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Development of techniques for the cultivation of lessonia trabeculata.etc

Development of techniques for the cultivation of lessonia trabeculata.etc






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    Development of techniques for the cultivation of lessonia trabeculata.etc Development of techniques for the cultivation of lessonia trabeculata.etc Document Transcript

    • Development of techniques for the cultivationof Lessonia trabeculata Villouta et Santelices(Phaeophyceae: Laminariales) in ChileMario E Edding & Fadia B TalaDepartamento de Biolog|¤a Marina, Facultad de Ciencias del Mar, Universidad Cato¤ lica del Norte, Coquimbo, ChileCorrespondence: Mario E Edding, Departamento de Biolog|¤a Marina, Facultad de Ciencias del Mar, Universidad Cato¤ lica del Norte,Casilla117, Coquimbo, Chile. E-mail: medding@ucn.clAbstractLarge quantities of brown algae have traditionallybeen exported from Chile as a raw material, of whichLessonia spp. has amounted to over 130 000 tons an-nually since1995. To the export demand has recentlybeen added the new demand for high-qualityLessonia spp. as a foodstu¡ for the expanding abaloneculture industry in Chile. The present study is basedon e¡orts to produce signi¢cant quantities of Lessoniatrabeculata in long-line culture as food for tank-cultured Haliotis rufescens Swainson and Haliotisdiscus-hannae Ino, which accept it as an excellentsource of nutrition. Small sporophytes of L. trabecula-ta were propagated in the laboratory from reproduc-tive blades harvested by diving near Coquimbo(301S). The best culture substrate was polyvinylchloride (PVC) in small pieces, inserted into the nyloncord for ¢nal culturing. Enrichment of seawater withagricultural-grade fertilizer produced no di¡erencesin growth and development of the Lessonia comparedwith results obtained using Provasoli medium. Spor-ophytes 1^2 cm in length cultured on 12-mm cordwere transferred to outdoor tanks with circulatingsea water and strong aeration where they were out-grown to 15^20 cm length; at this size, they weretransferred to a 50-m long line in the ocean. In a1-year period, individual plants reached up to 1.7 kgin mass, with average values per cord of about 9 kg.Total production from the long line was about500 kg fresh weight of the alga. In comparative test-ing, H. discus hannae grew as well on the culturedalgae as on naturally occurring L. trabeculata.Keywords: abalone culture, algae culture, algalpropagation, Chile, Lessonia, long-line cultureIntroductionThe use of marine algae as food for humans and mar-ine organisms has an extensive history in Asia (Ohno& Critchley1993). Harvesting of such algae from nat-ural beds has been replaced by the arti¢cial culture ofnumerous marine algal species on di¡erent coastsaround the world (de Oliveira & Kautsky 1990; Ohno& Critchley1993). Some of the better knownalgal cul-tures include Laminaria in China (Tseng 1987) andJapan (Kawashima1984), Undaria inJapan and Korea(Ohno & Matsuoka 1993), Porphyra in Japan, Koreaand China (Oohusa 1993), Eucheuma in the Philip-pines (Trono 1993), Chondrus in Canada (Craigie &Shacklock 1989) and Gracilaria in Chile (Santelices &Ugarte1987). E¡orts to culture these algae are a con-sequence of an increase in commercial demands andconcern for maintaining the natural equilibriumwithin the ecosystem from which they are harves-ted. Culture of Laminariales in Chile is recentand has been developed in university researchwith experimental cultures of Lessonia trabeculata(Edding,Venegas, Orrego & Fonck1990).The feeding of cultured herbivores, such as lim-pets, sea urchins and abalone, requires di¡erenttypes of algae as food, depending on the growth stageof the grazer (Corazani & Illanes 1998; Serviere,Go¤ mez & Ponce 1998). As their feeding apparatusmatures, herbivores switch from the initial stages inwhich they graze on benthic microalgae to the stageswhenthey begintoaccept macroalgal thalli (Corazani& Illanes1998; Serviere et al.1998).In the feeding of commercially cultured organismssuch as abalone, signi¢cant amounts of algae arerequired, as they may consume between 10% and30% of their body weight in algae daily (CorazaniAquaculture Research, 2003, 34, 507^515r 2003 Blackwell Publishing Ltd 507
    • & Illanes 1998; Serviere et al. 1998). Parallel harvest-ing e¡orts are required to provide these amounts ofalgae for invertebrate cultures. Experimentation inChile has demonstrated that the alga L. trabeculata isone of the best sources of food for tank-cultured aba-lone, producing high growth rates (Owen, DiSalvo,Ebert & Fonck 1984; Maureira, Takeda & Martinez1993; Castillo 2000). Unsustainable harvest of algalresources leads to a decrease in their populations byoverexploitation, an example of which is the case ofGracilaria chilensis Bird, McLachlan & Oliveira inChile, which occurred during the 1970s (Santelices& Ugarte 1987). Flora and fauna co-occurring in themacroalgal communities may also be at risk fromextensive algal harvesting.In addition to protecting macroalgae as a renew-able resource, the culture of seaweeds would be astrategy for price stabilization at acceptable levels, asthe price of the algae harvested from natural beds bylocal divers is governed by prices in the world algi-nate market. In Chile, regulations are in place thatpermit associations of local ¢shermen to exploit,manage and culture marine resources within‘Artisa-nal Fishery Reserve Areas’ (ARPA) from the beach to5 miles o¡shore. Culture of algae could provide astable source of the product for invertebrate culturesystems with ¢xed demands, more stable employ-ment for local workers and a more reliable productin terms of quality and quantity. A stable source ofalgae would also allow for better management offeeding regimes for cultured organisms (Basuyaux &Mathieu1999) making growth more predictable.The present study evaluates the technical feasibil-ityof carrying out large-scale culture of L. trabeculataas a complementary step to abalone culture.Materials and methodsSporulation and seedingRelease of spores was carried out using the methoddescribed by Edding et al. (1990) for L. trabeculata,following the additional recommendations of Fonck,Venegas,Tala & Edding (1998) for this species. Repro-ductive fronds were collected from a populationlocated on the Tongoy Peninsula (301150S; 711300W)in north-central Chile. The collection dates of thealgal material are presented below, and collectionwas always carried out 1 day before initiation of cul-tures. In all case, the fronds were transported to thelaboratory in humid conditions in the dark, at atemperature similar to that of their habitat. Immedi-ately on arrival at the laboratory, the fronds wererinsed with fresh water and drained in the dark for6 h at1571 1C.The fronds (n 5 70^100) were then in-duced to sporulate in 3-L plastic trays containing1.5 Lof 0.45 mm for E90 min. About10 fronds were placedhorizontally in each tray with water just covering thereproductive tissue. Spore-containing water wasdecanted in the dark for 30 min at1571 1C; the lowerone-third of the liquid was discarded in order toreduce contamination of the cultures by diatoms.The spore-containing water was then ¢lteredthrough sterile gauze to remove contaminants andseeded over arti¢cial substrates described below toallow settlement of spores. Spore concentration wasdetermined using a haemocytometer.Inthe initial phase, settled spores were maintainedin a controlled environmental chamber at 1571 1Cwith a12 h:12 h light/dark photoperiod and light irra-diance of 90 mmol photons m^2s^1with constantaeration. Sea water for the cultures was enrichedusing 0.114 g L^1agriculture-grade fertilizer (potas-sium nitrate and diammonium phosphate) at a ratioof 23:1 (N:P) as in Provasoli medium (Starr & Zeikus1993); this water was replaced weekly. As these re-agents were not of analytical grade, their trace ele-ment content was unknown.Development of the microscopic phase of L. trabe-culata was observed in parallel with development onarti¢cial substrates by culturing in Petri dishes withspores from the same suspension used to seed thesubstrates for the mass culture. Observations weremade weekly of developing microscopic stages of thealga in both Petri dishes and scrapings from the arti-¢cial substrates using a stereoscopic microscope at200 Â magni¢cation.Substrate types and con¢gurationsThe ¢rst spore seedings were carried out ontwo typesof spore collector, the ¢rst including rectangularpolyvinyl chloride (PVC) tubing frames of 60 Â80cm, each of which was wrapped with 6-m lengths of12-mm-diameter nylon cord. A total of10 PVC collec-tors were prepared, each supporting10 nyloncords togive a total of 600 m of spore-seeded cords. The sec-ond type of collector was a galvanized wire frame60 Â70 cm (n 510) covered with plastic mesh with1-mm openings. Seeding was carried out on thesesubstrates placed horizontally in seeding tanks.Afteran initial seeding period of 24 h, the sea water waschanged, and culture was initiated in tanks with thecollectors in the vertical position.Lessonia trabeculata cultivation M E Edding & FB Tala Aquaculture Research, 2003, 34, 507^515508 r 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515
    • Another experiment was conducted to determinewhether spores were capable of settling on a solidsubstrate such as PVC. The experiment was carriedout on a small scale in six 5-L sea-water aquaria.Each aquarium received six 20-mm-diameter PVCtubes, each 20 cm in length.This seeding was carriedout in three aquaria containing the tubes in a hori-zontal position, whereas in another three aquaria,the tubes were exposed to seeding in the verticalposition. After sporulation, each aquarium received725 mL of spore suspensioncontaining 21000 sporesmL^1, and the aquarium was then ¢lled with ¢ltered,sterilized sea water as above. After a 24-h seedingperiod, water in the aquaria was changed, and alltubes were maintained in the vertical position forculture. Based on the success of this experiment (seeResults), subsequent spore settling was carried out in20-L aquaria with 90 PVC tubes (as above) placedhorizontally.Experiments with varying nutrientenrichmentAs the initial tests on culture of Lessonia producedslow development and growth of the sporophytes,an experiment was carried out to evaluate di¡erentnutrient regimes for the procedure in June 1998.Comparative testing of spore growth and develop-ment was carried out using the following nutrientconditions: sea water control (no enrichment); sea water enriched with 100% Provasoli medium(Starr & Zeikus1993); sea water enriched with 100% Provasoli mediumplus iodine; sea water enriched with agricultural fertilizer(0.114 g L^1).Sea water enriched with agriculturalfertilizer plus iodineThe source of iodine was KI at 0.4% (wt/vol) made upin Provasoli stock solution before its addition to thesea water. The agricultural-grade fertilizer waspotassium nitrate and diammonium phosphate, withan N:P ratio of 23:1.The experiment was carried out with spores re-leased using the same methodology as describedabove with seeding into Petri dishes. Variablesrecorded included percentage germination after7 days, sexual di¡erentiation of the gametophytesafter15 days and percentage fertilityof the female ga-metophytes on day 25 (Fonck et al.1998).The same experiment was carried out using juve-nile sporophytes (o2.5 mm frond length) producedin culture, using 30 individuals for each nutrientregime, maintained under the same culture condi-tions as the spores. Total lengths of plantlets weremeasured at the beginning of the experiment andafter 15 days in culture, using an ocular micrometerin a stereoscopic microscope. Daily growth wasexpressed as a percentage compared with the meaninitial size.Culture experiment in outdoor tanksOnce sporophyte plantlets were grown under con-trolled conditions and were visible to the naked eye(E3 months), nylon cords with juvenile sporophyteswere placed in 1000-L outdoor circulating sea-water(150 L h^1) tanks with constant aeration in prepara-tion for culture at sea. This treatment favoured thedevelopment of the algae, primarily in length of thefronds and attachment to the substrate.Time of culti-vation in these tanks varied with development ofthe plantlets, with the substrates removed to seaat irregular intervals according to their degree ofdevelopment.The rate of elongation of the tank-cultured plantswas measured using the method of Parker (1948) asmodi¢ed by Edding et al. (1990). The tanks wereenriched weekly with 0.114 g L^1agriculture-gradefertilizer (N:P 23:1) and shaded with sunscreennetting, which reduced light intensity by about 50%to prevent excessive development of epiphytes.Culture experiment at seaCulture at sea was carried out using a long-line sys-tem, based on the design described by Kawashima(1984) for Japanese Laminariales and later modi¢edfor L. trabeculata by Edding et al. (1990). A 50-m linewas used (20 mm diameter) with hanging seaweedcultivation ropes (12 mm diameter,6 m length) every1 m. The main line was held at 1-m depth, usingplastic buoys.During March 1998, 26 cords carrying a total of296 juvenile sporophytes of L. trabeculata (1278plants per cord) with frond lengths from 5 to150 mm were installed within the marine concessionmanaged by the UCN in Herradura Bay, Coquimbo(291590S). This ¢rst group of cords was not precul-tured in outdoor tanks. A second group of 30 cords,Aquaculture Research, 2003, 34, 507^515 Lessonia trabeculata cultivation M E Edding & FB Talar 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515 509
    • whichwas inoculated inJune1998 and had remainedin outdoor tanks during the summer of 1999, wasplaced at sea in three stages (March, April and July1999). A third group of 10 cords was maintainedwithin the outdoor tanks for comparison with algaeplaced at sea. Algae maintained at sea were routinelymeasured for elongation of fronds according to themethods described above. Cords and algae were peri-odically cleaned of fouling, and algal tissue denselycovered with epiphytes was removed.Experiment on the feeding of abalone withL. trabeculataJuveniles of the abalone Haliotis discus hannai werefed with laboratory-propagated L. trabeculata in orderto compare the nutritional value of the cultured al-gae with that of naturally harvested L. trabeculata.Test abalone were obtained from cultures at the UCNshell¢sh hatchery. Three feeding regimes were testedon groups of 80 juvenile abalone with two replicateseach, all maintained in separate 60-L sea-watertanks. All abalone were from the same productioncohort, with an average initial size of 9 mm maxi-mum shell length and 6 mm width, with a fresh,drained weight of 85 mg each. The feeding regimesincluded: (a) L. trabeculata harvested from naturalbeds (control); (b) the same species from long-lineculture; and (c) L. trabeculata cultured in outdoortanks and enriched with agricultural fertilizer. Feed-ing was carried out once a week, using a quantityequal to 50% of the body weight of the abalone testpopulation. The experiment had a duration of 2months, in which all abalone were measured andweighed at the beginning and end of the test period.Growth was expressed as the monthly percentage in-crement with respect to initial measurements foreach variable.ResultsSubstrate typesInitial settlement of sporophytes on the cord andplastic mesh substrates from the ¢rst culture carriedout in May 1997 were unfavourable, based on thehigh degree of detachment of the microscopic game-tophyte and sporophyte embryos. A high degree ofcontamination by microorganisms, mainly diatomsand Protozoa, was observed, which overgrewor evenconsumed the gametophytes.When PVC sections were used as a substrate inMarch1998, their surfaces appeared brown in colour1month after inoculation, indicating the presence ofthe microscopic phases of settled L. trabeculata. After1.5 months, the ¢rst microscopic sporophytes couldbe detected. After 3.5 months a sample of 150 sporo-phytes had a mean length of 1.6970.57 mm. PVCtubes seeded in the vertical position demonstratedpoor ¢xation of sporophytes, whereas those exposedin the horizontal position produced a high degree ofsettlement.Based on the preceding results, a culture was car-ried out inJune1998 using 20-cm PVC tubes that hadbeen seeded and cultivated inthe horizontal position.The tubes were placed undisturbed on the bottoms ofthe aquaria. Settlement of spores was apparentlyuni-form on the PVC tubes, as sporophyte plantlets devel-oped uniformly over the tube surfaces. Subsequently,during October1998, PVC tubes set with L. trabeculatawere cut into subsamples 3 cm in length.These ringswere threaded onto the ¢nal culture lines, at 30 cmintervals, placing seven or eight pieces on lines 6 min length. About 90 such lines were prepared andmaintained in outdoor culture tanks during thethree summer months. During this period, the plantsgrew to sizes of 0.5^3 cm in length. Over the cultureperiod, the PVC tubes became adherent to the line be-cause of the growth of the algae.Experiment with varying nutrient enrichmentTable 1 shows that, at the microscopic scale,fewer spores germinated and a low degree of sexualdi¡erentiation was obtained for L. trabeculatagametophytes in the control treatment, di¡eringsigni¢cantly (one-way ANOVA, Po0.001) from theother treatments. Signi¢cantly highest (one-wayANOVA, P o 0.001) fertilities were observed using theagricultural fertilizer as nutrients (Table1). Low den-sities (o10%) of microscopic sporophytes could beobserved after 25 days of culture in the Provasoli 1I, agricultural fertilizer, and agricultural fertilizer 1Itreatments.The experiment using nutrients with juvenilesporophytes did not show signi¢cant di¡erences(Kruskal^Wallis, P40.05) in growth between treat-ments (Table 2). Some juvenile sporophytes showednegative growth because of loss of apical tissue.Culture experiment in outdoor tanksThe growth of algae in tanks during the summer of1999 produced a mean frond elongation of 1.670.8Lessonia trabeculata cultivation M E Edding & FB Tala Aquaculture Research, 2003, 34, 507^515510 r 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515
    • mm day^1. Range in frond length varied between 5and 10 cm and was 420 cm in 8 months (Fig. 2).Growth of the fronds occurred primarily in the zonebetween the stipe and the blade.Algae maintained in tanks showed less frondgrowth than those cultured at sea (Figs1and 2), andelongation of the fronds in the tanks was stable overtime without showing the seasonal di¡erencesobserved in frond growth at sea (Fig.1).Culture experiment at seaThe main problem detected in culture at sea wasthe high degree of biofouling observed on the linesTable1 Meanand standard deviationvalues forgermination, gametophyte sex ratioand fertilityof Lessonia trabeculata in ¢venutrient regimesGermination Gametophyte proportions FertilityTreatment (%) (female/male) (%)Control 83.875.16 No differentiation 0Provasoli 91.773.01 1.770.38 28.5377.52Provasoli 1 I 90.174.19 1.670.26 51.85716.27N* 90.274.18 1.870.25 60.62713.03N* 1 I 90.673.35 1.570.27 60.0274.73*Agricultural fertilizer (potassium nitrate 1 diammonium phosphate).I, iodine (KI).Table 2 Mean and standard deviation for lengths of Lessonia trabeculata sporophytes from laboratoryculture with ¢ve di¡er-ent nutrient regimes, and growth [(100 Lf/Li)/15 days]TreatmentInitial length(mm)Length after15 days (mm)Growth(% day^1)Sea water 1.3570.49 1.6370.47 1.3371.31Provasoli 1.6570.54 2.2870.75 2.3971.94Provasoli 1 I 1.6470.43 2.3070.56 2.1371.75N* 2.0270.53 2.4470.64 1.8771.54N* 1 I 1.8770.68 2.4070.69 1.4871.31*Agricultural fertilizer (potassium nitrate 1 diammonium phosphate).I, iodine (KI).Figure1 Frond elongation rate over time (mm day^1) ofLessonia trabeculata cultured in outdoor tanks (E) and onlong-line systems at sea (I, II and III) after tank cultureduring1999.Figure 2 Variation in average length of the fronds overtime (cm) in Lessonia trabeculata cultured in outdoortanks (E) and on long-line systems at sea (I, II and III)after tank culture during1999.Aquaculture Research, 2003, 34, 507^515 Lessonia trabeculata cultivation M E Edding & FB Talar 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515 511
    • within 1 month of their installation. Smaller sporo-phytes were overcome by the growth of ascidians(mostly Ciona) and hydrozoans, which precipitatedthe death and decomposition of the algae. Plants thatsurvived were those with the greatest length at thetime of their transfer to sea (410 cm), although eventhese plants became heavily encrusted with epi-bionts, which had to be removed each time the plantswere measured.The group of algae placed at sea without inter-mediate culture in outdoor tanks experienced highmortality in their initial months of culture. Of a totalof 26 cords (plant n 5 296) installed on the long linein March 1998, only 105 plants remained among se-ven cords (65% mortality). After 5 months, only 22plants remained on three cords, representing a mor-tality of 79%. It was impossible to measure thegrowth of these plants successfully because of thehigh degree of epiphytism and mortality.Figures 1 and 2 show the rates of elongation andsizes of fronds of plants placed at sea at di¡erent sea-sons of the year after their culture in the outdoortanks. All plants were from a single cohort as de-scribed in the Materials and methods. Elongation offronds occurred during the spring months and wassimilar among the di¡erent groups of cords, with va-lues ranging from 2 to 6 mm day^1(Fig.1).The frondsshowed gradual growth, reaching lengths of 50 cmduring October (Fig.2). Complete harvest of the cords(n 510) in November1999 gave a meanvalue for totalfresh drained weight of 972.6 kg per cord.Formation of reproductive tissue in the fronds was¢rst observed in August 1999 and did not depend onthe date when the individual cord was placed at sea.This phenomenon was not observed in plants main-tained in the outdoor tanks. Although quantitativedata were not obtained, an informal laboratory testsuggested that spores from the cultured algae wereviable and capable of producing sporophytes.Experiment on the feeding of abalone withL. trabeculataTable 3 presents the monthly mean increments inmorphometric characteristics measured on abalonefed three di¡erent diets of Lessonia described in Mate-rials and methods. Analysis of variance (ANOVA)showed no signi¢cant di¡erences (P40.05) amongthe growth values measured in the abalone amongthe food treatments.DiscussionEarly experimentation with microscopic gameto-phytes and sporophytes produced mixed resultswhen seeding cords because of the high degree ofdetachment. This may have resulted from the micro-structure of the nylon cord used, as its ¢ne ¢lamen-tous structure underwent constant £exion as thecord was stressed under environmental conditions.This cord did not present a stable base for the attach-ment of the algal haptera. Settlement of the spores onsolid substrates such as PVC provided a viablesolution to this problem.Agricultural nutrients used during the culturescontained almost no trace elements or the vitaminsthat are provided in the Provasoli medium that mayin£uence the development of the microscopic phaseof the L. trabeculata life cycle. Culture media are en-riched with iodine in the culture of Laminariales inJapan as it appears to be an essential element in frondelongation in these algae (Kawashima 1984; Lobban& Harrison1994). Based on the results of the presentstudy showing lack of statistical di¡erences, andbecause of the relatively high cost of large-scaleproduction of Provasoli medium and the small e¡ectof iodine addition on the growth of L. trabeculata, itwas concluded that agricultural nutrients providedthe most viable alternative for our tank cultures.Table 3 Comparative increases (mean and standard deviation) in three growth characteristics of the abalone Haliotis discushannai cultured for 2 months using Lessonia trabeculata from three di¡erent originsIncrease per month (%)Treatment Length Width WeightL. trabeculata natural stand 6.4970.11 5.7070.23 24.0176.69L. trabeculata long line 7.8070.77 6.8270.29 27.8470.26L. trabeculata outdoor tank 6.9070.25 5.9170.43 26.5573.69Initial sizes of abalone were L 51571mm,W 51071mm,Wt fresh 5 419784 mg (n 5180).ANOVA analysis showed no signi¢cant di¡erences between treatments at P40.05.Lessonia trabeculata cultivation M E Edding & FB Tala Aquaculture Research, 2003, 34, 507^515512 r 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515
    • Once the sporophytes reached a size visible to thenaked eye under controlled conditions, it was recom-mended to transfer them into intermediate culture inoutdoor tanks. During this stage, the shading of thetanks, as described in Materials and methods, suc-cessfully decreased the proliferation of microalgaeand epiphytes that otherwise grew on the culturedalgae and reduced their growth. Also, disintegrationof tissue in the fronds decreases with decreasing am-bient light. It must be considered that L. trabeculata isa subtidal alga, ranging from 1 to 20 m deep (Edding,Fonck & Machiavello1994), and is adapted to low lightoccurring at1-m depth inthe culture tanks. For exam-ple, during November (spring) in the middle day, thelight intensity can average up to 1400 mmol photonsm^2s^1in air; it is reduced to 35% at 1 m,65% at 3 mand to 90% at 7 m depth (Edding et al.1990).The ¢rst experiments in culturing at sea were ad-versely a¡ected by biofouling particularly when cul-tures were initiated in the spring at a time of heavyphytoplankton blooms and at the peak reproductiveperiod of many fouling species. Greater coverage ofsporophytes with fouling organisms when they areplaced at sea at an early stage reduces light absor-bance of the fronds, and thus lowers their photo-synthesis and growth. Moreover, repeated cleaningof fouling organisms from growing plants may re-move apical tissue, and thus reduce the growth inlength of the fronds.The values for the elongation of fronds and theirseasonal trends during culture at sea (Fig. 3) wereFigure 3 Elongation rate (mm day^1) of Lessonia trabe-culata fronds cultured on long-line systems during1988and1999.Figure 4 Long line-cultivated Lessonia trabeculata, E10 months from initiation of culture on a long-line system at1-m depth, as described by Kawashima (1984).Aquaculture Research, 2003, 34, 507^515 Lessonia trabeculata cultivation M E Edding & FB Talar 2003 Blackwell Publishing Ltd, Aquaculture Research, 34, 507^515 513
    • similar to those measured previously for the samespecies in culture (Edding et al.1990) and in naturalbeds (Tala 1999). The main di¡erences in the magni-tude of growth and loss of frond tissue occurred atthe beginning as a response to changed conditionsof the culture from the tanks to the sea.Laminariales may be harvested whole or by prun-ing; the fronds are the most useful part of the plantfor feeding abalone (Owen et al.1984; Corazani & Ill-anes 1998; Castillo 2000). Observations in the ¢eldshow that the typical morphology of the plants tendsto change with greater productionof the holdfast andfrond and lower production of stipe. Good develop-ment of the holdfast permits more secure ¢xation tothe substrate, and the fronds contribute principally tophotosynthetic activity and reproduction. In culture,as haptera develop, it is recommended that the hold-fasts be tied to the cords to ensure theirattachment inorder to reduce the loss of plants as they increase inweight.Abalone cultures require large amounts of algaeas feed, particularly in advanced growth stages(Maureira et al. 1993). Present results suggest thatL. trabeculata can be cultured throughout the year.The reproductive characteristics of L. trabeculata(Tala 1994) suggest there should be no problem in¢nding reproductive material during any season ofthe year in natural beds. Out-of-phase cultures couldthus be initiated throughout the year. However, thequality of spores and the production of sporophytesmay vary over time, and it is therefore suggested thatautumnal reproductive tissue be preferred as this isthe time of the year when the greatest number ofspores are produced bysporophytes (Tala1994). In thisway, allowing for the time required for the develop-ment of the microscopic phase in the laboratory, plant-lets could be placed in tank culture during the springand summer months, followed by placement at sealate in the summer or early the following autumn.Results of the present experiments demonstratethe feasibility of large-scale culture of L. trabeculata(Fig. 4). The main problems include the detachmentof small plants from cords in the early phases of cul-ture and biofouling of the fronds both in the labora-tory and at sea. In terms of potential yield, it ispossible that each 50-m long line, supporting algae-seeded cords at 1-m intervals, could produce 500 kgfresh weight of material from the same cohort ofspores. Aculture of 500 000 juvenile abalone (length20 mm) would require about 2 tons of algae in their¢rst year of culture, equivalent to four successfullyseeded and cultured Lessonia long lines. Futureresearch needs to be directed at improvement of thealgal biomass yields from long lines, with culturescomplementing the harvesting of this species fromnatural beds. The costs involved in these parallelactivities greatly in£uence the ¢nal pro¢tability ofinvertebrate cultures. Additionally, harvesting ofLessonia from natural beds should be subject toresource management regulations in order to main-tain them over time and protect natural commu-nities associated with these beds. In view of thegeneral reproductive characteristics of the Laminar-iales, it is possible that other species along the Chi-lean coast, such as Lessonia nigrescens Bory andMacrocystis spp., could be brought into culture usingthe presently described methods.AcknowledgmentsThe authors are grateful for support given to this pro-ject by the Chilean National Commission of Scienti¢cand Technological Research (CONICYT) as ProjectFONDEF no.1102.ReferencesBasuyaux O. & Mathieu M. 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