinus albus were maintained

in cages on a long-line system and in labora-tory aquaria. Four diets were tested: two ex-truded feeds, one with and one without kelp,and Macrocystis pyrifera and Ulva lactuca. The

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experiment was conducted for two 4-monthperiods, one during the summer (December toMarch) and one during the spring (August toNovember). Whole live weight was 72 g at the

start of both experiments. Gonad index was sig-nificantly greater for L. albus fed the prepareddiet in the spring for both culture systems com-pared to the algae diets (19% vs. 8%) and hadsignificantly increased from the initial sample.In the summer, gonad index results showed thesame pattern, but gonadal growth was greater.Sea urchins fed the prepared diet increased from5.5% to 20% compared to a gonad index of 11.7%found in the algal diet treatments (Lawrence etal. 1997). This study confirmed that for some

species, gonad production is greater with pre-pared diets than algal diets or fishery yields.Large S. franciscanus collected from a natu-

ral population off northern California had aninitial gonad index of 3.4% and weighed 248 g.Sea urchins were fed the prepared diet with kelp

(as for L. albus, Lawrence et al. 1997) or freshNereocystis luetkeana from June to November attwo seawater temperatures, 12.9°C and 16.1°C.Final gonad production was not significantlydifferent between treatments and was 19.2%

(McBride et al. 1997). For this species, it appearshigh gonad indices are possible from both al-gal and prepared diets.

A very comprehensive study with three sizesof Evechinus chloroticus examined four prepareddiets and a combination algal diet of Macrocystis pyrifera and Ulva lactuca. This study was con-ducted during three stages of the reproductiveseason, postspawning (February to May), go-nadal growth (June to September), and late ga-metogenesis (October to December). The three

size-classes were small (30–40 mm), medium(50–60 mm), and large (70–80 mm). All compari-sons included an initial and final sample fromthe natural population. Field samples from thesmall size-class did not develop gonads. Gonadindices from small and medium urchins weregenerally similar in the postspawning and lategametogenic stages, and the prepared diets sup-ported greater gonadal growth than algae. Be-tween June and September, there were no sig-nificant differences in gonad indices between the

prepared and algal diet for small and mediumE. chloroticus, but they were all greater than thefield samples. Large E. chloroticus gonad indiceswere greater in the prepared diets than algae but

not the field samples in the postspawn season.During gonad growth and late gametogenesis,large E. chloroticus gonad indices were larger forurchins fed the prepared diets compared to al-

gal diet treatments and the field samples (Barkeret al. 1998).In Scotland, polyculture of Psammechinus

miliaris and Atlantic salmon showed some inter-esting results. The sea urchins efficiently utilizeda prepared salmon diet rich in protein and lipidresulting in acceptable somatic and gonadalgrowth. In another study, gonadal production

was greatest for P. miliaris-fed salmon feed (20–57%) compared to natural algal diets (2–12%) overa 12-month period (Cook et al. 1998). The gonad

indices of monthly subsamples showed a largegonad mass with negligible decline after spawn-ing and an extended spawning period for urchinsfed the prepared diet treatment. The sea urchinsfed an algal diet, Laminaria saccharina, had aspawning period of 8 weeks with substantialdeclines in gonad mass, lipid, and protein con-tent. The elevated gonad production results sug-gest a more refined diet could result in success-ful aquaculture for this valuable species. Thepattern of extended spawn season and no large

changes in gonad index during the annual re-productive cycle is validated in studies withother prepared diets.

Prepared Diet Only

The suggestion to develop prepared diets forsea urchin nutrition research (Lawrence 1975)has been a stimulus for many studies. Agar- based research diets and extruded pellets have been developed and tested with many sea ur-

chin species. So far, most of these studies have been on nutrition using wild sea urchins, notcultured ones. This situation is changing rap-idly as many research laboratories are devel-oping mass culture techniques.

The first published study using a prepared

diet was Nagai and Kaneko (1975). Strong- ylocentrotus pulcherrimus was fed a prepared dietto examine feed ingestion and assimilation ef-ficiencies. The prepared diet contained 23.3%each of fish, soy, corn, yeast, and 0.1% vitamins

and was bound by cooking with agar. Mortali-ties were dissected and found to have a gonadindex of 20–25%.

Since Nagai and Kaneko’s study, sea urchin

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prepared diets have been used in Japan (Hagen1996). The preferred food for cultured sea ur-chins is kelp, but prepared pellets are usedwhen algae are not available.

Gonad production of small (5 g) and large(60 g) Paracentrotus lividus was examined usingagar-based diets that were similar except for theprotein source. One diet utilized fish and the

other soybean. Groups of each size-class of P.lividus were fed the diets either continuously orevery 3–4 d. Gonad index increased from 0.5%to 4.4% and was similar in both feed regimes

for small P. lividus. Gonad index for large P.lividus increased from 0.8% to 5.5% and was notsignificantly different between diets or feed

schedules. These results suggest the proteinavailable from both fish and soy is suitable forgonad enhancement (Lawrence et al. 1989).

In a large and complex study, small cul-tured and large wild P. lividus were fed threeprepared diets or an algal diet Cymodocea nodosain laboratory tanks with recirculating seawateror fresh incoming seawater. The diets containedfish, vegetable or mixed protein sources. Tem-perature was controlled at 18–20°C or main-tained at ambient seawater temperature. Tanks

were either in total darkness or natural photo-period. Mixed diets, fresh seawater, and natu-ral temperatures resulted in higher gonad indi-ces for all size-classes and ranged from 11% to15%. These values were higher than naturalpopulations or P. lividus fed C. nodosa. In the re-circulating system, final gonad indices were 5–7% in all treatments. Interactions between diet-recirculation versus continuous flow and sizeshows that a mid-size-class, 20–25 mm diam-

eter P. lividus had the highest gonad indices.

Gonad index results can be grouped into threecategories: 1. sea urchins fed C. nodosa, 2. alldiets and light conditions at the controlled tem-perature and 3. all diets and light treatmentswith flowing seawater. Groups 1 and 2 hadsimilar gonad indices and group 3 had thehigher value (Fernandez and Pergent 1998).

Three papers have tested extruded pelletdiets developed by Dr. John M. Lawrence (De-partment of Biology, University of SouthFlorida) and Dr. Addison L. Lawrence (Texas

A & M Shrimp Mariculture Project) and manu-factured by Wenger International, Inc. (KansasCity, Missouri). The pellets are approved bythe U.S. Food and Drug Administration and the

U.S. Department of Agriculture. In the follow-ing section, these diets are referred to as thepellet diet.

Adult S. droebachiensis (50.4 ± 3.9 mm, 47 ±

2 g) were fed the pellet diet during two sea-sons, prior to the annual spawning (8-week ex-periment) and after spawning (12 week). Twopellet diets were used: one with fish meal asthe protein source, and a second using soywere fed ad libitum. Sea urchins were collectedfrom natural populations and the experimentwas conducted in a recirculation system at 34parts per thousand, 6–8°C, and 12/12 photo-period. In the winter prespawn study, initialgonad index was 17.1% and increased slightly

to 19.7% in both diet treatments. In the sum-mer post-spawn study, initial gonad index was4.9% and increased to 20%, comparable tomaximum gonad production for this speciesfrom natural populations. Both feeds were suf-ficient to support gonad growth (Klinger et al.1998).

The same diet was tested with S. droebachiensiscollected by diving and placed in ambient photo-period or a photoperiod set four months aheadusing artificial lights. The experiment began in

March and the altered photoperiod treatment setfor July sunrise and sunset was a 4-month photo-period advance. A subsample from each tank wastaken monthly. All subsamples resulted in gonadindices around 20%, significantly higher thanthose taken from concurrent field samples. Resultsof the reproductive condition of these sea urchinswill be presented in the Reproduction section(Walker and Lesser 1998).

A ration study with a soy-based pellet was

tested with wild S. franciscanus. Adult S.

franciscanus, 91 mm, 295 g, were fed 1 g/d, 3g/d, or not fed. Initial gonad index was 3.3%and increased to 7.1% and 12% in the low andhigh rations, respectively. There was no changein the gonad index of unfed urchins. The ex-periment lasted 60 d. The results show S. franciscanus can also be fed pellet diets and thatgonadal production may be controlled by foodration (McBride et al. 1999).

In the recirculation system described byGrosjean et al. (1998), Paracentrotus lividus were

fed a pellet diet for 1 month (30 d). In each 48 hperiod, diets were fed ad libitum for 8, 16, 24,

32, 40, or 48 h. Paracentrotus lividus with foodavailable for 35 h or more had the highest go-

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nad production. These results suggest P. lividusdoes not feed continually to produce large go-nads and that the quantity of food can be esti-mated to prevent waste (Spirlet et al. 1998).

Agar-based diets have also been used to testeffects of protein on gonad enhancement. Dietswith 30%, 40%, or 50% protein were fed to smallS. franciscanus for 10 months. Initially, the seaurchins were immature and had very small go-nads. This range of diet protein content was rela-tively high and did not impact gonad produc-tion. Gonad index increased equally in all diettreatments to 16% (McBride et al. 1998). Gonadindex was not significantly different for S.droebachiensis-fed agar based diets with protein

concentration ranging from 19% to 29% (Pearceet al. 2002).Adult Lytechinus variegatus (37–64 mm, 30–

110 g) were fed one of two prepared diets for 10weeks. Diet 1 was a pellet diet from WengerInternational, Inc. Diet 2 was agar-based andsimilar to a catfish diet. Both diets resulted inequally large gonad production (Watts et al.1998).

As can be seen from studies with algal orprepared diets, sea urchin gonad enhancement

is quite readily achieved. Laboratory and in-water studies feeding sea urchins algal or pre-pared diets have shown an average increasegonad size of about 1% per week. The difficultpart is controlling the quality of the gonads.Often when sea urchins are fed in a controlledenvironment, the gonad becomes soft or an un-desirable color. Researchers are now examin-ing additional quality aspects that can be im-proved or manipulated by diet. Among the im-portant factors under consideration are color

and reproductive stage.

Gonad Color

Color is among the most important appearancefactors in sea urchin roe products and was rec-ognized as an early challenge to sea urchinaquaculture (Matsui 1968). Prepared diets tendto give a light tan or pale gonad color. This has been noted by nearly every study mentioned

above in the nutrition section. Algal diets tendto give excellent color unless the urchins arecollected from an extremely food limited envi-ronment where the gonads tend to be very dark,

almost black or brown. In some species, thisdark color persists after feeding for 2 to 3months. Research on pigments that influencegonad color has not been successful (Motnikar

et al. 1997), as the pigments tested have gener-ally had no influence on gonad color. An inno-vative method to investigate the efficiency of transfer of pigment from prepared diets to go-nads, used reflected light fiber optic spectro-photometer using CIE (Commission Inter-nationale de l’Eclairage) L * a * b * units of mea-surement (Robinson et al. 2002). This methodimproves on previous approaches of determin-ing gonad color by comparison with colorswatches. Distinct pigment sources can be quali-

tatively and definitively measured using theCIE system. Robinson et al. (2002) found a natu-ral source of b-carotene from dry Duneliella salinaproduced the most acceptable color in S.droebachiensis.

Feed Ingestion Rates

Reports of sea urchin feed ingestion rates aregiven in most of the studies presented in theNutrition section and are summarized in Table

3. Trends seen include the inverse relationshipof protein content and feed ingestion. A word of caution, most sea urchin studies cited here donot consider energy content of the diets. Sinceenergy is the first limiting factor in biologicalsystems, the feed ingestion rates presentedshould be considered with this in mind.

Control of Reproduction

Many elegant studies have described the an-nual reproductive cycle of a wide variety of edible and other species of sea urchins. In gen-eral, edible sea urchins reach sexual maturityat about 1–2 years of age and 25–30 mm in testdiameter or when they reach approximately30% of their adult size (Pearse and Cameron1991; Lawrence 1982; Walker et al. 2001). How-ever, sustainable sea urchin aquaculture re-quires maintenance of breeding populationsin addition to understanding the natural repro-

ductive cycle. The development of sea urchinaquaculture has been primarily focused ongonad production. Regulation of gonadalgrowth and gamete development has been

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198 MCBRIDE

T a b l e 3 . — D i e t c o m p o s i t i o n a n d f e e d i n g r a t

e s o f s e a u r c h i n s f e d n a t u r a l o r p r e p a r e d d i e t s ( p e l l e t = e x t r u d e d d

i e t , a g a r = a g a r - b a s e d r e s e a r c h d

i e t , n o d a t a =

n . d . , c a r b o

h y d r a t e = c a r b , a

d l i b i t u m = a d l i b . ) . A

l g a l d i e t s a r e g i v e n a s g e n u s a n d s p e c i e s . F o o d i n g e s t e d i s g i v e

n a s d r y f e e d i n g e s t e d / a n i m a l / d

. S i z e i s g i v e n

a s t e s t d i a m e t e r ( m m ) o r w h o l e a n i m a l w e

i g h t ( g ) .

D i e t c o m p o s i t i o n ( % d r y m a t t e r )

S p e c i e s

S i z e

p r o t e i n

c a r b .

l i p i d

a s h

F o o d t y p e

F o o d o f f e r e d

F o o d i n g e s t e d

S t u d y

E v e c h i n u s

c h l o r o t i c u s

3 0 – 4 0 m m

2 0

6 4

7

9

p e l l e t

a d l i b .

0 . 0

9 – 0 . 1

2

B a r k e r e t a l . 1 9

9 8

5 0 – 6 0 m m

0 . 0

9 – 0 . 4

7 0 – 8 0 m m

0 . 1

6 – 0 . 5

4

3 0 – 4 0 m m

5 – 1 0

2 5 – 5 4 1 – 4

2 0 – 4 0

M a c r o c y s t i s

p y r i f e r a

a d l i b .

0 . 1 – 0 . 1

4

5 0 – 6 0 m m

0 . 1 – 0 . 2

7 0 – 8 0 m m

0 . 1 – 0 . 2

4

3 0 – 4 0 m m

3 7

4 9

0 . 5

n . d .

a g a r

0 . 0

5 – 0 . 0

6

5 0 – 6 0 m m

0 . 0

4 – 0 . 1

2

7 0 – 8 0 m m

0 . 0

4 – 0 . 1

8

S t r o n g y l o c e n t r o t u s

p u l c h e r r i m u s

3 0 m m

3 6

3 6

5

n . d .

a g a r

a d l i b .

0 . 1

0

N a g a i a n d K a n e k o 1 9 7 5

P a r a c e n t r o t u s

l i v i d u s

4 . 4 g

3 7

4 9

0 . 5

n . d .

a g a r

a b l i b .

0 . 0

5

L a w r e n c e e t a l .

1 9 9 1

4 . 4 g

e v e r y 3 – 4 d

0 . 0

5

6 0 g

e v e r y 2 – 3 d

0 . 1

0

P . l i v i d u s

n . d .

1 2 . 4

4 1 . 7

n . d

2 1 . 3

R i s o e l l a

v e r r u c u l o s a

a d l i b i t u m

0 . 4

F r a n t i s a n d G r é

m a r e 1 9 9 2

L y t e c h i n u s

v a r i e g a t u s

n . d .

3 7

4 9

0 . 5

n . d .

a g a r

a d l i b . ,

1 6 ° C

0 . 0

5

K l i n g e r e t a l . 1

9 8 6

a g a r

a d l i b . ,

2 3 ° C

0 . 0

8

L . v a r i e g a t u s

5 1 m m ,

6 3 g

4 0 ( f i s h +

s o y ) 3 2

5 . 1

1 7

a g a r

a d l i b .

0 . 3

1


9 9 4

4 0 ( s o y )

3 2

5 . 1

1 7

a g a r

a d l i b .

0 . 3

4

L . v a r i e g a t u

s

3 7 – 6 4 m m

2 3

6 4

1

n . d .

p e l l e t

a d l i b .

0 . 4

4

W a t t s e t a l .

1 9 9

8

4 0

3 1

7

n . d .

a g a r

a d l i b .

0 . 4

7

S .

d r o e b a c

h i e n s i s

4 7 m m ,

5 0 g

2 3

6 4

2

9

p e l l e t w i t h

p r e s p a w n

0 . 1

8


9 9 7

k e l p m e a l

p o s t s p a w n

0 . 4

4

p e l l e t w i t h -

p r e s p a w n

0 . 1

4

o u t k e l p

p o s t s p a w n

0 . 6

3

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T r i p n u e s t e s

g r a t i l l a

1 6 m m ,

2 g

2 3 . 3

3 5 . 6

3 . 1

n . d .

U l v a

p e r t u s a

a d l i b .

0 . 0

6

F l o r e t o e t a l . 1

9 9 6

2 2 . 1

4 3 . 9

1 . 4

n . d .

G l o i o

p e l t i s f u r c a t a

a d l i b .

0 . 0

5

2 5 . 5

7 . 4

6 . 9

n . d .

U n d a r i a

p i n n a t i f i d a

a d l i b .

0 . 0

7

n . d .

n . d .

n . d .

n . d .

m i x e d a l g a e

a d l i b .

0 . 0

8

S . n u d u s

1 5 m m ,

2 g

n . d .

L a m i n a r i a

r e l i g i o s a

a d l i b .

0 . 5 – 1 . 0

A g a t s u m a e t a l .

1 9 9 3

2 5 m m ,

8 . 6 g

0 . 5 – 1 . 5

3 3 m m ,

1 9 . 7 g

0 . 6 – 1 . 8

4 0 m m ,

3 7 . 8 g

1 . 0 – 2 . 5

5 4 m m ,

7 6 . 8 g

1 . 0 – 4 . 0

S . f r a n c i s c a

n u s

9 0 m m ,

2 4 8 g

2 . 5 – 4 . 9

2 3 – 5 4 1 . 4 – 4 . 4

2 7 – 4 9

N e r e o c y s t i s

l u e t k e a n a

a d . l

i b . ,

1 2 ° C

2 . 7

5

M c B r i d e e t a l .

1 9 9 7

a d l i b . ,

1 6 ° C

4 . 0

2 3

1 4

0 . 0

5

2 . 5

p e l l e t

a d . l

i b . ,

1 2 ° C

0 . 9

9

a d l i b . ,

1 6 ° C

1 . 3

1

S . f r a n c i s c a

n u s

3 5 m m ,

2 0 g

3 0

4 2 . 2

7 . 0

8 . 4

a g a r

a d l i b .

1 . 4

2

M c B r i d e e t a l . 1 9 9 8

4 0

3 0 . 7

7 . 0

8 . 7

a g a r

a d l i b .

1 . 2

5

5 0

2 0 . 2

7 . 0

9 . 0

a g a r

a d l i b .

0 . 8

9

S .

f r a n c i s c a

n u s

9 1 m m ,

2 9 5 g

2 0

6 4

0 . 0

5

8 . 8

p e l l e t

1 g / d

0 . 5

5

M c B r i d e e t a l .

1 9 9 9

3 g / d

1 . 4

2

T a b l e 3 . — C o n t i n u e d .

D i e t c o m

p o s i t i o n ( % d r y m a t t e r )

S p e c i e s

S i z e

p r o t e i n

c a r b .

l i p i d

a s h

F o o d t y p e

F o o d o f f e r e d

F o o d i n g e s t e d

S t u d y

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200 MCBRIDE

studied for several sea urchin species. In stud-ies that have focused on reproduction, diet,temperature, and photoperiod have been in-vestigated.

The recirculating system developed andused in France has resulted in a successful breeding method (Grosjean et al. 1998). Brood-stock has also been maintained in laboratorypopulations by holding the animals in dark-ness with controlled temperature (Leahy et al.1978). Both of these systems feed the adult seaurchins ad libitum, either kelp or prepareddiet. Both algal diets and prepared diets have been shown to produce healthy viable larvae(de Jong-Westman et al. 1995a; George et al.

2000) when adults were held in ambient light.Size at sexual maturity is an importantcomponent of reproduction. Well-fed, labora-tory-reared sea urchins can have huge gonadsyear round and may also develop gonads at a

very small size. S. purpuratus were full of ga-metes by 6 months of age when they were only10 mm in test diameter (Pearse et al. 1986) com-pared to wild populations where gonads were

not found until S. purpuratus versus 25–40 mm(Gonor 1972).

The effect of diet on sea urchin reproduc-tion is mostly seen in the size of the gonads anddoes not effect gametogenesis. Sea urchins pro-duce large gonads when a preferred food isavailable, which results in high food ingestion.In wild and laboratory populations, high feed-ing rates often result in extended gametogen-esis and spawning activity. Reproductive de-velopment is often inversely related to somaticgrowth in wild populations (Fuji 1967; Gonor1972; Pearse et al. 1986) and in laboratory stud-

ies (Unuma et al. 1996; Cook et al. 1998; Klingeret al. 1998). In poor food conditions, naturalpopulations tend to allocate more resources toreproduction than somatic growth (Thompson1982). Laboratory ration studies with sea ur-chins have resulted in lower gonadal indices but similar reproductive development (McBrideet al. 1999). When starved, sea urchins can de-crease in overall size and in gonad size(Lawrence and Lane 1982; Levitan 1988).

Diet does not appear to influence gameto-

genesis except to possibly extend the maturestage. Gonadal changes during the reproduc-tive cycle result in reorganization of nutrientstores in the body wall and gonad. Nutrient

stores are generally depleted during gameto-genesis and after spawning (Giese 1966; Hol-land and Holland 1969; Fernandez 1998).

Seasonally, changes of seawater tempera-

ture are also often suggested to be responsiblefor annual reproductive cycles. However, thereis little relationship between temperature andspawning season

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